Colonization of artificial substrate by freshwater macroinvertebrates, in the Jacuí River Delta, Rio Grande do Sul State, Brazil

Abstract

Experiments to evaluate the limnic macroinvertebrates that colonize artificial substrates were performed at two experimental stations located in Jacui Channel (CJ) and Cais do Porto (PO), both part of the Jacui Delta in Porto Alegre, RS, southern Brazil. Substrates were built in PET bottles containing an internal nylon screen. In CJ, L. fortunei (8229.0 ind.m-2), Chironomidae (188.9 ind.m-2), and Heleobia piscium (39.6 ind.m-2) presented the highest values of average density. In PO, L. fortunei (3233.0 ind.m-2), Chironomidae (288.9 ind.m-2), and Oligochaeta (211.1 ind.m-2) presented the highest values of average density. The freshwater sponge, Trochospongilla paulula, presented an incrustation area of 0.016m2, that corresponded to 31% of the total external substrate surface (PET bottles). Trochospongilla paulula also grew over the golden mussel valves (epizoism). Significant differences between average densities of Oligochaeta verified in the sustrates from CJ (lowest value) and PO (highest value) were found using the statistics Mann-Whitney Test (p=0.01). Other significant differences (p<0.0001) between the bioincrustation areas of T. paulula in the substrates from CJ (highest value) and PO (lowest value) were found. The average densities of other taxa in substrates from both CJ and PO did not differ statistically. The substrate was adequate for the sampling of macroinvertebrates, especially Porifera, a group that is difficult to sample.

Keywords

• bioincrustation
• biomonitoring
• epizoism
• Limnoperna fortunei
• Trochospongilla paulula