Food sources of the coral reef ophiuroid Ophiocoma scolopendrina

摘要

Ophiocoma scolopendrina is one of the predominant species on intertidal reef flats and plays an important role in the biogeochemical cycle of coral reef ecosystems. We investigated the food sources of 0. scolopendrina on the Odo reef flat located in Okinawa, Japan. Analyses of fatty acid (FA) compositions (% of total FAs), found that bacterial FA biomarkers were predominant in ophiuroid tissues (3.0-7.1%), as well as in the dust films (an aggregation of particulate matter floating on the water surface; 2.7-4.0%), sediments (2.2-6.5%), and suspended particulate matter (SPM; 1.0-4.8%), suggesting that bacteria attached to sediment particles, dust films, and SPM were the major food sources of 0. scolopendrina. The results also showed a substantial accumulation of macroalgal biomarkers (18:2ω6, 18:3ω3, 18:3ω6, and 20:4ω6; 0.8-6.7%) and diatom biomarkers (16:1ω7 and 20:5ω3; 0.1-3.8%), indicating that macroalgae and diatoms are important dietary components, especially in winter. Dinoflagellates were found to be minor food sources, as indicated by the relatively low occurrences of dinoflagellate biomarkers (18:4ω3 and 22:6ω3) in ophiuroid tissues (0-1.5%), as well as in the dust films (0.1-3.2%) and sediments (0-1.2%). Of all of the FAs, even-numbered long-chain FAs, which are biomarkers of vascular plants, were detected least often in ophiuroid tissues (0.0-0.1%), dust films (0.0-0.3%), sediments (0.0-0.1%), and SPM (0.0-0.3%), suggesting that terrestrial vascular plants contribute very little to the diet of O. scolopendrina on the Odo reef flat. Although all food sources appeared to vary seasonally, the most important food source for O. scolopendrina was bacteria attached to sediment particles, dust films, and SPM. O. scolopendrina assimilates bacterial and macroalgal material from the reef sediments and represents a trophic link between decomposers, primary producers, and higher-level consumers.