As comunidades macrobentÃnicas na avaliaÃÃo da qualidade ambiental de Ãreas estuarinas de Pernambuco

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Estuarine environments are known by its importance in terms of complexity and biodiversity; however, anthropogenic activities continue to have a detrimental effect on its biodiversity levels on a worldwidescale. Several studies have emphasized the role of benthic macroinvertebrates as indicators of environmental quality status in these ecosystems, which have lead a growing number of tools and methods based on macrofauna attributes (abundance, biomass, species composition). Among them, biotic indices has been chosen in terms of accuracy and cost-benefit, being the AMBI (AZTI Marine Biotic Index) the most successfully applied to different geographic areas and under different impact sources. However, few studies regarding ecological characteristic of soft-bottom macrobenthic communities on the Atlantic coast of South America are available and thoroughly concentrated in the south and southeast coasts. Hence, the main objectives of this contribution were to describe composition and distribution of macrobenthos from estuarine areas of Pernambuco and tests if particular sieve mesh sizes (1.0mm x 0.5mm) and sampling depth (0-10cm x 0-20cm) alter the macrobenthic association descriptors; in addition, to examine the efficiency of AMBI index to evaluate the environmental quality of these estuaries. Samples for abiotic variables of water (salinity, temperature, dissolved oxygen and ammonia-N) and sediment (organic matter, granulometry, redox potential, total-N), microphytobenthos and also macrofauna were collected at fourteen estuarine sites located in Pernambuco coastline, in October 2007. A total of 14,257 individuals, from 78 taxa and with a biomass of 83.64gAFDW were observed. In general, the differences between 1.0mm and combined sieves retention are hardly evident for biomass but it is very important for the abundance (1.0mm sieve retained only 28% of total individuals but, at the same time, was responsible for 92% of total biomass). Regarding sampling depth, the top layer (0-10cm) presented almost all individuals (94% total abundance); however, contributed with only 39.06% of the overall biomass. Significant interactions were observed only for âmesh-sieveâ factor in terms of diversity N1 (two-way ANOVA: F1;13=5.17; p=0.02) and community structure (two-way ANOSIM: Rglobal= 0.142; p=0.002). Pearsonâs correlation have selected the variables total-N (r=0.860; p<0.0001), organic matter (r=0.801; p<0.001) and microphytobenthos (r=0.749; p=0.005 and r=0.795; p=0.002, for chlorophyll-a and phaeopigments, respectively) as the most fit for explaining the âchangesâ in fauna from 1.0mm to 0.5mm. The results showed that these estuarine macrobenthos were mainly composed by small species (1,0-0.5mm), thus the use of the 0.5mm sieve will permit a more accurate interpretation of the data; besides for taxa composition and abundance, the top layer (0-10cm) is clearly the most important whereas for biomass the bottom layer (10-20cm) presents this function. In terms of environmental quality, the AMBI index indicated that all ecosystems presented some level of disturbance, ranging from 2.395 (slightly disturbed, in AriquindÃ) to 5.236 (heavily disturbed, in Capibaribe). According to the index, most sites were situated between the slightly-moderate disturbed boundaries, due to higher proportion of Nematoda and Oligochaeta, both assigned here as ecological group III. In summary, AMBI proved to be efficient in evaluating the quality status of Pernambuco estuaries, although its applicability in tropical waters requests some adaptations in speciesâ ecological groups

ASSUNTO(S)

profundidade de amostragem sieve mesh-size qualidade ambiental Ãndice ambi macrobenthos macrobentos oceanografia tamanho da peneira environmental quality status ambi index sampling depth

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