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Shallow lakes in tropical floodplains provide significant ecosystem services that can be altered by natural and anthropogenic forces. Despite their importance, little is known about the infill patterns and timescales and the magnitude of these changes in tropical floodplain lakes. Here, we present a global meta-analysis of sediment core-derived accumulation rate data for shallow floodplain lakes in tropical lowlands to quantify the timescales of basin infill. Environmental variables (e.g., sediment accumulation rates, bathymetry, surface area) were compiled from the literature or derived from remote sensing imagery, resulting in a database (n = 76 lakes) that includes various lake morphologies. Our results show an exponential increase in sediment accumulation rates in many of these lakes over the past 50 years, which we interpret as a response to growing human populations and deforestation, particularly in topographically steep watersheds with pronounced seasonal rainfall. Over centennial periods, tropical floodplain lakes accumulate sediment faster than many other extratropical lakes. The dataset suggests that complete infill of some tropical floodplain lakes will occur in as little as a few centuries. Our findings also reveal the critical environmental and human factors that influence sediment accumulation patterns and affect ecosystem services in shallow tropical floodplain lakes. These findings have important implications for water and sediment management in low latitude watersheds, many of which are located in densely populated and/or developing nations. Made available in DSpace on 2022-09-26T13:09:47Z (GMT). No. of bitstreams: 1 Sediment-Infill-of-Tropical-Floodplain-2022.pdf: 2517609 bytes, checksum: 6bc91753bdc7df5372a66592bcf02913 (MD5) Previous issue date: 2022

The environmental history of the central Pantanal wetlands of western Brazil is inferred for the last 19 kyrs based on a multi-indicator paleolimnological analysis of a sediment core from Lake Negra. The core, dated by 14C and OSL, shows variations in the abundance, diversity, and preservation of sponge spicules and phytoliths through time, consistent with changing aquatic environments. In the late Pleistocene, Lake Negra was influenced by a strong monsoon and fluvial depositional processes, whereas in the Holocene, there was a drier interval where the lake was more isolated on the floodplain. Hiatuses in the stratigraphy resulted from both wet and dry conditions, through fluvial channel scour or subaerial exposure of the lake floor, respectively. Data suggest that floodplain lakes in the Pantanal wetlands and similar riverine wetlands respond in a complex and, at times, indirect manner to climate change, and the dynamics of the adjacent fluvial system must be accounted for when interpreting paleohydrology and vegetation patterns. Made available in DSpace on 2019-09-26T00:41:54Z (GMT). No. of bitstreams: 1 Spongespiculeandphytolith2019.pdf: 4067671 bytes, checksum: 5caced2646298e03d3b5b5e1a77f9810 (MD5) Previous issue date: 2019

The Pantanal is the most conserved biome in Brazil and among the last wild refuges in South America, but intensification of agriculture and other land use changes present challenges for protecting this exceptionally biodiverse wetland ecosystem. m. Recent studies have shed new light on the origins and biogeochemistry of a suite of >600 small saline-alkaline lakes in Nhecolândia, a floodplain setting located south ofthe Taquari River in south-central Pantanal. These soda lakes form a unique aquatic environment in Pantanal and nascent research on their geomicrobiology suggests that their biota may be analogous to early life, and extreme life in Earth?s deep biosphere. We argue that the conservation of the soda lakes in the lower Nhecolândia region should be an important strategic component of any conservation plan that aims to mitigate the advance of unsustainable land-use change in the Pantanal. Soda lake conservation has important implications for the carbon cycle, as these landforms sequester carbon dioxide and transmit considerably lower concentrations of methane in comparison to macrophyte-rich freshwater lakes in the region. Further, minerals precipitated in the saline-alkaline lakes are leveraged for cattle consumption, and therefore the continued presence of the lakes is critical for allowing pantaneiro ranchers to pursue certified organic, sustainable beef production systems. Beyond protecting soda lakes and their surrounding forests (mata de cordilheiras) for food systems security, the conservation strategy would also allow further research of little studied extremophile biodiversity and biogeochemistry, with potential for biotechnological innovations attendant to UN Sustainable Development Goals. Made available in DSpace on 2019-09-26T00:43:53Z (GMT). No. of bitstreams: 1 ThesodalakesNhecolandia2019.pdf: 3939848 bytes, checksum: 11e2681e26fc1e0d00afe58641bff8b6 (MD5) Previous issue date: 2019