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Assessing zooplankton biodiversity is essential to support freshwater management/conservation programs. Here, we investigated the zooplankton community structure from 180 shallow lakes in northeastern Brazil and analyzed them according to biome (Atlantic Forest or Caatinga), the origin of ecosystems (natural or man-made lakes), and habitat type (pelagic or littoral). Additionally, we provided an updated list of zooplankton species. We registered 227 species (137 Rotifera, 65 Cladocera, 25 Copepoda). The most common species of each major group among all lakes were the cladoceran Ceriodaphina cornuta, the rotifers Brachionus havanaensis and Lecane bulla, and the copepod Termocyclops decipiens. Species related to aquatic vegetation, as the Lecanidae rotifers and phytophilous cladocerans, were more frequent along Atlantic Forest biome and natural lakes. On the other hand, species that are bioindicators of eutrophic waters were more common at the Caatinga biome and man-made lakes. Atlantic Forest and Caatinga biomes had similar species richness, but different community compositions for all zooplankton groups, reinforcing the Caatinga significance for the Brazilian aquatic biodiversity. The type of habitat was the most important factor structuring species richness, with higher richness in the littoral region when compared to the pelagic. A result of many unique species of Cladocera and Rotifera associated with the aquatic vegetation were observed. The findings demonstrated that conservation/management plans cannot generalize zooplankton species distribution across different biomes, origins and even within a single lake, between the pelagic and littoral zones. This study provided a zooplankton species list from 180 lakes in northeastern Brazil and showed that species distribution, richness and composition vary according to biome (Atlantic Forest or Caatinga), the lake origin (natural or man-made lakes), and the lake habitat (pelagic or littoral). [ABSTRACT FROM AUTHOR]

Predation can generate a cascading effect (top-down control) within the aquatic food web. On the other hand, the bottom-up control can also significantly influence the behavior patterns of shredders, especially on their leaf-shredding activity. We aimed to assess the individual and interactive effects of the predation risk by fishes from the genus Astyanax and the quality of leaf discs in the behavioral patterns of shredders from the genus Phylloicus (Trichoptera). The experimental design consisted of two levels of predation risk (absence and presence) and two levels of quality of leaf discs (high and low) in three experimental blocks. All experiments were run for nine days. Our results showed that the quality of the leaf discs affected the percentage of the general body movements of Phylloicus sp, with these caddisflies foraging for more extended periods in the presence of high-quality leaf discs. Moreover, the presence of invertebrates in cases can be influenced by the detritus quality and the interaction between predation risk and detritus quality. Therefore, the predation associated with low-quality nutrition might affect the behavioral patterns of Phylloicus sp., reflecting a shorter time spent in the construction of its larval case, which might lead to higher predation. This might explain this functional feeding group's low abundance and density in tropical streams. On the other hand, their capacity to consume their larval case could be an adaptative advantage over other shredders. Still, more field and microcosm experiments are necessary to arrive reality of tropical streams. We showed a way to explain the natural selection of this species and how interactions are running now. [ABSTRACT FROM AUTHOR]

Globally, conversion of pristine areas to anthropogenic landscapes is one of the main causes of ecosystem service losses. Land uses associated with urbanization and farming can be major sources of pollution to freshwaters promoting artificial inputs of several elements, leading to impaired water quality. However, how the effects of land use on freshwater quality are contingent on properties of the local landscape and climate is still poorly understood. The aim of this study was to evaluate the effects of landscape properties (morphometric measurements of lakes and their catchments), precipitation patterns, and land use properties (extent and proximity of the land use to freshwaters) on water quality of 98 natural lakes and reservoirs in northeast Brazil. Water quality impairment (WQI) was expressed as a composite variable incorporating parameters correlated with eutrophication including nitrogen (N), phosphorus (P) and Chlorophyll-a concentration. Regression tree analysis showed that WQI is mainly related to highly impacted "buffer areas". However, the effects of land use in these adjacent lands were contingent on precipitation variability for 13% of waterbodies and on surface area of the buffer in relation to the volume of waterbody (BA:Vol) for 87% of waterbodies. Overall, effects on WQI originating from the land use in the adjacent portion of the lake were amplified by high precipitation variability for ecosystems with highly impacted buffer areas and by high BA:Vol for ecosystems with less impacted buffer areas, indicating that ecosystems subjected to intense episodic rainfall events (e.g. storms) and higher buffer areas relative to aquatic ecosystem size (i.e. small waterbodies) are more susceptible to impacts of land use. Land use at the catchment scale was important for the largest ecosystems. Thus, our findings point toward the need for considering a holistic approach to managing water quality, which includes watershed management within the context of climate change. Unlabelled Image • Landscape features and precipitation can mediate land use effects on water quality. • Human land use near shores of lakes and reservoirs decreases their water quality. • Precipitation patterns mediate the effects of land use on water quality. • Climate and geomorphology of lakes are needed to understand land use effects. • Effective policies for climate change and land use are vital to protect freshwater. [ABSTRACT FROM AUTHOR]

The role of tropical lakes and reservoirs in the global carbon cycle has received increasing attention in the past decade, but our understanding of its variability is still limited. The metabolism of tropical systems may differ profoundly from temperate systems due to the higher temperatures and wider variations in precipitation. Here, we investigated the spatial and temporal patterns of the variability in the partial pressure of carbon dioxide (pCO 2 ) and its drivers in a set of 102 low-latitude lakes and reservoirs that encompass wide gradients of precipitation, productivity and landscape properties (lake area, perimeter-to-area ratio, catchment size, catchment area-to-lake area ratio, and types of catchment land use). We used multiple regressions and structural equation modeling (SEM) to determine the direct and indirect effects of the main in-lake variables and landscape properties on the water pCO 2 variance. We found that these systems were mostly supersaturated with CO 2 (92% spatially and 72% seasonally) regardless of their trophic status and landscape properties. The pCO 2 values (9-40,020 μatm) were within the range found in tropical ecosystems, and higher (p < 0.005) than pCO 2 values recorded from high-latitude ecosystems. Water volume had a negative effect on the trophic state (r = -0.63), which mediated a positive indirect effect on pCO 2 (r = 0.4), representing an important negative feedback in the context of climate change-driven reduction in precipitation. Our results demonstrated that precipitation drives the pCO 2 seasonal variability, with significantly higher pCO 2 during the rainy season (F = 16.67; p < 0.001), due to two potential main mechanisms: (1) phytoplankton dilution and (2) increasing inputs of terrestrial CO 2 from the catchment. We conclude that at low latitudes, precipitation is a major climatic driver of pCO 2 variability by influencing volume variations and linking lentic ecosystems to their catchments., (Copyright © 2019 Elsevier B.V. All rights reserved.)