You are here:
Contribution of Allochthonous Carbon Subsidies to the Minho Estuary Lower Food Web
Citation:
DIAS, E., P. MORAIS, A. M. COTTER, C. ANTUNES, AND J. HOFFMAN. Contribution of Allochthonous Carbon Subsidies to the Minho Estuary Lower Food Web. Presented at Ecology and Conservation of Freshwater Fish Conference, Vila Nova de Cerveria, PORTUGAL, May 28 - June 02, 2012.
Impact/Purpose:
To document research results
Description:
To study the contribution of autochthonous and allochthonous organic matter (OM) sources fuelling the lower food web in Minho River estuary (N-Portugal, Europe), we characterized the carbon (?13C) and nitrogen (?15N) stable isotope ratios of zooplankton and their potential OM sources, as well as the concentration and stable isotope ratios of dissolved inorganic carbon (DIC) and particulate OM (POM) along the estuarine salinity gradient, during a summer flow base. The ?13CDIC values were lowest in the tidal freshwater (TFW) portion and higher toward the river mouth, following the expected conservative mixing. In the TFW portion, particulate organic carbon (POC) ?13CPOC values (bottom: -28.5‰ to -25.5‰; surface: -29.3‰ to -26.3‰) and C:N (>10) of particulate samples indicated that terrestrial-derived sediment comprised a large portion of the bulk POM pool. In the polyhaline portion, ?13CPOC values (bottom: -20.5‰ to -18.8‰; surface: -25.5‰ to -23.2‰) indicated that the bulk POM pool was generally derived from phytoplankton. In the brackish estuary, zooplankton ?13C values were similar to bottom ?13CPOC values, suggesting that marine-derived OM provided a subsidy to the planktonic food web. In contrast, zooplankton ?13C values in the TFW were similar to surface and bottom ?13CPOC values, suggesting increasing importance of terrestrial- derived OM. Our stable isotope data suggest that the Minho River estuary has a high degree of connectivity along the estuarine salinity gradient and that both marine and freshwater inputs provide a food web subsidy. Therefore, any activity that disconnect the estuary from its adjacent systems (e.g. river, sea, land) may have profound impacts on the estuarine food web.