Changes in the Zooplankton of the Eastern Sea of Marmara

Date

2024-01-01

Author

Işinibilir Okyar, Melek
Svetlichny, Leonid
Türkeri, Ezgi E.
Topçu Eryalçin, Nur Eda
Kıdeyş, Ahmet Erkan

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The study conducted in the eastern Sea of Marmara from 2016 to 2022 aimed to investigate the spatio-temporaldistributions of mesozooplankton in relation to changing environmental conditions. A total of 43 zooplankton taxa wereidentified, with the number of species varying between 4 and 19 in the brackish upper layer (resembling the Black Sea)and between 1 and 17 in the saline lower layer (resembling the Mediterranean Sea). The abundances of zooplanktonranged from 28 to 43,359 ind.m-3 in the upper layer and from 5 to 3,851 ind.m-3 in the lower layer. Significantdifferences were observed between the upper and lower layers in terms of the number of species, total zooplanktonabundances, evenness, and Shannon diversity (p<0.0001). The most significant differences in zooplankton abundanceand community structure were found to be seasonal rather than inter-year or regional variations. The highest totalzooplankton abundance was recorded at station M14 during the summer season (June 2022), primarily due to thepresence of Paracalanus parvus and Penilia avirostris (906 ind.m-3 and 722 ind.m-3, respectively). The heterotrophicdinoflagellate Noctiluca scintillans, a major component of net samples in the Sea of Marmara, exhibited a clear seasonaldistribution, with higher abundances consistently observed during winter months. The highest abundance of Noctilucascintillans was recorded in February 2016 at station MD102 (42,514 ind.m-3). Paracalanus parvus, Acartia clausi, andOithona nana were identified as important year-round species in both the upper and lower layers of the Sea of Marmara.The presence of N. scintillans and P. avirostris distinguished the upper layer communities from the lower layer, with N.scintillans being more prevalent during winter and P. avirostris during summer. Notably, P. avirostris exhibited verylow abundances during the summers of 2019, 2021, and 2022. The large-scale mucilage event that occurred in June2021 had a significant impact on zooplankton, as evidenced by the low abundance and biomass observed during thisperiod. The chlorophyll-a values, which reflect phytoplankton biomass, increased sharply during the dominatingmucilage event, ranging from 12.2 to 14.2 µg.l-1. Overall, this study emphasizes the vulnerability of the Sea of Marmaraecosystem, particularly zooplankton, to large-scale environmental disturbances such as mucilage events.

URI

https://hdl.handle.net/11511/117350

Collections

Graduate School of Marine Sciences, Book / Book chapter