Coastal lagoons are usually subjected to several kinds of human impacts, especially eutrophication. The breaching of the sand bar, which separates the lagoon from the ocean, by human action, is a common process used to decrease the negative effects of eutrophication. The aims of this research were to evaluate the effects of the artificial sand bar breaching on the populations of the aquatic macrophyte Typha domingensis and the subsequent effects on nutrients concentration in a tropical coastal lagoon. Samplings were carried out monthly from February/01 to January/02 in a monospecific stand of T. domingensis at Imboassica lagoon (Rio de Janeiro/Brazil). Two sampling sites, in the middle and in the border of the stand, were marked in three different transects. Water depth was measured and the aerial biomass sampled with a 0.25 m 2 quadrat. The macrophyte samples were separated into live and dead material and the shoot length, shoot density and number of leaves were analyzed. All plant material was oven dried till constant weight and net primary production, dead stand crop production and the nutrients release through decomposition were estimated at each site. The decrease in water level due to sand bar opening affected negatively T. domingensis populations, but the most intense effects were observed in the middle of the stand. The shoot mortality was highly enhanced after the sand bar breaching and the nutrients were released through decomposition to the water column. It reflected on an input of 11.5 kg C m )2 , 0.22 kg N m )2 and 0.13 kg P m )2 into the lagoon, which represent from 22.5 to 44.8 ton P and 35.9 to 71.8 ton N to the lagoon. The decrease of nutrients concentration after the sand bar breaching was not successfully accomplished. The decay of T. domingensis stands due to the sand bar breaching neutralized the exportation of nutrients to the ocean, and contributed to the phosphorous increase in the water column. Thus, to a better management of aquatic ecosystems subjected to human eutrophication, the role of aquatic macrophytes decomposition on internal fertilization of aquatic ecosystems should be accounted.
The aim of this study was to evaluate methane concentration in water column and pore water at limnetic and littoral regions of a coastal lagoon. At the littoral region samples were taken from three monospecific macrophytes stands (Typha domingensis, Eleocharis interstincta and Potamogeton stenostachys). The methane concentration in the pore water at the littoral region was higher than the concentration found at the limnetic region in each fraction
Soundscape ecology has gained prominence in the monitoring of marine ecosystems due to its non-invasive characteristics and spatiotemporal efficiency. However, the development of ecoacoustic indices is a recent field that needs to address many challenges to fulfill its great potential, especially in the context of marine ecology. Here, we reviewed the most recent studies that used ecoacoustic indices in marine ecosystems. The literature search was conducted in the Scopus (Elsevier) database and used the chain referral sampling in the list of references of each publication. In total, we identified 27 publications that used ecoacoustic indices in marine environments such as coral reefs, rocky shores, coastal regions, and offshore regions. A total of four major limitations were identified and addressed, including: the challenge to find adequate acoustic bioindicators; the lack of a universal index or standardized protocol; the issue that most acoustic indices applied to marine environments have been developed to be used in terrestrial environments; and the lack of studies that have tested ecoacoustic indices under different environmental conditions. Once these challenges are addressed, the analysis of marine sound based on the interpretation of ecoacoustic indices has a great potential to become one of the most cost-effective tools for monitoring environments.
Aim: Coastal wetlands are potential zones for methane (CH 4 ) production. The present study aims to evaluate the spatial variation of CH 4 production and concentration in ten tropical coastal lagoons, the influence of aquatic macrophytes on the sediment CH 4 concentration and how the magnitude of these potential CH 4 production rates compare to those in other ecosystems. Methods: Sediments were sampled in ten coastal lagoons, with one site in the limnetic region and another site in aquatic macrophyte stands when they were present in the littoral region. We measured the CH 4 production as a potential rate, and CH 4 concentration was directly measured from sediment samples. Results: The highest potential CH 4 production (PMP) rates were found in alkaline and hypersaline lagoons. However, Cabiúnas, which is a freshwater lagoon densely colonized by aquatic macrophytes, also exhibited a high PMP rate. We also observed that the sediment CH 4 concentration in the littoral region was higher than in the limnetic region in all of the investigated lagoons except Paulista, which presented the opposite pattern. The PMP rates observed in the studied lagoons were low compared to other aquatic ecosystems. Conclusion: Our results suggest that the sediments of saline lagoons are important CH 4 production sites, and in general, aquatic macrophytes have a positive influence on methanogenesis, which was evident based on the CH 4 concentrations present in the sediments of these lagoons. Further studies should focus on the processes underlying the CH 4 patterns observed in the tropical coastal lagoons, especially concerning the coupling between CH 4 production and concentration.Resumo: Objetivo: Áreas alagadas costeiras são zonas potenciais para produção de metano (CH 4 ). O presente estudo tem como objetivo avaliar a variação espacial da produção e concentração de CH 4 em dez lagoas costeiras tropicais, a influência de macrófitas aquáticas na concentração de CH 4 no sedimento e como a magnitude dessas taxas de produção potencial de CH 4 é em comparação com outros ecossistemas. Métodos: Os sedimentos foram amostrados em dez lagoas costeiras, com um ponto na região limnética e outro ponto nos bancos de macrófita aquática, quando estas estavam presentes na região litorânea. Nós medimos a produção de CH 4 como uma taxa potencial e a concentração de CH 4 foi diretamente medida das amostras de sedimento. Resultados: As maiores taxas de produção potencial de CH 4 (PPM) foram encontradas em lagoas alcalinas e hipersalinas. Contudo, Cabiúnas, que é uma lagoa de água doce densamente colonizada por macrófitas aquáticas também exibiu alta taxa de PPM. Nós também observamos que a concentração de CH 4 do sedimento na região litorânea foi mais alta que na região limnética em todas as lagoas investigadas, exceto Paulista, que apresentou o padrão oposto. As taxas de produção de CH 4 observadas nessas lagoas estudadas foram baixas comparadas com outros ecossistemas aquáticos. Conclusão: Nossos resultados sugerem que os sedimentos de lagoas salinas são...
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