Effects of dredging operations on soft bottom macrofauna in a harbor in the Patos Lagoon estuarine region of southern Brazil

Abstract

An evaluation was made of the effects of dredging on the soft bottom community in the channel of the Rio Grande harbor in the Patos Lagoon estuarine region of southern Brazil. During four seasonal cruises, samples were collected from nine biological stations, one of which was located outside the dredged area. Three macrobenthic samples were collected on each cruise from each station, using a 0.08 m2 van Veen grab. A cluster analysis was applied to group summer and autumn cruise stations before the dredging period, revealing larger numbers of species (35-36 spp.) and higher densities of organisms. The station located outside the dredging area was always included in this group, regardless of the sampling period or conditions of salinity. Another group comprised the winter and spring stations during the dredging period. This group was characterized by stations with the fewest species (20-18 spp.) and the lowest and most variable organism densities. The efficient strategies of resilience of the dominant estuarine species may minimize the effects of dredging on the biota through the rapid recolonization of the soft bottom of the harbor channel.

Soft-bottom polychaetes from the Brazilian harbors of Mucuripe and Pecém (state of Ceará) and Santos (state of São Paulo)

“…Regarding the occurrence of species, recent literature was checked and data were compared with records provided for Patos Lagoon (Bemvenuti et al 2005), the states of Santa Catarina (Almeida et al 2012) and Paraná (Lana et al 2006), São Sebastião Channel (Pires-Vanin et al 2014), São Paulo continental shelf (Paiva 1993), Guanabara Bay (Santi and Tavares 2009) and Vitória Bay Estuarine System (Nalesso et al 2005). All taxa that occurred in this study were previously found in those regions.…”

“…Brazilian coast has 34 seaports and some studies have demonstrated degradation of sediment quality associated to port areas, with negative effects on benthic fauna (Bemvenuti et al 2005;Abessa et al 2008;Choueri et al 2009). Most investigations focused on ecotoxicological aspects of sediment contamination and their effects on soft-bottom communities, and thus, the record of the species has been poorly explored.…”

Biodiversidade no estuário do Saco da Fazenda, Itajaí-SC

“…A atividade de dragagem em áreas costeiras constitui um impacto comum, seja para facilitar a entrada de navios em portos ou para execução de obras costeiras 22 . Dragagens promovem a remoção da camada superficial do sedimento, causando mudanças na estrutura e dinâmica das comunidades bentônicas, assim como dispersão na coluna d'água de poluentes eventualmente retidos no fundo 5,23 Apesar da destruição de habitats bentônicos e da elevada mortalidade de organismos durante o período de dragagem, ocorreu um incremento no número de espécies, de exemplares e biomassa, após o período de instabilidade; possivelmente influenciado pelo aumento da profundidade, melhoria dos padrões de circulação local e do maior ingresso de peixes no estuário.…”

Spatial Patterns in Diversity and Distribution of Benthic Molluscs in a Weak Tidal Tropical Lagoon

“…This variability is dependent on physical and chemical factors and biological interactions. Salinity fluctuations in estuarine systems have a strong influence on temporal patterns and daily and inter-annual variations; sediment characteristics have more influence on the spatial structure of benthic assemblages (Neves et al, 2012).Other factors should not be disregarded, since they can act in synergy (Bemvenuti et al, 2005). Benthic macrofauna in estuarine systems forms a mosaic of patches, which are maintained by a variety of disturbances and other biotic and abiotic factors (Morrisey et al, 1992).…”