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Changes in the Abundance and Species Composition of Phytoplankton in the Last 150 Years in the Southern Black Sea |
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| Authors: | Erik Askov Mousing Thorbjørn Joest Andersen Marianne Ellegaard |
| Institution: | 1. Center for Macroecology, Evolution and Climate, Department of Biology, University of Copenhagen, Universitetsparken 15, 2100, Copenhagen, Denmark 3. Department of Geography and Geology, University of Copenhagen, ?ster Voldgade 10, 1350, Copenhagen, Denmark 2. Marine Biological Section, Department of Biology, University of Copenhagen, ?ster Farimagsgade 2D, 1353, Copenhagen, Denmark |
| Abstract: | Changes in total abundance and in species composition of phytoplankton in the last 150 years in the southern Black Sea were investigated through a paleoecological study of two sediment cores. The results show changes in the species composition and a marked increase in total abundance of siliceous protists after around 1960. In core 22 (42°13.534′ N/36°29.555′ E), the dominating species before 1960 were Cyclotella choctawhatcheeana and Thalassiosira oestrupii. In core 25 (42°6.212′ N/36°37.460′ E), the dominating species before 1960 were T. oestrupii, Cyclotella meneghiniana, C. choctawhatcheeana, and Pseudosolenia cf. calcar-avis. Core 22 was located in closer proximity to the rim current than core 25, and the differences in total abundance between the cores could be related to differences in local nutrient loading prior to 1960. After around 1960, both cores changed to a community dominated by C. choctawhatcheeana. The changes in total abundance and species composition after around 1960 could be related to the increased nutrient loading from the Danube River into the rim current after the late 1960s. The results also showed changes in both total abundance and in species composition of dinoflagellate cysts. The dominating dinoflagellate cysts recorded were Lingulodinium polyedrum, Polykrikos schwartzii, and Spiniferites spp. |
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