Microfitobenton del Canal Mercante (Provincia de Buenos Aires) en dos condiciones hidrológicas

Abstract

In lotic environments, the erosion-sedimentation processes related to the hydrological conditions differ throughout the hydrological cycle, mainly due to rainfall. These processes can produce disturbances in the phytobenthic community. In canals, the current velocity and the water level are the main forcing variables that act on benthic communities, promoting changes in their structure, composition and biomass. Sediment samples were collected in the canal Mercante during two hydrological conditions: 1) at the beginning of spring, during a period of low rainfall (September 2009) and 2) in early autumn after a summer period with heavy rains (March 2010) to determine the content of organic matter, total phosphorus, chlorophyll a, and also the abundance of microphytobenthic individuals and cells. Simultaneously, some variables were measured in the water column. We identified two states of the community that could be associated with the phenomena of erosion / deposition related to the effect of water flow. In September the algal community in sediments showed a vertical architecture, mainly constituted by benthic algae among which several species had an aggregated distribution. In March, a decrease of the proportion and number of benthic algae was observed coinciding with the presence of planktonic species in sediments. Some benthic taxa exhibited similar abundances in the two periods and could be consider as tolerant to changes in flow velocity and as typical members of the canal Mercante. In conclusion, hydrological changes could have a significant role on the structure and dynamic of phytobenthon.