Does dredging activity exert an influence on benthic macrofauna in tropical estuaries? Case study on the northern coast of Brazil (original) (raw)
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Ecological Engineering, 2009
From July 2006 to November 2007 the effects of sediment disposal on a macrobenthic association were evaluated at the dredged material disposal site, located 3 km northeast of Itajaí Harbour navigation channel. Seven sample sites were chosen, five inside the licensed disposal area and two outside. Five samples were collected from each site with a 0.042 m 2 Van-Veen grab. Nine sampling campaigns took place, one before, one during, and seven after the disposal operations. Evaluations were carried out through sediment and macrofauna composition analysis. An increase in coarse fractions of sediments was found during the first months, mainly within the licensed disposal area. Sites outside the area kept the same granulometric characteristics. Nested ANOVA showed that abundance, taxa richness and Shannon-Weaver diversity were significantly smaller after the disposal, and recovered the initial mean values after the disposal ends. PERMANOVA showed a high heterogeneity between the sites. It decreased until the fifth month after disposal operations, mainly in the sites inside the licensed area. These sites were characterized by low abundance and high variability among the samples. Eight to 16 months after disposal sites recovered their heterogeneity, indicating less variability among the samples of each site and distinct benthic macrofaunal composition. The high volume and frequency of sediment disposal were the main factors of environmental modifications, since the amount of deposited sediment on the seabed probably exceeded the natural sedimentation rates. The presence of a benthic macrofauna adapted to natural/human disturbances was crucial to the fast recovery verified in the area.
2001
The present work is part of an environmental assessment undertaken in the Sado estuary (Southern Channel and Mitrena Peninsula), western coast of Portugal, on February 1999 prior to maintenance dredging works. The macrofauna communities in the study area are generally rich and abundant. A single exception was found: a sampling site in the Mitrena area, with extreme impoverishment, probably related to sediment characteristics, i.e., fluid mud, unfavourable to the establishment of individuals. A comparative analysis of these macrofauna results to previous data from 1986 showed that this biological component had suffered no significant changes, especially as far as the most characteristic species. Although the Southern Channel had been dredged in 1995, no clear signs of such operation were apparent in the present survey.
Marine Pollution Bulletin, 2011
A meta-analysis approach was used to assess the effect of dredging induced changes in sediment composition, under different conditions of natural physical disturbance, for the structure and function of marine benthic macrofaunal communities. Results showed the sensitivity of macrofaunal communities increased as both the proportion of gravel increased and the level of natural physical disturbance decreased. These findings may be explained by the close association of certain taxa with the gravel fraction, and the influence of natural physical disturbance which, as it increases, tends to restrict the colonisation by these species. We conclude that maintaining the gravel content of surface sediments after dredging and, where practicable, locating extraction sites in areas of higher natural disturbance will minimise the potential for long-term negative impacts on the macrofauna. Crown
Open Journal of Marine Science, 2013
The regime of disturbance with natural or anthropogenic origin can lead to the destabilization or even to a mass mortality of benthic communities. Due to the heterogeneity of the disturbance there is a formation of patches in different stages of ecological succession. The aim of this study is to follow and describe the resilience in artificial disturbed sediment in a polluted bay in Rio de Janeiro. The sediment was collected, sterilized and placed inside corers (10 cm diameter × 15 cm height) in the same place where it was collected. We allocated the samples in two structures, the difference between them was that one was placed closed to the bottom and the other was placed 50 cm height. We found 2352 organisms distributed in 14 taxons. The class Polychaeta and the order Amphipoda showed the highest density in all the survey and treatments. We identified the factors influencing the scenarium: different mechanisms of dispersal, the posi-tion of the structures and life history of each group. Disturbance can be the main cause of the patch's diversity found in estuaries and coastal areas. Because of this, monitoring of selected areas becomes an important tool to understand the regime of disturbance as a key factor structuring benthic communities in soft sediment, also suggesting a metapopula-tion dynamics.
2011
Structure of intertidal and subtidal benthic macrofauna in the northeastern region of Todos os Santos Bay (TSB), northeast Brazil, was investigated during a period of two years. Relationships with environmental parameters were studied through uni-and multivariate statistical analyses, and the main distributional patterns shown to be especially related to sediment type and content of organic fractions (Carbon, Nitrogen, Phosphorus), on both temporal and spatial scales. Polychaete annelids accounted for more than 70% of the total fauna and showed low densities, species richness and diversity, except for the area situated on the reef banks. These banks constitute a peculiar environment in relation to the rest of the region by having coarse sediments poor in organic matter and rich in biodetritic carbonates besides an abundant and diverse fauna. The intertidal region and the shallower area nearer to the oil refinery RLAM, with sediments composed mainly of fine sand, seem to constitute an unstable system with few highly dominant species, such as Armandia polyophthalma and Laeonereis acuta. In the other regions of TSB, where muddy bottoms predominated, densities and diversity were low, especially in the stations near the refinery. Here the lowest values of the biological indicators occurred together with the highest organic compound content. In addition, the nearest sites (stations 4 and 7) were sometimes azoic. The adjacent Caboto, considered as a control area at first, presented low density but intermediate values of species diversity, which indicates a less disturbed environment in relation to the pelitic infralittoral in front of the refinery. The results of the ordination analyses evidenced five homogeneous groups of stations (intertidal; reef banks; pelitic infralittoral; mixed sediments; Caboto) with different specific patterns, a fact which seems to be mainly related to granulometry and chemical sediment characteristics. R E S U M O A estrutura da macrofauna bêntica das regiões entre marés e infralitoral raso na porção nordeste da Baia de Todos os Santos (BTS), nordeste do Brasil, foi investigada durante um período de dois anos. Sua relação com os parâmetros ambientais mensurados foi estudada através de análises estatísticas uni-e multivariadas, sendo os principais padrões de distribuição espacial e temporal relacionados principalmente ao tipo de sedimento e ao conteúdo de três indicadores da matéria orgânica sedimentar (Carbono, Nitrogênio e Fósforo). A macrofauna, composta majoritariamente por anelídeos poliqueta (cerca de 70% do total), apresentou baixa densidade, riqueza de espécies e diversidade, exceto nas estações amostradas nos bancos recifais. Estes se destacam como ambiente peculiar, formado por sedimentos grosseiros, pobres em matéria orgânica e ricos em carbonatos, apresentando fauna abundante e diversificada. A região entre marés e os locais rasos adjacentes à refinaria RLAM são formados por sedimentos compostos principalmente por areia fina e baixo conteúdo orgânico e constituem ambiente instável, com poucas espécies altamente dominantes, como Armandia polyophthalma e Laeonereis acuta. Em outras regiões da BTS, onde dominam os sedimentos pelíticos, densidade e diversidade foram muito baixas, especialmente nas proximidades da refinaria. Aqui, os indicadores biológicos apresentaram seus mais baixos valores, sendo as estações mais próximas (4 e 7) algumas vezes azóicas. A região adjacente de Caboto, inicialmente considerada como controle, apresentou baixa densidade, porém valores médios para diversidade, o que indica ser este ambiente relativamente menos perturbado. Foi possível identificar a existência de 5 grupos com padrões estruturais próprios (entremarés; bancos recifais; infralittoral pelitico; sedimentos mistos; Caboto), que parecem estar relacionados principalmente às características físicas e químicas do sedimento.
Community Ecology, 2019
The Santos Estuarine System (SES) is a complex of bays, islands, estuarine channels, and rivers located on the Southeast coast of Brazil, in which multiple contaminant sources are situated in close proximity to mangroves and other protected areas. In this study, the composition and structure of the macrobenthic communities of SES were described and ninetynine species were identified, with the predominance of polychaetes and bivalve mollusks. The benthic assemblages also showed strong signs of stress, as indicated by the low abundance, richness and diversity, and the dominance of opportunistic species. Integrated analysis including sediment characteristics related to natural and anthropogenic factors (e.g., sediment chemistry, and toxicity) indicated that benthic fauna from the inner portions of the SES and vicinities of the SSOS diffusers as Santos Bay were affected. Some locations at the mouths of Santos and Sao Vicente estuaries exhibited moderate disturbance. In other sites from the mouth of São Vicente and Bertioga channels, and Santos Bay, the benthic fauna were considered not degraded. Our results suggest that a combination of both environmental factors and contaminants were responsible for the benthic community structure.
The influence of submerged macroalgae bed on sediment community structure and composition were examined by one year sampling from two distances from the bed in Cabo Frio Island SE, Brazil. The sediment samples for faunal, mean grain size, sorting and organic carbon content were collected with one plastic tube (15 cm in diameter x 15 cm depth). The bottom was characterized by well sorting fine sand. One total of 5278 individuals were collected from august 1996 to November 1997. Polychaetes and mollusks detain 48% of total macrofauna. Transenella stimpsoni (bivalve), Prionospio steenstrupi and Aricidea cf. albatrossae (polychaetes) were the most abundant animals collected. Significant differences were found in total density between locations and time with the greatest density obtained near the macroalgae bed in the end of summer. No significant differences were found in the diversity and evenness, considering the mollusks and polychaetes species, in relation to locations although they...
Structure and dynamics of the macrobenthic communities of Ubatuba Bay, Southeastern Brazilian coast
Brazilian Journal of Oceanography, 2004
Species composition, distribution, density, biomass, diversity and trophic relationships of the macrobenthic communities in Ubatuba Bay, southeastern Brazilian coast, were investigated seasonally from August 1995 to June 1996. Sampling was carried out at 9 stations of between 4 and 13 m depth and taken in duplicate with a 0.1m² van Veen grab. Two hundred and five macrofaunal species were identified, presenting low dominance and frequency. Polychaetes and nematodes dominated, representing 89% of the whole fauna. Spatial variations in the structure of the communities were correlated to sediment type whereas seasonal variations were correlated to the increase in wave size and current disturbance over the substrate during the rainy period. Carnivore and surface deposit-feeder polychaetes were dominant, totalling 81% of the species. Mean grain size, fine sand, very fine sand, silt and clay contents were among the main factors related to the patterns of macrofaunal distribution, density and diversity and to the dominance of trophic groups. Multivariate analysis showed that the area may be divided into two groups of stations each of them characterized, respectively, by the presence of Magelona papillicornis and Mediomastus capensis. R E S U M O A composição, distribuição, densidade, biomassa, diversidade e relações tróficas das comunidades macrobênticas da Enseada de Ubatuba, costa sudeste brasileira, foram estudadas sazonalmente, de agosto de 1995 a junho de 1996. As amostragens foram realizadas em 9 estações de coleta, situadas entre 4 e 13 m de profundidade, e obtidas em duplicata com pegador de fundo van Veen de 0,1 m² de área amostral. Duzentas e cinco espécies macrobênticas foram obtidas, a maioria apresentando baixa dominância e freqüência. Poliquetas e nemátodes dominaram, representando 89% da fauna total. As variações espaciais na estrutura das comunidades foram correlacionadas ao tipo de sedimento, ao passo que as variações temporais o foram com o aumento da perturbação causada pelas ondas e correntes sobre o substrato durante o período de chuvas. Poliquetas carnívoros e detritívoros foram dominantes, totalizando 81% das espécies. O diâmetro médio das partículas, conteúdo de areia fina, areia muito fina, silte e argila estiveram entre os principais fatores relacionados aos padrões de distribuição da fauna, densidade, diversidade e com a dominância dos grupos tróficos. Análises multivariadas mostraram que a área de estudo pode ser dividida em dois grupos de estações, caracterizados, respectivamente, pela presença de Magelona papillicornis e Mediomastus capensis.
Ocean and Coastal Research
Composition and spatiotemporal distribution of benthic macrofauna in a macrotidal estuary on the Amazonian Coast of the State of Maranhão, Brazil The aim of the present study was to analyse the composition and spatiotemporal distribution of the benthic macrofauna in the estuary of the Perizes River (state of Maranhão, Brazil). Biological and environmental samples were collected at five sampling sites along the estuary during six campaigns covering the months of September, October and November 2016 (dry period) and February, March and April 2017 (wet period). Sampling was performed with a van Veen grab sampler (682cm2). Environmental variables as temperature, pH, salinity, dissolved oxygen, saturation and water transparency were measured and related to the biological data at each sampling site. After collection the samples were sieved through a 0.5 mm mesh and the organisms fixed in a 10% formaline solution. A total of 35,597 individuals belonging to 84 taxa were identified, corresponding to Insecta, Mollusca, Crustacea, Annelida, Nematoda, Nemertea, Sipuncula and Collembola. Polychaeta showed the greatest species richness, while Tanaidacea were the most abundant. No gradient was found throughout the sampling sites with regard to the environmental variables, but marked differences were found in the temporal distribution. The temporal distribution of the benthic macrofauna was influenced by salinity and rainfall. Oligochaeta and Tanaidacea were abundant at all sampling sites. Acari were abundant in the inner portion of the estuary, while the number of Ostracoda was very high in the outer portion. The structure of the macrobenthic community differed in composition from the majority of the studies on estuaries, with the dominance of Tanaidacea and Oligochaeta. The higher abundance of Tanaidacea is related to environments rich in fine sediments with organic matter and the occurrence of this characteristics was determinant for the distribution of other taxa. The results indicate that the wet period favours the establishment of the benthic community, as evidenced by the increase in diversity and equitability.