Seasonal Dynamics of Pelagic Larvae and Settling of the Fouling Organisms in Conditions of Thermal Pollution

Abstract

Year-round comprehensive study of fouling of the cooling system of the Vladivostok Heat Power Plant (VTETs-2) was carried out. The seasonal dynamics of pelagic larvae, their settling, and succession of fouling communities on test plates were analyzed in the intake scoop (Ussuriiskii Bay) and in Zolotoi Rog Bay (Amurskii Bay), which are subjected to thermal pollution by dump waters of VTETs-2. It was shown that the barnacles Balanus crenatus, B. improvisus, and B. amphitrite; bivalves Mytilus trossulus and Crassostrea gigas; polychaetes Polydora limicola and Hydroides ezoensis; and ascidians Molgula manhattensis and Diplosoma mitsukurii were background species in the plate fouling. A high correlation between the seasonal dynamics of larval plankton and the settling of spat was recorded only in some species. The total larval density in Zolotoi Rog Bay, despite the critical level of its pollution, more than 4 times exceeded that of the relatively clean Ussuriiskii Bay. The number of recorded species on the test plates was 2 times higher in Ussuriiskii Bay than in Zolotoi Rog Bay; however, the biomass and population density of settled spat of the dominant forms was several times lower in Ussuriiskii Bay. Thanks to thermal pollution, Zolotoi Rog Bay is an intermediate step for the introduction and acclimation of tropical species, such as B. amphitrite and M. manhattensis, brought by long-distance vessels. Measures aimed at the prevention of intensive settling of mytilids in the cooling system of VTETs-2 are suggested.