Acta Biológica Colombiana
Print version ISSN 0120-548X
RIVERA RONDON, Carlos Alberto et al. Limnological characterization of wetlands of the floodplain of the Orinoco river ( Orinoco , Colombia ). Acta biol.Colomb. [online]. 2010, vol.15, n.1, pp. 145-166. ISSN 0120-548X.
We carried out a physical and chemical characterization of the major rivers, streams and wetlands of the surrounding area of the town of Puerto Carreño ( Vichada , Colombia ) in the flooding and dry seasons, as well as a biological characterization in the dry season. Most of the studied systems showed an acid pH and low ion and nutrient concentrations. The hydrologic regime has an important impact on aquatic ecosystems: during the flooding season, transparency and the concentration of some nutrients increased but conductivity and chlorophyll-a levels decreased. During the dry season, the dominant algal groups were Bacillariophyceae and Zygnemaphyceae, and the taxonomic composition of zooplankton was similar to those found in other systems of the Amazon-Orinoco complex. Macroinvertebrate communities were dominated by Coleoptera, Odonata and Ephemeroptera, and the greatest diversity of functional groups and morphotypes was recorded in litter substrates. Results suggest that the bank vegetation plays a very important role in providing a source of energy and shelter to aquatic communities during the dry season, but at the same time the low mineralization of these ecosystems renders them very susceptible to pollution from urban, agricultural and cattle ranching sources.
Keywords : Orinoco River; flooding pulse; algae; aquatic macroinvertebrates; zooplankton.