Ecotoxicology and geostatistical techniques employed in subtropical reservoirs sediments after decades of copper sulfate application

Zooplankton functional diversity in subtropical reservoirs of distinct trophic states (São Paulo state, Brazil)

Studies on functional traits of aquatic communities are useful for understanding the ecosystem dynamics as well as the diversity of ecological niches. Here, we characterize zooplankton functional groups and which limnological factors are responsible to changes in traits. Water samples were collected to evaluate limnological parameters and vertical hauls with plankton net (68 μm) were performed to characterize the community in seven reservoirs (Itupararanga, Atibainha, Salto Grande, Rio Grande, Igaratá, Barra Bonita, and Broa, São Paulo state, Brazil). Each species identified was classified according to a trophic group, reproduction mode, body length, habitat, and feeding habitats. Our results showed a predominance of pelagic suspensory herbivores with cilia (31%) followed by pelagic herbivore suspension filter feeders (17%) and raptorial omnivores (15.38%). The other individuals were categorized as pelagic herbivore suspension with oral device (12.3%), littoral herbivores suspensive with cilia (12.3%), pelagic-sucking herbivores (9.2%), and littoral grazing herbivores (3%). The dominance of herbivores may be influenced by the availability of nutrients, influencing their food sources. The abundance of omnivores engaged in predatory behavior can be attributed to disponible prey, thereby exerting significant repercussions on the organization of biological communities.

Past environmental changes: using sedimentary photosynthetic pigments to enhance subtropical reservoir management

The historical impacts of eutrophication processes were investigated in six subtropical reservoirs (São Paulo, Brazil) using a paleolimnological approach. We questioned whether the levels of pigment indicators of algal biomass could provide information about trophic increase and whether carotenoid pigments could offer additional insights. The following proxies were employed: organic matter, total phosphorus, total nitrogen, photosynthetic pigments (by high-performance liquid chromatography), sedimentation rates, and geochronology (by 210 Pb technique). Principal component analysis indicated a gradient of eutrophication. In eutrophic reservoirs (e.g., Rio Grande and Salto Grande), levels of lutein and zeaxanthin increased over time, suggesting growth of Chlorophyta and Cyanobacteria. These pigments were significantly associated with algal biomass, reflecting their participation in phytoplankton composition. In mesotrophic reservoirs, Broa and Itupararanga, increases and significative linear correlations (r > 0.70) between pigments and nutrients are mainly linked to agricultural and urban activities. In the oligotrophic reservoir Igaratá, lower pigment and nutrient levels reflected lesser human impact and good water quality. This study underscores eutrophication's complexity across subtropical reservoirs. Photosynthetic pigments associated with specific algal groups were informative, especially when correlated with nutrient data. The trophic increase, notably in the 1990s, may have been influenced by neoliberal policies. Integrated pigment and geochemical analysis offers a more precise understanding of eutrophication changes and their ties to human factors. Such research can aid environmental monitoring and sustainable policy development.

Chronostratigraphy elucidates environmental changes in lacustrine sedimentation rates and metal accumulation

All changes taking place in a watershed have repercussions on lacustrine environments, being these, the sink of all activities occurring in the basin. Lake Titicaca, the world's highest and navigable lake, is not unfamiliar with these phenomena that can alter the sedimentation dynamics and metal accumulation. This study aimed to identify temporal trends of sedimentation rates by employing a geochronological analysis (²¹⁰Pb, ¹³⁷Cs) and to propose metal background values in Puno Bay, as well as to identify metal concentrations (As, Ba, Ca, Cr, Cu, K, Mg, Mo, Ni, Pb, Zn) in the projected timeline to propose, for the first time, background values in Puno Bay. Two sediment cores were collected from the outer and inner bays. Sediment rate (SR) was calculated through the excess of ²¹⁰Pb (²¹⁰Pb_xs) applying the Constant Flux Constant Sedimentation (CFCS) model. Results show that SR in the outer bay was 0.48 ± 0.08 cm a^-1 and for the inner bay was 0.64 ± 0.07 cm a^-1. Sediment quality guidelines (SQGs) did not indicate toxicity was likely to occur, except for As. However, enrichment factors (EFs) indicated that all metal accumulation is geogenic. Climatic factors had a marked influence on sedimentation rates for the outer bay, and in the case of the inner bay, it was a sum of climatic and human-based factors.