engleski

Diatoms response on silicate variations in the hyperhaline marine lakes, Eastern Adriatic

Phytoplankton and physical-chemical parameters were investigated for the first time in the only natural hyperhaline marine lakes (salinity >40) along Croatia’ s Adriatic coast, Mala Solina and Velika Solina. Nutrient limitation appears to have been important in defining the lakes’ seasonal phytoplankton composition. PO4 was most likely limiting from October to December, SiO4 from January to April, and N from June to September when NO3 was depleted. Diatoms and dinoflagellates were the major components of microphytoplankton (cells >20  m) community structure. Diatoms were most abundant during November-January when temperature and salinity were low and nitrate and ammonium were high. In that period silicate varied between 2 - 26 μ mol L-1, what is above the typical half-saturation constant for coastal diatoms. They collapsed in March when SiO4 was depleted and fell below the reported half-saturation constant. The concentration of SiO4 increased with the onset of higher temperatures and salinities in May and reached its annual maximum in August. Maximum diatom abundance was related to peak silicate, and both diatoms and silicate subsequently declined in September and October. Amphora, Navicula, and other naviculoid diatoms were the most frequent genera. Nitzschia longissima was the most abundant species.

Diatoms; silicate; hiperhaline marine lakes; Mala Solina; Velika Solina; Adriatic Sea

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