Physical, chemical and optical properties of estuaries in the Gulf of Finland, River Kymijoki

The purpose of this project was to examine the physical, chemical and optical properties of the estuaries in the Gulf of Finland and to estimate the influence of the seasonal sea ice. One year of successive measurements (2011) took place in River Kymijoki estuaries, Gulf of Finland. The expeditions occurred during the ice break up season in 2011, and before the initial ice formation of the winter 2011-2012. Temperature, salinity, oxygen, pH and Photosynthetically Active
Radiation (PAR) data were collected by the CTD90M multiparameter probe. In addition, open access data records from OIVA - Ympäristö- ja paikkatietopalvelu asiantuntijoille (Environmental and Location-based Expert Services) were analyzed for seasonal variations. Here, we present some preliminary analysis of the properties in order to examine their seasonal
variations in four years 2010-2013. The strongest thermocline occurred in August at 10 m depth. Salinity in the summer was on average higher by 1-1.5. Minimum pH values occurred in the winter, just below the landfast ice cover. Dissolved oxygen in the summer was lower by 5.5 mg/l compared to the winter average. The PAR values decayed exponentially down to 2m and got almost zero below 10 m depth.