Seasonal dynamics of the nutrition spectrum of Dreissena polymorpha in the Rybinsk Reservoir

Abstract

The bivalve mollusk Dreissena polymorpha (Pallas, 1771) is a species that populates an increasing number of new water bodies to threaten the native ecsystem stability [1]. Studying the biological characters of D. polymorpha is required to prevent undesired invasion and to reduce the negative ecological effect of this organism. Food composition of D. polymorpha under natural conditions is scarcely known by now. Because of some technical obstacles, it is difficult to determine the nutrition spectrum of D. polymorpha and other invertebrates in natural water bodies. Visual microscopic analysis of the contents of their gut often leads to erroneous conclusions because, first, many food particles cannot be identified visually and, second, numerous food particles that have been swallowed are not assimilated and pass off through the gut [2, 3]. Analysis of the fatty acid (FA) composition of tissue triacylglycerol (TAG) makes it possible to trace trophic interactions between hydrobionts and determine food assimilation [4, 5]. We studied the seasonal nutrition spectrum of D. polymorpha inhabiting the Rybinsk Reservoir. The mollusks were sampled in June‐September, 2007 at three stations of the Volga Stretch of the Rybinsk Reservoir, at a depth of 4‐6 m. Total seston samples from surface to bottom were obtained at the same stations. The TAG fatty acid composition was determined using thin-layer chromatography and chromatography‐mass spectrometry [5]. The results obtained were statistically processed using the correlation graph method described in detail in [6].