The Effect of Dreissena polymorpha on Bacterioplankton, Nematode Fauna and their Relations to Environmental Factors in Ogosta Reservoir (Danube Basin)

Abstract

Spatial, seasonal, and annual bacterioplankton dynamics in recently infested by the species Dreissena polymorpha Ogosta Reservoir were studied for the first time during three year period. Bacterioplankton total number was higher in spring in ecotone zones, than in summer at thermocline. NH4-N, PO4-P, turbidity, dissolved oxygen, COD and chlorophyll-a correlate positively, while transparency and Ca2+ negatively with bacteria. Nematode species composition, included 22 species studied (13 rarely found and Rhabditis brevispina new for Bulgaria) belonging to nine families. The D. polymorpha impact is positive on nematodes and phytoplankton, negative on zooplankton and bacterioplankton, but weak positive on larger bacteria, rods and attached bacteria.

A Morphometric Approach to Understand Prokaryoplankton: A Study in the Sicily Channel (Central Mediterranean Sea)

“…Such trait-based studies suggest a significant ecological role in structuring the planktonic food web in relation to bottom-up/top-down controls [2]. In fact, in aquatic systems, protozoan predation is selective on the size and shape of prokaryotic cells (top-down pressure) [3], and bottom-up control affects the variability in microbial community phenotypic traits [4]. In addition, the dimensional characteristics of prokaryotic cells are of great importance for their use in estimating biomass using a conversion factor to transform cell numbers to carbon content.…”