ESTRUCTURA FUNCIONAL DE LA MACROFAUNA BENTÓNICA EN SISTEMAS ESTUARINOS URUGUAYOS

The functional structure of the macrobenthos present in two morphologically different estuarine systems (coastal lagoons and estuaries) was studied. The objective was to determine differences between the predominant functional traits of both systems. Macrobenthos were classified into functional traits through the use of the Biological Trait Analysis (BTA). Given the scale-dependence of the macrobenthos, it was sampled in winter and spring at three spatial scales: habitat (streams, lagoons), habitat sectors (internal, external), and replicate sites (three in each sector). Two hypotheses were tested: (1) the geomorphology of the water body would determine the presence of functional traits and (2) the trophic state of the environment would condition the functional traits. Both hypotheses were true for most of the sites. As a result, it was observed that higher temperatures and finer sediments conditioned the presence of more degraded organic matter and with lower nutritional value in April, lagoons, and internal sectors. This conditioned the presence of surface depositivorous, epifaunal and first and second order opportunistic, typical characteristic of sites disturbed by nutrients. On the contrary, in October, estuaries and external sectors were characterized by filter feeders, infaunal, and organism's sensitive to organic enrichment, typical of undisturbed sites.