Isotopic determination of Japanese scallop Patinopecten (Mizuhopecten) Yessoensis (Jay) tissues shows habitat-related differences in food sources.ABSTRACT Using stable isotope stable isotope n. An isotope of an element that shows no tendency to undergo radioactive breakdown. analysis, this study examined the potential food sources of the Japanese scallop Japanese scallop see pecten yessoensis. , Patinopecten (Mizuhopecten) yessoensis (Jay) and determined whether the isotopic i·so·tope n. One of two or more atoms having the same atomic number but different mass numbers. [iso- + Greek topos, ratios inferred from tissues of cultured scallops varied according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. culture systems (hanging and sowing Not to be confused with sewing. Sowing is the process of planting seeds. Hand sowing is the process of casting handfuls of seed over prepared ground: broadcasting. Usually, a drag or harrow is employed to incorporate the seed into the soil. ). Different tissues (i.e., muscle, ctenidia, and digestive gland digestive gland n. A gland, such as the liver or pancreas, that secretes into the alimentary canal substances necessary for digestion. ) of scallops nesting in Saloma Lake (18.3-113.0 mm shell height) and Tokoro (66.8-121.4 mm shell height) and their potential food sources were analyzed for stable carbon and nitrogen isotope isotope (ī`sətōp), in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of isotope was introduced by F. ratios. Average isotope ratios obtained in scallop scallop or pecten, marine bivalve mollusk. Like its close relative the oyster, the scallop has no siphons, the mantle being completely open, but it differs from other mollusks in that both mantle edges have a row of steely blue "eyes" and muscle and ctenidia (-20.6 and -21.0[per thousand] for [delta][sup.13]C; 3.3 and 3.0[per thousand] for [delta][sup.15]N) from Tokoro area (sowing culture; ~65 m depth) had close affinities to suspended particulate par·tic·u·late adj. Of or occurring in the form of fine particles. n. A particulate substance. particulate composed of separate particles. organic matter (-21.6[per thousand] and 2.7[per thousand] for [delta][sup.13]C and [delta][sup.15]N, respectively) suggesting that the scallops from Tokoro area depends on detritus detritus /de·tri·tus/ (de-tri´tus) particulate matter produced by or remaining after the wearing away or disintegration of a substance or tissue. de·tri·tus n. pl. as an important food source. Saloma Lake (hanging culture; ~20 m depth) scallop muscle and ctenidia tissues however had relatively enriched [delta][sup.13]C values (-17.7 and -18.1[per thousand]) and were relatively closer to either net plankton plankton: see marine biology. plankton Marine and freshwater organisms that, because they are unable to move or are too small or too weak to swim against water currents, exist in a drifting, floating state. (-21.1[per thousand]) and particulate organic matter (-22.1[per thousand]). [delta][sup.15]N values were also higher in particulate organic matter taken in Saloma Lake (5.0[per thousand]) and showed a 5.1[per thousand] difference when muscle tissues in two sites are compared. Digestive gland tissues however showed depleted de·plete tr.v. de·plet·ed, de·plet·ing, de·pletes To decrease the fullness of; use up or empty out. [Latin d [delta][sup.13]C and [delta][sup.15]N signatures relative to other tissues in both systems. The observed variations in isotopic ratios in scallops reared in two systems thus reflect differences in carbon and nitrogen sources related to culture habitats. KEY WORDS: Japanese scallop, plankton, stable isotope, Patinopecten, food source INTRODUCTION The long stretch of coastline along the Okhotsk Sea, Japan serves as rearing sites for sowing culture of the Japanese scallop Patinopecten (Mizuhopecten) yessoensis (Jay), which extend up to 10 km offshore (Uki 2006). It harbors the sowing areas of Sarufutsu, Tokoro, and Abashiri, all adjacent to Saroma Lake, wherein spat spat juvenile aquatic shellfish, especially oysters ready for settlement on solid surfaces—'spat fall'. collection and suspension or hanging culture of scallops have been practiced. In hanging culture, scallops are suspended in the water column using either nets or cage structures whereas sowing culture involves releasing them in culture seabeds (MacDonald & Thompson 1985, Paturusi et al. 2002, Mendoza et al. 2003, Uki 2006). However, an intermediate culture is initially done to ensure high survivorship survivorship n. the right to receive full title or ownership due to having survived another person. Survivorship is particularly applied to persons owning real property or other assets, such as bank accounts or stocks, in "joint tenancy. before the scallops are released for grow-out culture either in hanging or sowing. This stage is usually done in embayment areas such as in Saloma Lake. The growth of the scallop depends primarily on the quality and quantity of food sources in their habitats (MacDonald & Thompson 1985). As widely practiced in Hokkaido, Japan, scallops in hanging culture are harvested after 2 y of farming whereas 4 y are required to reach the desired marketable size in sowing culture. Past studies done on P. yessoensis are centered on intensive monitoring intensive monitoring Intensive care The continuous monitoring of Pt vital signs, with electronic hookups to the nursing station; IM encompasses real time measurement of BP and ABGs via arterial lines, pulse oximetry, continuous cardiac monitoring, respiration, of larval larval 1. pertaining to larvae. 2. larvate. larval migrans see cutaneous and visceral larva migrans. species and its environmental correlates (Fujita & Mori 1990, Ito 1990), distribution and abundance (Goshima & Fujiwara 1994), optimum flow velocity In fluid dynamics the flow velocity, or velocity field, of a fluid is a vector field which is used to mathematically describe the motion of the fluid. Definition The flow velocity of a fluid is a vector field Shumway et al. (1987) compare the various scallop species in terms of their feeding habits. In general, a mixture of food sources has been used by suspension-feeding bivalves, which consist mainly of phytoplankton phytoplankton Flora of freely floating, often minute organisms that drift with water currents. Like land vegetation, phytoplankton uses carbon dioxide, releases oxygen, and converts minerals to a form animals can use. (Shumway et al. 1987, Cranford & Grant 1990). To date, the only literature on the food sources of P. yessoensis is described by Mikulich and Tsikhon-Lukanina (1981 as cited in Shumway et al. 1987). Using gut content analysis, they observe a wide size range (9-950 [micro]m) of more than 150 different algae algae (ăl`jē) [plural of Lat. alga=seaweed], a large and diverse group of primarily aquatic plantlike organisms. These organisms were previously classified as a primitive subkingdom of the plant kingdom, the thallophytes (plants that and animal species with detritus as the main food source. However, the use of carbon and nitrogen stable isotope studies will give us better understanding on the assimilated diet of the organism. The utility of this technique has been demonstrated in a number of studies that focused on understanding bivalve bivalve, aquatic mollusk of the class Pelecypoda ("hatchet-foot") or Bivalvia, with a laterally compressed body and a shell consisting of two valves, or movable pieces, hinged by an elastic ligament. diets (Reira & Richard 1996, Lancaster & Waldron 2001, Raikow & Hamilton 2001, Lorraine et al. 2002, Jennings & Warr 2003, Page & Lastra 2003, Yokoyama & Ishihi 2003, Piola et al. 2006, Yokoyama & Ishihi 2006). It is also possible to examine whether the organisms are utilizing food sources of different origin based on [delta][sup.13]C and [delta][sup.15]N isotopic relationship (Yokoyama & Ishihi 2003). In food web studies, separate tissue types of bivalves have been used recently to examine the natural isotope abundance of carbon and nitrogen, because isotope composition varies with tissues and not homogeneous as previously understood (Lorraine et al. 2002, Piola et al. 2006). In most cases however, one specific age, size, or wet weight of the study animal are considered in the analysis. The trophic trophic /tro·phic/ (tro´fik) (trof´ik) pertaining to nutrition. troph·ic adj. Of, relating to, or characterized by nutrition. relationships being studied will be more insightful if different age classes are sampled and covered in the measurements. Depths of culture habitats have been regarded as a factor controlling food availability to suspension-feeding bivalves. Shumway et al. (1987) demonstrated that the food sources of Placopecten magellanicus are habitat-related using the traditional approach. They compare two scallop populations of P. magellanicus from shallow and deep habitats (approx. 20 and 180 m, respectively) and found that pelagic pelagic living in the middle or near the surface of large bodies of water such as lakes or oceans. and benthic ben·thos n. 1. The collection of organisms living on or in sea or lake bottoms. 2. The bottom of a sea or lake. [Greek. food items are both found in shallow populations only. For scallops mostly inhabiting the seabed, flocs, which are formed from collision and aggregation of particles during plankton bloom and resuspension Noun 1. resuspension - a renewed suspension of insoluble particles after they have been precipitated suspension - a mixture in which fine particles are suspended in a fluid where they are supported by buoyancy events can be a potential food source (Thorton 2002 as cited in Cranford et al. 2005). Patinopecten yessoensis is the main fishery resource in Northern Japan boosting the development of its fishing industry in recent years. In this study, different tissues of the Japanese scallops from two culture systems (hanging and sowing method) were examined in combination with the potential food sources to determine any differences in their assimilated diet. The two systems are different in culture depth and other aspects, and ascertaining whether isotopic composition of the scallop tissues differ accordingly will thus reflect their primary food sources. MATERIALS AND METHODS Study Sites The Tokoro seabed, Hokkaido, Japan situated at 44[degrees]13'N, 143[degrees]55'E is one of the major scallop farming sites along the Okhotsk Sea (Fig. 1a). The description of the area and the culture system practiced are described in Goshima and Fujiwara (1994). The sowing ground is affected by high temperature and high salinity Soya Warm Water, which flows through the Sea of Japan and drift eastward through the Soya Strait Soya Strait: see La Pérouse Strait, Japan–Sakhalin island. (Fujita & Mori 1990). Saloma Lake (44[degrees]11 'N, 143[degrees]49' E) is the 3rd largest brackish brack·ish adj. 1. Having a somewhat salty taste, especially from containing a mixture of seawater and fresh water: "You could cut the brackish winds with a knife/Here in Nantucket" tidal lake in Japan with a total area of approximately 150 k[m.sup.2] and mean and maximum depth of 14 and 20 m, respectively (Fig. 1b). It is connected to the coast of the Okhotsk Sea through two narrow inlets, measuring 300 and 50 m wide. The lake houses not only the suspension culture of scallops but also other bivalve organisms such as oysters. [FIGURE 1 OMITTED] Collection and Processing of Scallop Samples Adult-sized (ages 1-4) populations of P. yessoensis were obtained from Tokoro seabed on the following dates: July 14, 2005, May 17, July 11, August 9, and September 8, 2006, respectively. A total of 23 one-year-old and 31 two- to four-year-old scallop individuals were obtained over the five-month period. One batch of five-year-old samples (n = 10) was also obtained in that area on May 2006. Scallop spat or juveniles (n = 37) and l-y to 2-y old (n = 15 for age 1, n = 5 for age 2) scallops were also obtained from Saroma Lake on September 27, 2006, but additional 1-y-old scallops were also received on May 17, 2006. Scallop samples were received approximately 24 h after collection and were packed on ice in a styropore box. Upon receipt, samples were either immediately processed or frozen at -30[degrees]C before processing. If the samples were frozen, scallops were first thawed thaw v. thawed, thaw·ing, thaws v.intr. 1. To change from a frozen solid to a liquid by gradual warming. 2. under room temperature and shell dimensions (shell height and length) were measured to the nearest 0.5 mm using venier caliper caliper Instrument that consists of two adjustable legs or jaws for measuring the dimensions of material parts. Spring calipers have an adjusting screw and nut; firm-joint calipers use friction at the joint to hold the legs unmoving. . Whole tissue was picked from the shell, dissected dis·sect·ed adj. 1. Botany Divided into many deep, narrow segments: dissected leaves. 2. Geology Cut by irregular valleys and hills. Adj. 1. using a scalpel or surgical blade to separate the tissues (i.e., muscle, digestive gland and ctenidia) and individual wet weights were taken using a toploading balance. Potential Food Sources of Scallops in Both Sites Two vertical tows were made to collect samples of net plankton (composed mainly of micro and meso- zooplankton zooplankton: see marine biology. zooplankton Small floating or weakly swimming animals that drift with water currents and, with phytoplankton, make up the planktonic food supply on which almost all oceanic organisms ultimately depend (see and minority of small, chain-forming phytoplankton) using NORPAC (standard North Pacific) nets of 100 and 330 [micro]m mesh sizes. These were done during field surveys in the coastal stations along the Okhotsk Sea conducted on May 13 14 and July 17-18, 2005 and July 19-20, 2006, respectively onboard Refers to a chip or other hardware component that is directly attached to the printed circuit board (motherboard). Contrast with offboard. See inboard. the Training Ship (T/S T/S Troubleshoot T/S Training Ship ) Ushio-Maru of the Faculty of Fisheries fisheries. From earliest times and in practically all countries, fisheries have been of industrial and commercial importance. In the large N Atlantic fishing grounds off Newfoundland and Labrador, for example, European and North American fishing fleets have long , Hokkaido University History Hokkaido University (Hokudai for short) was originally founded in 1876 as Sapporo Agricultural College (札幌農學校 during its 75th, 81st, 103rd oceanographic cruises. Samples were transferred either into 250 or 500 mL wide-mouth polyethylene (PE) bottles and kept frozen onboard before transit to laboratory. Frozen net samples were thawed under room temperature before filtration. An aliquot aliquot (al-ee-kwoh) adj. a definite fractional share, usually applied when dividing and distributing a dead person's estate or trust assets. (See: share) of 1-5 mL and 10-30 mL depending on the sample density were collected using a graduated cylinder or micropipette mi·cro·pi·pette n. 1. A very small pipette used in microinjection. 2. A pipette used to measure very small volumes of liquids. micropipette a pipette for handling small quantities of liquids (up to 1 ml). and filtered onto precombusted 25 mm Whatman GF/F filters. Seawater seawater Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. samples for suspended particulate organic matter (SPOM SPOM Schizosaccharomyces Pombe ) analysis were taken at 0 and 20 m depths using 10 L Niskin bottle Niskin bottle See under Nansen bottle. at Stn. S-0 on July 17, 2006. SPOM samples were dispensed into 1 L PE bottle and filtered through 25 mm Whatman GF/F filters. Another 2 L seawater samples were collected at the same depths and passed through a 10 Jam polycarbonate A category of plastic materials used to make a myriad of products, including CDs and CD-ROMs. filter to collect <10 [micro]m fraction. The filtrate filtrate /fil·trate/ (fil´trat) a liquid or gas that has passed through a filter. fil·trate v. To put or go through a filter. n. was finally filtered through 0.7 [micro]m GF/F filters (25 mm) to represent size-fractionated SPOM samples. In Saloma Lake, water samples for suspended POM measurements were taken at the surface and 1 m above the bottom in four stations (Stns. 4, 5, 7, and 8, respectively, Fig. 1b) using Van Dorn water sampler sampler, sample piece of needlework or embroidery, of silk, cotton, or worsted, for the preservation of some pattern or as an example of the ability of a child or a beginner. In museums and private collections there are samplers dating from as early as 1643. and dispensed into an acid cleaned 1 L PE bottles using plastic bucket. Size-fractionation of POM samples and collection of net samples were only undertaken at Stn. 7 where 53% of the total area has been allocated for scallop farming. Net plankton (100 and 330 [micro]m fractions) was sampled using twin-towed plankton NORPAC nets. Samples were immediately processed after collection at the Saloma Lake Fishermen Cooperative Association's center. Isotopic Analysis of Tissues and Filter Samples Small portion of each tissue (i.e., muscle, digestive gland, and ctenidia) was cut, frozen and freeze-dried using Yamato freeze-drier unit. Tissues from 7 8 scallop spat or juveniles were pooled together to have enough ground samples for analysis. Drying of digestive gland tissues were assisted by puncturing In coding theory, puncturing is the process of removing some of the parity bits after encoding with an error-correction code. This has the same effect as encoding with an error-correction code with a higher rate, or less redundancy. the outer surface a number of times to allow water vapor to be released (T. Jennings, pers. comm.). Samples were ground into homogenous homogenous - homogeneous , fine powder using mortar and pestle A mortar and pestle is a tool used to crush, grind, and mix substances. The pestle is a heavy stick whose end is used for pounding and grinding, and the mortar is a bowl. The substance is ground between the pestle and the mortar. , transferred to preweighed vials using paraffin paraffin, white, more-or-less translucent, odorless, tasteless, waxy solid. It melts between 47°C; and 65°C; and is insoluble in water but soluble in ether, benzene, and certain esters. paper and the dry weights were recorded. Ground samples amounting to 1 mg were weighed and put into tin capsules (5 x 9 mm) and folded. On the other hand, filter samples were freeze-dried, exposed to HCl fume fume Occupational medicine A solid suspension resulting from condensation of the products of combustion. See Inhalant Vox populi verbTo be in the midst of a mental mini-meltdown. for 4-5 h and placed into tin capsules before analysis. Triplicate analysis of selected sample was done to determine the analytical precision and was found at 0.04[per thousand] and 0.02[per thousand] (S.E.) variations for [delta][sup.13]C and [delta][sup.15]N along with the running or internal standards (i.e., alanine alanine (ăl`ənēn'), organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer participates in the biosynthesis of proteins (see stereochemistry). and tyrosine tyrosine (tī`rəsēn), organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein. ). Separate tissues of scallop samples in all age classes were all analyzed in duplicate. Isotopic data are processed and retrieved using ISODAT 2.5 Gas Isotope Ratio MS Software (Thermo International Corporation). Isotopic values are expressed in delta notation ([delta][sup.13]C or [delta][sup.15]N) and are reported in per mil per mil also per mill adv. Per thousand. [per + mil (short for Latin m ([per thousand]) using the equation: [delta][sup.13][C.sub.sample] or [delta][sup.15][N.sub.sample]([per thousand]) = ([R.sub.sample]/[R.sub.standard] - 1) x 1000; where R = [sup.13]C/[sup.12]C or [sup.15]N/[sup.14]N Standards or international reference material used for C is Vienna Pee Dee Pee Dee or Great Pee Dee, river, c.435 mi (700 km) long, rising in the Blue Ridge, W N.C., and flowing NE then SE to Winyah Bay, S.C. It is called the Yadkin until it is joined by the Uharie River W of Troy, N.C. Belemnite bel·em·nite n. A cone-shaped, fossilized internal shell of any of an extinct genus of cephalopods related to the cuttlefish. [New Latin belemn (VPDB VPDB Vienna PeeDee Belemnite ), which is originally the Cretaceous belemnite material picked from the Pee Dee formation in South Carolina South Carolina, state of the SE United States. It is bordered by North Carolina (N), the Atlantic Ocean (SE), and Georgia (SW). Facts and Figures Area, 31,055 sq mi (80,432 sq km). Pop. (2000) 4,012,012, a 15. (Werner & Brand 2001) and atmospheric molecular nitrogen (AIR-[N.sub.2]) for nitrogen isotope ratio analyses. Data Analysis Differences in the average carbon and nitrogen isotopic values for one and two-year-old scallops in two sites were tested employing Student t-test. Because the scallops cultured in Saloma Lake reached marketable size after 2 y of farming, possible differences in stable carbon and nitrogen isotopic values with the four-year-old scallops from Tokoro, Okhotsk Sea were also compared. Variability in [delta][sup.13]C and [delta][sup.15]N isotopic values between tissues was determined separately for each scallop tissue between two sites from their variance followed by F-test. RESULTS Isotopic Composition of P. yessoensis in Two Culture Systems In hanging cultured scallops, muscle, digestive gland, and ctenidia tissues averaged -17.7 [+ or -] 0.1, -22.1 [+ or -] 0.1, and -18.1 [+ or -] 0.1[per thousand] for [delta][sup.13]C and 8.4 [+ or -] 0.1, 7.0 [+ or -] 0.4, and 8.1 [+ or -] 0.1[per thousand] for [delta][sup.15]N, respectively (Table 1b). Observed average muscle [delta][sup.13]C signatures showed an enrichment of 0.5[per thousand] relative to ctenidia, and 4.5[per thousand] compared with digestive gland. Tissues [delta][sup.15]N values showed a small enrichment by 0.3-0.8[per thousand] in similar order. Scallop spat was relatively more positive in [delta][sup.13]C and [delta][sup.15]N compared with 1 and 2-y-old scallop samples (Table 1a). The small standard error denotes that [delta][sup.13]C and [delta][sup.15]N signatures showed little intratissue variability within a sampling collection except for the digestive gland [delta][sup.15]N of one-year old scallops. Relationship of [delta][sup.13]C and [delta][sup.15]N isotopic signatures An isotopic signature (also isotopic fingerprint) is a ratio of stable or unstable isotopes of particular elements found in an investigated material. The atomic mass of different isotopes affect their chemical kinetic behavior, leading to natural isotope separation processes. in various tissues however showed higher interage variability in digestive gland tissues (Fig. 2a). Scallop muscle and ctenidia showed distinct [delta][sup.13]C and [delta][sup.15]N isotopic ratios. Bottom or sowing cultured scallops from Tokoro showed that the scallop muscle was always consistently more positive in [delta][sup.13]C relative to ctenidia and digestive gland tissues in all age classes (Table 1a). Average [delta][sup.13]C isotopic values were -20.6 [+ or -] 0.2, -21.0 [+ or -] 0.2, and -25.2 [+ or -] 0.3[per thousand] for muscle, ctenidia and digestive gland tissues, respectively and slight interage difference was observed in three tissue types (Table 1b, Fig. 2b). With respect to [delta][sup.15]N isotopic signatures, muscle tissues averaged 3.3 [+ or -] 0.6[per thousand], 0.3 and 3.6[per thousand] more enriched compared with ctenidia and digestive gland, respectively. Comparison between one, two-year-old and two and four-year-old scallops in Saloma Lake and Tokoro, respectively showed significant differences in [delta][sup.13]C and [delta][sup.15]N isotopic ratios (Table 1 a, p < 0.05). Of the three tissues analyzed, ctenidia was the least variable in [delta][sup.13]C isotopic ratios relative to muscle and digestive gland but muscle [delta][sup.15]N isotopic ratios showed small variance in two sites (Table 2). In both sites, variance components in [delta][sup.15]N values showed a different order with muscle, ctenidia, and digestive gland exhibiting ascending ascending /as·cend·ing/ (ah-send´ing) having an upward course. ascending progressing to higher levels, usually used in reference to the nervous system. variability. Apparent small variance in [delta][sup.13]C and [delta][sup.15]N isotopic ratios in Saloma Lake populations was found relative to Tokoro. Results of F-test showed that ctenidia was significantly the least variable in [delta][sup.13]C relative to muscle and digestive gland. However, digestive gland was significantly variable in [delta][sup.15]N than the other tissues. In Tokoro samples, digestive gland was more variable in [delta][sup.13]C than ctenidia, and relative to muscle and ctenidia in [delta][sup.15]N at significant level. Potential Food Sources In Saloma Lake, net plankton [delta][sup.13]C and [delta][sup.15]N values obtained on July 2006 (mean [+ or -] SE, n = 2) averaged -21.1 [+ or -] 0.5 and 7.6 [+ or -] 0.4[per thousand], respectively (Table la). Surface SPOM samples were 1.8[per thousand] more enriched in [delta][sup.13]C but 0.2[per thousand] less enriched in [delta][sup.15]N relative to bottom samples. Fractions of SPOM samples (0.7 and <10 [micro]m; mean [+ or -] SE, n = 6) collected at surface and bottom depths showed an average of-22.1 [+ or -] 0.5[per thousand] in [delta][sup.13]C and 5.0 [+ or -] 0.2[per thousand] in [delta][sup.15]N. Bulk SPOM sample collected from 1 m above the bottom at Stn. 7 was 2.9[per thousand] less positive in [delta][sup.13]C but relatively had the same [delta][sup.15]N isotopic ratio with the adjacent Stn. 8. Net plankton samples of 100 and 330 [micro]m fractions collected during May, July 2005, and July 2006 in coastal areas adjacent to Tokoro sowing farming sites exhibited an average of -25.1 [+ or -] 1.4[per thousand] in [delta][sup.13]C and 7.9 [+ or -] 2.1[per thousand] in [delta][sup.15]N values (mean [+ or -] SE, n = 12). SPOM bulk and < 10 [micro]m fractions sampled at Station S-0 averaged -21.6 [+ or -] 1.4 and 2.7 [+ or -] 0.2[per thousand] respectively for [delta][sup.13]C and [delta][sup.15]N values. Bottom SPOM samples were more positive in both [delta][sup.13]C and [delta][sup.15]N values compared with samples collected at surface depths. DISCUSSION Isotopic Signatures of Scallop Tissues in Two Culture Systems Stable isotope ratios reflected in tissues of the study animal are said to show the assimilated portion of its diet (Jardine et al. 2003). Isotopic relationship in muscle and ctenidia tissues in scallops from Saroma Lake showed that there were no changes in their assimilated diet (Fig. 2a). Digestive gland [delta][sup.13]C and [delta][sup.15]N have high interage differences and tend to assimilate a relatively less enriched [delta][sup.13]C and [delta][sup.15]N sources. As shown in Figure 2b, tissues [delta][sup.13]C and [delta][sup.15]N values in Tokoro samples formed a cluster that indicates distinct isotope values in each tissue. Isotopic [delta][sup.13]C values inferred from all tissues examined were less enriched in [delta][sup.13]C for most of tissues compared with the observations of Lorraine et al. (2002) and in other bivalve diet studies (Yokoyama & Ishihi 2003, Page & Lastra 2003). This observation might be explained by the lipid content in the tissues, because lipids are known to have relatively depleted in [delta][sup.13]C. In fact, Lorraine et al. (2002) found that the digestive gland of the scallops contains 25% of lipid as Lipid A is a lipid component of an endotoxin held responsible for toxicity of Gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS, also called endotoxin) molecule, and its hydrophobic nature allows it to anchor the LPS to the outer opposed to 4% lipid of muscle tissue. Lipid extraction or either normalization In relational database management, a process that breaks down data into record groups for efficient processing. There are six stages. By the third stage (third normal form), data are identified only by the key field in their record. was not done in this study resulting to depleted values in digestive gland tissues. Related to this, Yokoyama and Ishihi (2006) compare the [delta][sup.13]C and [delta][sup.15]N values of three suspension-feeding estuarine es·tu·a·rine adj. 1. Of, relating to, or found in an estuary. 2. Geology Formed or deposited in an estuary. Adj. 1. estuarine - of or relating to or found in estuaries estuarial bivalves with lipid and nonlipid containing tissue samples. Their results showed that extraction of lipids significantly increases the [delta][sup.13]C and [delta][sup.15]N values for all of the tissues examined. However, this technique has also implications on the consistency of isotopic fractionation fractionation /frac·tion·a·tion/ (frak?shun-a´shun) 1. in radiology, division of the total dose of radiation into small doses administered at intervals. 2. between the consumer and its diet with the generally accepted fractionation factors in the literature (DeNiro & Epstein 1978, Minagawa & Wada 1984). [FIGURE 2 OMITTED] Muscle tissue is said to integrate the dietary changes in the diet of the scallops in the long term and thus will not show much variability with time. Similarly, digestive gland reflects the diet of an organism in a shorter period because of faster turnover rates of these tissues. However, ctenidia was the least variable in [delta][sup.13]C values in Saloma Lake scallops. Observed variations in [delta][sup.13]C and [delta][sup.15]N were also small in Saroma than in Tokoro scallop tissues, because limited samples were obtained in the former site. Contrary to [delta][sup.13]C values found between tissues, muscle tissues showed the least variance in [delta][sup.15]N values. This is similar to the findings of Piola et al. (2006) for oyster tissues in an impacted estuary estuary (ĕs`ch  ĕr'ē), partially enclosed coastal body of water, having an open connection with the ocean, where freshwater from inland is mixed with saltwater from the sea. though their estimated variance component was
relatively much lower than the variance examined in this study.
Isotopic values in Tokoro scallops were less enriched in [delta][sup.13]C relative to Saloma Lake representative populations despite proximity in location. The Japanese scallops, before they are released for grow-out culture or into the seabed were cultured first in suspended nets or cages in Saloma Lake during the first year until they reach a shell height of 30-50 mm (Paturusi et al. 2002, Uki 2006). In this case, scallops might have assimilated a more enriched C and N sources in early period and switched into a less depleted [delta][sup.13]C and [delta][sup.15]N sources when they settled into the seabed until they are harvested. Habitat-related differences could possibly explain the above observation based on the observed significant differences in the isotope [delta][sup.13]C and [delta][sup.15]N ratios in one, two, and four-year-old scallop tissues (Table la; P < 0.05). Scallops reared in Saloma Lake reached marketable size two years earlier than in Tokoro area, Okhotsk Sea. Nadon and Himmelman (2006) however observe no [delta][sup.13]C differences between nearshore near·shore n. The region of land extending from the backshore to the beginning of the offshore zone. near and offshore consumers as well as those grown at different depths and distances in terms of [delta][sup.13]C. Spatial variation in [delta][sup.15]N of queen scallops The Queen Scallop (Aequipecten opercularis) is a medium-sized member of the scallop family, a species of edible marine bivalve mollusk. At about 7 cm in size, it is one of the smaller scallops that is commercially exploited. Aequipecten opercularis is statistically significant with depth and other physical variables such as temperature and salinity (Jennings & Warr 2003). Potential Food Sources of Scallops in Two Sites Isotopic relationship in various tissues and the potential food sources in both culture sites are presented in Figure 3. Results showed that there is a possibility that the hanging cultured scallops are feeding on net plankton as reflected by nearest isotopic values to ctenidia and muscle. This complements the results found by Shumway et al. (1987) from inshore in·shore adv. & adj. 1. Close to a shore. 2. Toward or coming toward a shore. inshore Adjective in or on the water, but close to the shore: sea scallops (Placopecten magellanicus) using gut content analysis. In such case, scallops might be relying on in situ In place. When something is "in situ," it is in its original location. phytoplankton production as a source for POC (Proof Of Concept) See PoC exploit. POC - Point Of Contact in the lake. Nakatsuka et al. (2004) showed that there are two major sources for DOC and POC in areas close to river mouths such as in situ phytoplankton production and input of terrestrial organic matter from the river. Saloma Lake in fact, served as a discharge area for two draining rivers. Contribution of freshwater discharge is believed to be very high during snow melting season and therefore would influence the isotopic characteristics of cultured scallops in hanging system. In fact, Saromabetsu River drains a mean annual discharge of 7.2 x [10.sup.6] [m.sup.3] to Saloma Lake. On June 2005, observed total dissolved carbon (TDC TDC Top Dead Center TDC Time-to-Digital Converter TDC Tabular Data Control TDC Total Development Cost TDC Texas Department of Corrections TDC The Discovery Channel TDC Torpedo Data Computer TDC Theater Deployable Communications ) in this river is 0.17 mmol [L.sup.-1] and a high dissolved inorganic nitrogen (DIN) level of 43.60 [micro]M. Tokoro River has a higher discharge of 8.43 x [10.sup.8] [m.sup.3] [yr.sup.-1] and has relatively the same TDC concentration of 0.19 mmol [L.sup.-1] but higher DIN level of 89.48 [micro]M relative to Saromabetsu River on the same month (M. Kato, pers. comm.). [FIGURE 3 OMITTED] On the other hand, scallops in Tokoro, Okhotsk Sea, which might have taken advantage only of the sinking pelagic organisms as food, are depended on particulate organic matter. Mikulich and Tsikhon-Lukanina (1981, as cited in Shumway et al. 1987) suggests that detritus is the main food source of the Japanese scallop and thus, the results in this study clearly supported this observation. Yet, another observation on the above isotopic relationships cannot be ignored. The relatively close values of suspended POM to digestive gland tissue showed that scallops in Saloma Lake are also assimilating only the suspended POM component with depleted [delta][sup.13]C and [delta][sup.15]N signatures, which could also be derived from inputs of terrestrial organic matter from the draining rivers. In Saloma Lake, results showed that muscle and ctenidia tissues were more positive in [delta][sup.13]C and [delta][sup.15]N relative to their potential food sources. In contrast, net plankton was enriched in [delta][sup.15]N relative to various tissues of Tokoro, Okhotsk Sea scallops. The reason why the net plankton had higher position (depleted [delta][sup.13]C but enriched [delta][sup.15]N signatures) compared with scallop tissues in Tokoro could not be explained in this study. For the meantime, the observation only suggests that it could not be a primary food source for the cultured scallops in Tokoro area. Observed enriched [delta][sup.15]N values in muscle and ctenidia tissues of Saloma Lake scallops would probably explain by the assimilation of enriched [delta][sup.15]N net plankton signature of the consumer and high protein content in muscle tissues (Yokoyama & Ishihi 2006). In Saloma Lake, net plankton enriched [delta][sup.15]N values of 7.6 [+ or -] 0.4[per thousand] was the only source for such enriched [delta][sup.15]N reflected in scallop tissues (Table 1a). Net plankton [delta][sup.15]N values did not differ much in both systems suggesting that plankton communities are utilizing a relatively enriched nitrogen source caused by the tidal water exchange, which keeps the salinity content of the lake similar to that of the Okhotsk Sea. Suspended POM [delta][sup.13]C values in Saloma Lake were also comparable to that of Okhotsk Sea station, which might be explained by the contribution of seagrass detritus or other macrophytes in the lake that could represent a significant component of the particulate detritus (Evans et al. 2006) but were not observed for [delta][sup.15]N signatures. Isotopic [delta][sup.13]C values of 0.1-50 [micro]m POM ranging from -17.6[per thousand] to -14.4[per thousand] determined in Florida Bay Florida Bay is the shallow bay located between the southern end of the Florida mainland (the Florida Everglades) and the Florida Keys. Nearly all of Florida Bay is included in Everglades National Park. are relatively higher than the observed values in the present study (Evans et al. 2006). Enrichment of POM [delta][sup.13]C may be attributed either to high productivity of phytoplankton or high abundance of [sup.13]C-enriched phytoplankton because of a change in species composition (Goering et al. 1990 as cited in Kang et al. 2006). The [delta][sup.13]C enrichment of POM reflects a considerable contribution of resuspended microphytobenthos, which have relatively high [delta][sup.13]C around -13.8[per thousand] to the bay POM pool that determine the growth and reproduction in intertidal in·ter·tid·al adj. Of or being the region between the high tide mark and the low tide mark. in bivalves (Kang et al. 2006). [FIGURE 3 OMITTED] Nutrient utilization by the phytoplankton tends to regulate the varying isotopic signatures of food sources such as suspended POM (Mullin et al. 1984, Altabet 1996, Montoya 1994). Comparing the observed [delta][sup.15]N signals in suspended POM in two sites, Tokoro, Okhotsk Sea station had depleted values relative to Saloma Lake stations. However, in terms of net plankton isotopic values, high [delta][sup.15]N was found at Stn. S-0 on May 2005 from 100 and 330 [micro]m fractions, which ranged from 15.3[per thousand] to 21.7[per thousand], respectively where surface chl a concentration was very high (5.42 [micro]g [L.sup.-1]) and N[O.sub.3.sup.-] levels were <1.0 [micro]M. Nitrogen fixation nitrogen fixation Any natural or industrial process that causes free nitrogen in the air to combine chemically with other elements to form more reactive nitrogen compounds such as ammonia, nitrates, or nitrites. Soil microorganisms (e.g. and denitrification de·ni·tri·fy tr.v. de·ni·tri·fied, de·ni·tri·fy·ing, de·ni·tri·fies 1. To remove nitrogen or nitrogen groups from (a compound). 2. can also regulate [delta][sup.15]N of nitrate (Minagawa et al. 2001). Evans et al. (2006) examine nearly 0[per thousand] [delta][sup.15]N values in western Florida Bay, which suggest that nitrogen fixation represents a significant nutrient source although this cannot be explained to Okhotsk Sea coastal station, because the SPOM values can still be considered higher compared with their results. Minagawa and Wada (1984) also found lower [delta][sup.15]N value in natural samples from the East China Sea and suggest that the primary producers in this area obtain their nutrition on atmospheric nitrogen fixation. The [delta][sup.15]N of sinking particles tend to be heavier (5% to 6[per thousand]) with decreasing N[O.sub.3.sup.-] levels and is being preserved in the surface sediments (Altabet and Francois, 1994, Usui et al. 2006). In case there is a partial utilization of N[O.sub.3.sup.-] by the phytoplankton, the SPOM produced will have lighter [delta][sup.15]N values otherwise, if the phytoplankton completely used the available N[O.sub.3.sup.-] pool, the [delta][sup.15]N largely increases and tend to become heavier similar to the isotopic composition of N[O.sub.3.sup.-] (5[per thousand] to 6[per thousand]). In Saloma Lake, suspended POM [delta][sup.15]N showed an average of 5[per thousand], which is relatively enriched compared with other habitats and fall within the estuarine POM values (Raikow & Hamilton 2001, Lorraine et al. 2002). The N[O.sub.3.sup.-] levels in this area might be sourced from land-derived inputs and the tidal water exchange between that and the Okhotsk Sea. In Saloma Lake, similarity of SPOM [delta][sup.15]N values of 5[per thousand] indicates that N[O.sub.3.sup.-] is used up or depleted by the phytoplankton. In contrast, Stn. S-0, which is very near to Tokoro area had relatively lighter [delta][sup.15]N values of SPOM (2.7[per thousand]) suggesting that SPOM is produced where N[O.sub.3.sup.-] levels are not completely depleted and presumably pre·sum·a·ble adj. That can be presumed or taken for granted; reasonable as a supposition: presumable causes of the disaster. affected by the prevailing water currents in the coastal region. In fact, estimated in situ production along the coastal region was very low in summer and therefore not enough for the food requirement of the cultured scallops (Aya 2007, I. Kudo ku·do n. pl. ku·dos Usage Problem A praising remark; an accolade or compliment: "Children's book author Virginia Hamilton added another kudo to her prize-laden career" unpub, data). Evans et al. (2006) further explains that the comparatively depleted estuarine POM isotopic signal indicates uptake of an isotopically light nitrogen source that is supported by higher N[H.sub.4.sup.+] levels compared with N[O.sub.3.sup.-] . Marine POM [delta][sup.15]N signal at Tokoro, Okhotsk Sea station showed this kind of scenario different from Saloma Lake samples, which might imply high N[H.sub.4.sup.+] levels in this area. However, marine phytoplankton might have not depended on regenerated production, because the resulting export production is very low to support the requirement of scallops. Checkley and Entzeroth (1985 as cited in Evans et al. 2006) show phytoplankton assimilating remineralized N[H.sub.4.sup.+] has more depleted [delta][sup.15]N signals. Higher bacterial and detrital de·tri·tus n. pl. detritus 1. Loose fragments or grains that have been worn away from rock. 2. a. Disintegrated or eroded matter: the detritus of past civilizations. abundances can also result to depleted POM signal (Evans et al. 2006). Fractionation Differences Between Scallop Tissues and Its Diet Lorraine et al. (2002) also demonstrate that results on diet and trophic group will vary depending on tissue type. Enrichment of [delta][sup.13]C and [delta][sup.15]N in tissues relative to diet of consumer were determined in both systems and the possibility of trophic transfer was observed (Fig. 3). Using classical tissue enrichment factors of 0[per thousand] to 1[per thousand] and 3[per thousand] to 4[per thousand] for[delta][sup.13]C and [delta][sup.15]N, respectively and the average isotope values of muscle (Saloma Lake; [delta][sup.13]C = -17.7[per thousand]; [delta][sup.15]N = 8.4[per thousand]), the expected scallop's diet will be -18.7[per thousand] for [delta][sup.13]C and 4.4-5.4[per thousand] for [delta][sup.15]N. The presumed diet of scallops (net plankton) reared at Saloma Lake has values of-21.1[per thousand] and 7.6[per thousand] for [delta][sup.13]C and [delta][sup.15]N, respectively, which are different of expected diet values. Similar results were observed for Tokoro scallops when classical tissue enrichment factors were used to determine the fractionation. With respect to the SPOM mean values of -22.1[per thousand] and 5.0[per thousand] for [delta][sup.13]C and [delta][sup.15]N observed in Saloma Lake and using the tissue enrichment factors, the resulting scallop tissue isotopic values were -21.1[per thousand] for [delta][sup.13]C and 8[per thousand] to 9[per thousand] for [delta][sup.15]N, which were different from the observed isotopic values of muscle but slightly closer to that of the digestive gland. Because the SPOM is the presumed diet of scallops in Tokoro area and [delta][sup.13]C signatures of muscle and ctenidia were used, an average of 0.8[per thousand] [+ or -] 0.2[per thousand] was found, which is comparable to the accepted [delta][sup.13]C enrichment of 1[per thousand]. In Saloma Lake, scallops, which might have also preferred SPOM as their source of nutrition had enrichment values relatively within the fractionation values examined by DeNiro and Epstein (1978) with reference to digestive gland values. The relatively higher fractionation values within muscle and net plankton and SPOM also suggests that the hanging cultured scallops are also assimilating food items of sizes in-between the two food sources. With respect to muscle, hanging cultured scallops are also showing a POM-net-plankton food chain or presumably POM-scallop trophic transfer but relative contribution of each potential food source should be estimated. The [delta][sup.15]N enrichment values for scallop tissues in either sites or culture systems were not within the fractionation values proposed by Minagawa and Wada (1984). Biochemical processes in animal species are said to influence the fractionation of consumer's tissues relative to its diet and are clearly discussed in related studies (Lancaster & Waldron 2001, Lorraine et al. 2002, Jardine et al. 2003). Information obtained in this study only shows that P. yessoensis differed markedly in isotopic [delta][sup.13]C and [delta][sup.15]N signatures as controlled by culture habitats differences and reflected in the isotopic ratios of their potential food sources. However, further investigation shall be pursued to confirm this result and be replicated in other areas of scallop culture. This observed variability may reflect differences in carbon but presumably for nitrogen sources as exhibited in [delta][sup.15]N signatures of suspended particulate organic matter in Tokoro area (sowing culture ground). This observation on the [delta][sup.15]N of suspended particulate organic matter will presumably provide insights on the source of food available for the sowing cultured scallops in periods of low primary productivity (Aya & Kudo, in prep.). ACKNOWLEDGMENTS The authors thank the Tokoro and Saloma Lake Fishermen's Cooperative Associations for providing the scallop samples in this study. The crew and officers of the Training Ship (T/S) Ushio-Maru of the Faculty of Fisheries are also greatly appreciated for their technical assistance during field sampling. This study was supported by a financial grant from the Ministry of Education, Culture, Sports, Science, and Technology and the Hokusui Society Foundation. LITERATURE CITED Altabet, M. A. 1996. Nitrogen and carbon isotopic tracers Tracers Refers to investment trusts which are populated by corporate bonds. In October 2001, Morgan Stanley's Tradable Custodial Receipts (Tracers) was launched. Tracers contain a number of coporate bonds and credit default swaps which are selected for liquidity and diversity. of the source and transformation of particles in the deep sea. In: V. Ittekkot, P. Schafer, S. Honjo & P. J. Depetris, editors. Particle Flux in the Ocean, SCOPE Report 57, Chichester: John Wiley John Wiley may refer to:
Altabet, M. A. & R. Francois. 1994. Sedimentary sed·i·men·ta·ry also sed·i·men·tal adj. 1. Of, containing, resembling, or derived from sediment. 2. Geology Of or relating to rocks formed by the deposition of sediment. nitrogen isotopic ratio as a recorder for surface ocean nitrate utilization. Glob glob - /glob/, *not* /glohb/ To expand wild card characters in a path name. In Unix the file name wild cards are: * = zero or more characters (E.g. UN*X) ? = any single character [] any of the enclosed characters . Biogeochem. Cycles 8:103-116. Aya, F. A. 2007. Food sources and requirement of the Japanese scallop, Patinopecten (Mizuhopecten) yessoensis (Jay) in two habitats examined using stable isotope analysis. Master Thesis, Graduate School of Environmental Science, Hokkaido University. Sapporo, Japan. 72 pp. Cranford, P. J. & J. Grant. 1990. Particle clearance and absorption of phytoplankton and detritus by the sea scallop Placopecten magellanicus (Gmelin). J. Exp. Mar. Biol. Ecol. 137:105-121. Cranford, P. J., S. L. Armsworthy, O. A. Mikkelsen & T. G. Milligan. 2005. Food acquisition responses of the suspension-feeding bivalve Placopecten magellanicus to the flocculation flocculation /floc·cu·la·tion/ (flok?u-la´shun) a colloid phenomenon in which the disperse phase separates in discrete, usually visible, particles rather than congealing into a continuous mass, as in coagulation. and settlement of a phytoplankton bloom. J. Exp. Mar. Biol. Ecol. 326:128-143. DeNiro, M. J. & S. Epstein. 1978. Influence of diet on the distribution of carbon isotopes An isotope a type of neutral atom but the number of neutrons is different from the number of protons in the nucleus. May be radioactive. Elements 1-15 Hydrogen
Evans, S. L., W. T. Anderson & F. J. Jochem. 2006. Spatial variability Spatial variability is characterized by different values for an observed attribute or property that are measured at different geographic locations in an area. The geographic locations are recorded using GPS (global positioning systems) while the attribute's spatial variability is in Florida Bay particulate organic matter composition: combining flow cytometry flow cytometry (flōˑ sī·t  ˑ·m with stable isotope analyses. Hydrobiologia
569: 151-165.
Fujita, N. & K. Mori. 1990. Effects of environmental instability on the growth of the Japanese scallop Patinopecten yessoensis in Abashiri sowing-grounds. In: A. K. Sparks, editor. Marine Farming and Enhancement, Proceedings of the 15th US-Japan Meeting on Aquaculture aquaculture, the raising and harvesting of fresh- and saltwater plants and animals. The most economically important form of aquaculture is fish farming, an industry that accounts for an ever increasing share of world fisheries production. , NOAA NOAA abbr. National Oceanic and Atmospheric Administration Noun 1. NOAA - an agency in the Department of Commerce that maps the oceans and conserves their living resources; predicts changes to the earth's environment; Technical Report NMFS NMFS National Marine Fisheries Service NMFS National Mortality Followback Survey NMFS Network Multimedia File System NMFS Nested Mount File System 85:81-89. Goshima, S. & H. Fujiwara. 1994. Distribution and abundance of cultured scallop Patinopecten yessoensis in extensive sea beds as assessed by underwater camera. Mar. Ecol. Prog. Ser. 110:151-158. Ito, H. 1990. Some aspects of offshore spat collection of Japanese scallop. In: A. K. Sparks, editor. Marine Farming and Enhancement, Proceedings of the 15th US-Japan Meeting on Aquaculture, NOAA Tech. Report NMFS 85. pp. 35-48. Jardine, T. D., S. A. McGeachy, C. M. Paton, M. Savoie & R. A. Cunjack. 2003. Stable isotopes in aquatic systems: sample preparation, analysis, and interpretation. Can. Manuscr. Rep. Fish. Aquat. Sci. No. 2656.39 pp. Jennings, S. & K. J. Warr. 2003. Environmental correlates of large-scale spatial variation in the [delta][sup.15]N of marine animals. Mar. Biol. 142: 1131-1140. Kang, C. K., Y. W. Lee, E. J. Choy, J. K. Shin, I. S. Seo & J. S. Hong. 2006. Microphytobethos seasonality determines growth and reproduction in intertidal bivalves. Mar. Ecol. Prog. Set. 315:113-127. Lancaster, J. & S. Waldron. 2001. Stable isotope values of lotic lo·tic adj. Of, relating to, or living in moving water. [From Latin l invertebrates: Sources of variation, experimental design, and statistical interpretation. Limnol. Oceanogr. 46:723-730. Lorraine, A., Y. M. Paulet, L. Chauvaud, N. Savoye, A. Donval & C. Saout. 2002. Differential [delta][sup.13]C and [delta][sup.15]N signatures among scallop tissues: implications for ecology and physiology. J. Exp. Mar. Biol. Ecol. 275:47-61. MacDonald, B. A. & R. J. Thompson. 1985. Influence of temperature and food availability on the ecological energetics Ecological energetics The study of the flow of energy within an ecological system from the time the energy enters the living system until it is ultimately degraded to heat and irretrievably lost from the system. , on the giant scallop Plucopecten magellanicus: I. Growth rates Growth Rates The compounded annualized rate of growth of a company's revenues, earnings, dividends, or other figures. Notes: Remember, historically high growth rates don't always mean a high rate of growth looking into the future. of shell and somatic somatic /so·mat·ic/ (so-mat´ik) 1. pertaining to or characteristic of the soma or body. 2. pertaining to the body wall in contrast to the viscera. so·mat·ic adj. tissue. Mar. Ecol. Prog. Ser. 25:279-294. Mendoza, Y., L. Frietes, C. J. Lodeiros, J. A. Lopez & J. H. Himmelman. 2003. Evaluation of biological and economical aspects of the culture of scallop Lyropecten (Nodipecten) nodosus in suspended and bottom culture. Aquaculture 221:207-219. Minagawa, M. & E. Wada. 1984. Stepwise stepwise incremental; additional information is added at each step. stepwise multiple regression used when a large number of possible explanatory variables are available and there is difficulty interpreting the partial regression enrichment of [sup.15]N along food chains: Further evidence and the relation between [delta][sup.15]N and animal age. Geochim. Cosmochhn. Acta 48:1135-1140. Minagawa, M., M. Ohashi, T. Kuramoto & N. Noda. 2001. [delta][sup.15]N of PON (Passive Optical Network) An optical point-to-multipoint access network. There are no optical repeaters or other active devices in a PON, hence the name "passive. and nitrate as a clue to the origin and transformation of nitrogen in the subarctic sub·arc·tic adj. Of or resembling regions just south of the Arctic Circle. subarctic Relating to the geographic area just south of the Arctic Circle. North Pacific and its marginal sea A marginal sea is a part of ocean partially enclosed by land such as islands, archipelagos, or peninsulas. Unlike mediterranean seas, marginal seas have ocean currents caused by ocean winds. . J. Oceanogr. 57:285-300. Montoya, J. P. 1994. Nitrogen isotope fractionation There are three types of isotope fractionation:
adj. 1. a. Of, relating to, or derived from a glacier. b. Suggesting the extreme slowness of a glacier: Work proceeded at a glacial pace. 2. a. ocean: constraints on the ocean's role in global change. Berlin: Springer-Verlag. pp. 259-279. Mullin, M. M., G. H. Rau & R. W. Eppley. 1984. Stable nitrogen isotopes in zooplankton: some geographic and temporal variations in the North Pacific. Limnol. Oceanogr. 29:1267-1273. Nadon, M. O. & J. H. Himmelman. 2006. Stable isotopes in subtidal food webs: Have enriched carbon ratios in benthic consumers been misinterpreted? Limnol. Oceanogr. 51:2828-2836. Nakatsuka, T., M. Toda, K. Kawamura & M. Wakatsuchi. 2004. Dissolved and particulate organic carbon in the Sea of Okhotsk Noun 1. Sea of Okhotsk - an arm of the Pacific to the east of Asia Pacific, Pacific Ocean - the largest ocean in the world : transport from continental shelf to ocean interior. J. Geophys. Res. 109:1-10. Page, H. M. & M. Lastra. 2003. Diet of intertidal bivalves in the Ria de Arosa (NW Spain): evidence from stable C and N isotope analysis Isotope analysis is the identification of isotopic signature, the distribution of certain stable isotopes and chemical elements within chemical compounds. This can be applied to a food web to make it possible to draw direct inferences regarding diet, trophic level, and subsistence. . Mar. Biol. 143:519-532. Paturusi, A., S. Chiba & S. Goshima. 2002. The magnitude of natural recruitment in a cultured population of Japanese scallop Patinopecten (Mizuhopecten) yessoensis on Yubetsu seabed (Japan), Sea of Okhotsk. Benthos benthos: see marine biology. Res. 57:69-75. Piola, R. F., S. K. Moore & I. M. Suthers. 2006. Carbon and nitrogen stable isotope analysis of three types of oyster tissue in an impacted estuary. Estuar. Coast. Shelf Sci. 66:255-266. Raikow, D. & S. Hamilton. 2001. Bivalve diets in a Midwestern U.S. stream: A stable isotope enrichment study. Limnol. Oceanogr. 46: 514-522. Reira, P. & P. Richard. 1996. Isotopic determination of food sources of Crassostrea gigas along atrophic atrophic /atro·phic/ (a-tro´fik) pertaining to or characterized by atrophy. Atrophic A wasting of cells and tissues. gradient in the estuarine bay of Marennes-Oleron, Estuar. Coast. Shelf Sci. 42:347 360. Sakurai, I. & M. Seto. 2000. Movement and orientation of the Japanese scallop Patinopecten yessoensis (Jay) in response to water flow. Aquaculture 181:269-979. Shumway, S. E., R. Selvin & D. F. Schick. 1987. Food resources related to habitat in the scallop Placopecten magellanicus (Gmelin, 1791): a qualitative study. J. Shellfish shellfish, popular name for certain edible mollusks (see Mollusca), e.g., oysters, clams, and scallops, and for certain edible crustaceans, e.g., crabs, lobsters, and shrimps. All are aquatic invertebrates with shells; they are not fish. Res. 6:89-95. Uki, N. 2006. Stock enhancement of the Japanese scallop Patinopecten yessoensis in Hokkaido. Fish. Res. 80:62-66. Usui, T., S. Nagao, M. Yamamoto, K. Suzuki, I. Kudo, S. Montani, A. Noda & M. Minagawa. 2006. Distribution and sources of organic matter in surficial sur·fi·cial adj. Of, relating to, or occurring on or near the surface of the earth. [surf(ace) + (superf)icial.] Adj. 1. sediments on the shelf and slope off Tokachi, western North Pacific, inferred from C and N stable isotopes and C/N C/N abbr. credit note ratio. Mar. Chem. 98:241 259. Werner, R. A. & W. A. Brand. 2001. Referencing strategies and techniques in stable isotope ratio analysis. Rapid Commun. Mass Spectrom. 15:501-519. Yokoyama, H. & Y. Ishihi. 2003. Feeding of the bivalve Theora lubrica on benthic microalgae: isotopic evidence. Mar. Ecol. Prog. Ser. 255:303-309. Yokoyama, H. & Y. Ishihi. 2006. Variation in [delta][sup.13]C and [delta][sup.15]N among different tissues of three estuarine bivalves: implications for dietary reconstructions. Plankton and Benthos Res. 1:178 182. FROLAN A. AYA (1)* AND ISAO ISAO Internationale Stichting Alzheimer Onderzoek (Netherlands) KUDO (1,2) (1) Graduate School of Environmental Science, Hokkaido University, Kita 10 Nishi 5, Kita-ku, Sapporo Kita-ku (北区 , Hokkaido 060-0810, Japan; (2) Faculty of Fisheries Science, Hokkaido University, 3-1-1 Minato-cho, Hakodate 041-8611, Japan * Corresponding author. E-mail: frolan@ees.hokudai.ac.jp
TABLE 1a.
Isotopic [delta][sup.13]C and [delta][sup.15]N values (mean
[+ or -] SE, [per thousand]) examined from three tissue types of
scallops in two sites and the potential food sources (values in
parenthesis represent the number of samples).
Saloma Lake
[[delta]. [[delta].
sup.13]C sup.15]C
Spat
Muscle -17.5 [+ or -] 0.1 (2) 9.0 [+ or -] 0.1 (2)
Ctenidia -18.0 [+ or -] 0.1 (2) 8.6 [+ or -] 0.1 (2)
DG -21.7 [+ or -] 0.1 (2) 8.0 [+ or -] 0.1 (2)
Age 1
Muscle -17.5 [+ or -] 0.3 (4) (1) 7.9 [+ or -] 0.1 (4) (1)
Ctenidia -18.1 [+ or -] 0.1 (4) (1) 7.4 [+ or -] 0.3 (4) (1)
DG -21.5 [+ or -] 0.1 (4) (1) 5.7 [+ or -] 1.0 (4) (1)
Age 2
Muscle -18.0 [+ or -] 0.0 (2) (1) 8.3 [+ or -] 0.1 (2) (1)
Ctenidia -18.2 [+ or -] 0.1 (2) (1) 8.2 [+ or -] 0.0 (2) (1)
DG -23.1 [+ or -] 0.1 (2) (1) 7.2 [+ or -] 0.2 (2) (1)
Age 3
Muscle
Ctenidia
DG
Age 4
Muscle
Ctenidia
DG
Age 5
Muscle
Ctenidia
DG
Plankton (2) -21.1 [+ or -] 0.5 (2) 7.6 [+ or -] 0.4 (2)
SPOM (3) -22.1 [+ or -] 0.5 (6) 5.0 [+ or -] 0.2 (6)
Tokoro
[[delta]. [[delta].
sup.13]C sup.15]C
Spat
Muscle
Ctenidia
DG
Age 1
Muscle -19.8 [+ or -] 0.6 (8) (2) 3.3 [+ or -] 1.8 (8) (2)
Ctenidia -20.9 [+ or -] 0.4 (8) (2) 2.2 [+ or -] 1.7 (8) (2)
DG -25.0 [+ or -] 0.6 (8) (2) -2.8 [+ or -] 2.9 (8) (2)
Age 2
Muscle -20.9 [+ or -] 0.4 (10) (2) 3.8 [+ or -] 1.3 (10) (2)
Ctenidia -21.1 [+ or -] 0.4 (10) (2) 3.0 [+ or -] 1.5 (10) (2)
DG -25.7 [+ or -] 0.6 (10) (2) -0.8 [+ or -] 2.5 (10) (2)
Age 3
Muscle -20.8 [+ or -] 0.5 (10) 2.8 [+ or -] 1.4 (10)
Ctenidia -21.3 [+ or -] 0.4 (10) 3.3 [+ or -] 1.2 (10)
DG -25.3 [+ or -] 0.6 (10) 0.4 [+ or -] 1.9 (10)
Age 4
Muscle -20.5 [+ or -] 0.5 (10) (2) 3.6 [+ or -] 1.1 (10) (2)
Ctenidia -20.9 [+ or -] 0.4 (10) (2) 3.8 [+ or -] 1.2 (10) (2)
DG -24.7 [+ or -] 0.3 (9) (2) 2.1 [+ or -] 1.6 (9) (2)
Age 5
Muscle -20.8 [+ or -] 0.3 (2) 1.6 [+ or -] 0.5 (2)
Ctenidia -20.9 [+ or -] 0.0 (2) 0.8 [+ or -] 1.0 (2)
DG -24.1 [+ or -] 0.4 (2) -2.3 [+ or -] 1.8 (2)
Plankton (2) -25.1 [+ or -] 1.4 (12) 7.9 [+ or -] 2.1 (12)
SPOM (3) -21.6 [+ or -] 1.4 (4) 2.7 [+ or -] 0.2 (4)
(1) Values of [delta][sup.13]C and [delta][sup.15]N (in rows) with
similar superscripts are not significantly different (p < 0.05).
Isotopic values of two-year-old samples from Saloma Lake were also
compared with that of four-year-old scallop tissues from Tokoro area.
(2,3) Average of 100 and 330 [micro]m fractions; SPOM include both
bulk and <10 [micro]m fractions.
TABLE 1b.
Mean [delta][sup.13]C and [delta][sup.15]N isotopic values
(SE, [per thousand]) in different tissues of scallops
(spat to 2-y old) from Saroma Lake and Tokoro, Okhotsk Sea
(1-y to 5-y-old).
Saroma Lake
[delta][sup.13]C [delta][sup.15]N
Muscle -17.7 [+ or -] 0.1 8.4 [+ or -] 0.1
Ctenidia -18.1 [+ or -] 0.1 8.1 [+ or -] 0.1
Digestive Gland -22.1 [+ or -] 0.1 7.0 [+ or -] 0.4
Tokoro
[delta][sup.13]C [delta][sup.15]N
Muscle -20.6 [+ or -] 0.2 3.3 [+ or -] 0.6
Ctenidia -21.0 [+ or -] 0.2 3.0 [+ or -] 0.6
Digestive Gland -25.2 [+ or -] 0.3 -0.3 [+ or -] 1.1
TABLE 2.
Summary of variability ([per thousand]) in [delta][sup.13]C
and [delta][sup.15]N isotopic values between tissues of scallops
(spat to 2-y-old) from Saroma Lake and Tokoro,
Okhotsk Sea (1-y to 5-y-old).
Saroma Lake
[delta] [delta]
[sup.13]C [sup.13]C
(a) Variance component
Muscle 0.20 0.27
Ctenidia 0.02 0.49
Digestive Gland 0.54 2.72
(b) Summary of
variance components (1)
Digestive Gland > Muscle ns (F= 2.67) ** (F= 10.07)
Digestive Gland > Ctenidia *** (F= 27.37) * (F= 5.61)
Muscle > Ctenidia ** (F= 10.26)
Ctenidia > Muscle ns (F = 1.79)
Tokoro
[delta] [delta]
[sup.13]C [sup.13]C
(a) Variance component
Muscle 2.0 16.4
Ctenidia 1.4 16.5
Digestive Gland 2.6 43.6
(b) Summary of
variance components (1)
Digestive Gland > Muscle ns (F= 1.32) ** (F= 2.66)
Digestive Gland > Ctenidia * (F= 1.86) ** (F= 2.64)
Muscle > Ctenidia ns (F= 1.41)
Ctenidia > Muscle ns (F = 1.01)
(1) Values preceded by asterisk and label indicates
* p < 0.05. ** p < 0.01, *** p < 0.001, and
ns = no significance.
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