Many inland waters exhibit complete or partial desiccation, or have vanished due to global change, exposing sediments to the atmosphere. Yet, data on carbon dioxide (CO₂) emissions from these sediments are too scarce to upscale emissions for global estimates or to understand their fundamental drivers. Here, we present the results of a global survey covering 196 dry inland waters across diverse ecosystem types and climate zones. We show that their CO₂ emissions share fundamental drivers and constitute a substantial fraction of the carbon cycled by inland waters. CO₂ emissions were consistent across ecosystem types and climate zones, with local characteristics explaining much of the variability. Accounting for such emissions increases global estimates of carbon emissions from inland waters by 6% (~0.12 Pg C y⁻¹). Our results indicate that emissions from dry inland waters represent a significant and likely increasing component of the inland waters carbon cycle.

However, the inundation pattern of the Pantanal has been changing. For years researchers have shown that the Pantanal is sensitive to environment transformation, where faster flow and increased sediment loading may harm the inundation of the Pantanal (^{Hamilton, 2002}; ^{Junk et al., 2012}, ²⁰¹⁴; ^{De Campos et al., 2020}). Direct activities in the catchment area of the Pantanal, as the construction of dams (^{Da Silva & Girard, 2005}; ^{Da Silva et al., 2015}), and in the Paraguay River itself, as the waterway implementation (^{Gottgens et al., 2001}) impact the Pantanal inundation patterns. Moreover, we argue that the association of the direct activities and the climate change exert a fundamental effect on the river water level and the inundation time implying in serious consequences to the flood pulse of the Pantanal.

Aquaculture is increasing globally, providing protein to a growing population, but little is known regarding the nutrient budgets in aquaculture. To obtain insight into how management practices impact nutrient fluxes in freshwater aquaculture earthen ponds worldwide, we conducted a literature review. Our literature search yielded 23 papers in which nutrient budgets were reported. Our results showed that the main nutrient inputs are inlet water, feed, and fertilizers, but they varied according to location and management practices. Overall, feed and fertilizers constituted the predominant nutrient sources, accounting for up to 99% of the total inputs. The most quantified outputs were outlet water, fish, and sedimentation. Our findings indicate that only up to 20% of carbon, 45% of nitrogen, and 60% of phosphorus are assimilated by the fish. In some systems, up to 80% of carbon, 80% of nitrogen, and 60% of phosphorus accumulate in pond bottoms; in other systems, the outflow represents substantial losses of up to 16% of carbon, 76% of nitrogen, and 55% of phosphorus. More insight into nutrients’ fate in fishponds is crucial from a sustainability perspective, as feed and fertilizer use can likely be optimized, reducing operational costs and the potential impact on the surrounding environment and atmospheric greenhouse gas concentrations.

Ingestion of fish is considered the main pathway of human exposure to methylmercury (MeHg), particularly for riverside populations, where fish is the main source of protein. The objective of this study was to estimate concentration of MeHg based on total concentration of mercury in muscles of three species of carnivorous fish: Boulengerella cuvieri (bicuda), Serrasalmus rhombeus (piranha), and Hydrolycus armatus (cachorra), collected from Teles Pires River, Brazil. Furthermore, we calculated human health risk related to MeHg contamination caused by fish consumption. Fish were collected in 20 field campaigns from December 2011 to September 2016 at Teles Pires River, in area of influence of Colíder hydroelectric plant. Risk index (RI) related to ingestion of MeHg through fish intake was calculated considering that MeHg corresponds to around 90% of mercury in fish. There were no significant differences in average mercury concentration between all species: S. rhombeus (0.304 mg/kg^–1), H. armatus (0.229 mg/kg^–1), and B. cuvieri (0.199 mg/kg^–1). RI calculated for sensitive groups (lactating women, breastfeeding infants and children) and RI calculated for general population presented average values, suggesting adverse health effects. This first assessment on MeHg and human exposure to people from Teles Pires River area through fish consumption suggests that mercury concentrations might be posing health adverse effects on people of this sensitive group. Further studies involving more fish specimens and considering fish biological factors are needed to fully understand health risks of mercury exposure to humans in this region.