Does dredging activity exert an influence on benthic macrofauna in tropical estuaries? Case study on the northern coast of Brazil

The aim of the present study was to investigate the effect of dredging activities on the structure of the macrobenthic community of a port complex in Sao Luis do Maranhao (2 degrees S, Brazil). Sampling was performed on four occasions: pre-dredging, dredging 1 (25% of the material dredged), dredging 2 (75% of the material dredged) and post-dredging. Total mean density was 430.8 +/- 55.0 ind/m2, with 147.76 +/- 280.82 ind/m2 at pre-dredging, 161.90 +/- 285.67 ind/m2 at dredging 1, 53.83 +/- 72.15 ind/m2 at dredging 2 and 67.29 +/- 72.58 ind/m2 after dredging, revealing a reduction during dredging 2. The most representative groups were Polychaeta, Oligochaeta, Crustacea and Mollusca. Lumbrineris sp. (Polychaeta) was present in all sampling periods and was the dominant species. Richness and Shannon diversity of the species were higher in the pre-dredging and post-dredging periods, with reductions during the dredging activities (dredging 1 and 2). Principal component analysis revealed a correlation with granulometry and heavy metals in the sediment. The dredging activities led to a reduction in the macrobenthic community. Moreover, post-dredging recovery was insufficient for the recovery of the community.