Investigation of environmental factors which affect distribution of modern dinoflagellate cysts in İzmir Bay

In this study, it is aim to investigate factors which affects dinoflagellate cysts distribution in İzmir Bay which is one of the important coastal areas of Aegean Sea. Sea surface physicochemical parameters (temperature, salinity, pH, dissolved oxygene, nitrite+nitrate nitrogene, ammonium nitrogene, phosphate and chlorophyll-a) were measured seasonally from at 12 station in the bay in 2013. Surface sediment samples were taken once (2013-spring) and dinoflagellate cyst distribution were investigated at the same stations. Sea surface temperature 12.99-27.88 C°, salinity 37.97-39.39 ‰, pH 7.08-8.40, dissolved oxygene 5.91-11.46 mg l-1, nitrite+nitrate nitrogen 0.10-9.63 µM, ammonium nitrogen 0.10-8.01 µM, phosphate 0.01-4.06 µM and chlorophyll-a concentration 0.12-14.66 µg l-1 were measued during sampling period in İzmir Bay. Sea surface temperature and dissolved oxygene concentration showed significant differences seasonally and locally in the bay. Surface water temperature showed the highest value in summer whereas the lowest value were measured in winter. The highest and lowest temperature values were found in inner bay and temperature differences between two seasons has decreased from inner bay to outer bay. Dissolved oxygene concentration were found the highest in spring and the lowest in summer. The lowest and highest value were meaused in inner bay and differences between minumum and maximum concentration has decreased from inner bay to outer bay. Sea surface salinity and pH values showed no significant diversity as seasonally and locally. nitrite+nitrate nitrogen, ammonium nitrogen and phosphate concentration in inner and middle bay were measured higher than the outer bay. Seasonal differeces of nutrient concentration were significant in inner and middle bay but insignificant in outer bay. Chlorophyll-a concentrations have decreased from inner bay to outer bay as similar to nutrient values. Spring and summer seasoans when phytoplankton blooms are high, chlorophyll-a concentration has increased significantly. Total 44 cyst type were identified in İzmir Bay and dinoflagellate cyst diversity changed 12-36 cyst. Protoperidinoid and Gonyaulacoid cyst taxa were abundant for cyst diversity in the bay. Cyst concentraion were ranged 384-9944 cyst g-1 dry weight sediment in the bay. Cyst concentration of Gymnodinoid and Gonyaulacoid species were higher than other groups. Gymnodinium nolleri, Lingulodinium machaerophorum, Spiniferites bulloideus were abundant cyst species in the bay. Cyst diveristy and concentration in the bay have decreased from the inner bay to outer bay. Based on cyst concentration and relative abundance data, two different dinoflagellate cyst assemblages were found in two different part in İzmir Bay. Lingulodinium machaerophorum, Spiniferites bulloideus, Scrippsiella spp, Polykrikos kofoidii, Protoperidinium minutum, Quinquecuspis concreta, Xandarodinium xanthum, Dubridinium caperatum were first cyst assemblages and localized in inner and middle bay. Alexandrium affine type, Operculodinium centrocarpum, Spiniferites delicatus, Spiniferites ramosus, Gymonidinium nolleri were second cyst assemblages and locolized in outer bay. Detrended Correspondence Analysis (DCA) showed that two different cyst assemblages were identified depend on locations of the bay. Inner, middle and outer bay stations were observed also as grouped with each other in DCA . Pearson correlation showed that distribution of cyst assemblages were affected by sea surface temperature, dissolved oxygene, nutient and chlorophyll-a concentrations in the bay. Cyst species which is located in outer bay did not showed poor or any correlations with environmental data while cyst assemblages in inner and middle bay showed possitive correlation with present environmental parameters. In this study, nutrient pollution in the bay has decreased compared to past years however impact of pollution and eutrophication in inner and middle bay still can be observed. Dinoflagellat cysts were used as an indicator for eutrophication and pollutionin the bay and important results were determined for the bay. Cyst diversity were ovserved higher where nutrient levels were measured in high. Due to the autotrophic cysts were determined high levels in the bay, autotrophic and heterotrophic cyst rate were not suitable proxy for eutrophication and primary productivity in İzmir Bay. In this study, Lingulodinium machaerophorum is detected a good indicator for eutrophication in İzmir inner bay. Cyst of Gymnodinium nolleri is also good indicator for oligotrophic characterised İzmir outer bay. Lingulodinium machaerophorum, Operculodinium spp, Alexandrium spp. are species which can cause potentially toxic and harmful microalgal blooms in İzmir Bay. These species concentration were observed high level in especially in inner bay.