FATTY-ACIDS AS MARKERS OF FOOD SOURCES IN A SHALLOW-WATER HYDROTHERMAL ECOSYSTEM (KRATERNAYA BIGHT, YANKICH ISLAND, KURILE ISLANDS)

The contribution of different food sources in the food web of a shallo w-water hydrothermal ecosystem was estimated using fatty acids as mark ers. The markers were selected based on the results of analyzing the f atty acid composition of potential food sources in Kratemaya Eight, Ya nkich Island, Kurile Islands. Most animals had markers characteristic of diatoms: the 16:0/16:1 omega 7 ratio close to 1 and a high 20:5 ome ga 3 content. We assume that the bivalves Macoma calcarea and Macoma l ukini, polychaetes Amphitrite cirrata and Pectinaria hyperborea, and h olothurians Eupentacta pseudoquin-quesemita and Psolus sp. feed mainly on diatoms. Fatty acids specific to bacteria - branched, odd and 18:1 omega 7 - were found in considerable amounts in the bivalve Axinopsid a orbiculata, as well as in E. pseudoquinquesemita, Psolus sp. and P. hyperborea; hence we concluded that there was a substantial bacterial input into the food of these species. A high concentration of C-18 and C-20 PUFAs (polyunsaturated fatty acids), suggested to be an indicato r of brown algae, was detected merely in the gastropod Littorina kuril a. Although bacteria are more important as a food source in Kraternaya Eight than in typical coastal ecosystems, the major food source for a nimals here is photosynthetic organisms, rather than chemosynthetic sy mbionts as is the case with deep-sea hydrothermal vents.