Abstract:Aim: The objective of this study was to evaluate the influence of water and sediment characteristics on the abundance, richness and diversity of the benthic invertebrate community in Peri lagoon, a freshwater coastal lagoon located in central coast of Santa Catarina State; Methods: Samplings were performed in April, May and June 2009, in five different sites of Peri lagoon. The samples were taken with an EckmanBirge drag, totalizing 60 for the invertebrate community, and 45 for sediment. Water physicochemical variables were also measured. Environmental influences in benthic community have been measured using a Canonical Correspondence Analysis (CCA). Linear regressions were also plotted for main correlations; Results: A total of 5,535 specimens were collected, identified into 18 taxa. Tanaidacea was the most abundant representing 54% of relative abundance, followed by Diptera (23%), and Ostracoda (17%). The richest family was Chironomidae with 6 taxa. CCA results indicated positive correlation between Chaoborus and Stenocypris with local depth, and negative correlation between Odonata, Gastropoda, Cytheridella and Coleoptera with the finest grains of sediment, as well as between Tanaidacea, Lopescladius, Annelida and Nematoda with both organic matter (OM) content in sediment and local depth. Linear regression analysis demonstrated inverse relation of Tanaidacea in response to OM (y = 0.6 -0.62.OM) and sand (y = 0.6 -0.6.sand), and of Lopescladius in response to OM (y = 0.37 -0.41. OM) and sand (y = 0.37 -0.46.sand). The fact that Peri lagoon has no marine influence and has Tanaidacea as the most abundant taxa, a group not expected in freshwaters, gives to this lagoon a particular relevance among coastal lagoons. The study concluded that sediment characteristics and local depth are more significant than water variables in determining the benthic community structure in Peri lagoon, which varied in accordance with different local conditions.

Allochthonous organic matter is a major energy source for headwater stream ecosystems. Therefore, examinations of how energy flows throughout these streams requires knowledge of mechanisms driving leaf input, retention and export. In this study we quantified the major input pathways and retention dynamics of coarse particulate organic matter (CPOM) in an Atlantic Rainforest stream in southern Brazil. We hypothesised that much of the temporal variability in the CPOM budget would be driven by precipitation, and thus we focus especially on the importance of vertical v. lateral input pathways, precipitation-driven inputs v. stocks, and composition of CPOM throughout 1 year. Most leaf litter entered the stream by the lateral input pathway (70.5gm–2month–1±108s.d.) compared with the vertical (32.4gm–2 month–1 ±17.5s.d.), and lateral input was correlated with precipitation and bank slope. In addition, torrential rainfall caused a net decrease in CPOM by reduction in the benthic stocks. Finally, six species represented 52.9% of total leaf input, where the most important (~25% of total input) was Schizolobium parahyba. Overall, this research confirms our prediction that the CPOM budget of this Atlantic Rainforest stream is driven in large part by precipitation.

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We review the biologically driven decomposition processes that take place in riverine ecosystems.• We identify important gaps in our understanding of decomposition processes in rivers from temperate and tropical biomes. • We propose a novel analytical approach to predict decomposition processes from metabolic scaling theory. • Using metadata from 30 rivers, we demonstrate that the slope of community size spectra can predict rates of decomposition.