engleski

First occurrence of Synedropsis roundii Torgan, Menezes, & Melo (Bacillariophyta) in Europe with description of habitat and ecological preferences

Synedropsis roundii is planktonic diatom species with a single chloroplast. Other important morphological characteristics are apical pore fields composed of three slits and striae composed of a single round areola. Synedropsis roundii was described in 2003 from tropical Imboassica lagoon in south-eastern Brazil. The lagoon is shallow and polymictic system. It has strong anthropogenic influence because of sewage disposal and artificial openings on the seaward side, allowing coastal water to enter the lagoon. The lagoon is oligohaline and slightly alkaline habitat. In Croatia, S. roundii was identified through routine monitoring of phytoplankton from April until September in years 2014, 2016 and 2017 in Lake Vransko on South Adriatic coast. Lake Vransko is also oligohaline and slightly alkaline lake with strong anthropogenic influence through intensive agriculture in the catchment area and artificial channel towards the sea that allows coastal water to enter the lake during low water level. Synedropsis roundii was part of phytoplankton in all three investigated years, although with very different biomass values and proportion in total phytoplankton biomass. Maximum values were measured in 2017 when biomass of S. roundii was 3.55 mgL-1 with proportion to total phytoplankton biomass of high 82%. Comparison of Imboassica lagoon and Lake Vransko suggests that appearance of S. roundii in Europe is conditioned by specific habitat preferences like low salinity, warm water, availability of nutrients and continuous mixing of water column, although a dispersal pattern will stay unknown until more data about the its dispersion are collected.

diatoms, brackish lake, diatom morphology, oligohaline

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