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Turkish Journal of Fisheries and Aquatic Sciences 2018, Vol 18, Num, 8     (Pages: 937-949)

Grazing and Feeding Selectivity of Oithona davisae in the Black Sea: Importance of Cryptophytes

Antonina Khanaychenko 1 ,Vladimir Mukhanov 1 ,Larisa Aganesova 1 ,Sengul Besiktepe 2 ,Nelly Gavrilova 1

1 Institute of Marine Biological Research, Sevastopol, Russia
2 Dokuz Eylul University, Institute of Marine Sciences and Technology, Izmir, Turkey
DOI : 10.4194/1303-2712-v18_8_02 Viewed : 4215 - Downloaded : 2589 Feeding of non-indigenous cyclopoid copepod Oithona davisae in natural coastal phytoplankton assemblages from the Sevastopol Bay, the Black Sea, in late July and in late November 2013 and in artificial phytoplankton assemblage (mixture of 5 cultured microalgae) have been studied in laboratory experiments using flow cytometry. Three distinct main clusters of phytoplankton (2 μm < ESD < 20 μm) were identified in the natural water samples in both sampling period: photosynthetic picoeukaryotes, nanophytoplankton and nanoplanktonic cryptomonads (NanoPE). Female O. davisae grazed on all 3 phytoplankton groups but the highest ingestion rate in terms of carbon was on NanoPE with the value of 0.29±0.03 μg Cprey cop-1 d-1 in July. Low abundance of 3 phytoplankton groups in late November resulted in a very low but significant carbon ingestion on cryptophytes (0.008±0.002 μg Cprey cop-1 d-1) than on the other groups. Clearance rates and electivity indices confirmed positive selection only for cryptophytes from natural phytoplankton assemblages, and for cryptophyte strain IBSSCr54 and Tetraselmis suecica from artificial plurialgal mixture. Highest daily specific carbon-rations of O. davisae females were found on cryptophytes (ESD 7 - 12 μm): up to 135% and 184% body carbon d-1 in late July and on artificial phytoplankton assemblage, respectively. Keywords : Copepod, phytoplankton assemblages, ingestion rate