Temporal variability of the macroinvertebrate community associated with Eichhornia azurea (Swarts) Kunth (Pontederiaceae) in a lake marginal to a tropical river

Abstract

Aquatic macroinvertebrates have a close relationship with associated floating macrophytes, especially with the roots. The plantroot mass is an environment favorable to the development of the macroinvertebrate fauna, supplying both food resources and refugeagainst predators. The present study aimed to analyze the structure of the macroinvertebrate community associated with the roots ofEichhornia azurea (Sw.) Kunth (Pontederiaceae) in a lake marginal to a tropical river. Sampling was performed quarterly in three standsof E. azurea. One plant specimen was selected from each stand and five root mass samples were collected. The study was carried out in anextremely rainy year, with high rainfall in July, when the river level increased quickly, causing an extreme inundation and an increase inthe root biomass of E. azurea. A higher abundance of macroinvertebrates was found in April, around four to five times the total densityof the other periods. Taxa richness presented no significant temporal differences. Oligochaeta and Chironomidae were the predominantgroup of invertebrates in all periods. The extraordinary flood in June–July caused a modification in the macroinvertebrate fauna (anincrease in the abundance and a reduction in the taxon richness), and was apparently a controlling factor for the community structure.