Picophytoplankton predominance in hypersaline lakes (Transylvanian Basin, Romania)

Somogyi, Boglárka and Vörös, Lajos and Pálffy, Károly and Székely, Gyöngyi and Bartha, Csaba and Keresztes, Zsolt Gyula (2014) Picophytoplankton predominance in hypersaline lakes (Transylvanian Basin, Romania). EXTREMOPHILES, Online. pp. 1-10. ISSN 1431-0651

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Abstract

The occurrence and importance of photoautotrophic picoplankton (PPP, cells with a diameter <2μm) was studied a long a trophic and salinity gradient in hypersaline lakes of the Transylvanian Basin (Romania. The studied lakes were found to be rich in PPP, with abundances (maximum:7.6 x 106 cells mL - ) higher than in freshwater and marine environments of similar trophic conditions. The contribution of PPP to the total phytoplankton bio volume did not decrease with in creasing trophic state as it was generally found in other aquatic environments. Regardless of the trophic conditions, the contribution of PPP could reach 90-100% in these hypersaline lakes. We hypothesized that the PPP predominance might be the result of the low grazing pressure, since heterotrophic nanoflagellates (the main grazers of PPP) were absent in the studied samples. There were significant differences in community composition among the lakes a long the salinity gradient. CyPPP predominated in less saline waters (mainly below 5%), while EuPPP were present along the entire salinity range (up to 18.7%), dominating the phytoplankton between 3 and 13% salin ity . Above 13% salinity, the phytoplankton was composed mainly of Dunaliella species.

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