Total nitrogen and pH are key variables for functional structure of zooplanktonic communities in an agropastoral landscape.

Changes in land use are one of the main impacts on aquatic ecosystems. The conversion of natural areas into agropastoral, such as pasture or monocultures, can affect the limnological characteristics of the water that in turn influence the structure of aquatic communities. But the impact is still unclear, particularly on zooplankton communities. The objective of this study was to evaluate the effect of water parameters from eight reservoirs inserted in an agropastoral landscape on the functional structure of zooplankton. The functional characterization of the zooplankton community was based on four traits: body size, feeding type, habitat type, and trophic group. Functional diversity indices (FRic FEve and FDiv) were estimated and modeled water parameters, using generalized additive mixed models (GAAM). The water parameters investigated were total nitrogen (TN) and total phosphorus (TP), dissolved oxygen (OD), temperature and pH. Moreover, we used RDA to analyze the influence of these environmental variables on the sharing of traits among the sample sites. FRic was high in the reservoirs with low TN concentration and low pH values. FEve was also high in low pH and high TP concentration. FDiv was high with unsharp increases of pH and high concentrations of TN and DO. Our analyses showed pH as a key variable for functional diversity, since it was related to the variation in all indices. Data also pointed out changes in diversity functional with small pH changes. The big and medium size, raptorial-cop and filtration-clad functional traits were positively associated with high concentrations of TN and alkaline pH. The small size and filtration-rot were negatively associated with high concentrations of TN and alkaline pH. Density of filtration-rot was lower in pasture landscapes. In conclusion, our study indicated that pH and TN are key variables for the functional structure of zooplanktonic communities in an agropastoral landscape.

Pelagic and littoral cladocerans (Crustacea, Anomopoda and Ctenopoda) from reservoirs of the Northwest of São Paulo State, Brazil / Cladóceros (Crustacea, Anomopoda e Ctenopoda) pelágicos e litorâneos em reservatórios na região noroeste do estado de São Paulo, Brasil

There are few studies on the zooplankton from the northwestern region of São Paulo State, Brazil, compared to other regions of the State. Cladocerans are a very representative zooplankton group with high species diversity. Most of this diversity can be found at littoral zones of lakes and reservoirs, especially those occupied by macrophytes. This study was part of a thematic project FAPESP/BIOTA Program - The Virtual Institute of Biodiversity (www.biotasp.org.br), and its aim is to catalogue and analyze the distribution of cladoceran species (Crustacea, Anomopoda and Ctenopoda) in pelagic and littoral zones from small reservoirs in the northwest of the São Paulo State, in dry and rainy seasons. Zooplankton samplings were carried out in littoral and pelagic zone of 10 small shallow reservoirs (mean depth: 2.8 m) using a plankton 45 µm mesh net. Water physical and chemical parameters were also monitored with a multiparameter Horiba U10. pH and dissolved oxygen concentration were lower at rainy than dry seasons, indicating high decomposition rates of organic matter introduced from the rural environment, being the main factor contributing to reservoirs' eutrophication. Fifty eight cladocerans species were recorded, with four new occurrences for the São Paulo State. This high richness contrasts with the high devastation of the northwestern region in the State. During the two seasons, littoral zones presented higher cladoceran richness and diversity than pelagic zone. Littoral zones with higher macrophytes diversity also showed higher cladocerans richness and diversity than that with low macrophyte diversity. Littoral and pelagic zones comparisons emphasized the importance of studies on different regions of the aquatic environments, confirming the elevated richness in the littoral zone, as reported in previous works. This study revealed also the strong influence of the macrophyte community and the adjacent terrestrial environment, which is occupied by forest or agriculture.

A região noroeste paulista é uma das regiões com menor quantidade de dados sobre o zooplâncton, comparado a outras regiões do estado. Os Cladocera constituem um grupo bastante representativo do zooplâncton, apresentando elevada diversidade de espécies. A maior parte desta diversidade pode ser encontrada nas regiões litorâneas de lagos e reservatórios, especialmente aquelas ocupadas por muitas macrófitas. Como parte de um projeto temático mais amplo (Programa Biota-Fapesp - Instituto Virtual da Biodiversidade, www.biotasp.org.br), o presente trabalho tem o objetivo de caracterizar as comunidades de cladóceros (Crustacea, Anomopoda e Ctenopoda) pelágicos e litorâneos presentes em pequenos reservatórios na região noroeste do estado de São Paulo, nas estações seca e chuvosa. As amostragens foram realizadas tanto na zona litorânea quanto pelágica de 10 pequenos reservatórios rasos (média de 2,8 m), através de arrastos verticais com rede de plâncton de 45 µm de malha. Parâmetros físicos e químicos da água também foram avaliados utilizando-se o aparelho Horiba U10. As concentrações de oxigênio e o pH foram mais baixos na estação chuvosa, indicando maiores taxas de decomposição. A entrada de matéria proveniente do ambiente rural pode ser o principal fator que contribui para a eutrofização dos reservatórios. No total, foram identificadas 58 espécies de cladóceros, sendo que destas, quatro constituem novas ocorrências para o estado de São Paulo. Esta elevada riqueza contrapõe-se com o fato de que a região noroeste paulista tem sido considerada uma das mais devastadas do estado. Maiores valores de riqueza e diversidade foram observados na zona litorânea, comparado à zona pelágica, durante as duas estações. Zonas litorâneas com maior diversidade de macrófitas também apresentaram maiores riqueza e diversidade de espécies de cladóceros do que zonas com menor diversidade de macrófitas. As comparações entre as zonas litorâneas e pelágicas evidenciaram a importância dos estudos nos diferentes compartimentos dos ambientes aquáticos, confirmando a elevada riqueza na zona litorânea, já relatada em tantos outros trabalhos, bem como revelando a forte influência da comunidade de macrófitas e do ambiente terrestre adjacente.