Distribution of phytoplankton found along Turkish coasts of the Mediterranean Sea

The sampling within the scope of this thesis was carried out in June-July 2019 in the coastal and relatively open part of the Turkish Mediterranean coast between Mersin (Taşucu)-Muğla (Datça). The Mediterranean coast of Turkey is an area of high anthropogenic impacts, including tourism, agriculture, fisheries and maritime transportation. Although past studies have suggested that the Mediterranean Sea is a nutrient-poor (oligotrophic) sea, recent studies show that it is not as poor as thought. Increasing population growth and favorable climatic conditions increase the impact of tourism and agriculture sectors on the region and increase the nutrient load locally. Considering all these, it is extremely important to determine and monitor the impact of the region on the aquatic ecosystem. Phytoplankton constitute the lowest step of the food chain in aquatic ecosystems, are rapidly affected by changes in environmental factors and react quickly to these changes. For these reasons, phytoplankton are very important for the health and sustainability of our seas. Considering all these, knowing the phytoplankton distribution of the Mediterranean coasts of our country and identifying and monitoring the environmental factors affecting them are of great importance today and in the future. Within the scope of the study, 69 stations were sampled in 4 sub-regions. Phytoplankton samples were collected from the surface with a Nansen bottle and fixed with Glutaraldehyde. Physical, chemical and optical parameters of water were measured to correlate phytoplankton species composition and distribution. In this study, when the general characteristics of the water were analyzed by PCA analysis, it was seen that the components were not very explanatory and significant in terms of the percentage variance obtained. Regions 1, 2 and 4 along the PCA1 axis are relatively separated from each other. While basic physical and chemical parameters were correlated in the PCA1 component, optical variables were more effective in the PCA2 axis besides the aforementioned parameters. When the physical parameters of the water were evaluated separately, it was seen that the percent variances were quite explanatory in the PCA solution of the components. While the effect of salinity and density was low in the distribution of stations, the relationship developed more within the pH and temperature components. When the distribution of the stations in terms of physical parameters is analyzed, it is seen that the 2nd and 4th regions are clearly separated, while the 1st and 3rd regions have a relatively similar distribution. When the chemical parameters were analyzed by PCA, it was seen that the percent variances were not very explanatory. The stations in the 1st region showed a negative relationship with NO2 and NO3 values on the PCA2 axis and formed a relatively cluster. Stations in regions 2 and 4 exhibit a disorganized structure, while some stations in region 3 are positively correlated with NO2 and NO3 values. When the optical parameter components are analyzed by PCA, it is seen that the 1st and 3rd regions are relatively separated, but there is no significant difference between the regions in the optical variables of water. It was noticed that the Secchi disk value was slightly higher in the open stations depending on the depth of the station. Since the coastal stations have higher terrestrial effects, the amount of organic and inorganic matter they contain affected the Secchi depth. Within the scope of this study, 69 stations were sampled in 4 sub-regions and a total of 459 phytoplankton species were identified. While 257 of these species were Dinoflagellates, 193 of them were Diatoms. According to the Soyer index, 10 of the 459 species identified in the study area were determined as permanent and 20 as common species. While 6 of the 10 permanent species were included in the Miozoa phylum and 3 in the Bacillariophyta phylum, only 1 Emiliania huxleyi was included in the Haptophyta phylum. The highest average number of species was found in the 2nd region (Mediterranean Gulf) and the lowest in the 3rd region (Finike-Kaş). In terms of abundance values, the highest average abundance value was found in region 1 with 7,68×104 cells L-1, while the lowest average abundance value was found in region 3 with 1,72×103 cells L-1. The highest species richness was found in region 2 (d: 3,40) in accordance with the number of species, while the lowest abundance was found in region 1 (d: 2,58) where the abundance value peaked. According to the Shannon-Wiener index data, the highest biodiversity was found in region 3 (H': 2.75) and the lowest in region 1 (H': 1.72). While the 2nd and 4th regions had similar biodiversity, it was noteworthy that biodiversity generally increased from east to west. When the species composition of phytoplankton was analyzed by cluster analysis, it was seen that there were 3 main floristic communities. Accordingly, it was observed that the stations in these communities were generally clustered on the east-west axis. When the phytoplankton communities were compared, especially heterocapsa species among dinoflagellates were found to be important discriminating species in the difference between regions. Emiliania huxleyi from coccolithophores was found to be an important distinctive species in regions other than regions 1 and 2, while Pseudo-nitzschia delicatissima from diatoms was found to be an important species representing and contributing to all regions. When the correlation of phytoplankton with environmental parameters was evaluated by Canonical Correspondence Analysis (CCA), the stations in the 1st region showed positive correlation with chl-a and pH values, especially temperature and salinity. Within the 2nd region formed by the Gulf of Antalya, it was observed that the stations under the influence of the river were completely separated from the other regions by showing positive correlation with temperature, especially after reactive silicate. Stations in the 4th region, located in the westernmost part of the study area, showed positive correlations with density and nitrate values, but negative correlations with temperature and pH. Stations in the 3rd region showed a quite different distribution. While the difference between the regions in the distribution of phytoplankton communities was statistically significant (Monte Carlo test p value= 0,001; p<0,05), there was no statistically significant difference between the distance from the coast and the region/coastal-open. Within the scope of this thesis study, the species composition and distribution of phytoplankton species in the study area were determined and their relationships with environmental parameters were revealed as a result of analyzes.