engleski

Planktonic diatoms and their environment in the lower Neretva River estuary (Eastern Adriatic Sea, NE Mediterranean)

The seasonal distribution of planktonic diatoms was investigated at one station in the lower Neretva River estuary (Middle Adriatic) at monthly intervals from April 1999 to April 2000. According to the TRIX trophic index, the lower estuary is mesotrophic. Ninety-six diatom taxa within 51 genera were identified. Of these, 32 occurred in at least 10 % of all samples and 12 rare taxa occurred in ≤ 1 % of samples. Nine, mostly rare, taxa were only found in brackish layer, and 27 taxa were exclusively presented in marine layer. Anosim analysis revealed that no significant difference occurred between these two layers in terms of diatom taxa abundances. The continuous presence of some benthic taxa, underlines the importance of wind-induced sediment resuspension, currents and tides. Unidentified phytoflagellates (55.68 – 99.60 %) and diatoms (0.20 – 42.10 %) represented the major proportion of total phytoplankton abundance. The diatom community of marine origin varied over five orders of magnitude (30 –1.2 × 10*6* cells L–1) and showed three peaks throughout the year: April 1999 (1.2 × 10*6* cells L–1), August 1999 (7.9 × 10*6* cells L–1), and October 1999 (1.3 × 10*6* cells L–1), while the lowest abundance was observed in November 1999. The most abundant diatoms (exceeding 10*5* cells L–1) were Nitzschia longissima, Leptocylindrus minimus, Skeletonema marinoi, and Thalassiosira sp. N. longissima (max. 7.9 × 10*6* cells L–1) dominated the highest peak (August 1999) and represented the 98.08 % and 29.26 %, respectively, of total diatom and phytoplankton abundance. Canonical Correspondence Analysis (CCA) showed that temperature, salinity and TIN were the main factors influencing diatom community structure in the estuary. No relationship was noted between the monthly distribution of diatom abundances, water column transparency, and microzooplankton abundance. A main feature of the diatom assemblages was the dominance of more than one species during the blooms. This, likely, is owed to the frequent and rapid environmental changes typical of this dynamic estuarine ecosystem.

diatoms; phytoplankton communities; microzooplankton; environmental variables; CCA; estuary; Croatia; eastern Adriatic Sea

ISBN 978-3-443-51063-3 ; Diatom taxonomy and ecology : From local discoveries to global impacts : Festschrift in honor of Prof.Dr. Horst Lange-Bertalot's 75th birthday ; Andrzej Witkowski, John P. Kociolek, Pierre Compère (ur.).