Predation on microcrustaceans in evidence: the role of chaoborid larvae and fish in two shallow and small Neotropical reservoirs

This study was focused on the predation upon microcrustaceans by an invertebrate predator (chaoborid larvae), and vertebrate predators (fish), in two small reservoirs in southeastern Brazil, with and without macrophytes, in two climatic periods (dry and rainy seasons). Chaoborus larvae were sampled in the limnetic zone, as they are scarce in the littoral, and fish in both limnetic and littoral zones. Their diets were evaluated by the analysis of the crop (chaoborid) or stomach contents (fish). Chaoborid larvae consumed the dinoflagellate Peridinium sp. or other algae, rotifers, and planktonic microcrustaceans. The fish species that included microcrustaceans in their diets were juveniles caught in the littoral. Aquatic insects, plant fragments, and detritus were their major dietary items, microcrustaceans representing a minor item. Planktonic copepods contributed more to the diet of chaoborid larvae than planktonic cladocerans. Fish preyed on planktonic microcrustaceans, as well as on benthic and macrophyte-associated species. Microcrustaceans were not heavily preyed on by chaoborid larvae and fish in both reservoirs

Zooplankton community dynamics in response to water trophic state in integrated multitrophic aquaculture

Integrated multitrophic aquaculture (IMTA) is an alternative means to optimize feed usage in aquaculture which combines species of different trophic levels. The addition of substrate to IMTA has also been used to promote a lower release of phosphorus, thus minimizing eutrophication and impacts of effluents. In these aquaculture systems, the zooplankton community is important because it acts as a link in trophic chains. This study aimed to verify the dynamics and the structure of the zooplankton community in IMTA (tilapia-prawn), in response to trophic conditions in earthen ponds with different substrates. The object of the study was 12 earthen ponds organized in three treatments: no substrate (control), geotextile substrate, and bamboo substrate. Zooplankton samples were taken biweekly through a water bilge pump. Rotifers and microcrustaceans were identified and counted to determine changes in community diversity during the experiment. Eutrophication was determined through phosphorus and chlorophyll water concentrations. There were no differences in zooplankton communities among treatments, even though increases in levels of eutrophication of the system heavily influenced this community, by altering its diversity and abundance. Small organisms were the most representative ones under polyculture eutrophic conditions

Mesocosm experiment on the impact of invertebrate predation on zooplankton of a tropical lake

Invertebrate predation on zooplankton was investigated in mesocosms in the shallow tropical Lake Monte Alegre, Sauo Paulo State, Brazil, in the summer of 1999. Two treatments were applied: one with natural densities of prey and the predators Chaoborus brasiliensis and the water mite Krendowskia sp. (Pr+), and another without predators (Pr-). Three enclosures (volume: 6.6 m(3) of water per enclosure) per treatment were installed in the sediment of the deepest area of the lake (5.0 m). At the beginning, Chaoborus larvae were present in Pr- enclosures, because of technical difficulties in preventing their entrance, but they virtually disappeared in the course of the experiment. Water mites were almost absent in Pr- enclosures. Chaoborus predation negatively influenced the Daphnia gessneri population, but not the populations of the copepods Tropocyclops prasinus and Thermocyclops decipiens and the rotifers Keratella spp. Death rates of Daphnia were generally significantly higher in the Pr+ treatment; Daphnia densities increased after the disappearance of Chaoborus in Pr-. Copepod losses to predation in the experiment may be compensated by higher fecundity, shorter egg development time, and lower pressure on egg-bearing females, resulting in a lower susceptibility to Chaoborus predation. The predation impact of water mite on microcrustaceans and rotifers in the experiment was negligible

Predation on microcrustaceans in evidence: the role of chaoborid larvae and fish in two shallow and small Neotropical reservoirs

This study was focused on the predation upon microcrustaceans by an invertebrate predator (chaoborid larvae), and vertebrate predators (fish), in two small reservoirs in southeastern Brazil, with and without macrophytes, in two climatic periods (dry and rainy seasons). Chaoborus larvae were sampled in the limnetic zone, as they are scarce in the littoral, and fish in both limnetic and littoral zones. Their diets were evaluated by the analysis of the crop (chaoborid) or stomach contents (fish). Chaoborid larvae consumed the dinoflagellate Peridinium sp. or other algae, rotifers, and planktonic microcrustaceans. The fish species that included microcrustaceans in their diets were juveniles caught in the littoral. Aquatic insects, plant fragments, and detritus were their major dietary items, microcrustaceans representing a minor item. Planktonic copepods contributed more to the diet of chaoborid larvae than planktonic cladocerans. Fish preyed on planktonic microcrustaceans, as well as on benthic and macrophyte-associated species. Microcrustaceans were not heavily preyed on by chaoborid larvae and fish in both reservoirs

Pelagic and littoral cladocerans (Crustacea, Anomopoda and Ctenopoda) from reservoirs of the Northwest of São Paulo State, Brazil

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.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.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Copepods (Crustacea, Maxillopoda) from shallow reservoirs

OBJETIVO: Dentre os microcrustáceos planctônicos, os copépodes Cyclopoida e Calanoida são um dos grupos mais representativos, contribuindo com a maior biomassa para a comunidade planctônica. O presente trabalho tem o objetivo de caracterizar as comunidades de copépodes (Crustacea, Maxillopoda) pelágicos e litorâneos presentes em pequenos reservatórios na região noroeste do Estado de São Paulo, nas estações seca e chuvosa de 2007 a 2009. MATERIAL E MÉTODOS: As amostragens foram realizadas tanto na zona litorânea quanto pelágica de 13 pequenos reservatórios rasos (média de 2,6 m), através de arrastos verticais com rede de plâncton (45 µm). Parâmetros físicos e químicos da água também foram avaliados utilizando-se o aparelho Horiba® U10. RESULTADOS: Foram identificadas 18 espécies de copépodes, sendo 13 Cyclopoida e 5 Calanoida. Não houve diferença estatística entre as distribuições das espécies nas zonas litorâneas e pelágicas bem como entre as estações. Três espécies ocorreram exclusivamente na zona litorânea - Eucyclops elegans, Paracyclops chiltoni e Mesocyclops ogunnus. As espécies Tropocyclops prasinus e Thermocyclops decipiens foram as mais frequentes nos ambientes estudados. CONCLUSÃO: Nossos dados sugerem que, em reservatórios rasos, Copepoda não apresenta diferenças significativas na ocupação das regiões litorânea e pelágica e que a diversidade de Cyclopoida é maior do que Calanoida. Características tais como baixa profundidade e estado eutrófico podem ser consideradas como condições limitantes para o desenvolvimento de espécies de Calanoida nesses reservatórios estudados.AIM: Among the planktonic microcrustaceans, copepods Cyclopoida and Calanoida are the most representative groups, being the largest biomass of the plankton community. The aim of this work is to catalogue and analyze the distribution of copepod species (Crustacea, Maxillopoda) in pelagic and littoral zones from small reservoirs in the northwest of the São Paulo State, in dry and rainy seasons (2007 and 2009). METHODS: Zooplankton samplings were carried out in littoral and pelagic zones of 13 small shallow reservoirs (mean depth: 2.6 m) using vertical hauls and plankton net (45 µm). Water physical and chemical parameters were also monitored with a multiparameter Horiba® U10. RESULTS: Eighteen species of copepods were identified, 13 Cyclopoida and 5 Calanoida. There was no statistical difference between the distributions of species from the littoral and pelagic zones and neither between dry and rainy seasons. Three species occurred exclusively in the littoral zone - Eucyclops elegans, Paracyclops chiltoni and Mesocyclops ogunnus. Tropocyclops prasinus and Thermocyclops decipiens were the most frequent species in the studied environments. CONCLUSION: Our data suggest that in shallow reservoirs copepods present a homogeneous distribution between the littoral and pelagic zones and Cyclopoida are more diverse than Calanoida. Shallow depths and eutrophic state may be regarded as limiting conditions for the development of Calanoida in these reservoirs.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Você conhece a represa?

The Municipal Dam of São José do Rio Preto is located in downtown. As an aquatic environment inserted in the urban landscape it offers many ecosystem services such as water source and leisure location for population. Urban natural environments have been little considered in conservation projects, since they are seen only as urban facilities and not as ecosystems. This project aims bringing people to visit the park dam information about the aquatic ecosystem in order to develop an awareness of the ecosystem preservation. During several Sundays throughout the year at Dam Park we have presented present many ecological aspects of aquatic ecosystems (e.g.: the watershed, environmental conditions, plankton community, the fish community, the birds, etc.). People who participated in the project were distributed in all age groups. In individual reports, the words "health" and "life" were the most frequent, reflecting the view that the dam has high value to people's lives. The project has shown strong potential for the development of the natural environment conservation awareness of the dam.A Represa Municipal de São José do Rio Preto, localizada no centro da cidade, é um ambiente aquático inserido na paisagem urbana e oferece vários serviços ecossistêmicos, tais como fonte de água para abastecimento e local de lazer. Os ambientes naturais urbanos têm sido pouco considerados em projetos de conservação, uma vez que são vistos apenas como equipamentos urbanos e não como ecossistemas. Este projeto pretende levar à população que frequenta o parque da Represa informações sobre o ecossistema aquático da Represa, com o intuito de desenvolver nas pessoas a consciência da preservação do ecossistema. Durante vários domingos, ao longo do ano, serão realizadas exposições no parque da represa, onde são abordados vários aspectos ecológicos do ecossistema aquático (p.ex.: a bacia hidrográfica, as condições ambientais, a comunidade planctônica; a comunidade de peixes; as aves da represa e outros). As pessoas que participam do projeto estão distribuídas em todas as faixas etárias. Nos registros obtidos, as palavras 'saúde' e 'vida' foram as mais frequentes, refletindo a visão de que a represa tem alto valor para a vida das pessoas. O projeto tem demonstrado forte potencial para o desenvolvimento de uma consciência de conservação do ambiente natural da represa