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Microplastics are a global ubiquitous problem, which is becoming a major issue of concern at scientific and political levels around the world. This study presents physical and chemical characterizations of microplastic debris and a comparison between the spatial distribution and anthropogenic activities in 4 Panamanian beaches located in both sides of the Isthmus. Two of them (Juan Diaz and San Carlos beaches) are located toward the Pacific Ocean, Panamá Province, whereas the others (Palenque and Punta Galeta beaches) are located at the Caribbean Sea, Colón Province. They were chosen to show different landscape management and environmental impacts: touristic and protected areas; coastal areas that receive pollutants and marine litter from urban rivers or are used for local fishing activities. Plastic debris samples were collected and visually analyzed following the protocol proposed by the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP). The physical characterization of the samples consisted in the determination of variables associated with the number of plastic particles, shape, color, and size. The characterization of the polymers was performed by the attenuated total reflectance-Fourier transform infrared spectroscopy technique. A high concentration of microplastics (353 items/m2) were found at the studied sites at the Caribbean coast, whereas a lesser concentration with a greater diversity of shapes and polymer categories were found at the Pacific Coast (187 items/m2). The results indicate that, in addition to anthropogenic activities, the proximity to Panama Canal installations, as well as seasonality, natural phenomena, winds, and ocean currents may be influencing the increase in microplastic contents and the types of polymers observed.

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Geomorphological features and sedimentary characteristics are analized from five sets of shallow sediment cores collected in lakes in the Fildes Peninsula, King George Island. The geomorphology of the area was observed and sediments samples were obtained at field activities during the XXXI Brazilian Antarctic Operation (March-April/2013). Biogeochemical characteristics, physical parameters, mineralogical composition, particle size distribution, macroscopic characteristics of the sediments and satellite images were analized. Preliminary results indicate climatic and environmental changes in north-south transect of the peninsula. The mineralogical composition is associated with geological structure of the area, where basaltic rocks predominate. The particle size variation reflects different sediment source environments. Macroscopic analysis and mineralogical composition variation reflect the action of weathering along the peninsula. The sediments also have potential mineralization and subsequent release of greenhouse gases. A preliminary map of the classification of the lakes is presented. In addition, it was identified that wetland sediment presents methane production rates (CH4) about 40 times larger and more sensitive to the effect of global warming compared to lake sediment. Subpolar aquatic ecosystems sediments from Maritime Antarctica can be a preferential site for the effects of climate variability.

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Methane (CH4) oxidation is a critical process to reduce CH4 emissions from aquatic environments to the atmosphere. Considering the continuous increase in nitrogen in rivers, lakes, and lagoons from human sources, we re-evaluated the still controversial potential effect of inorganic nitrogen on CH4 oxidation. Here, we approached three shallow coastal lagoons that represent great environmental heterogeneity and used slurry sediments as a model system. The addition of ammonium chloride (NH4Cl) and potassium nitrate (KNO3) significantly stimulated CH4 oxidation in the sediments of all studied lagoons, indicating the potential limitation of nitrogen for the growth of CH4 oxidizing bacteria. Our findings contrast to some previous reports, where ammonium and nitrate inhibited CH4 oxidation in sediments. Indeed, our experiment was performed in a more realistic range in relation to natural concentrations of inorganic nitrogen in aquatic systems (0.5 to 1 mM) and was opposed to extreme concentrations previously used (2 to 50 mM). Our results point to the need to further assess the connection between nitrogen inputs and CH4 budgets in aquatic sediments, considering the potential fuel for CH4 oxidation that may affect the global greenhouse gas balance

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