Macrophytobenthos of Kazach’ya Bay (Black Sea) in autumn 2017

Abstract

Over the last two decades Kazach’ya Bay area has been subjected to intensive coastal development resulted in deterioration of the environment quality. Considering the fact that the anthropogenic impact has already led to degradation of the key macrophythobenthos communities at many sites of Sevastopol coast, the assessment of the current state of the bottom phytocoenoses in Kazach’ya Bay is of great importance. The aim of the study was to investigate the species composition and quantitative parameters of the macrophytobenthos in Kazach’ya Bay and to analyze long-term changes in its bottom vegetation. Investigation was carried out in the western branch of the bay in September 2017 at depth of 3, 5, 6, 8 and 17 m; 41 macrophyte species were identified: 13 – Chlorophyta, 1 – Charophyta, 10 – Phaeophyceae, 13 – Rhodophyta, and 4 – Angiospermae. Such species as Chaetomorpha gracilis, Cladophora vagabunda, Lamprothamnium papulosum, Myrionema strangulans were recorded for the first time. Zostera noltii + Stuckenia pectinata phytocoenosis with biomass 905 g·m-2 was found at 3 m depth on the soft bottom, at 6 and 8 m it was replaced by monodominant Zostera noltii communities with biomass 691 and 390 g·m-2 respectively. At 5 m depth where alongside with soft sediments hard substrata occur, mosaic of patches dominated by Zostera noltii and Cystoseira crinita with mean biomass 1017 g·m-2 was found. Phyllophora crispa phytocoenosis with the biomass 290 g·m-2 was registered near the mouth of the bay at the depth of 17 m. Between 1999 and 2017 biomass of the seagrass communities decreased 2–3 times, moreover, Zostera marina phytocoenoses were replaced by the Zostera noltii dominated communities. Biomass of the Phyllophora community almost doubled over the same period.

Keywords

• macrophytobenthos
• species composition
• biomass
• coenopopulations
• Cystoseira
• Phyllophora