Carbon sources for demersal fish in the western Seto Inland Sea, Japan, examined by δ¹³C and δ¹⁵N analyses

Abstract

The relative importance of benthic and pelagic primary production for demersal fish and some invertebrates in the western Seto Inland Sea of Japan was examined using carbon and nitrogen stable isotope analyses. A few fishes, such as juvenile black rockfish Sebastes inermis and large Japanese anchovies Engraulis japonicus, had isotopic carbon signatures similar to pelagic particulate organic matter (Ϫ20.1 Ϯ 1.7‰), which indicates that their food was derived from production in the water column. However, 92% of the 401 demersal fish that were analyzed had ␦ 13 C signatures (Ϫ17.0 to Ϫ13.0‰) similar to those of benthic crustaceans, epilithic microphytobenthos, and macroalgae and unlike the signature of pelagic particulate organic matter or zooplankton. These results suggest that in the Seto Inland Sea there is not a tight coupling between pelagic primary production and the food web of demersal fishes, but rather that these fishes are dependent on carbon from benthic primary production.

Stable isotopes in subtidal food webs: Have enriched carbon ratios in benthic consumers been misinterpreted?

“…The experimental aging of algal-and plant-derived organic matter for 2 months in field and laboratory conditions did not result in a change in their d 13 C (Stephenson et al 1986). Finally, the possible influence of decomposition on d 13 C values would also fail to explain why benthic consumers suspended near the surface, which have access to fresh particles, still have the same highly enriched carbon ratios as observed in consumers on the bottom (current study; Machas et al 2003;Takai et al 2002). All these lines of argument tend to show that the diagenesis of organic matter does not cause an increase in d 13 C and that the ingestion of refractory organic matter does not satisfactorily explain the elevated d 13 C found in benthic consumers of polar and temperate oceans.…”

“…These observations, however, do not form a general pattern. Our study and others (a, Takai et al 2002;b, Machas et al 2003;c, Kang et al 2003;d, Kaehler et al 2000;e, Hobson et al 1995;f, Fry 1988;g, Iken et al 2005), and the dashed line connects the minimum and maximum depth sampled in the present study. The dashed horizontal line at the bottom is the predicted location of organisms feeding strictly on POM (with the usual 1% enrichment).…”

“…Many studies have made use of this difference to evaluate the relative importance of the different benthic primary producers and phytoplankton in coastal food webs. Although most studies in subtidal systems focus on the importance of kelp (Duggins et al 1989;Kaehler et al 2000;Fredriksen 2003), a number also consider the importance of benthic microalgae (Takai et al 2002;Kang et al 2003). All of these studies show that most benthic consumers are rich in 13 C, suggesting that benthic primary producers are major contributors to benthic food webs.…”

The seasonal trophic link between Great Cormorant Phalacrocorax carbo and ayu Plecoglossus altivelis altivelis reared for mass release

“…Similarly high isotopic values were reported for marine fish and invertebrates in another eutrophicated area (Takai et al 2002). It is well known that the home range of the cormorants is broad in some cases.…”

Variation in ^|^delta;13C and ^|^delta;15N among different tissues of three estuarine bivalves: implications for dietary reconstructions

“…Kasai et al 2004), lipid-removed (e.g. Takai et al 2002) or lipid-containing (e.g. Page & Lastra 2003) adductor muscle, or whole bodies with lipids (e.g.…”