FAUNA OF FREELIVING NEMATODES IN THE UKRAINIAN PART OF THE DANUBE RIVER MOUTH AREA IN THE MODERN PERIOD

Abstract

Problem. The Problem links with variability of modern state environmental condition of the Danube river mouth area and the whole Black sea system as well. Thus the taxonomic diversity and quantitative development of free-living nematodes (the dominant component of meiobenthos) is under the euthrophication press because of directly Danube water input. Among the benthic organisms, only meiobenthos can react very quickly to changes in hydrochemical and hydrological parameters. Due to their small size and short-cycle development, they are the first to respond to deteriorating environmental conditions.The purpose is to identify the species composition and quantitative indicators of free-living nematodes of the meiobenthos in different parts in the Danube mouth area in modern period.Materials and methods. The data of long-term monitoring of meiobenthos in the Ukrainian part of the Danube mouth area located under the direct technogenic influence (dumping and shipping way construction), carried out by the Institute of Marine Biology of the National Academy of Sciences of Ukraine during from November 2004 to November 2019, were used.Main results of the research. The fauna of nematodes is represented by 69 species of 37 genera, 18 families and 6 orders. The orders Monhysterida and Enoplida dominate by the number of species. The increase in the number of species in each of the orders from the river mouth to the open sea was observed. The predominant trophic group is non-selective deposit feeders (1B). The distribution of quantitative indicators of the density of nematodes in different areas varies within significant limits: from 1000 ind.∙m-2 up to 682 500 ind.∙m-2. (average – 119 474 ind.∙m-2). The biomass varied from 1.3 mg∙m-2 to 425.4 mg∙m-2 (average – 57.4 mg∙m-2).Conclusions. The quantity changes of fauna of nematodes in the Ukrainian part of the Danube mouth area depends on the influence of naturally changing environmental conditions, as well as on the technogenic load. Keywords: meiobenthos; nematodes; species diversity; Ukrainian part of the Danube mouth area.