Species, taxonomic and ecological diversity of phytoplankton of the Kiliya Danube delta

Abstract

An integral component of the biota of aquatic ecosystems is phytoplankton, which plays a fundamental role in the formation of the autotrophic link. The Danube delta is characterized by unique biotopes, which are characterized by a high diversity of species. Phytoplankton is an indicator of the quality of the aquatic environment and is a convenient object for research, as it can quickly respond to changes in the ecosystem. Phytoplankton species diversity of the Kiliya Danube Delta in the summer of 2019 includes 158 species and intraspecific taxa belonging to 8 divisions. The most numerous are the division Bacillariophyta (52 intraspecific taxons) and Chlorophyta (45 intraspecific taxons); orders Sphaeropleales (24), Naviculales (16), Euglenida (15), Chlorellales (13); families: Euglenidae (9), Scenedesmaceae (9), Naviculaceae (8), Selenastraceae (7), and genera Nitzschia (6), Navicula (5), Monoraphidium (5), Trachelomonas (5), Lepocinclis (5). The phototrophic link is formed mainly by diatoms and green phytoplankton planktonic and planktonic-benthic forms and indicates a dynamic hydrological regime of the object. According to saprobic species indicators, the diversity is dominated by β-saprobic (46%) and oligosaprobic (28%) forms. The water of the Kiliya Danube delta corresponds to class III in terms of organic pollution. water quality, which is characterized as "moderately polluted" and refers to β-saprobic waters. To determine the similarity of the floristic spectrum presented in different sampling locations, Sorensen coefficients in the range from 0.10 to 0.46 were calculated. types of diversity, in terms of amplitude, the stations on the Danube River (Reni, port) and the Kiliya delta (below the sea station) are most similar to each other, other areas are less similar to each other. It was found that, based on the similarity of the floristic spectrum presented in the samples, the Sorensen coefficients are quite low, and it is justified by the geographical location of the studied object, the dynamics of its hydrological regime, and different environmental conditions. The phytoplankton of the Kiliya Danube delta has a wide spectrum of species diversity relative to its spatial distribution.