Trophic relationships between macroinvertebrates and fish in St. Petersburg methane seep community in abyssal zone of Lake Baikal

摘要

Trophic relationships were examined for macroinvertebrates and fish inhabiting the St. Petersburg methane seep (central part of Lake Baikal, similar to 1400 m depth). The analyses of the values of carbon and nitrogen stable isotopes showed that all animals associated with the seep were heterotrophs with different feeding strategies; symbiotrophes were absent. Seep animals consumed combined food with different portion of methanederived carbon ranged from 2.7 to 89%. The average delta D-13 values varied in the range of-26.2aEuro degrees (in benthopelagic amphipods) to-64.5aEuro degrees (in gastropods). The trophic food web in the methane seep consists of filter feeders (pelagic amphipods, trophic position (TP) is 1.9), detritophages (gastropods, TP of 2.2, and burrowing amphipods, TP of 2.1), polyphages and necrophages (nectobenthic and benthopelagic amphipods of TP 2.8-3.2), and predators (planarians of TP 3.6-4.2 and cottoid fish of TP 3.0-3.8). Animals occupying similar trophic positions significantly differed in the delta D-13 values and have partially overlapping components of food.