Structure, dynamics and stability of a Mediterranean river food web

Abstract

We present the results of a study of the food web of a Mediterranean river in the four seasons of the year. A high-resolution taxonomic description has been produced to characterise the different community components. We have also determined the trophic relationships among organisms by analysing their gut contents. From the network topology, we extracted several descriptors of structural complexity of the comunity in terms of number of nodes and links. We found a positive relationship between connectance and diversity (both biological and functional). Moreover, we developed and applied a quantitative approach to estimate the link strength, which showed that not all links constituting the network are equally important. In the present paper, we show that the strength of the food-web links vary over time, but there is a natural tendency to keep a small set of strong links throughout the year. However, the existence of two consecutive strong links is not common, meaning that trophic cascades are not promoted.