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Spatial distribution of marine benthic habitats in the Estonian coastal sea, northeastern Baltic Sea.

INTRODUCTION

Annex I of the Habitat Directive (Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora) defines the habitat types of higher importance and in need of conservation within Europe. Together with the Birds Directive this directive forms a solid base for the European nature conservation policy and the Natura 2000 network. In order to implement the requirements of the directive and to resolve the existing needs for local conservation purposes, a benthic habitat classification system EBHAB (Eastern Baltic marine benthic HABitats) was developed in the frame of the multinational EU LIFE project 'Marine Protected Areas in the Eastern Baltic Sea (Baltic MPAs)'.

In the current study a detailed inventory of the EBHAB habitat classes was performed within six study areas covering the most valuable nearshore marine areas and including several protected areas, i.e. the Natura 2000 areas in the Estonian coastal range. In general, prior to this inventory the knowledge on the distribution of habitats and associated biota in the coastal areas was very poor including only a few publications each containing a handful sampling sites only (e.g. Martin, 2000; Kotta & Orav, 2001; Kotta et al., 2008, Kovtun et al., 2009). Moreover, the published background information was very scattered and owing to differences in methodologies there was no way to systematize such knowledge. Thus, there was a need to examine the species composition and identify typical communities within their environment. The current inventory allowed us for the first time (1) to summarize the range of large-scale variability of the studied habitats in terms of benthic biodiversity, species composition, and dominance structure; (2) to provide a knowledge base for follow-on biological and ecological studies; and (3) thus, to provide important information for managing our marine resources.

MATERIAL AND METHODS

Study area

Altogether six areas representing various environmental and climatic conditions in the northeastern Baltic Sea were studied in detail with the aim of classifying the observed benthic habitats according to the recently established EBHAB classes (Fig. 1). An overview of the study areas is given below.

Eastern and western Gulf of Finland areas

The average depth of the Gulf of Finland is 37 m and the maximum depth 123 m. The coastal slope is quite steep and depths reach over 30 m in all bays of the study area. Sand, silt, or sandy clay bottoms dominate in deeper areas, boulders and stones prevail near the coast. The coastline is diverse and disjuncted by peninsulas, many small islands occur in the area. The eastern gulf receives runoff from a huge drainage area and the western gulf is a direct continuation of the Baltic Proper. Therefore the gulf has a permanent east-west gradient of salinity. The salinity range of the study area is 4.5-6.2. The area is strongly influenced by diffuse and point-source nutrient loads.

West-Estonian Archipelago Sea

The area comprises shallow bays with many small islets and mudflats. The average depth of the area is less than 4 m with the maximum close to 20 m. The bottom morphology of the area is flat, with gentle slopes towards deeps. The whole water basin is semi-exposed. Sand and sandy clay sediments prevail in the entire area of the archipelago. Due to the shallowness and clayey sediments already moderate winds result in strong resuspension of bottom sediments and poor underwater light conditions. Salinity varies from 0 to 7, being the lowest in the estuary of the Kasari River in the eastern part of the area and around 6-7 in the western, open-sea area. Haapsalu and Matsalu bays are the most eutrophied bays within the West-Estonian Archipelago Sea.

Western Saaremaa Island

Similarly to the previous study area this area consists of small shallow bays with many scattered islets. However, as the entire area is exposed to the Baltic Proper, salinities are relatively high and the values below 7 are rarely recorded. Being situated away from the major pollution sources, the diffuse and point-source nutrient loads are small. The base rock is composed of firm limestone, while offshore islets consist of dolomite banks belonging to the skerry type of islands, which are rare for Estonia. The sediment consists primarily of mixed sand, gravel, and boulders. The climate is maritime and storms occur nearly 60 days every year.

Southern Saaremaa Island

This study area is located in the Gulf of Riga and encompasses the coastal sea area of southern and southeastern Saaremaa Island. The coastline is extremely disjuncted with many small bays invading the land. The area is rather shallow, depths over 20 m are reached only within 10 km distance from the coast. The Gulf of Riga is a wide, shallow, semi-enclosed brackish-water ecosystem of the Baltic Sea. The gulf receives fresh water from a large drainage area, primarily entering the southern part of the basin. The average salinity varies from 0.5-2.0 in surface layers in its southern and northeastern areas to 7 in the straits. In most parts, however, the salinity is 5.0-6.5. Sediments are very diverse with inner bays characterized by fine silty-clayey sediments whereas boulder fields are found adjacent to the exposed peninsulas. Because of the limited water exchange, the gulf is more eutrophicated than the Baltic Proper, and the outflow of nutrients through the straits is higher than the inflow. The riverine loading is the most important pathway of nutrients into the Gulf of Riga, exceeding the combined contribution from atmospheric deposition, point emission from cities and industries along the coast, and nitrogen fixation by marine organisms (Olli et al., 2008).

Irbe Strait

Similarly to the previous study area the Irbe Strait is also located in the Gulf of Riga but partly in the Baltic Proper. The coastline is slightly disjuncted with some small bays and capes. The area is shallow and depths over 20 m are reached only in the Baltic Proper part of the area. The interaction of water masses from the saline Baltic Proper and the less saline Gulf of Riga defines the salinity dynamics in the Irbe Strait area. The salinity values remain predominantly between 5 and 7. Both inshore and offshore areas are dominated by sandy bottoms with a few boulder and gravel fields down to 15 m.

Quantitative sampling

The total area covered by the current mapping activities was approx. 8400 [km.sup.2]. In total 1220 locations were sampled by means of remote underwater video, grab sampling, and SCUBA diving. The stations and areas were selected so as to cover the full diversity of the benthic habitats and the range of environmental gradients. Information from previous underwater investigations and the available geological maps and nautical charts were also considered. Fieldwork was carried out in July-August 2005-2008.

Quantitative sampling of offshore soft-bottom benthic organisms was performed from the R/V Vilma, otherwise small motorboats were used. Samples of benthic invertebrates (benthic animals whose size exceeds 1 mm) and macrophytes were taken with a 0.1 [m.sup.2] Van Veen grab sampler (50 kg) or in the case of operating from smaller workboats with a handheld Ekman-Lenz sampler (0.02 [m.sup.2]). All samples were washed through a 0.25-mm mesh sieve and deep frozen at -20[degrees]C. Further treatment of the material was performed according to HELCOM COMBINE guidelines (HELCOM, 2008). In the laboratory, plants and animals were counted and identified under stereo dissecting microscope. Dry weights (g m-2) of all taxa were obtained after keeping the material for 2 weeks at 60[degrees]C.

SCUBA diving was primarily used to collect samples of benthic organisms from hard-bottom substrates. In every dive the total coverage and the coverage of species and of different substrate types were estimated. Sediment was classified as rock, boulders, stones, gravel, sand, silt, clay, or any combination of these. Biomass samples from macrophyte communities were collected using a 0.04 [m.sup.2] metal frame (20 x 20 [cm.sup.2]). One to three samples were taken per station. All quantitative samples obtained by SCUBA divers were registered and treated in the same way as indicated for grab samples.

Remote underwater video surveys were performed using a handheld 'drop' camera operated from small motorboats. The 'drop' method bases on a 'habitat mapping suitcase', designed by Turvakamera OY in co-operation with the Finnish nature conservation experts and addressed to the special needs of habitat inventories in underwater conditions. This equipment has been further developed to meet the conditions of habitat mapping in the Baltic Sea. Here we used the submersible camera TS-6021PSC together with Archos 5th and 6th generation devices for video recording, the latter being operated on the surface. The camera was set at an angle of 35[degrees] below horizontal to maximize the field of view; the range of the forward view was about 2 m in clear waters. The camera sled was towed from a 5-m-long boat 1 m above the sea floor at an average speed of 50 cm [s.sup.-1]. Depth and navigational data (from GPS) were recorded at start and finish during camera deployments. In every station the minimum recording time was one minute. Videos were analysed using a freeware video watching program in the laboratory. The observer estimated the coverage of different sediment types, total community, and macrophyte and invertebrate species.

Supplementary environmental information

Among abiotic parameters wave exposure defined the first hierarchical level of habitat classification. Bottom sediment, light availability, and biological parameters such as the coverages of key species were considered on the next hierarchical levels.

The Simplified Wave Model method was used to calculate the wave exposure for mean wind conditions represented by the 10-year period between 1 January 1997 and 31 December 2006 (Isaus, 2004; Nikolopoulos & Isaus, 2008). A nested-grids technique was used to take into account long-distance effects on the local wave exposure regime. The resulting grids had a resolution of 25 m. In the modelling the coastal sea was divided into suitable calculation areas, fetch and wave exposure grids were calculated, and subsequently the separate grids were integrated into a seamless description of wave exposure along the study area. This method results in a pattern where the fetch values are smoothed out to the sides, and around islands and skerries so that refraction and diffraction make waves deflect around islands. In the EBHAB habitat classification system wave exposure was divided into two classes: sheltered and moderately exposed. Based on the Simplified Wave Model, the borderline between sheltered and moderately exposed classes was set at 75 000.

In the EBHAB habitat classification system sediment is divided into hard and soft bottoms. The borderline between hard and soft substrates was set according to the dominating substrate type. Hard bottoms consist of rock, pebbles, cobbles, boulders, or any combination of these. Soft bottoms refer to a dominance of gravel, sand, clay, mud, or any combination of these.

According to the generic knowledge on the underwater light level, the sea area was divided into photic and aphotic zones. In the current classification scheme the borderline between the photic and the aphotic layer was set at 20 m. This level reflects the deepest occurrences of macroalgal species in most of the Estonian coastal range (either nowadays or historically). We acknowledge that such borderline may vary spatially and temporally. Nevertheless, as spatially explicit data on the light level were not available, it was not possible to refine the distinction between photic and aphotic habitats in the current study.

In our study area salinity varies between 2 and 7, being the highest in the open sea of the Baltic Proper and the lowest in the eastern Gulf of Finland and the estuaries of the West-Estonian Archipelago Sea and the Gulf of Riga. Although salinity is not considered as an important driving force within the EBHAB classification, it was nevertheless recorded to analyse the relevance of salinity in determining the spatial patterns of benthic macroalgal and invertebrate communities.

In addition, based on bathymetry charts (available in the Estonian Marine Institute, University of Tartu), the inclination of coastal slopes was calculated at 50 m pixel resolutions using the Spatial Analyst tool of ArcGIS software (ESRI, 2011). High values of coastal slopes indicate the occurrence of topographic depressions or humps at the measured spatial scale. Low values refer to flat bottoms.

The values of water velocity were obtained from the results of hydrodynamical model calculations. The calculations were based on the COHERENS model (Bendtsen et al., 2009), which is a primitive equation ocean circulation model. It was formulated with spherical coordinates on a 1 x 1 minute horizontal grid and 30 vertical sigma layers. The model was forced with hourly meteorological fields of 2 m air temperature, wind speed, wind stress vector, cloud cover, and relative humidity. The meteorological fields were obtained from an operational atmospheric model. The model was validated against water velocity measurements from the study area.

The Finnish Meteorological Institute provided data on ice cover and thickness over the study area. These data were produced on daily basis at a nominal resolution of 500 m and were based on the most recent available ice chart and a synthetic aperture radar (SAR) image. The ice regions in the ice charts were updated according to a SAR segmentation and new ice parameter values were assigned to each SAR segment based on the SAR backscattering and the ice thickness range at that location.

We used the MODIS satellite-derived water chlorophyll a values as a proxy of eutrophication. The frequency of satellite observations was generally weekly over the whole ice-free period; however, several observations were discarded due to cloudiness. The spatial resolution of satellite data was 1 km. False zeroes were removed from the data prior to the statistical analysis.

Habitat classification

If more than one biomass sample (either grab or frame) was collected from a station, the replicate samples were averaged in order to avoid later conflicts on interpolation. Interpolation of benthic sediments and coverages of key habitat-forming species was done within the study area applying Inverse Distance Weighting (IDW) (using 12 points maximal). The used IDW interpolation method is robust enough to handle sediment and cover data providing a large number of samples within each study polygon and large-scale mapping purposes.

The coverage of the species had to equal or exceed 10% level in order to be classified as a habitat of this particular species. The use of such borderline is justified for two reasons: (1) a 10% coverage represents the lowest level that can be systematically detected using a standardized sampling effort (e.g. one minute video observations) and (2) a 10% coverage level corresponds to the lowest biomass level that is stable in the yearly scale. In the EBHAB classification macrophytes prevailed over benthic invertebrates, i.e. when a key macrophyte exceeded 10% coverage, this habitat was assigned as the particular macrophyte habitat. Nevertheless, if the key macrophyte species did not reach a 10% cover limit, the habitat could be assigned as the invertebrate habitat in case the invertebrate cover exceeded 10%. The following taxa were considered as the key species (habitat-forming species) in the study area: Fucus vesiculosus, Furcellaria lumbricalis, Zostera marina, other higher plants (Stuckenia pectinata, Potamogeton spp., Ruppia sp., Zannichellia palustris, Myriophyllum spicatum, Ranunculus baudotii, etc.), charophytes, bivalves, and cirripeds (Mytilus trossulus, Dreissena polymorpha, Macoma balthica, Mya arenaria, and Amphibalanus improvisus). The list of habitats according to the EBHAB classification is shown in Table 1.

Statistical analyses

The CCA analysis was conducted using PRIMER 6 software (Clarke & Gorley, 2006). ANOSIM analysis was used to examine differences in the patterns of variation in species composition and biomass between the EBHAB habitats. Prior to analysis, a Bray-Curtis similarity matrix was calculated using raw data (untransformed) and presence/absence transformation to detect whether the potential differences between the communities were due to differences in relative biomass or species composition. Taxa responsible for the observed differences were identified by SIMPER analysis, where the cut-off percentage was set to 90. Canonical correspondence analysis (CCA) was used to visualize variability of different habitats along a multitude of abiotic environmental gradients. The analyses were done in the statistical software R version 2.15.1 using the vegan package (The R Foundation for Statistical Computing, 2012).

RESULTS

Description of the habitats

1. Sheltered hard bottoms with F. vesiculosus

The spatial distribution of the sheltered F. vesiculosus and other EBHAB habitats in the study area is shown in Fig. 2. The F. vesiculosus habitat was largely dominated by the habitat-forming brown alga F. vesiculosus. Other species contributed less than 10% of the total biomass. The F. vesiculosus habitat hosted a relatively large number of plant and invertebrate species. Other benthic species that were regularly found in this habitat were the filamentous algae Cladophora glomerata, Ceramium tenuicorne, Polysiphonia fucoides, and Pilayella littoralis; the bivalves M. trossulus and Cerastoderma glaucum; the gastropod Theodoxus fluviatilis; and gammarid amphipods. The sheltered F. vesiculosus habitat was wide-spread on different types of hard substrate: rock, boulders, and stones. Due to the lower water-current velocity the sedimentation is relatively high and thus also the share of soft substrates (sand, mud) is high. As a consequence of decreased physical disturbance due to ice scouring and waves, F. vesiculosus individuals tended to be larger and more branched compared to those from more exposed habitats. The F. vesiculosus habitat was found in a depth range of 0.5-6 m. The lowest salinity tolerance of F. vesiculosus was around 4.

2. Sheltered hard bottoms with bivalves and the cirriped Amphibalanus improvisus

Besides the habitat-forming species, this habitat typically hosted either the red alga F. lumbricalis, some green and brown algal species, or higher plants. The number of benthic macrophyte and invertebrate species was high. The substrate ranged from boulders to rock, and due to reduced water movement the share of soft substrates (sand, mud) was relatively high. The habitat was found in a depth range of 0.3-13 m at salinities down to 3.7.

3. Sheltered hard bottoms with no particular species dominance

In this habitat charales and the green filamentous alga C. glomerata were often found; however, the coverage of charales did not exceed 10%. Among benthic invertebrates the snails Lymnaea peregra and T. fluviatilis, gammarids, and chironimids were most common. The habitat hosted a moderate number of plant and invertebrate species. The substrate ranged from boulders to rock, and due to reduced water movement the share of soft substrates (sand, mud) was relatively high. The habitat was found in a depth range of 0-1.5 m at salinities around 5.

4. Sheltered soft bottoms with higher plants

Besides higher plants, the brown alga F. vesiculosus and filamentous algae often occurred. Invertebrate biomass was low and mainly dominated by gastropods and bivalves. The habitat was characterized by a high number of macrophyte and invertebrate species. Soft sand, silt, and clay substrates dominated but patchy presence of hard substrate was not uncommon. The habitat was found in a depth range of 0.2-8 m at salinities down to 3.7.

5. Sheltered soft bottoms with charophytes

Besides charophytes, the brown alga F. vesiculosus often occurred. Invertebrate biomasses were low and mainly dominated by gastropods and bivalves. The habitat was characterized by a moderate number of plant and invertebrate species. Sand, silt, and clay substrates dominated but patchy presence of hard substrate was not uncommon. Hypoxic conditions were common. The habitat was found in a depth range of 0.4-7 m and at salinities 4.5-7.3.

6. Sheltered soft bottoms with bivalves

Various bivalve species dominated and many gastropods were found in this habitat. The biomass of macrophytes was low. The characteristic plants were filamentous ephemeral algae, the brown perennial alga F. vesiculosus, and the red perennial alga F. lumbricalis either as loose forms or attached to stand-alone stones. The habitat hosted a low number of macrophyte and a moderate number of invertebrate species. Sand and clay substrates dominated but patchy presence of hard substrate was not uncommon. The habitat was found in a depth range of 0.5-22 m at salinities down to 3.8.

7. Sheltered soft bottoms with no particular species dominance

This habitat had a high biomass of higher plants, charophytes, filamentous algae, the loose form of the brown alga F. vesiculosus, and the red alga F. lumbricalis. Among invertebrates various bivalve and gastropod species prevailed. The habitat hosted a low number of macrophyte and invertebrate species. Sand and clay substrates dominated and the share of hard substrate varied. The habitat was found in a depth range of 0.3-14 m at salinities down to 3.8. Owing to its sheltered location and high benthic biomasses short-term hypoxic conditions can occasionally develop in this habitat.

8. Moderately exposed hard bottoms with F. vesiculosus

This habitat was largely dominated by the brown alga F. vesiculosus and the bivalve M. trossulus. Other species contributed less than 10% of the total biomass. This habitat hosted a large number of plant and invertebrate species. The moderately exposed F. vesiculosus habitat was wide-spread on different types of hard substrate: rock, boulders, and stones. The habitat was found in a depth range of 0.2-12 m at salinities down to 3.7.

9. Moderately exposed hard bottoms with F. lumbricalis

This habitat was largely dominated by the red alga F. lumbricalis and the bivalve M. trossulus. The brown alga F. vesiculosus also occurred in some areas. Other species contributed less than 10% of the total biomass. This habitat hosted moderate to high numbers of plant and invertebrate species. The habitat usually formed a belt just below the moderately exposed F. vesiculosus habitat. The bottom substrate of the habitat consisted mainly of boulders, stones, and limestone. The habitat was found in a depth range of 0.5-22 m at salinities down to 3.8.

10. Moderately exposed hard bottoms with bivalves and A. improvisus

Besides the habitat-forming species, this habitat was often dominated by brown filamentous algae. Other filamentous algae C. tenuicorne, P. fucoides, C. glomerata, and Ectocarpus siliculosus were also common. This habitat hosted moderate numbers of macrophyte and invertebrate species. The bottom substrate of the habitat consisted mainly of rock, boulders, or stones. The habitat was found in a depth range of 0.3-30 m at salinities down to 3.7.

11. Moderately exposed hard bottoms in photic zone with no particular species dominance

The prevailing species of the habitat were various filamentous algae. A mass occurrence of filamentous algae in this habitat has a seasonal character supporting occasional outbreaks of herbivorous invertebrates. Besides, different bivalves and gastropods were characteristic of this habitat. The habitat hosted low numbers of macrophytes and invertebrate species. The bottom substrate ranged from rock to pebbles. The habitat was found in a depth range of 0.5-20 m at salinities down

to 3.8.

12. Moderately exposed hard bottoms in aphotic zone with no particular species dominance

The overview of the habitat is given based on video surveys as no biomass samples were collected from the habitat during the project. This habitat supported very few species and no macrophyte species. Hydrozoans and the bivalve M. trossulus were commonly found with low coverage. The bottom substrate of the habitat consisted mainly of rock or stones. Also dynamic sediments consisting of pebbles, cobbles, and coarse gravel were characteristic. As such sediment may move during storms, conditions are not favourable for the settlement of epifauna. The habitat was found at depths below 20 m at salinities down to 3.

13. Moderately exposed soft bottoms with Z. marina

This habitat was largely dominated by the higher plant Z. marina and filamentous brown algae. Other higher plants occurred occasionally. Among invertebrates various bivalves were found but their biomasses were very low. This habitat hosted high numbers of plant and invertebrate species. The substrate ranged from fine to coarse sands. The habitat was found in a depth range of 1-9 m at salinities down to 4.

14. Moderately exposed soft bottoms with higher plants excluding Z. marina

The habitat hosted a large number of higher plant species. In addition, the loose filamentous algae F. vesiculosus and F. lumbricalis and charophytes were found in this habitat. Among invertebrates various bivalve species prevailed but their biomasses were very low. This habitat hosted a moderate to high number of plant and invertebrate species. The bottom substrate consisted of clay, sand, and gravel. The habitat was found in a depth range of 0.2-7.6 m at salinities down to 4.

15. Moderately exposed soft bottoms with charophytes

The habitat hosted a large number of charophyte species and was also characterized by the presence of some higher plants. Among benthic invertebrates various bivalve species prevailed but their biomasses were very low. The habitat hosted a moderate to high number of macrophyte and invertebrate species. The bottom substrate consisted of clay, sand, and pebbles. The habitat was found in a depth range of 0.2-5 m at salinities down to 5.

16. Moderately exposed soft bottoms with drifting F. lumbricalis

This habitat hosted the drifting red algae F. lumbricalis and Coccotylus truncatus, which formed an up to 0.3-m-thick carpet on the seafloor dominated by soft sediments. The share of the habitat-forming red algal species varied both in space and time but usually about 60-70% of the biomass was made up by F. lumbricalis whereas C. truncatus accounted for 30-35%. The share of other species was usually low, less than 5%. Among invertebrates the bivalves M. balthica, Mya arenaria, and M. trossulus prevailed with high biomasses. This habitat hosted a small number of plant and invertebrate species. The bottom substrate consisted of clay and sand. The habitat was found in a depth range of 4-10 m. This habitat was found at salinities around 6. The habitat is spatially confined to the western part of the West-Estonian Archipelago Sea.

17. Moderately exposed soft bottoms with bivalves

Besides bivalves, the habitat occasionally hosted a low to moderate number of macrophyte and benthic invertebrate species. In general, macrophytes had a low and benthic invertebrates a high biomass. The bottom substrate consisted of clay and sand. The habitat was found in a depth range of 0-52 m at salinities down to 3.6.

18. Moderately exposed soft bottoms with no particular species dominance

Among macrophytes the most characteristic species were brown filamentous algae but their biomasses were low. Among invertebrates various gastropod and bivalve species prevailed. This habitat hosted a small number of plant and invertebrate species. The substrate consisted of all different mixtures of soft and hard bottoms with a total coverage of hard substrate never exceeding 50%. The habitat was found in a depth range of 0-100 m at salinities down to 3.6.

Comparison of habitats and areas

Moderately exposed soft-bottom habitats (13-18) prevailed in the study area whereas sheltered hard-bottom habitats (1-3) were the rarest (Tables 1 and 2). In general, all habitats that included no habitat-forming species tended to be less diverse compared to those having any of such characteristic species. In addition, bivalve-dominated habitats did not support high benthic diversity. Among the studied habitats hard-bottom habitats hosting F. vesiculosus and F. lumbricalis and soft-bottom habitats hosting higher plants, charophytes, and F. lumbricalis were in general the most diverse benthic habitats. The diversity patterns were the same regardless of whether macrophyte, benthic invertebrate, or total benthic diversity was considered (Fig. 3). Many habitats hosted the following macrophyte and invertebrate taxa: C. tenuicorne, P. fucoides, C. truncatus, F. lumbricalis, C. glomerata, Ulva intestinalis, P. littoralis, F. vesiculosus, Battersia arctica, T. fluviatilis, M. balthica, M. trossulus, Idotea spp., Hediste diversicolor, Peringia ulvae, and Gammarus spp. (Tables 3, 4). Other species had stronger affinity to specific habitats. Nevertheless, there were very few species that were found in one habitat only (e.g. Chara horrida, R. baudotii).

The ANOSIM tests showed that the majority of EBHAB habitats did not distinguish from each other in terms of the studied abiotic variables (Table 5). In contrast, many habitats were statistically different either in terms of species composition or dominance structure of benthic macrophyte and invertebrate species (Tables 6, 7). Moreover, the degree of dissimilarity in terms of global R values was higher for biotic comparisons than for abiotic environmental data. The SIMPER analysis also identified other than habitat-forming species that contributed most to the similarities within the habitats. In general, these species were the filamentous brown and green algal species P. littoralis and C. glomerata, the amphipod Bathyporeia pilosa, and the gastropod T. fluviatilis (Table 8). Complex interactions between the abiotic environment and the biota were also supported by the CCA analysis showing the presence of a multitude of abiotic environmental gradients and the grouping of different habitats along the observed EBHAB habitat types (Fig. 4).

DISCUSSION

The Baltic Sea lacks important biotic modifiers of seabed structure such as corals and oysters in true marine areas and thus, the type of seabed sediment is believed to primarily define the foundation of benthic habitats in the region (e.g. Kotta & Orav, 2001). Besides, due to strong natural disturbance by waves and ice, physically driven fluxes are believed to control the dynamics of benthic communities (e.g. Herkul et al., 2006). Consequently, another key driver defining benthic habitats is the level at which the area is exposed to such disturbances. Our analyses showed that regardless of the presence of strong physically driven disturbances in the study area, some macrophyte and invertebrate species were capable of creating a specific local environment that enabled colonization of other benthic species. Specifically, although some habitats statistically significantly differed in terms of the abiotic environment, the species composition and dominance structure of benthic invertebrate communities were better explained by the presence of the habitat-forming species than by the ambient abiotic environment. This allows us to conclude that many of the EBHAB habitats are 'real', i.e. each is characterized by its distinct macrophyte and invertebrate communities. Such communities are most likely not found under similar abiotic environmental conditions without the presence of habitat-forming species. These results also suggest that biotic interactions between the key species and associated species are more commonplace in the studied shallow-water areas than was previously thought.

The presented habitat maps should allow an objective and comprehensive biological valuation of a marine area. Some studied habitats can be categorized under habitat types listed in Annex I of the Habitat Directive and thus be of higher importance for the needs of conservation within Europe. Nevertheless, our analyses clearly showed that there were few unique species that were characteristic of a specific habitat only and that many valuable species such as Z. marina and F. vesiculosus were found within a broad range of habitats. Therefore, an efficient protection strategy should focus broader than on the valuable habitat only. It is known that effectively managed protected areas sustain wilderness values and maintain connectivity among habitats whereas the same habitats are highly fragmented elsewhere (Rioja-Nieto & Sheppard, 2008). Thus, in order to have positive effects on biodiversity on a larger scale, the action of designating protected areas should involve analyses of species distribution not just habitat-level mapping. Specifically, some areas need not host the habitat-forming species due to natural succession or anthropogenic disturbances (Kendrick et al., 2000; Kotta et al., 2012). Therefore, it is rewarding to perform a supplementary habitat suitability modelling in order to predict the potential of the environment for the species of high conservation value (Araujo & New, 2007) and use these modelled layers together with the actual mapping results when creating the boundaries of a protected area.

This study aimed at describing large kilometre-scale patterns of benthic habitats. Although large sea areas were mapped, we are still data-limited as only a minor fraction of the studied seascapes were actually sampled and vast areas between sampling stations were left unstudied. The commonly used Inverse Distance Weighting interpolation technique was then used to predict habitat values at those locations where no samples or measurements were taken. We are aware that the obtained interpolation may give an erroneous result if the number of study stations is too low. Nevertheless, as stated above, the current mapping study primarily focussed on the broad habitat patterns. High-resolution hydro-acoustic scanning (multibeam backscatter, sidescan sonar) and high-resolution multi- and hyperspectral imagery collected by means of autonomous underwater vehicles (deeper areas) and airplanes (shallow areas) are the methods to capture small metre-scale variability of benthic habitats. However, these methods were not applicable considering the large spatial extent of the study area, the financial resources, and available time. No benthic habitat maps had been produced for the Estonian sea area before the EU LIFE project 'Marine Protected Areas in the Eastern Baltic Sea (Baltic MPAs)'. Considering these constraints and the aim of producing large-scale maps, interpolation was the best option in the current study.

Owing to the complex interactions among the abiotic environment and the biota as well as many biotic interactions involved (Stevens & Connolly, 2004), the traditional biotic mapping still remains the key methodology for the assessment of the distribution of habitat types in the marine realm. In the near future such habitat mapping can be supported by many novel tools, e.g. hyperspectral remote sensing of benthic habitats (Herkul et al., 2013), spatial predictive modelling (Elith et al., 2008), and machine learning capable of effectively handling multiple interactions (Kotta et al., 2013). Such techniques are especially valuable in shallow-water areas where due to the constraints shown above high spatial complexity cannot be covered using the traditional sampling methodology.

ACKNOWLEDGEMENTS

The fieldwork was done in the framework of the LIFE project 'Marine Protected Areas in the Eastern Baltic Sea (Baltic MPAs)' (LIFE05NAT/LV/000100). This work was also funded by Institutional research funding IUT02-20 of the Estonian Research Council and partly by the project 'The status of marine biodiversity and its potential futures in the Estonian coastal sea' No. 3.2.0801.11-0029 of the Environmental protection and technology programme of the European Regional Fund.

doi: 10.3176/eco.2013.3.01

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Georg Martin ([mail]), Jonne Kotta, Tiia Moller, and Kristjan Herkul

Estonian Marine Institute, University of Tartu, Maealuse 14, 12618 Tallinn, Estonia

([mail]) Corresponding author, georg.martin@ut.ee

Received 8 March 2013, revised 29 May 2013, accepted 5 June 2013

Table 1. Main characteristics of the EBHAB habitats

Code           Habitat                    Main characteristics

1      Sheltered hard bottoms     High biomass and species
         with Fucus vesiculosus     diversity. F. vesiculosus
                                    dominates. Depth range 0.5-6 m
2      Sheltered hard bottoms     Medium or high biomasses, high
         with bivalves and          species diversity. Vegetation
         Amphibalanus               generally missing. The
         improvisus                 invertebrates Mytilus trossulus,
                                    Dreissena polymorpha, A.
                                    improvisis dominate. Depth range
                                    0.3-13 m
3      Sheltered hard bottoms     Low biomass and moderate species
         with no particular         diversity. Filamentous algae
         species dominance          dominate in shallow area. Depth
                                    range 0.5-1.5 m
4      Sheltered soft bottoms     High biomass and species
         with higher plants         diversity. Sandy, silty, and muddy
                                    substrate with higher plants.
                                    Depth range 0.2-8 m
5      Sheltered soft bottoms     Medium or high biomass, moderate
         with charophytes           species diversity. Soft
                                    substrates, often mud, dominated
                                    by charophytes. Hypoxic conditions
                                    common. Depth range 0.4-7 m
6      Sheltered soft bottoms     Low biomass and species diversity.
         with bivalves              Vegetation mostly missing. Sandy
                                    and silty substrate dominated by
                                    bivalves. Depth range 0.5-22 m
7      Sheltered soft bottoms     High biomass, low species
         with no particular         diversity. Sandy or silty
         species dominance          substrate, often hypoxic. Depth
                                    range 0.3-14 m
8      Moderately exposed hard    High biomass and species
         bottoms with               diversity. F. vesiculosus
         F. vesiculosus             dominates. Depth range 0.2-12 m
9      Moderately exposed hard    Medium biomass and high species
         bottoms with               diversity. F. lumbricalis
         Furcellaria lumbricalis    dominates. Depth range 0.5-22 m
10     Moderately exposed hard    Medium to high biomass and medium
         bottoms with bivalves      species diversity. Vegetation
         and A. improvisus          generally missing or has low
                                    biomass. Depth range 0.3-30 m
11     Moderately exposed hard    Low to medium biomass, low species
         bottoms in photic zone     diversity. Filamentous algae may
         with no particular         dominate in shallow areas. Depth
         species dominance          range 0.5-20 m
12     Moderately exposed hard    Low biomass and species diversity.
         bottoms in aphotic         Vegetation missing, mussels occur
         zone with no particular    but coverage <10%. Found in depths
         species dominance          > 20 m
13     Moderately exposed soft    Medium to high biomass, moderate
         bottoms with Zostera       to high species diversity. Sandy
         marina                     substrate dominated by Z. marina.
                                    Depth range 1-9 m
14     Moderately exposed soft    Medium to high biomass, high
         bottoms with higher        species diversity. Sandy substrate
         plants excluding           dominated by higher plants
         Z. marina                  (excluding Z. marina). Hypoxic
                                    conditions may occur. Depth range
                                    0.2-7.6 m
15     Moderately exposed soft    Medium to high biomass, low to
         bottoms with               moderate species diversity. Sandy
         charophytes                bottoms dominated by charophytes.
                                    Depth range 0.2-5 m
16     Moderately exposed soft    Medium to high biomass, low to
         bottoms with               moderate species diversity. Sandy
         F. lumbricalis             substrate dominated by loose F.
                                    lumbricalis. Found only in
                                    Vainameri area. Depth range 4-10 m
17     Moderately exposed soft    Low to medium biomass, low to
         bottoms with bivalves      moderate species diversity. Sandy
                                    and silty substrate dominated by
                                    bivalves. Depth range 0-52 m
18     Moderately exposed soft    Low biomass and species diversity.
         bottoms with no            Sandy, silty, or muddy substrates
         particular species         in depth range 0-100 m
         dominance

Table 2. Total surface area of benthic habitats in the study area.
Inverse distance weighting interpolation was used to convert habitat
defining point data (abiotic environment and biota) to habitat surfaces

Habitat   Total area,       % of          Habitat not found in
code      [km.sup.2]    studied areas

1              6.1          0.07        Southern Saaremaa,
                                          Irbe Strait
2              4.2          0.05        Eastern Gulf of Finland,
                                          southern Saaremaa
3              3.6          0.04        Southern Saaremaa
4            315.2          3.76
5            184.7          2.20
6            356.5          4.25
7            350.5          4.18
8             46.9          0.56        Irbe Strait
9             61.4          0.73        Western Gulf of Finland
10           200.9          2.40
11           151.4          1.81
12            29.8          0.36        West-Estonian
                                          Archipelago Sea,
                                          southern Saaremaa
13           155.5          1.85
14           230.6          2.75
15            42.8          0.51        Eastern Gulf of Finland
16           472.0          5.63
17          2477.3         29.54
18          3296.0         39.31

Table 3. Macroalgal taxa recorded within EBHAB habitats. '0' denotes
absence and '1' presence

Taxon                                                  Habitat

                                                1    2    3    4    5

Aglaothamnion roseum (Roth) Maggs &
  L'Hardy-Halos                                 1    0    0    1    0
Battersia arctica (Harvey) Draisma              1    1    1    1    1
Ceramium tenuicorne (Kiitzing) Waern            1    1    0    1    1
Ceramium virgatum Roth                          1    0    0    1    1
Ceratophyllum demersum Linnaeus                 0    0    1    1    1
Chaetomorpha linum (0. F. Miiller) Kiitzing     1    1    1    1    1
Chara aspera Willdenow                          1    1    1    1    1
Char a baltica Bruzelius                        1    1    0    1    1
Chara canescens Desvaux & Loiseleur             0    1    1    1    1
Chara connivens Salzmann ex A. Braun            0    1    1    1    1
Chara horrida Wahlstedt                         0    0    0    1
Chara sp.                                       1    0    0    1    1
Chara tomentosa Linnaeus                        0    0    1    1    1
Chorda filum (Linnaeus) Stackhouse              1    0    0    1    1
Cladophora glomerata (Linnaeus) Kiitzing        1    1    1    1    1
Cladophora rupestris (Linnaeus) Kiitzing        1    1    1    1    1
Coccotylus truncatus (Pallas) M. J. Wynne
  & J. N. He                                    1    1    0    1    1
Coleofasciculus chthonoplastes (Gomont)         0    1    0    1    0
Cyanobacteria                                   1    1    0    1    1
Dictyosiphon foeniculaceus (Hudson) Greville    1    1    0    1    0
Ectocarpus siliculosus (Dillwyn) Lyngbye        1    0    0    0    0
Elachista fucicola (Velley) Areschoug           1    0    0    1    0
Elodea canadensis Michx.                        0    0    0    0    1
Eudesme virescens (Carmichael ex Berkeley)
  J. Agar                                       0    0    0    1    0
Fontinalis sp.                                  0    0    1    1    1
Fucus radicans L. Bergstrom & L. Kautsky        1    0    0    1    0
Fucus vesiculosus Linnaeus                      1    0    0    1    1
Furcellaria lumbricalis (Hudson) J. V.
  Lamouroux                                     1    1    0    1    1
Furcellaria lumbricalis f. aegagropila Reinke   0    0    0    1    0
Halosiphon tomentosus (Lyngbye) Jaasund         0    0    0    0    0
Leathesia marina (Lyngbye) Decaisne             1    0    0    0    0
Lemna trisulca Linnaeus                         0    0    1    0    1
Monostroma balticum (Areschoug) Wittrock        1    0    0    1    1
Myriophyllum spicatum Linnaeus                  1    1    1    1    1
Najas marina Linnaeus                           0    0    0    1    1
Percursaria percursa (C. Agardh) Rosenvinge     0    0    0    1    0
Pilayella littoralis (Linnaeus) Kjellman        1    1    1    1    1
Pilayella/Ectocarpus                            1    1    0    1    1
Polysiphonia flbrillosa (Dillwyn) Sprengel      1    1    0    1    1
Polysiphonia fucoides (Hudson) Greville         1    1    1    1    1
Potamogeton perfoliatus Linnaeus                0    1    0    1    1
Ranunculus baudotii Godr.                       0    0    0    1    0
Ranunculus circinatus Sibth.                    0    0    0    1    0
Rhizoclonium riparium (Roth) Kiitzing ex
  Harvey                                        1    1    1    1    1
Rhodochorton purpureum (Lightfoot) Rosenvinge   0    0    0    1    0
Rhodomela confervoides (Hudson) P. C. Silva     1    0    0    1    1
Ruppia cirrhosa (Petagna) Grande                0    0    0    1    0
Ruppia maritima Linnaeus                        1    1    0    1    1
Stictyosiphon tortilis (Ruprecht) Reinke        1    0    0    1    1
Stuckenia pectinata (L.) Borner                 1    1    1    1    1
Zannichellia palustris Linnaeus                 1    1    1    1    1
Zostera marina Linnaeus                         1    1    0    1    1
Tolypella nidiflca (0. F. Miiller) Leonhardi    1    1    1    1    1
Ulothrix sp.                                    1    1    0    1    1
Ulva intestinalis Linnaeus                      1    1    1    1    1
Urospora penicilliformis (Roth) Areschoug       0    1    1    1    1
Vaucheria sp.                                   0    0    1    1    0

No. of taxa recorded within habitat             36   29   21   52   40

Taxon                                                  Habitat

                                                6    7    8    9    10

Aglaothamnion roseum (Roth) Maggs &
  L'Hardy-Halos                                 1    0    1    0    0
Battersia arctica (Harvey) Draisma              1    0    1    1    1
Ceramium tenuicorne (Kiitzing) Waern            1    0    1    1    1
Ceramium virgatum Roth                          0    0    1    1    1
Ceratophyllum demersum Linnaeus                 0    0    0         0
Chaetomorpha linum (0. F. Miiller) Kiitzing     1    0    1    1    0
Chara aspera Willdenow                          0    0    1    1    1
Char a baltica Bruzelius                        0    0    0    1    0
Chara canescens Desvaux & Loiseleur             0    0    1    1    1
Chara connivens Salzmann ex A. Braun            0    0    0    0    0
Chara horrida Wahlstedt                         0    0    0    0    0
Chara sp.                                       0    0    1    0    0
Chara tomentosa Linnaeus                        0    0    0    0    0
Chorda filum (Linnaeus) Stackhouse              0    0    1    1    1
Cladophora glomerata (Linnaeus) Kiitzing        1    1    1    1    1
Cladophora rupestris (Linnaeus) Kiitzing        0    0    1    1    1
Coccotylus truncatus (Pallas) M. J. Wynne
  & J. N. He                                    1    0    1    1    1
Coleofasciculus chthonoplastes (Gomont)         0    0    1    0
Cyanobacteria                                   1    0    0    0    1
Dictyosiphon foeniculaceus (Hudson) Greville    1    0    1    1    1
Ectocarpus siliculosus (Dillwyn) Lyngbye        0    0    1    1    1
Elachista fucicola (Velley) Areschoug           0    0    1    0
Elodea canadensis Michx.                        0    0    0    0    1
Eudesme virescens (Carmichael ex Berkeley)
  J. Agar                                       0    0    1    1    1
Fontinalis sp.                                  0    0    0    0    1
Fucus radicans L. Bergstrom & L. Kautsky        0    0    0    0    0
Fucus vesiculosus Linnaeus                      1    1    1    1    0
Furcellaria lumbricalis (Hudson) J. V.
  Lamouroux                                     1    1    1    1    0
Furcellaria lumbricalis f. aegagropila Reinke   0    0    0    1    0
Halosiphon tomentosus (Lyngbye) Jaasund         0    0    0    1    1
Leathesia marina (Lyngbye) Decaisne             0    0    1    0    1
Lemna trisulca Linnaeus                         0    0    0    0    0
Monostroma balticum (Areschoug) Wittrock        0    0    1    1    0
Myriophyllum spicatum Linnaeus                  0    0    1    1    1
Najas marina Linnaeus                           0    0    0    0    0
Percursaria percursa (C. Agardh) Rosenvinge     0    0    0    0    0
Pilayella littoralis (Linnaeus) Kjellman        1    1    1    1    1
Pilayella/Ectocarpus                            1    0    1    1    1
Polysiphonia flbrillosa (Dillwyn) Sprengel      1    0    1    1    1
Polysiphonia fucoides (Hudson) Greville         1    1    1    1    1
Potamogeton perfoliatus Linnaeus                0    0    1    1    1
Ranunculus baudotii Godr.                       0    0    0    0    0
Ranunculus circinatus Sibth.                    0    0    0    0    0
Rhizoclonium riparium (Roth) Kiitzing ex
  Harvey                                        0    0    1    1    1
Rhodochorton purpureum (Lightfoot) Rosenvinge   0    0    0    0    0
Rhodomela confervoides (Hudson) P. C. Silva     1    0    1    1    1
Ruppia cirrhosa (Petagna) Grande                0    0    1    0    0
Ruppia maritima Linnaeus                        0    0    1    1    1
Stictyosiphon tortilis (Ruprecht) Reinke        1    0    1    1    1
Stuckenia pectinata (L.) Borner                 0    0    1    1    1
Zannichellia palustris Linnaeus                 0    0    1    1    1
Zostera marina Linnaeus                         0    0    1    1    1
Tolypella nidiflca (0. F. Miiller) Leonhardi    0    0    1    1    1
Ulothrix sp.                                    1    0    0    0    1
Ulva intestinalis Linnaeus                      1    1    1    1    1
Urospora penicilliformis (Roth) Areschoug       1    0    0    1    1
Vaucheria sp.                                   0    0    0    0    0

No. of taxa recorded within habitat             19   6    37   35   34

Taxon                                                  Habitat

                                                11   12   13   14   15

Aglaothamnion roseum (Roth) Maggs &
  L'Hardy-Halos                                 0    0    1    0    0
Battersia arctica (Harvey) Draisma              0    0    1    1    1
Ceramium tenuicorne (Kiitzing) Waern            1    0    1    1    1
Ceramium virgatum Roth                          0    0    1    1    1
Ceratophyllum demersum Linnaeus                 0    0    0    1    0
Chaetomorpha linum (0. F. Miiller) Kiitzing     0    0    1    1    1
Chara aspera Willdenow                          0    0    1    1    1
Char a baltica Bruzelius                        0    0    0    1    1
Chara canescens Desvaux & Loiseleur             0    0    1    1    1
Chara connivens Salzmann ex A. Braun            0    0    1    1    1
Chara horrida Wahlstedt                         0    0    0    0    0
Chara sp.                                       0    0    1    0    0
Chara tomentosa Linnaeus                        0    0    1    0    1
Chorda filum (Linnaeus) Stackhouse              1    0    1    1    0
Cladophora glomerata (Linnaeus) Kiitzing        1    0    1    1    1
Cladophora rupestris (Linnaeus) Kiitzing        0    0    0    1    0
Coccotylus truncatus (Pallas) M. J. Wynne
  & J. N. He                                    1    0    1    1    1
Coleofasciculus chthonoplastes (Gomont)         0    0    0         0
Cyanobacteria                                   0    0    0    1    0
Dictyosiphon foeniculaceus (Hudson) Greville    1    0    1    1    1
Ectocarpus siliculosus (Dillwyn) Lyngbye        0    0    0    1    0
Elachista fucicola (Velley) Areschoug           0    0    0    1    0
Elodea canadensis Michx.                        0    0    0    0    0
Eudesme virescens (Carmichael ex Berkeley)
  J. Agar                                       0    0    0    0    0
Fontinalis sp.                                  0    0    0    0    0
Fucus radicans L. Bergstrom & L. Kautsky        0    0    0    1    0
Fucus vesiculosus Linnaeus                      0    0    1    1    1
Furcellaria lumbricalis (Hudson) J. V.
  Lamouroux                                     0    0    1    1    1
Furcellaria lumbricalis f. aegagropila Reinke   0    0    0    0    0
Halosiphon tomentosus (Lyngbye) Jaasund         0    0    0    0    0
Leathesia marina (Lyngbye) Decaisne             0    0    0    0    0
Lemna trisulca Linnaeus                         0    0    0    0    0
Monostroma balticum (Areschoug) Wittrock        0    0    1    0    0
Myriophyllum spicatum Linnaeus                  0    0    1    1    1
Najas marina Linnaeus                           0    0    0    0    0
Percursaria percursa (C. Agardh) Rosenvinge     0    0    0    0    0
Pilayella littoralis (Linnaeus) Kjellman        1    0    1    1    1
Pilayella/Ectocarpus                            0    0    1    1    1
Polysiphonia flbrillosa (Dillwyn) Sprengel      0    0    1    1    1
Polysiphonia fucoides (Hudson) Greville         1    0    1    1    1
Potamogeton perfoliatus Linnaeus                0    0    1    1    1
Ranunculus baudotii Godr.                       0    0    0    0    0
Ranunculus circinatus Sibth.                    0    0    0    0    0
Rhizoclonium riparium (Roth) Kiitzing ex
  Harvey                                        1    0    1    1    1
Rhodochorton purpureum (Lightfoot) Rosenvinge   0    0    0    0    0
Rhodomela confervoides (Hudson) P. C. Silva     0    0    1    1    1
Ruppia cirrhosa (Petagna) Grande                0    0    0    0    0
Ruppia maritima Linnaeus                        0    0    1    1    1
Stictyosiphon tortilis (Ruprecht) Reinke        1    0    1    1    1
Stuckenia pectinata (L.) Borner                 0    0    1    1    1
Zannichellia palustris Linnaeus                 0    0    1    1    1
Zostera marina Linnaeus                         0    0    1    0    0
Tolypella nidiflca (0. F. Miiller) Leonhardi    0    0    1    1    1
Ulothrix sp.                                    0    0    0    1    1
Ulva intestinalis Linnaeus                      0    0    1    1    1
Urospora penicilliformis (Roth) Areschoug       0    0    1    0    0
Vaucheria sp.                                   0    0    0    0    0

No. of taxa recorded within habitat             9    0    33   35   29

Taxon                                                          Habitat
                                                                No. of
                                                               habitats
                                                16   17   18   where sp.
                                                                  was
                                                               recorded

Aglaothamnion roseum (Roth) Maggs &
  L'Hardy-Halos                                 0    1    0       6
Battersia arctica (Harvey) Draisma              0    1    1      14
Ceramium tenuicorne (Kiitzing) Waern            0    1    1      14
Ceramium virgatum Roth                          0    1    0      10
Ceratophyllum demersum Linnaeus                 0    0    0       4
Chaetomorpha linum (0. F. Miiller) Kiitzing     0    1    0      12
Chara aspera Willdenow                          0    0    0      11
Char a baltica Bruzelius                        0    0    0       7
Chara canescens Desvaux & Loiseleur             0    0    0      10
Chara connivens Salzmann ex A. Braun            0    0    0       7
Chara horrida Wahlstedt                         0    0    0       1
Chara sp.                                       0    0    0       5
Chara tomentosa Linnaeus                        0    0    0       5
Chorda filum (Linnaeus) Stackhouse              0    1    0      10
Cladophora glomerata (Linnaeus) Kiitzing        0    1    1      16
Cladophora rupestris (Linnaeus) Kiitzing        0    1    0      10
Coccotylus truncatus (Pallas) M. J. Wynne
  & J. N. He                                    1    1    1      15
Coleofasciculus chthonoplastes (Gomont)         0    0    0       3
Cyanobacteria                                   0    1    0       8
Dictyosiphon foeniculaceus (Hudson) Greville    0    1    0      12
Ectocarpus siliculosus (Dillwyn) Lyngbye        0    0    0       5
Elachista fucicola (Velley) Areschoug           0    0    0       4
Elodea canadensis Michx.                        0    0    0       2
Eudesme virescens (Carmichael ex Berkeley)
  J. Agar                                       0    0    0       4
Fontinalis sp.                                  0    0    0       4
Fucus radicans L. Bergstrom & L. Kautsky        0    0    0       3
Fucus vesiculosus Linnaeus                      0    1    1      12
Furcellaria lumbricalis (Hudson) J. V.
  Lamouroux                                     0    1    1      13
Furcellaria lumbricalis f. aegagropila Reinke   1    1    0       4
Halosiphon tomentosus (Lyngbye) Jaasund         0    1    0       3
Leathesia marina (Lyngbye) Decaisne             0    0    0       3
Lemna trisulca Linnaeus                         0    0    0       2
Monostroma balticum (Areschoug) Wittrock        0    1    0       7
Myriophyllum spicatum Linnaeus                  0    0    0      11
Najas marina Linnaeus                           0    0    0       2
Percursaria percursa (C. Agardh) Rosenvinge     0    0    0       1
Pilayella littoralis (Linnaeus) Kjellman        0    1    1      16
Pilayella/Ectocarpus                            0    1    0      12
Polysiphonia flbrillosa (Dillwyn) Sprengel      0    1    0      12
Polysiphonia fucoides (Hudson) Greville         0    1    1      16
Potamogeton perfoliatus Linnaeus                0    0    0       9
Ranunculus baudotii Godr.                       0    0    0       1
Ranunculus circinatus Sibth.                    0    0    0       1
Rhizoclonium riparium (Roth) Kiitzing ex
  Harvey                                        0    1    0      13
Rhodochorton purpureum (Lightfoot) Rosenvinge   0    0    0       1
Rhodomela confervoides (Hudson) P. C. Silva     0    1    0      11
Ruppia cirrhosa (Petagna) Grande                0    0    0       2
Ruppia maritima Linnaeus                        0    0    0      10
Stictyosiphon tortilis (Ruprecht) Reinke        0    1    1      13
Stuckenia pectinata (L.) Borner                 0    0    0      11
Zannichellia palustris Linnaeus                 0    0    0      11
Zostera marina Linnaeus                         0    0    0       8
Tolypella nidiflca (0. F. Miiller) Leonhardi    0    0    0      11
Ulothrix sp.                                    0    0    0       8
Ulva intestinalis Linnaeus                      0    1    1      15
Urospora penicilliformis (Roth) Areschoug       0    1    0       9
Vaucheria sp.                                   0    0    0       2

No. of taxa recorded within habitat             2    25   10

Table 4. Benthic invertebrate taxa recorded within EBHAB habitats.
'0' denotes absence and T presence

                Taxon                           Habitat

                                         1    2    3    4    5

Alderia modesta (Loven)                  1    0    0    1    1
Amphibalanus improvisus (Darwin)         1    1    0    1    0
Asellus aquaticus (Linnaeus)             1    1    1    1    1
Bathyporeia pilosa Lindstrom             1    0    0    1    0
Bithynia tentaculata (Linnaeus)          1    1    1    1    1
Bylgides sarsi (Kinberg in Malmgren)     0    0    0    0    0
Calliopius laeviusculus (Kroyer)         0    0    0    0    0
Cerastoderma glaucum (Poiret)            1    1    0    1    1
Ceratopogonidae Newman                   0    0    0    0    1
Cordylophora caspia (Pallas)             1    1    1    1    0
Corophium volutator (Pallas)             1    1    0    1    1
Crangon crangon (Linnaeus)               1    0    0    1    0
Cyanophthalma obscura (Schultze)         1    1    0    1    1
Dreissena polymorpha (Pallas)            0    0    0    1    0
Echinogammarus stoerensis (Reid)         0    0    0    0    0
Ecrobia ventrosa (Montagu)               1    1    1    1    1
Einhornia crustulenta (Pallas)           0    0    0    1    0
Erpobdella octoculata (Linnaeus)         0    0    0    1    1
Familia Planorbidae Rafmesque            0    0    1    1    1
Familia Chironomidae                     1    1    1    1    1
Gammarus duebeni Liljeborg               0    0    0    0    0
Gammarus Fabricius juveniles             1    1    1    1    1
Gammarus lacustris Sars                  0    0    0    1    0
Gammarus locusta (Linnaeus)              1    1    0    1    1
Gammarus oceanicus Segerstrale           1    1    0    1    1
Gammarus salinus Spooner                 1    1    0    1    1
Gammarus zaddachi Sexton                 1    1    1    1    1
Gammarus tigrinus Sexton                 1    1    1    1    1
Gonothyraea loveni (Allman)              1    0    0    1    1
Halicryptus spinulosus von Siebold       0    0    0    0    0
Hediste diversicolor (0. F. Miiller)     1    1    1    1    1
Hydrobia Hartman                         1    0    0    1    0
Idotea balthica (Pallas)                 1    1    0    1    1
Idotea chelipes (Pallas)                 1    1    0    1    1
Idotea granulosa Rathke                  0    1    0         0
Jaera albifrons Leach                    1    1    0    1    1
Laomedea flexuosa Alder                  0    0    0    1    0
Leptocheirus pilosus Zaddach             1    1    0    1    1
Lymnaea sp.                              0    1    0    1    1
Lymnaea stagnalis (Linnaeus)             0    0    1    1    1
Macoma balthica (Linnaeus)               1    1    0    1    1
Marenzelleria neglecta Sikorski & Bick   1    0    0    1    1
Melita palmata (Montagu)                 1    0    0    0    0
Monoporeia affinis (Lindstrom)           0    1    0    1    0
Mya arenaria Linnaeus                    1    1    0    1    1
My sis mixta Lilljeborg                  0    1    0    1    1
Mytilus trossulus Gould                  1    1    0    1    1
Neomysis integer (Leach)                 0    0    0    1    1
Ordo Coleoptera                          0    1    1    1    1
Ordo Diptera                             0    1    0    1    1
Ordo Ephemeroptera                       0    0    0    1    0
Ordo Lepidoptera                         0    1    1    1    1
Ordo Odonata                             1    1    1    1    1
Ordo Trichoptera                         1    1    1    1    1
Palaemon adspersus Rathke                1    0    0    1    0
Peringia ulvae (Pennant)                 1    1    1    1    1
Physa fontinalis (Linnaeus)              0    0    0    1    0
Piscicola geometra (Linnaeus)            1    0    0    1    0
Pontoporeia femorata Kroyer              0    0    0    0    0
Potamopyrgus antipodarum (J. E. Gray)    0    0    0    1    1
Praunus flexuosus (Miiller)              0    0    0    0    0
Praunus inermis (Rathke)                 0    0    0    0    0
Radix balthica (Linnaeus)                1    1    1    1    1
Saduria entomon (Linnaeus)               0    0    0    1    0
Subclass Hirudinea                       1    0    0    1    0
Subclass Oligochaeta                     1    1    1    1    1
Tenellia adspersa (Nordmann)             0    0    0    1    0
Theodoxus fluviatilis (L.)               1    1    1    1    1

No. of taxa recorded within habitat      38   36   19   57   42

                Taxon                           Habitat

                                         6    7    8    9    10

Alderia modesta (Loven)                  1    1    1    1    1
Amphibalanus improvisus (Darwin)         1    0    1    1    1
Asellus aquaticus (Linnaeus)             1    1    1    1    1
Bathyporeia pilosa Lindstrom             1    1    0    0    1
Bithynia tentaculata (Linnaeus)          1    1    1    1    1
Bylgides sarsi (Kinberg in Malmgren)     0    0    0    1    0
Calliopius laeviusculus (Kroyer)         0    0    0    1    1
Cerastoderma glaucum (Poiret)            1    0    1    1    1
Ceratopogonidae Newman                   0    0    0    0    0
Cordylophora caspia (Pallas)             0    0    1    0    1
Corophium volutator (Pallas)             1    1    1    1    1
Crangon crangon (Linnaeus)               1    0    1    0    1
Cyanophthalma obscura (Schultze)         1    1    1    1    1
Dreissena polymorpha (Pallas)            0    0    0    1    0
Echinogammarus stoerensis (Reid)         0    0    0    1    1
Ecrobia ventrosa (Montagu)               1    0    1    1    1
Einhornia crustulenta (Pallas)           0    0    0    1    1
Erpobdella octoculata (Linnaeus)         0    0    0    0    0
Familia Planorbidae Rafmesque            0    0    0    0    0
Familia Chironomidae                     1    1    1    1    1
Gammarus duebeni Liljeborg               0    0    1    0    0
Gammarus Fabricius juveniles             1    0    1    1    1
Gammarus lacustris Sars                  0    0    0    0    0
Gammarus locusta (Linnaeus)              1    0    1    1    1
Gammarus oceanicus Segerstrale           1    0    1    1    1
Gammarus salinus Spooner                 1    0    1    1    1
Gammarus zaddachi Sexton                 1    0    1    1    1
Gammarus tigrinus Sexton                 1    0    1    1    1
Gonothyraea loveni (Allman)              0    0    0    1    1
Halicryptus spinulosus von Siebold       1    0    0    0    1
Hediste diversicolor (0. F. Miiller)     1    1    1    1    1
Hydrobia Hartman                         1    0    1    1    0
Idotea balthica (Pallas)                 1    0    1    1    1
Idotea chelipes (Pallas)                 1    0    1    1    1
Idotea granulosa Rathke                  0    0    0    0    0
Jaera albifrons Leach                    1    0    1    1    1
Laomedea flexuosa Alder                  0    0    1    1    0
Leptocheirus pilosus Zaddach             1    0    1    1    1
Lymnaea sp.                              0    0    0    0    0
Lymnaea stagnalis (Linnaeus)             0    0    0    0    0
Macoma balthica (Linnaeus)               1    0    1    1    1
Marenzelleria neglecta Sikorski & Bick   1    0    1    1    1
Melita palmata (Montagu)                 0    0    1    1    0
Monoporeia affinis (Lindstrom)           1    0    1    1    1
Mya arenaria Linnaeus                    1    0    1    1    1
My sis mixta Lilljeborg                  0    0    1    1    0
Mytilus trossulus Gould                  1    0    1    1    1
Neomysis integer (Leach)                 1    0    0    0    1
Ordo Coleoptera                          0    0    1    1    1
Ordo Diptera                             0    1    1    0    0
Ordo Ephemeroptera                       0    1    0    0    0
Ordo Lepidoptera                         0    0    1    1    0
Ordo Odonata                             1    0    0    0    0
Ordo Trichoptera                         1    0    1    0    1
Palaemon adspersus Rathke                0    0    1    1    0
Peringia ulvae (Pennant)                 1    1    1    1    1
Physa fontinalis (Linnaeus)              0    1    0    0    0
Piscicola geometra (Linnaeus)            0    0    1    1    1
Pontoporeia femorata Kroyer              0    0    0    0    0
Potamopyrgus antipodarum (J. E. Gray)    1    0    0    1    0
Praunus flexuosus (Miiller)              1    0    0    1    0
Praunus inermis (Rathke)                 0    0    1    1    1
Radix balthica (Linnaeus)                1    1    1    1    1
Saduria entomon (Linnaeus)               1    0    1    1    1
Subclass Hirudinea                       0    0    0    0    0
Subclass Oligochaeta                     1    1    1    1    1
Tenellia adspersa (Nordmann)             0    0    0    1    0
Theodoxus fluviatilis (L.)               1    1    1    1    1

No. of taxa recorded within habitat      38   15   43   47   43

                Taxon                           Habitat

                                         11   12   13   14   15

Alderia modesta (Loven)                  0    0    0    0    0
Amphibalanus improvisus (Darwin)         0    0    1    1    0
Asellus aquaticus (Linnaeus)             0    0    1    1    1
Bathyporeia pilosa Lindstrom             1    0    0    1    0
Bithynia tentaculata (Linnaeus)          0    0    1    1    0
Bylgides sarsi (Kinberg in Malmgren)     0    0    0    0    0
Calliopius laeviusculus (Kroyer)         0    0    0    0    0
Cerastoderma glaucum (Poiret)            0    0    1    1    1
Ceratopogonidae Newman                   0    0    0    0    0
Cordylophora caspia (Pallas)             0    0    0    1    0
Corophium volutator (Pallas)             0    0    1    1    1
Crangon crangon (Linnaeus)               0    0    0    0    0
Cyanophthalma obscura (Schultze)         0    0    1    1    1
Dreissena polymorpha (Pallas)            0    0    0    0    0
Echinogammarus stoerensis (Reid)         0    0    0    0    0
Ecrobia ventrosa (Montagu)               0    0    1    1    0
Einhornia crustulenta (Pallas)           0    0    1    0    0
Erpobdella octoculata (Linnaeus)         0    0    0    0    0
Familia Planorbidae Rafmesque            0    0    0    0    0
Familia Chironomidae                     0    0    1    1    1
Gammarus duebeni Liljeborg               0    0    0    0    0
Gammarus Fabricius juveniles             1    0    1    1    1
Gammarus lacustris Sars                  0    0    0    0    0
Gammarus locusta (Linnaeus)              0    0    0    1    0
Gammarus oceanicus Segerstrale           0    0    1    1    1
Gammarus salinus Spooner                 0    0    1    1    1
Gammarus zaddachi Sexton                 0    0    1    1    1
Gammarus tigrinus Sexton                 0    0    1    1    1
Gonothyraea loveni (Allman)              0    0    1    1    1
Halicryptus spinulosus von Siebold       0    0    0    1    1
Hediste diversicolor (0. F. Miiller)     1    0    1    1    1
Hydrobia Hartman                         0    0    0    1    0
Idotea balthica (Pallas)                 0    0    1    1    1
Idotea chelipes (Pallas)                 1    0    1    1    1
Idotea granulosa Rathke                  0    0    0 1       0
Jaera albifrons Leach                    0    0    1 1       1
Laomedea flexuosa Alder                  0    0    0 1       1
Leptocheirus pilosus Zaddach             0    0    1 1       1
Lymnaea sp.                              0    0    0 0       0
Lymnaea stagnalis (Linnaeus)             0    0    1 0       0
Macoma balthica (Linnaeus)               0    0    1 1       1
Marenzelleria neglecta Sikorski & Bick   0    0    1 1       1
Melita palmata (Montagu)                 0    0    1 1       0
Monoporeia affinis (Lindstrom)           0    0    1 1       0
Mya arenaria Linnaeus                    0    0    1 1       1
My sis mixta Lilljeborg                  0    0    0 0       0
Mytilus trossulus Gould                  0    0    1 1       1
Neomysis integer (Leach)                 0    0    0 1       0
Ordo Coleoptera                          0    0    0 1       1
Ordo Diptera                             0    0    0 1       1
Ordo Ephemeroptera                       0    0    0 0       0
Ordo Lepidoptera                         0    0    0 1       0
Ordo Odonata                             0    0    1 1       0
Ordo Trichoptera                         0    0    1 1       1
Palaemon adspersus Rathke                0    0    0 1       0
Peringia ulvae (Pennant)                 1    0    1 1       1
Physa fontinalis (Linnaeus)              0    0    0 0       0
Piscicola geometra (Linnaeus)            1    0    0 1       0
Pontoporeia femorata Kroyer              0    0    0 0       0
Potamopyrgus antipodarum (J. E. Gray)    0    0    0 1       0
Praunus flexuosus (Miiller)              0    0    0 1       1
Praunus inermis (Rathke)                 0    0    0 1       0
Radix balthica (Linnaeus)                0    0    1 1       1
Saduria entomon (Linnaeus)               0    0    1 1       1
Subclass Hirudinea                       0    0    0 1       0
Subclass Oligochaeta                     1    0    1 1       1
Tenellia adspersa (Nordmann)             0    0    1    0    0
Theodoxus fluviatilis (L.)               1    0    1    1    1

No. of taxa recorded within habitat      8    0    35   48   31

                Taxon                                   Habitat
                                                         No. of
                                                        habitats
                                         16   17   18   where sp.
                                                           was
                                                        recorded

Alderia modesta (Loven)                  0    1    0       9
Amphibalanus improvisus (Darwin)         0    1    0      10
Asellus aquaticus (Linnaeus)             0    1    0      14
Bathyporeia pilosa Lindstrom             0    1    1       9
Bithynia tentaculata (Linnaeus)          0    1    0      13
Bylgides sarsi (Kinberg in Malmgren)     0    1    0       2
Calliopius laeviusculus (Kroyer)         0    1    0       3
Cerastoderma glaucum (Poiret)            0    1    0      12
Ceratopogonidae Newman                   0    0    0       1
Cordylophora caspia (Pallas)             0    1    0       8
Corophium volutator (Pallas)             0    1    0      13
Crangon crangon (Linnaeus)               0    1    0       6
Cyanophthalma obscura (Schultze)         0    1    0      13
Dreissena polymorpha (Pallas)            0    0    0       2
Echinogammarus stoerensis (Reid)         0    0    0       2
Ecrobia ventrosa (Montagu)               0    1    0      12
Einhornia crustulenta (Pallas)           0    1    0       5
Erpobdella octoculata (Linnaeus)         0    0    0       2
Familia Planorbidae Rafmesque            0    0    0       3
Familia Chironomidae                     0    1    1      15
Gammarus duebeni Liljeborg               0    0    0       1
Gammarus Fabricius juveniles             0    1    1      15
Gammarus lacustris Sars                  0    0    0       1
Gammarus locusta (Linnaeus)              0    1    0      10
Gammarus oceanicus Segerstrale           0    1    0      12
Gammarus salinus Spooner                 0    1    0      12
Gammarus zaddachi Sexton                 0    1    1      14
Gammarus tigrinus Sexton                 0    1    0      13
Gonothyraea loveni (Allman)              0    1    0       9
Halicryptus spinulosus von Siebold       0    1    0       5
Hediste diversicolor (0. F. Miiller)     0    1    1      16
Hydrobia Hartman                         0    0    0       6
Idotea balthica (Pallas)                 0    1    1      13
Idotea chelipes (Pallas)                 0    1    1      14
Idotea granulosa Rathke                  0    0    0       2
Jaera albifrons Leach                    0    1    1      13
Laomedea flexuosa Alder                  0    1    0       6
Leptocheirus pilosus Zaddach             0    1    0      12
Lymnaea sp.                              0    0    0       3
Lymnaea stagnalis (Linnaeus)             0    0    0       4
Macoma balthica (Linnaeus)               0    1    0      12
Marenzelleria neglecta Sikorski & Bick   0    1    1      12
Melita palmata (Montagu)                 0    0    0       5
Monoporeia affinis (Lindstrom)           0    1    1      10
Mya arenaria Linnaeus                    0    1    0      12
My sis mixta Lilljeborg                  0    1    0       6
Mytilus trossulus Gould                  0    1    0      12
Neomysis integer (Leach)                 0    1    0       6
Ordo Coleoptera                          0    1    0      10
Ordo Diptera                             0    0    0       7
Ordo Ephemeroptera                       0    0    0       2
Ordo Lepidoptera                         0    0    0       7
Ordo Odonata                             0    0    0       8
Ordo Trichoptera                         0    1    0      12
Palaemon adspersus Rathke                0    0    0       5
Peringia ulvae (Pennant)                 0    1    1      16
Physa fontinalis (Linnaeus)              0    0    0       2
Piscicola geometra (Linnaeus)            0    1    0       8
Pontoporeia femorata Kroyer              0    1    0       1
Potamopyrgus antipodarum (J. E. Gray)    0    1    0       6
Praunus flexuosus (Miiller)              0    1    0       5
Praunus inermis (Rathke)                 0    0    0       4
Radix balthica (Linnaeus)                0    1    1      15
Saduria entomon (Linnaeus)               0    1    1      10
Subclass Hirudinea                       0    1    0       4
Subclass Oligochaeta                     0    1    1      16
Tenellia adspersa (Nordmann)             0    0    0       3
Theodoxus fluviatilis (L.)               0    1    1      16

No. of taxa recorded within habitat      0    48   15

Table 5. R-statistic values of the ANOSIM habitat pairwise test on
abiotic environmental variables. The closer the values to 0, the more
similar the habitats. Values in bold denote significant differences at
p < 0.05. The shading colour code is as follows: red--sheltered
habitat, blue--moderately exposed habitat, dark--hard-bottom habitat,
light--soft-bottom habitat. Habitat 12 was excluded from the analysis
due to the lack of biomass samples in that habitat

Habitat    1#     2#     3#     4~     5~     6~     7~     8^     9^

1#
2#        0.00
3#        0.00   0.00
4~        0.24   0.24   0.16
5~        0.23   0.13   0.18   0.00
6~        0.22   0.26   0.07   0.00   0.00
7~        0.16   0.18   0.00   0.00   0.00   0.00
8^        0.01   0.04   0.21   0.42   0.42   0.46   0.40
9^        0.03   0.03   0.18   0.39   0.40   0.39   0.37   0.00
10^       0.07   0.00   0.35   0.57   0.63   0.50   0.50   0.00   0.00
11^       0.00   0.01   0.00   0.48   0.42   0.37   0.25   0.07   0.00
13&       0.19   0.12   0.05   0.00   0.00   0.00   0.00   0.34   0.25
14&       0.18   0.22   0.40   0.00   0.00   0.00   0.00   0.32   0.25
15&       0.16   0.02   0.17   0.00   0.00   0.00   0.00   0.30   0.22
16&       0.35   0.60   1.00   0.38   0.21   0.13   0.00   0.65   0.49
17&       0.37   0.37   0.58   0.06   0.14   0.00   0.17   0.46   0.27
18&       0.11   0.12   0.00   0.06   0.00   0.02   0.06   0.28   0.16

Habitat   10^    11^    13&    14&    15&    16&    17&

1#
2#
3#
4~
5~
6~
7~
8^
9^
10^
11^       0.00
13&       0.35   0.28
14&       0.42   0.36   0.00
15&       0.44   0.13   0.00   0.00
16&       0.81   0.50   0.00   0.00   0.25
17&       0.37   0.44   0.01   0.00   0.02   0.17
18&       0.23   0.01   0.00   0.00   0.00   0.00   0.00

Note: The shading colour code is as follows is indicated with:
# red--sheltered habitat, ~ blue--moderately exposed habitat,
^ dark--hard-bottom habitat, & light--soft-bottom habitat

Table 6. R-statistic values of the ANOSIM habitat pairwise test on the
species composition of benthic macrophyte and invertebrate species.
The closer the values to 0, the more similar the habitats. Values in
bold denote significant differences at p < 0.05. The shading colour
code is as follows: red--sheltered habitat, blue--moderately exposed
habitat, dark--hard-bottom habitat, light--soft-bottom habitat.
Habitat 12 was excluded from the analysis due to the lack of biomass
samples in that habitat

Habitat    1#     2#     3#     4~     5~     6~     7~     8^     9^

1#
2#        0.08
3#        0.95   0.31
4~        0.22   0.32   0.91
5~        0.26   0.09   0.86   0.00
6~        0.26   0.26   1.00   0.53   0.51
7~        0.63   0.58   0.14   0.66   0.52   0.54
8^        0.04   0.43   1.00   0.47   0.64   0.47   0.71
9^        0.24   0.47   1.00   0.34   0.70   0.45   0.75   0.07
10^       0.24   0.38   1.00   0.47   0.79   0.49   0.72   0.22   0.05
11^       0.81   0.74   0.70   0.90   0.83   0.78   0.49   0.88   0.88
13&       0.19   0.18   0.96   0.29   0.30   0.24   0.62   0.33   0.29
14&       0.04   0.06   0.32   0.00   0.10   0.33   0.45   0.21   0.24
15&       0.00   0.00   1.00   0.31   0.13   0.42   0.36   0.34   0.35
16&       0.61   0.30   1.00   0.88   0.89   0.39   0.41   0.94   0.83
17&       0.38   0.53   1.00   0.48   0.76   0.18   0.73   0.34   0.14
18&       0.47   0.36   0.33   0.55   0.45   0.35   0.18   0.59   0.60

Habitat   10^    11^    13&    14&    15&    16&    17&

1#
2#
3#
4~
5~
6~
7~
8^
9^
10^
11^       0.89
13&       0.39   0.82
14&       0.33   0.72   0.16
15&       0.29   0.72   0.05   0.13
16&       1.00   0.67   0.34   0.38   1.00
17&       0.27   0.89   0.35   0.29   0.65   0.92
18&       0.57   0.09   0.44   0.37   0.28   0.19   0.56

Note: The shading colour code is as follows is indicated with:
# red--sheltered habitat, ~ blue--moderately exposed habitat,
^ dark--hard-bottom habitat, & light--soft-bottom habitat

Table 7. R-statistic values of the ANOSIM habitat pairwise test on the
biomass dominance structure of benthic macrophyte and invertebrate
species. The closer the values to 0, the more similar the habitats.
Values in bold denote significant differences at p < 0.05. The shading
colour code is as follows: red--sheltered habitat, blue--moderately
exposed habitat, dark--hard-bottom habitat, light--soft-bottom
habitat. Habitat 12 was excluded from the analysis due to the lack of
biomass samples in that habitat

Habitat    1#     2#     3#     4~     5~     6~     7~     8^

1#
2#        0.09
3#        0.49   0.09
4~        0.21   0.03   0.55
5~        0.42   0.05   0.00   0.16
6~        0.56   0.31   0.89   0.47   0.53
7~        0.39   0.42   0.00   0.53   0.42   0.45
8^        0.09   0.67   1.00   0.76   0.94   0.71   0.56
9^        0.57   0.29   0.93   0.77   0.86   0.32   0.56   0.82
10^       0.58   0.17   0.89   0.64   0.75   0.23   0.66   0.86
11^       0.99   0.71   0.96   0.98   0.97   0.77   0.51   1.00
13&       0.44   0.12   0.89   0.25   0.63   0.24   0.59   0.97
14&       0.02   0.02   0.33   0.06   0.18   0.11   0.26   0.42
15&       0.21   0.00   0.75   0.25   0.33   0.00   0.20   1.00
16&       0.76   0.51   1.00   0.98   1.00   0.36   0.30   1.00
17&       0.81   0.55   1.00   0.82   0.96   0.13   0.68   1.00
18&       0.47   0.31   0.20   0.38   0.27   0.32   0.05   0.54

Habitat    9^    10^    11^    13&    14&    15&    16&    17&

1#
2#
3#
4~
5~
6~
7~
8^
9^
10^       0.08
11^       0.92   0.84
13&       0.45   0.42   0.98
14&       0.45   0.42   0.46   0.16
15&       0.44   0.31   0.87   0.12   0.06
16&       0.28   0.86   1.00   1.00   0.50   1.00
17&       0.56   0.45   0.98   0.68   0.57   0.64   1.00
18&       0.48   0.39   0.00   0.39   0.19   0.09   0.35   0.44

Note: The shading colour code is as follows is indicated with:
# red--sheltered habitat, ~ blue--moderately exposed habitat,
^ dark--hard-bottom habitat, & light--soft-bottom habitat

Table 8. Biomass of the characteristic benthic macrophyte and
invertebrate species of the EBHAH habitats identified by the SIMPER
test. Only species that contributed at least 10% of the overall
similarity within each habitat were included. Habitat 12 was excluded
from the analysis due to the lack of biomass samples in that habitat.

Habitat           Species             Average      Contribution,
                                      biomass,           %
                                    g [m.sup.-2]

1         Fucus vesiculosus            177.5            52
          Pilayella littoralis          56.0            34
2         Pilayella littoralis          53.4            60
3         Cladophora glomerata          45.1            54
          Chara aspera                  49.8            42
4         Pilayella littoralis          42.1            40
          Stuckenia pectinata           19.1            12
          Cerastoderma glaucum          13.7            10
5         Chara aspera                  33.6            31
          Cladophora glomerata          23.5            18
          Cerastoderma glaucum          13.5            13
6         Macoma balthica               20.7            50
          Cerastoderma glaucum          6.1             21
7         Bathyporeia pilosa            0.1             94
8         Fucus vesiculosus            235.7            78
9         Mytilus trossulus             97.8            37
          Furcellaria lumbricalis       38.0            25
          Polysiphonia fucoides         7.5             11
10        Mytilus trossulus             47.6            41
          Macoma balthica               5.6             17
          Pilayella littoralis          15.2            13
11        Pilayella littoralis          0.8             57
          Theodoxus fluviatilis         0.5             43
13        Pilayella littoralis          30.4            40
          Macoma balthica               11.5            18
          Cerastoderma glaucum          8.0             13
14        Fucus vesiculosus             62.2            39
          Pilayella littoralis          33.9            23
15        Pilayella littoralis          38.9            24
          Macoma balthica               12.4            20
          Cerastoderma glaucum          10.9            17
16        Furcellaria lumbricalis      202.0            60
          Coccotylus truncatus          72.8            21
17        Macoma balthica               24.7            58
          Mytilus trossulus             12.2            20
18        Theodoxus fluviatilis         0.1             47
          Pilayella littoralis          0.8             31
          Hediste diversicolor          0.1             14
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Author:Martin, Georg; Kotta, Jonne; Moller, Tiia; Herkul, Kristjan
Publication:Estonian Journal of Ecology
Article Type:Report
Geographic Code:4EXES
Date:Sep 1, 2013
Words:12654
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