Dependence of consumers on macroalgal (Laminaria solidungula) carbon in an arctic kelp community: δ13C evidence
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- Dunton, K.H. & Schell, D.M. Mar. Biol. (1987) 93: 615. doi:10.1007/BF00392799
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Stable carbon isotope measurements (δ13C) were used to assess the importance of kelp carbon (-13.6 to-16.5‰) versus phytoplankton carbon (-25.5 to-26.5‰) to resident fauna of an isolated kelp bed community on Alaska's north arctic coast from 1979 to 1983. The predominant kelp, Laminaria solidungula, showed some seasonal variation in δ13C which was correlated with changes in the carbon content of the tissue. Animals that showed the greatest assimilation of kelp carbon (>=50%) included macroalgal herbivores (gastropods and chitons,-16.9 to-18.2‰), a nonselective suspension feeder (an ascidian,-19.0‰) and a predatory gastropod (-17.6‰). Animals that showed the least incorporation of kelp carbon into body tissues (<=7%) included selective suspension-feeders (hydroids, soft corals and bryozoans,-22.8 to-25.1‰). Sponges, and polychaete, gastropod and crustacean omnivores exhibited an intermediate dependence on kelp carbon (15 to 40%). Within some taxonomic groups, species exhibited a broad range in isotopic composition which was related to differences in feeding strategies. In the polychaete group alone, δ13C values identified four major feeding habits: deposit-feeders (-18.0‰), omnivores (-20.4‰), predators (-22.2‰) and microalgal herbivores (-23.0‰). Distinct seasonal changes in the δ13C values of several animals indicated an increased dependence on kelp carbon during the dark winter period when phytoplankton were absent. Up to 50% of the body carbon of mysid crustaceans, which are key prey species for birds, fishes and marine mammals, was composed of carbon derived from kelp detritus during the ice-covered period.