Effects of river bed regulation on habitats and communities: A case study for ostracods in the Oder River, Poland

Abstract

The effects of damming, groyne building, and channelizing on habitats and ostracod assemblages in the Oder River, one of the six largest European river systems, were analyzed. Regulation works had been conducted on the river from the 18th to the beginning of the 20th century. Main objectives of the study were to detect the effect of river bed regulation on attributes of habitats and ostracod communities. The values of nitrogen were the highest in the dammed stretch and the lowest in the channelized one. As for conductivity, TDS (total dissolved solids) and salinity were the highest in the groyned stretch. Hardness had the highest values in the channelized and groyned stretches. The lowest visibility was noted in the dammed stretched. The stretch influenced by damming was dominated by habitats with a considerable proportion of detritus in sediments. In the stretch influenced by groynes, the proportions of habitats with mineral and organic substrates were similar and the proportion of habitats covered with vegetation was the highest. Habitats with rocky, sandy bottoms dominated in the channelized stretch and nearly half of the habitats were covered with vegetation. The highest ostracod density characterized the groyned stretch (658 ind · m−2), was moderate in the case of the dammed stretch (290 ind · m−2) and the lowest in the channelized one (107 ind · m−2). Bradleystrandesia reticulata, Candona neglecta, and Limnocythere inopinata dominated in the groyned and channelized stretches. Cypridopsis vidua, Darwinula stevensoni, and Pseudocandona compressa dominated in the dammed stretch. The type of river bed regulation significantly differentiated both habitats and ostracod assemblages. Differences among ostracod assemblages were related to particular species, but also regarding density and evenness. The degree of vegetation coverage and detritus content in the sediments were strong predictors for ostracod community composition.