Ecology of Tidal Freshwater and Estuarine Tubificidae (Oligochaeta)

Abstract

There is an abrupt shift in the community composition of Tubificidae as one proceeds from tidal freshwater to estuarine habitats. Not only does the species composition change but also their relative trophic importance and, to a more variable degree, their importance to the community. Communities from tidal freshwater areas tend to resemble the fauna of large eutrophic lakes while the fauna of estuarine areas is comprised mainly of estuarine endemic and euryhaline marine species. Tidal freshwater forms tend to be larger than estuarine forms and are the major sediment burrowers and bioturbators. Estuarine forms do not appear to be important bioturbators. Competition or interaction with the large and diverse polychaete fauna most likely lessens the importance of oligochaetes in estuarine areas. Where pollution or other factors result in extreme environmental conditions or reduced habitat diversity, estuarine tubificids tend to become more important, while in tidal freshwater areas these conditions result in little change in community composition. The common bond between the faunas inhabiting tidal freshwater and estuarine areas is their opportunistic nature.