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Marine Ecology Progress Series

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MEPS 346:127-141 (2007)  -  DOI:

Variation in food sources of the macrobenthos along a land–sea transect: a stable isotope study

H. Yokoyama*, Y. Ishihi

National Research Institute of Aquaculture, Fisheries Research Agency, Minami-Ise, Mie 516-0193, Japan

ABSTRACT: To evaluate the relative importance for the macrobenthos of possible food sources, including riverine particulate organic matter, reeds, benthic microalgae, seaweeds, coastal phytoplankton and aquaculture-derived matter, over 194 macrofaunal species were collected from 9 intertidal and subtidal stations along the axis of Gokasho Bay, Japan, and their isotopic compositions analyzed. The δ13C values for terrestrial organic matter were very different from those of the consumers (>5‰), suggesting a negligible trophic role for this source. Differences in δ15 N between seaweeds and primary consumers were small, suggesting a minor contribution of seaweeds. The δ13C values of the majority of consumers fell between coastal phytoplankton and benthic microalgae, allowing the calculation of the relative contribution of these microalgae to the diets of consumers. The estimated contribution ratios and the between-site comparison of the δ13C value for the same species along the bay axis suggest a shift of the main food source from benthic microalgae on the mudflat to coastal phytoplankton at the subtidal seaward stations. Several consumers collected from the fish-farm area had enriched δ15N and depleted δ13C values relative to samples of the same species that occurred outside of the farm area. The δ13C values of the consumers at the fish farm were significantly more depleted than those at the other stations. These findings suggest that the consumers inhabiting the farming area incorporate 15 N-enriched fish meal and 13C-reduced cereals that are major constituents of fish feed.

KEY WORDS: stable isotopes · Macrobenthos · Benthic microalgae · Phytoplankton · Tidal flat · Fish farm

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Cite this article as: Yokoyama H, Ishihi Y (2007) Variation in food sources of the macrobenthos along a land–sea transect: a stable isotope study. Mar Ecol Prog Ser 346:127-141.

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