engleski

Cyclotella striata (Kützing) Grun. in the eastern coastal Adriatic Sea

The centric diatom Cyclotella striata is a common planktonic species in temperate estuaries as well as in the eastern coastal Adriatic Sea. We determined seasonal appearance of the species in the eastern Adriatic Zrmanja River estuary in the period from June 1998 - February 2001. The estuary is highly stratified (salt wedge), with sharp halocline. The depth of the halocline is determined by the Zrmanja river inflow. In summer salinity was high due to low river inflow. The highest inflow (avg 65 m3 s-1) and lowest salinity was registered in the period December - April. Annual temperature varies from 6.7 - 26.55 º ; ; C (avg 16.39 º ; ; C), and the salinity from 0 - 38 psu (avg 18.97 psu). Concentration of nutrients was low and transparency high, implying the oligotrophy of the estuary. In the Zrmanja Estuary microphytoplankton was mostly composed of diatoms (avg 1.9 x 105 cellsL-1), while dinoflagelates (avg 103 cellsL-1) and cocolithophorids (1.2 x 102 cellsL-1) were less abundant. Diatom Cyclotella striata was abundant species in spring (March - May), providing maximum of 2 x 106 cellsL-1. It appeared mostly in short chains of cells with valve diametar of about 8µ ; ; m and pervalval axis length of about 5 µ ; ; m. Cyclotella striata is marine diatom, but prefers decreased salinity. It could be mostly detected in the salinity range between 13 and 30 psu, with maximum development within the range of 13 to 17 psu. It was most abundant in and below the halocline. Due to such termohaline preferences C. striata was mostly distributed in the middle reach of the Zrmanja Estuary (in the area of stations N1 and Z1). In the upper reach of the estuary, average abundance was much lower. Cyclotella striata preferred temperatures from10 - 17 ˚ C. Outer stations were characterized by more stabile ecological conditions and more constant appearance of C. striata.

dijatoms; taksonomy; distribution; Adriatic Sea

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