THE EFFECT OF JUVENILE ABALONE HALIOTIS MIDAE (LINNAEUS, 1758) WEANING DIET ON GUT-BACTERIAL FORMATION.
Bacterial colonization in the digestive tracts of marine organisms is shaped by ontogeny, diet, and bacteria in the surrounding aquatic environment (Hansen & Olafsen 1999, Ingerslev et al. 2014). Marine bacteria can display rapid growth when subject to a nutrient-rich environment (Enger et al. 1990) such as that in the digestive tracts of aquatic organisms. The abalone gut harbors bacteria that aid in the digestion of seaweed and selectively fermentable polysaccharide substrates therein (Erasmus et al. 1997, Sawabe 2006, Tanaka et al. 2016), but not much is known about the composition of the gut microbiota in relation to ontogeny, environment, and diet. Zhao et al. (2012) have shown that successional changes of the composition of the gut microbiota occur in accordance with life stage and that ontogeny has a strong effect on the gut microbiota of farmed Haliotis diversicolor (Reeve, 1846).
Abalone feed on diatoms during the postsettlement phase (1-10 mm) during which time the digestive system develops and reaches maturity (Johnston et al. 2005) to accommodate a dietary switch from benthic diatoms to macroalgae. In abalone hatcheries, the cultured abalone are switched from diatoms to either macroalgae or formulated feed, a process known as "weaning." Zhao et al. (2012) found that the gut microbiota of Haliotis diversicolor resembled enzyme-secreting bacteria associated with their natural diets during different life stages, i.e., diatoms during the postsettlement diatom-feeding phase and a macroalgae diet during the adult phase (Zhao et al. 2012). During weaning onto formulated feed, there was, however, a reduction in enzyme-secreting bacteria in juvenile abalone, which displayed no similarity to bacteria that grew on submerged artificial feed. The results obtained by Zhao et al. (2012) suggest that the introduction of formulated feed during weaning influenced the gut microbiota of farmed abalone, possibly because of the nutrient richness of artificial feed (Tanaka et al. 2004).
Dietary supplements in the form of fermentable substrates such as macroalgae and other polysaccharides can promote the growth of enzyme-producing bacteria in the guts of abalone (Monje & Viana 1998, Garcia-Esquivel & Felbeck 2006, Sawabe 2006) and, therefore, some degree of gut-bacterial manipulation in farmed abalone can be effected through diet. The presence of selectively fermentable substrates in brown macroalgae such as alginate may promote the growth of beneficial bacteria that provide the abalone host with additional nutrients in the form of acetate (Sawabe et al. 2003). For example, the inclusion of macroalgae meal (>10%) in the formulated diets of Haliotis gigantea (Gmelin, 1791) corresponded with high numbers of alginate-degrading gut-bacterial isolates (Tanaka et al. 2016).
The weaning phase is a vulnerable life stage associated with high mortalities. Gut-bacterial regulation through dietary fermentable substrates can potentially aid in maintaining good health in abalone during this phase. Previous studies found that dietary supplements in the form of microalgae and spirulina promote higher growth performance in abalone weaned onto formulated feed (Ismail et al. 2009, Dyck et al. 2010), but the effects of prebiotic or probiotic supplements on the performance of weaning abalone have not been tested. The effect of kelp-supplemented feeds (0.9% of dry mass; Ecklonia maxima) on the gut microbiota has been investigated for subadult South African abalone Haliotis midae (Linnaeus, 1758) in grow-out (Nel et al. 2017) but not for abalone in the weaning phase.
The present study aimed to establish whether weaning of abalone onto different diets under commercial farming conditions results in different gut-bacterial communities. Therefore, hatchery-reared Haliotis midae (2-3 mm) were weaned from a diatom diet onto either a commercial formulated feed (Abfeed-S34), a kelp-supplemented feed (Abfeed-S34K), or fresh kelp (Ecklonia maxima), and gut bacterial communities were compared between diet treatments using 16S rRNA microbiome sequencing analyses.
MATERIALS AND METHODS
Experimental System and Animals
The study was conducted at HIK Abalone Farm (Pty) Ltd. in Hermanus on the southwestern coast of South Africa (34[degrees]26'S; 19[degrees]13'E). A pump-ashore flow-through system in the hatchery supplied filtered (30 [micro]m) ambient temperature (14.03 [+ or -] 3.58[degrees]C; n = 54) seawater to 12 fiberglass experimental tanks (18.5 x 15 x 14.5 cm; 2,000 [cm.sub.3] [tank.sup.-1]) at approximately 130 [cm.sub.3] [min.sup.-1] [tank.sup.-1]. Each tank contained a black polyvinyl-chloride plastic cone-shaped structure (height: 100 mm; diameter at the base: 150 mm) with an open apex (diameter: 30 mm) and 10 half circle arches (diameter: 30 mm) at the base positioned around the circumference of the cone. The cones serve to provide shelter from light and to add surface area within the tank. Air was supplied via an air-stone placed underneath each cone, similar to the production methods used in commercial abalone farm hatcheries in South Africa. Fluorescent lights were set at a 10-h light/14-h dark photoperiod for winter. The tanks were cleaned twice a week by siphoning uneaten feed and feces from the tank.
All abalone used in this experiment originated from the same spawning and they all had access to diatoms, grown on settlement plates in a commercial abalone hatchery, before the start of the trial. On April 25, 2016, the diatom-fed abalone (0.015 [+ or -] 0.0002 g SE; 2-3 mm; 94 days postsettlement) were removed from their diatom plates and stocked into the experimental tanks (361.7 [+ or -] 182.8 abalone [tank.sup.-1]; a stocking rate of abalone equivalent to 10%-20% of the available tank surface area). They were weaned onto either a commercial formulated feed with no kelp (Abfeed-S34: 34% protein, with a fishmeal and soya meal protein source; <5% lipid; Marifeed Pty Ltd., Hermanus, South Africa), a similar commercial feed that included dry kelp (Abfeed-S34K) or fresh kelp (Ecklonia maxima) only. Each diet was fed to abalone in three replicate tanks. All diets were fed ad libitum; fresh kelp was replaced once per week and the formulated feed was fed using commercial hatchery practices, which included placing 2-3 g feed per day per cone unless enough feed remained from the previous day in which case no feed was added.
After approximately 11 wk of weaning (July 2016), the abalone were moved to commercial raceway tanks (Naylor et al. 2011) in the grow-out section of the farm and stocked into one oyster mesh basket (70 X 25 X 60 cm; length X breadth X height) per treatment. Each basket contained 130-450 abalone and two tunnels (halved 11 cm diameter PVC pipes, 35 cm long) to add surface area in the basket. The abalone were maintained on their experimental diets and fed ad libitum for a period of 16 wk. They were subject to commercial water flow-rate and tank cleaning protocols.
Abalone Size Measurements
Three hundred early juvenile abalone (0.015 [+ or -] 0.0002 SE g [abalone.sup.-1]), which only ever had access to diatoms, were sampled before weaning. They were weighed in three batches of a hundred to establish the mean starting weight of the abalone. After 11 wk in the weaning phase on to the experimental diet treatments, abalone fed the kelp (n = 24 [tank.sub.-1]) and the formulated diet treatments (n = 41 [tank.sub.-1]) were collected randomly from each tank. Similarly, after 16 wk in the grow-out phase, 30 abalone from each diet treatment were collected randomly. Each abalone was weighed to the nearest milligram using an electronic balance and measured using scaled photographs and ImageJ version 1.46r software (National Institutes of Health, Bethesda, MD). Increase in shell length per day and percentage daily growth rate were calculated according to the methods of Knauer et al. (1996). All sampled abalone were frozen immediately and kept frozen until the extraction of DNA.
Collection of DNA from Autochthonous and Allochthonous Gut Bacteria
Before extraction of DNA, abalone were rinsed with diluted ethanol to remove surface-associated bacteria (Sawabe et al. 1995) and shucked. Because of the small size of the abalone, all soft tissues (including the foot muscle and viscera) were pooled for the DNA extractions (Zhao et al. 2012). Three DNA extraction replicates from diatom-fed abalone collected before the weaning experiment comprised tissue homogenates of approximately 50 abalone each. The genomic DNA was amplified separately for each extract and sequenced (n = 3). From the abalone that were weaned onto experimental diets for 11 wk, two DNA extractions per tank replicate, from tissue homogenates of 16-24 abalone each, were pooled and amplified to yield sequence data for each tank replicate (n = 3). Thirty abalone per treatment were collected from abalone grown for 16 wk in the grow-out section. Genomic DNA was extracted four times per treatment and pooled, and each composite DNA sample was amplified four times to account for variability during amplification. The polymerase chain reaction (PCR) products were pooled for each treatment and sequenced (n = 1).
An MO BIO Powerfecal DNA Isolation Kit (MO BIO Laboratories, Carlsbad, CA) with kinetic bead cell lysis, spin filter, and inhibitor removal technologies was used to extract DNA from 250 mg tissue homogenates. Proteinase K was added to the lysis buffer to break down the abalone tissue. The DNA (4.5-28.7 ng [micro][L.sup.-1]) was submitted to MR DNA (www.mrdnalab.com, Shallowater, TX) for sequencing. Barcoded 16S rRNA gene PCR primers 515/806 for the variable V4 region were used with a HotStarTaq Plus Master Mix Kit (Qiagen, USA) in a standard PCR reaction protocol (MR DNA).
Sequencing was performed on a MiSeq sequencer and sequence data were processed using the MR DNA analysis pipeline. Denoised and nonambiguous sequences (>150 base pairs) devoid of chimera sequences were clustered into operational taxonomic units (OTU) at a 97% sequence similarity level and classified using BLASTn against RDPII and NCBI databases (www.ncbi.nlm.nih.gov, http://rdp.cme.msu.edu).
Normality and homogeneity of variances tests were performed using the Shapiro-Wilk and Levene's tests, respectively, and all data analyses were performed using Statistica 12 (Statsoft, Tulsa, OK). A nonparametric Kruskal-Wallis analysis of variance (P < 0.05) was used to compare abalone mass, length, and mortalities (%) between weaning diet treatments.
Good's coverage, which is a measure of the degree to which the full diversity was sampled was calculated (Good 1953) as 1 -(F1/N), where F1 is the number of singleton OTU (having only one sequence read) and N is the total reads from all OTU in that sample. Shannon diversity (H) indices were calculated using PAST statistical software (Hammer et al. 2001) for which H = -sum[([n.sub.i],/n)ln([n.sub.i],/n)], where [n.sub.i] = number of individuals of taxon ('. For the weaning experiment, OTU relative abundances and diversities were compared between treatments using Kruskal-Wallis analysis of variance.
Differences in bacterial OTU composition between treatments were analyzed with a nonmetric multidimensional scaling plot, one-way analysis of similarities (ANOSIM) and similarity percentage (SIMPER) analyses using PAST statistical software (Hammer et al. 2001) with a Bray-Curtis similarity measure.
The abalone that had been weaned onto kelp were significantly smaller compared with those weaned onto the formulated diets (Kruskal-Wallis [H.sub.2,322] = 126.3, P < 0.0001 and [H.sub.2,322] = 124.4, P < 0.0001 for mass and length, respectively; Table 1). Because of variation between replicates, there were no significant differences in mortality (%) between treatments ([H.sub.2,9] = 1.9, P = 0.4; Table 1). During weaning, kelp-fed abalone grew at 42.5 [micro]m [day.sup.-1] with a daily mass gain (%) of 1.5% [day.sup.-1], whereas those fed formulated feed treatments had growth rates of 86.8 and 87.1 [micro]m [day.sup.-1] for abalone fed Abfeed-S34 (S34) and Abfeed-S34K (S34K), respectively. Daily percentage mass gains were 3.34% [day.sup.-1] for abalone weaned onto both formulated diets. After 16 wk of grow-out on the farm, kelp-fed abalone weighed 0.81 [+ or -] 0.35 g (17.59 [+ or -] 3.38 mm shell length) and abalone fed S34 and S34K weighed 1.95 [+ or -] 0.65 (23.63 [+ or -] 2.71 mm) and 1.79 [+ or -] 0.61 (22.65 [+ or -] 3.54 mm), respectively (n = 37 abalone per treatment).
Comparison of OTU Composition between Weaning Treatments
Sequence data for abalone weaned onto Abfeed-S34 were obtained from two tank replicates as the third replicate failed to amplify. All OTU database classification matches had highly significant lvalues (E < 1.6 X [10.sup.-22]). High coverage (>98%) of the full gut microbiome was obtained for all samples (Table 2) and most (93%-98%) OTU identified for all treatments occurred at relatively low abundances below 1% of the total community. The diversity of gut-bacterial OTU for abalone weaned onto kelp was significantly lower than that of abalone weaned onto Abfeed-S34 (Kruskal-Wallis [H.sub.2,8] = 6.3, p = 0.04; z = 2.46, P = 0.04; Table 2). There were no differences in gut-bacterial diversities between weaning abalone fed S34K and those fed either kelp or S34 (z = 1.1-1.5, P = 0.4-0.79).
Approximately half of the OTU (53.5%) that occurred in the guts of weaning abalone were shared between all treatments. There was a significant overall difference in the OTU composition of the gut microbiota of abalone fed different weaning diets (ANOSIM: R = 0.76, P = 0.02). Kelp-fed abalone gut-bacterial communities clustered separately from that of abalone fed formulated feeds (Fig. 1) (SIMPER: 82%-85.5% average dissimilarities between kelp and formulated diet treatments) and the Clostridium bacteria that were dominant in kelp-fed abalone contributed most to these differences (SIMPER: 23.8%-24.9% contribution to variation). The gut-bacterial composition did not differ significantly between abalone weaned onto the two formulated diet treatments (ANOSIM: R = 0.0, P = 0.6; SIMPER: 63.83% average dissimilarity).
Composition of Gut-Bacterial Communities during Different Life Stages
The proportion of identified OTU that was shared between the diatom-fed abalone and between all weaning diet treatments was 26.6%. After 16 wk of grow-out, 51.4% of OTU that occurred in weaning abalone were present in the abalone in grow-out.
During the postsettlement diatom-feeding stage, the gut microbiota of abalone comprised relatively high proportions of Planctomycetia and Verrucomicrobiae, but there was a general reduction in the proportions of these groups during weaning (Fig. 2). The dominant population of Clostridia bacteria in abalone weaned onto kelp decreased in older kelp-fed abalone during grow-out, whereas the proportions of Planctomycetia and Verrucomicrobiae increased again. After 16 wk of grow-out, there was a consistent decrease in the proportion of Actinobacteria and Betaproteobacteria, compared with that found in the guts of weaning abalone, and an increase in the proportion of Mollicutes (Fig. 2). There was also an increase in the proportions of Fusobacteria in the guts of abalone fed formulated feeds during grow-out.
The dominant OTU in the guts of diatom-fed abalone were Rubritalea and Pirellula species (Table 3) that had only low abundances in abalone during weaning (0.24%-2.4%). The guts of abalone weaned onto kelp were dominated by anaerobic Clostridium species, whereas a variety of bacterial genera from Proteobacteria (Stenoxybacter and Cardiobacterium), Actinobacteria (Micrococcus and Corynebacterium), and Flavobacteriia (Haloanella), were prevalent in abalone weaned onto S34 (Table 3). In abalone collected from grow-out, an uncultured Clostridium and Cardiobacterium strain that were dominant in the guts of weaning abalone were also dominant in older abalone in grow-out (Table 3). The Stenoxybacter, Micro-bacterium, and Micrococcus OTU that were dominant in weaning abalone were only present at low abundances in abalone in grow-out (0.0%-0.14%).
During grow-out, there was a selective increase among OTU that were present at low abundances in the guts of weaning abalone. These included an uncultured Mycoplasma, a Psychrilyobacter and a Haloferula strain (Table 3). The vibrios displayed relatively low abundances (<0.09%) in weaning abalone but one Vibrio strain became abundant in abalone grown on the farm (Table 3). A Tenacibaculum and Candidatus hepatobacter strain also became abundant in abalone grown on the farm.
Weaning abalone onto kelp resulted in relatively slow growth compared with that of abalone fed the formulated feed treatments, which may relate to the lower protein and energy content of the kelp compared with that of formulated feed (Britz 1996, Fleurence 1999) and possibly a limited ability to ingest kelp because most abalone only develop an adult-like radula during the later stages of weaning (Kawamura et al. 2001, Johnston et al. 2005).
The predominance of anaerobic Clostridium bacteria in the guts of kelp-fed abalone may be a reflection of higher fermentative activity (Huesemann et al. 2012) associated with the larger volume of fermentable polysaccharides in kelp (Lahaye & Kaeffer 1997, O'Sullivan et al. 2010). The selective growth of Clostridia corresponded with a lower gut-bacterial diversity in kelp-fed abalone compared with those fed formulated feed treatments. Similarly, Tanaka et al. (2004) found relatively low gut-bacterial diversities for Haliotis discus hannai (Ino, 1953) abalone fed Laminaria macroalgae compared with those fed formulated feeds (Tanaka et al. 2004). The lack of a target anaerobic bacterial group associated with the digestion of the energy-rich formulated feeds may thus have reduced the selectivity of the gut environment in abalone fed the two formulated feed treatments.
The proteobacteria that dominated the gut microbiota of abalone weaned onto formulated feed in the present study and of juvenile Haliotis discus hannai fed formulated feed (Tanaka et al. 2004) form part of a large and diverse phylum (Madigan et al. 2015). They may comprise bacteria from the surrounding environment that proliferate competitively in response to a high load of energy sources in the abalone digestive tract (Enger et al. 1990). Nel et al. (2017) found that the inclusion of a kelp substrate (0.9% kelp, dry mass) in formulated feed resulted in lower within-group variability of the gut-bacterial composition of abalone coupled with differences in the dominant bacteria between older abalone (40-50 mm) fed formulated feeds with or without kelp inclusion. The presence of the kelp substrate in the formulated feed did, however, not result in a significant effect on the profile of dominant gut bacteria in the present study.
The vast majority of identified OTU displayed low relative abundances and this confirms that most of the bacteria in the abalone gut are transient bacteria from the surrounding environment as is the case with other marine invertebrates (Harris 1993). For this reason, approximately half of the OTU that occurred in abalone weaned onto kelp were also present in abalone weaned onto formulated feeds and most of these shared species formed only a small part of the total communities. Similarly, most of the bacteria that were shared between abalone within different life stages also had low relative abundances. The free-living Verrucomicrobiae and Planctomycetia strains (Madigan et al. 2015) that were dominant in abalone during the postsettlement diatom-feeding stage probably originated from the water environment, whereas weaning resulted in the establishment of other groups of bacteria.
The abalone gut microbiota is influenced by development, diet, dietary ingredients in the form of fermentable substrates, health, and composition of the water environment (Sawabe et al. 2003, Tanaka et al. 2003, Sawabe 2006, Huang et al. 2010, Zhao et al. 2012). The dominant OTU differed between different life stages and this may be attributed to both the maturation of the abalone's gut and the different water environments encountered by abalone in the hatchery during weaning and those reared in outdoor tanks during grow-out, as the water environment and culture conditions are known to affect the gut microbiota of fishes (Nayak 2010). During weaning, diet was probably the main factor in shaping the gut microbiota as environmental factors were controlled through the use of water filters, artificial lighting, and regular tank cleaning. In contrast, conditions during grow-out would have comprised a richer ecosystem and more diverse food sources. Therefore, the dominant population of Clostridia in abalone weaned onto kelp decreased in kelp-fed abalone during grow-out when detritus, diatoms, and feces became more available as additional food sources.
The maturation of the digestive tract of abalone in grow-out likely increased the selectivity of the gut environment causing Actinobacteria and Betaproteobacteria strains, which were dominant during weaning, to decrease. At this stage, anaerobic bacteria that are adapted to live in close association with animal hosts such as Mollicutes and Fusobacteria (Razin 2007, Roeselers et al. 2011, Nelson et al. 2013) increased. Actinobacteria are generally beneficial symbionts of a wide diversity of aquatic organisms (Valliappan et al. 2014), but they were outcompeted by other bacteria during grow-out. The observed establishment of a Vibrio colony within the abalone gut is in agreement with other studies (Tanaka et al. 2003, 2004, Sawabe 2006, Zhao et al. 2012, Nel et al. 2017).
In conclusion, the abalone gut microbiota was affected by life stage, diet, and environmental variables. Diet, particularly one that comprises a high load of fermentative substrates, may exert a strong effect on the abalone gut microbiota during weaning. Because of the high occurrence of mortalities during weaning, biological control of the gut microbiota through diet may promote health and resilience in growing abalone.
Funding was provided by the National Research Foundation's (NRF) Research and Technology Fund (RTF) in collaboration with Marifeed Pty Ltd. We would like to thank our industry partners Mr. Rowan Yearsley and Mr. Matthew Naylor for their support. We also thank Ms. Taryn Bodill at the South African Institute of Aquatic Biodiversity (SAIAB) Molecular Laboratory for the use of the facility during the study.
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ALDI NEL, (*) CLIFFORD L. W. JONES, PETER J. BRITZ AND SIYAMTHANDA LANDZELA
Department of Ichthyology and Fisheries Science, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
(*) Corresponding author. E-mail: aldipieterse email@example.com
TABLE 1. The mean ( [+ or -] SE, n = 3) size of abalone and the average percentage mortality ( [+ or -] SD, n = 3) after being fed either kelp (Eklonia maxima), a formualted feed (Abfeed-S34), or the same formulated feed fortified with kelp (Abfeed-S34K) after 11 wk of weaning are displayed for each treatment. Significant differences within each column are denoted by different superscripts (P < 0.05). Treatment Mass (g) Length (mm) Kelp 0.05 [+ or -]0.01 (*) 5.8 [+ or -]0.1 (*) S34 0.18 [+ or -]0.0l ([dagger]) 9.2 [+ or -]0.3 ([dagger]) S34K 0.18 [+ or -]0.[dagger]1 ([dagger]) 9.2 [+ or -]0.4 ([dagger]) Treatment Mortality (%) Kelp 77.8 [+ or -] 12.8 (*) S34 36.6 [+ or -] 29.4 (*) S34K 55.7 [+ or -]43.1 (*) TABLE 2. The mean ([+ or -] SD) number of sequence reads, OTU, and Good's coverage indices of gut-bacterial samples taken from abalone fed diatoms (i.e., preweaning; n = 3) and from abalone that were weaned onto (n = 3) or grown (n = 1) on either kelp, a formulated feed (Abfeed-S34), or the same formulated feed fortified with kelp (Afeed-S34K) are displayed. Number of reads Number of OTU Diatoms 127,366 [+ or -]21,136.1 787.3 [+ or -] 59.6 Kelp_weaning 7,431.7 [+ or -]4,337.9 291.7 [+ or -] 157.3 S34_weaning 13,077.5 [+ or -] 12,031.4 304 [+ or -] 80.6 S34K_weaning 76,819.7 [+ or -] 54,242.3 534.3 [+ or -] 129.2 Kelp_grow-out 82,995 807 S34_grow-out 75,469 571 S34K_grow-out 95,119 553 Good's coverage (%) Shannon diversity Diatoms 99.9 [+ or -]0.01 4.8 [+ or -]0.08 Kelp_weaning 98.3 [+ or -]0.6 2.7 [+ or -]0.2 S34_weaning 98.5 [+ or -]1.1 4.0 [+ or -]0.01 S34K_weaning 99.6 [+ or -]0.3 3.8 [+ or -]0.07 Kelp_grow-out 99.9 4.9 S34_grow-out 99.9 3.6 S34K_grow-out 99.9 3.5 Dominance index Diatoms 0.03 [+ or -]0.01 Kelp_weaning 0.2 [+ or -]0.2 S34_weaning 0.03 [+ or -]0.01 S34K_weaning 0.06 [+ or -]0.02 Kelp_grow-out 0.02 S34_grow-out 0.07 S34K_grow-out 0.08 TABLE 3. The dominant OTU (with classes in parentheses) for abalone fed diatoms, kelp, Abfeed-S34, or a similar feed fortified with kelp (Afeed-S34K) are displayed as relative abundances (%) of the total community for different life stages. Treatment Genera of dominant OTU Diatoms_postsettlement Rubrilalea (Verrucomicrobiae; 11.1%), Pirellula OTU 6 (Planctomycetia; 6.8%), and PirellulaOTV 11 (3.7%) Kelp_weaning Uncultured Clostridium (Clostridia; 40.9%), Microbacterium (Actinobacteria; 7.3%), Stenoxybacter (Betaproteobacteria; 4.5%), and Skermanella (Alphaproteobacteria; 3.9%) S34_weaning Stenoxybacter (6.8%), Cardiobacterium (5.6%), Micrococcus (Actinobacteria; 4.4%), Corynebacterium (Actinobacteria; 4.3%), and Haloanella (Flavobacteriia; 4.2%) S34K_weaning Cardiobacterium (11.3%), Psychrobacter (Gammaproteobacteria; 6.4%), Candidatus phytoplasma (Mollicutes; 5.5%), Stenoxybacter (3.5%), and Ahrensia (Alphaproteobacteria; 3.1%) Kelp_grow-out Haloferula (Verrucomicrobiae; 8.9%), uncultured Clostridium (4.2%), and Ruegeria (Alphaproteobacteria; 3.3%) S34_grow-out Uncultured Mycoplasma (Mollicutes; 17.2%), Vibrio (Gammaproteobacteria; 9.8%), Psychrilyobacter OTU 9 (Fusobacteriia; 9.4%), Psychrilyobacter OTU 5 (8.4%), and Tenacibaculum (Flavobacteriia; 8.3%) S34K_grow-out Tenacibaculum (19.0%), Candidatus hepatobacter (Alphaproteobacteria; 15.2%), uncultured Mycoplasma (10.7%), Cardiobacterium (6.8%), and Psychrilyobacter OTU 5 (6.3%)
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|Author:||Nel, Aldi; Jones, Clifford L.W.; Britz, Peter J.; Landzela, Siyamthanda|
|Publication:||Journal of Shellfish Research|
|Date:||Apr 1, 2018|
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