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In situ application of inorganic fertilizer was used to simulate environmental eutrophication associated with the sugar cane monoculture. Meiofauna community structure is herein used to assess this experimental impact. Nine quadrangular areas (4m² each) were randomly defined in the midlittoral estuarine area. Three of these areas received a high dose of sugar cane fertilizer (375 g/m² Nitrogen-Phosphorus-Potassium), three areas received a low dose of the fertilizer (187.5 g/m²) and the other three areas represented the control. The fertilizer was applied every week. Environmental parameters and meiofauna were sampled using three-to-four week intervals. Six samplings were subsequently performed maintaining this interval. Meiofauna was counted and identified to major taxonomic groups. Meiofauna community structure varied throughout the experimental areas. Control areas maintained their abundance values during the study period, but within the enriched areas meiofauna abundance decreased greatly. MDS and ANOSIM analysis showed significant variation in the meiofauna community structure among experimental areas and also along the experimental period in the enriched areas.
A aplicação in situ de fertilizantes inorgânicos foi utilizada para simular a eutrofização associada ao cultivo da cana-de-açúcar. A estrutura da associação de meiofauna foi analisada com o objetivo de avaliar este impacto. O experimento de enriquecimento do sedimento foi desenvolvido em nove áreas quadrangulares de 4m² distribuídas de forma aleatória no mediolitoral da área estuarina. Três áreas foram enriquecidas com alta concentração (375 g/m²) de NPK (Nitrogênio-Fósforo-Potássio), três com baixa concentração (187,5 g/m²) e as demais tratadas como controle. Os fertilizantes foram aplicados semanalmente. Os parâmetros físico-químicos do sedimento e a meiofauna bentônica foram coletados após três a quatro semanas da aplicação dos fertilizantes. Obedecendo este intervalo foram realizadas 6 amostragens subseqüentes. As amostras foram triadas e a meiofauna contada e identificada em nível de grande grupo. As respostas da meiofauna variaram de acordo com a área: enquanto a área Controle manteve sua abundância total durante todo o experimento, as áreas tratadas apresentaram forte queda nas densidades totais. A ordenação MDS e a análise ANOSIM evidenciaram mudanças significativas na estrutura da associação de meiofauna entre as áreas e também ao longo do experimento nas áreas tratadas

Macrobenthic data from estuaries along the Pernambuco coast in north-eastern Brazil were analysed to evaluate the effect of sieve mesh size (1.0 mm × 0.5 mm) and sampling depth (0–10 cm × 0–20 cm) on the description of infaunal communities, in an attempt to discuss standardized sampling procedures for different ecological studies objectives in these ecosystems. In general, the difference in sieve retention was less evident for biomass but was important for abundance: the 1.0 mm sieve retained only 27% of total individuals but 77% of total biomass. Regarding sampling depth, the 0–10 cm layer contained most individuals (94%) but contributed just 64% of the overall biomass. Although no strong differences in community structure were observed at most sites with the use of different sieves, the correlations among community dissimilarity using different meshes with environmental parameters (organic matter, total-N and microphytobenthos) indicated that the use of the 0.5 mm sieve will allow a better evaluation of the status of these estuaries. The results also highlight the importance of taking the vertical distribution of tropical macrofauna into account for quantitative estimates: for taxa composition and abundance the top layer is clearly essential, whereas for biomass the deeper layers should also be considered.

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