Effects of food web complexity on top-down control in tropical lakes

Top-down control in ecosystems is dependent on food web structure. In this study, we developed 126 models describing different trophic link combinations in order to assess the effects of food web structure on the top-down response of shallow tropical lakes. We evaluated the effects of the presence of invertebrate predators, large-bodied herbivorous zooplankton and the degree of omnivory. The results showed that the presence of invertebrate predators and large-bodied herbivorous zooplankton can invert the relation between planktivorous/omnivorous fish and producers (algae). The fact that large herbivores are absent in tropical lakes and invertebrate predators are present in large quantities results in a positive correlation between piscivorous fish and algae biomass, contradicting the classical top-down response described for temperate lakes. We show that omnivory should not be analyzed as a feeding strategy in itself. Omnivory affects many food web processes and its effects are dependent on the trophic level. In our models, omnivory in intermediate trophic levels dampened the top-down control by fish, but omnivory in top trophic levels has an opposite effect increasing the fish carrying capacity and also the strength of the top-down trophic cascade, while simultaneously decreasing the shortest chain length between fish and algae, thus reversing the relation between these two trophic levels.</p

Benthic Macroinvertebrate Diversity in the Middle Doce River Basin, Brazil

This resource contains a checklist of the benthic macroinvertebrate community sampled biannually from 1999 to 2010 in eight natural lakes from the middle Rio Doce Valley lake system and eight river segments in the Piracicaba River basin (sub-basin of Doce river), Minas Gerais State, Brazil. Three of the lakes are located inside a protected state park and are surrounded by preserved vegetation (Atlantic Forest). The other five lakes are in private properties, surrounded by Eucalyptus plantations. The seven stretches of rivers have a distinct degree of anthropogenic impacts. Samples were collected with a kick net and fixed with formaldehyde solution. Four phyla were represented: Mollusca, Annelida, Arthropoda, and Platyhelminthes. For Insecta, 76 families were identified, one family was identified for Crustacea, and nine families were identified for Mollusca. This subproject belongs to the International Long-Term Ecological Research Project (ILTER&mdash;Programa de Pesquisas Ecol&oacute;gicas de Longa Dura&ccedil;&atilde;o&mdash;PELD) site 4