ON NIGHTTIME VERTICAL MIGRATIONS OF AMPHIPODS IN LAKE LADOGA

Abstract

Daily vertical migrations (DVM) of amphipods is a widespread phenomenon both in rivers and lakes, and in seas. The leader among freshwater bodies in terms of the number of amphipod species and the intensity of DVM is the ancient Lake Baikal. Lake Ladoga is also inhabited by several species of these crustaceans, and some of them are invaders from Lake Baikal. Therefore, the aim of this study was to check whether amphipods in Lake Ladoga perform nighttime vertical migrations. To test this assumption, we used a combination of video equipment (a video system consisting of a metal frame, a GoPro 4 video camera, 3 lighting elements, and an iButton temperature logger), a plankton net, and a bottom grab. Co-application of these methods did detect vertical nighttime migrations in amphipods in Lake Ladoga, but their intensity was extremely low and they were observed only in invasive species from Lake Baikal, Gmelinoides fasciatus and Micruropus possolskii . A comparison of depth-specific intensities of vertical nighttime migrations revealed no significant variation. In addition to amphipods, the nighttime migrants community in Lake Ladoga includes representatives of such groups as fish, chironomids, water bugs, opossum shrimps, and predatory cladocera Leptodora kindtii (Focke, 1844) .