engleski

Planktonic diatoms in marine lake Mir (Dugi Otok island, Eastern Adriatic Sea, Croatia)

There are several marine lakes along the Croatian coast and islands. The studied marine Lake Mir is situated on the Dugi Otok Island, Middle Adriatic and it is enclosed water-body without superficial and subterranean freshwater inlets and outlets. This study brings out the first data on phytoplankton of this karstic lake. The primary objective of this study was to report on the abundance and composition of the microphytoplankton (cells longer than 20 &micro ; m), as well as hydrographic conditions in the lake. Sampling was carried out at one station, from the surface (0.5 m) to the bottom (7 m), every one meter, monthly from November 1999 to November 2000. Temperature amplitudes of the lake water were very prominent (in the summer up to 27°C and in the winter up to 10°C, in January under the 5°C), and a lack of thermal stratification has been revealed. Salinity was high during the whole year, especially in summer months when values exceeded 40. Diatoms and dinoflagellates were the most important microphytoplankton constituents of the lake. Diatom abundances were ranged from 1.05 x 102 – 6.8 x 105 cells L-1. Their relative contributions to microphytoplankton abundance were from 23.5 % (in July 2000) to 99.9% (November 1999). There was predomination of small diatoms almost the whole investigated period, while dinoflagellates increased in number only in summer. Three peaks of microphytoplankton were observed throughout the year. Domination of Cyclotella sp. was evident during the peaks in November 1999 and April 2000. In July 2000, the microphytoplankton peak was dominated by dinoflagellate Scrippsiella trochoidea.

Diatoms; Lake Mir; Dugi Otok Island; Adriatic Sea

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