Ecological Changes in the Sea of Marmara
Determination of the Distribution of Dinoflagellate Cysts in Recent Marine Sediments of the Golden Horn Estuary Ecosystem and Their Effects on Eutrophication
Turgay Durmuş, Neslihan Balkıs ÖzdeliceThis study was carried out at five stations during two seasons (February and October 2016) to detect dinoflagellate cysts found on the surface sediment of the Golden Horn Estuary (GHE) ecosystem and their possible effects on eutrophication. Samples were taken with Van-Veen grab from sediment, and only the recent sediment (0–2 cm was taken with PVC cores) was used for analysis. In addition, the mud percentage of the sediment was investigated, and sediment grain size was measured via sieve analysis. Also, physicochemical variables such as temperature, salinity, dissolved oxygen and pH, and the concentrations of nutrients (NO2 +NO3-N, PO4-P and NH4-N) were determined. In this study, 19 dinoflagellate species’ cysts were identified. Only Heterocapsa rotundata was incubated and produced motile cells in culture. Besides, in February, the cyst abundance was detected highest at the H1 station, which is close to Istanbul Strait. The lowest was determined at the H5 station in both sampling periods, where streams flow through in GHE with dense pollution and shallow depth. According to frequency, Alexandrium minutum, Lingulodinium polyedra and Scrippsiella acuminata were the most common species’ cysts (≥ 70%). Also, A. minutum was the most abundant species with 680 cysts g-1 dry weights. Moreover, it was detected that the cysts of autotrophic species are more dominant compared to heterotrophic species. Also, it was noticed that more dinoflagellate cysts are found on the sediment with the lowest mud percentage. In this study, the distribution of dinoflagellate cysts in the GHE ecosystem, where pollution was intense in the past, eutrophication was observed from time to time, and the water quality began to change with the rehabilitation studies carried out in recent years, were determined. Also, this distribution was evaluated with the main physicochemical variables of the environment, and the changes in the ecosystem were tried to be monitored. In addition, possible effects of algal blooms that may occur in the future by potentially harmful species’ (HABs) cysts and preventive activities have been tried to be revealed.