CONICET | Buscador de Institutos y Recursos Humanos

Eutrophication due to anthropogenic supply of nitrogen is one of the major impacts of human activities on coastal ecosystems worldwide. As a consequence of the high availability of nutrients there is an increment of primary production followed by changes in composition and abundance of flora and fauna. Advanced states of eutrophication are characterized by the replacement of the original vegetation by dominant opportunistic seaweeds and by the reduction of abundance and diversity of consumers. This process occurs mostly in estuaries, bay, and semi-closed coastal areas where the nutrients originated in land (e.g., fertilizers, wastewaters) are retained due to the low water exchange, and then can be assimilated by opportunistic seaweeds. San Antonio bay (Patagonia, Argentina, 40º 48´ S) is a macrotidal system (up to 9 m) where signs of eutrophication (high nutrient concentration, seaweed blooms, high growth rate of macroalgae) have been reported. Here we evaluated the response to eutrophication in terms of abundance and diversity of flora and fauna in this semi-desert macrotidal coastal system. We compared abundances and species composition of macroalagae, small infaunal and epifaunal invertebrates, and birds associated to tidal channels of the San Antonio Bay subject to contrasting anthropogenic influence. Macroalgae was more abundant and diverse in the channel closer to human activity where nutrient concentrations were also higher. In contrast to other eutrophic sites, small invertebrates and birds were also more abundant and diverse in the channel with macroalgal blooms and high nutrient concentration. The large water flushing during the tidal cycle could prevent anoxic or hypoxic events making the environment suitable for consumers. Thus, this could be a case in which eutrophication supports high densities of consumers by increasing food availability, rather than negatively affect the survival of organisms

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