Mesozooplankton study in Odessa bay in 2016-2017

Abstract

Purpose. Study of the current state of mesozooplankton in Odessa Bay coastal waters, 2016-2017. Methods. Standard methods of sampling, determination of mesozooplankton species composition, number and biomass. Results. Mesozooplankton sampled every 10 days and monthly in the area of the University Hydrobiological Station has been studied, taxonomic composition, number and biomass of each species determined; the results have been analysed and presented. Mesozooplankton biodiversity indices have been assessed in the coastal waters. Seasonal changes in number and biomass of the main mesozooplankton groups have been studied. Two zooplankton sampling methods have been compared. Marine environment quality has been assessed using the metrics of mesozooplankton. Altogether 31 and 22 taxa belonging to 9 main mesozooplankton groups have been identified in 2016 and 2017 respectively. The dominant groups were Copepoda, Rotatoria, Protozoa, Cladocera and Harpacticoida. Mesozooplankton number and biomass in 2016-2017 varied within broad limits from 600 ind./m³ and 0.24 mg/m³ (10.03.2017) to 225920 ind./m³ (10.06.2017) and 5471.96 mg/m³ (29.06.2017). Significant differences in the values of mesozooplankton number and biomass were revealed through sampling at the stations with different depth, which can be explained by both spatial inhomogeneity and different vertical distribution of those characteristics due to the features of the vertical distribution of temperature and salinity with depth. It was established that in shallow areas sampling with Juday net was more effective and representative than sampling with modified Apstein net. Analysis of marine environmental quality assessments using three different metrics of mesozooplankton has shown that the method of quality assessment using biomass was the most representative. Conclusions. Marine environment quality was assessed mainly as «Bad» and «Very Bad» for 82% of samples, «Good» and «High» for 4%, «Moderate» for 14% of samples. The performed assessment proves unsatisfactory conditions for mesozooplankton community normal development and functioning in Odessa Bay coastal waters.