Browsing Journal Articles by Subject "Zooplankton"
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Nitrogen stable isotopes reveal age-dependent dietary shift in the Japanese scallop Mizuhopecten yessoensis -
Isotopes in Environmental and Health Studies, 2017 - Taylor & FrancisOntogenetic niche shifts in diet are a consequence of changes in body size or resource partitioning between age classes. To better resolve the feeding patterns of the Japanese scallop Mizuhopecten yessoensis, we examined the relative importance of age and size in the diet of this species using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) from 2006 to 2009. Contribution of food sources was quantified using an isotope mixing model by comparing the muscle tissue isotope ratios to those of suspended particulate organic matter (SPOM) and their zooplankton prey (e.g. micro- and meso-zooplankton). Unlike the δ13C values, which remained constant with age and size, muscle δ15N values were more positively correlated with age accounting for 69 % of variations than size with only 46 %. Increasing 15N values with age suggested that shifts in diet from SPOM to micro- and meso-zooplankton occurred during ontogeny in M. yessoensis. Results of the isotope mixing model indicated that SPOM contribution to scallop’s diet decreased from 68 to 8 % while those of zooplankton increased from 15 to 50 % with increasing age. This study concludes that age-related dietary shift explains the enrichment of 15N, as a result of predation on zooplankton by M. yessoensis.
Vertical distribution of euthecosomatous pteropods in the upper 100m of the Hilutangan Channel, Cebu, The Philippines -
Marine Biology, 1978 - Springer-VerlagThe vertical distribution of euthecosomatous pteropods in the upper 100 m of the Hilutangan Channel, Cebu, The Philippines was studied, based on 126 samples, comprising 47, 282 individuals. Thirty-min horizontal plankton tows were performed at depths of 1, 20, 50, 70 and 100 m in January and February 1972. Thirteen species -including 3 subspecies - of juvenile and adult euthecosomes were identified. In decreasing order of abundance the species are: Creseis acicula (20.4%), Limacina trochiformis (19.9%), Creseis virgula constricta (14.6%), L. inflata (10.5%), Clio pyramidata (9.9%), Creseis virgula conica (8.9%), L. bulimoides (7.3%), Diacria quadridentata (5.3%), Cavolinia longirostris (1.9%), Creseis virgula virgula (1.0%), Hyalocylix striata (0.1%), Cuvierina columella (0.08%), Cavolinia uncinata (0.002%). In 3 species, a large percentage were juveniles; for 1 species, Clio pyramidata , only juveniles were caught. The Vertical species distribution was similar to the distribution of the respective species in Caribbean and Bermuda waters. Temperature, salinity and dissolved oxygen influence vertical distribution little, if at all.