Abstract In this study we evaluated the effects of changes in salinity, temperature, pH and dissolved oxygen on the spatiotemporal variation of zooplankton. Samples were collected in January−March, May; October−December 2010; and January−March 2011 in the Araruama lagoon, state of Rio de Janeiro, Brazil. There were eight fixed stations sampled using a WP2 net equipped with a flow meter. The zooplankton diversity of the Araruama lagoon was low and dominated by Cirripedia larvae and by the copepod Acartia tonsa, which is an indicator species of eutrophication. In general, a few species from the Cabo Frio region were able to adapt to the conditions of this hypersaline lagoon. In addition, a specimen of Monstrilla bahiana (Monstrilloidae) was found at a salinity of 46‰. This is the first record of the order Monstrilloida in the region of Cabo Frio. Temperature, salinity and pH were shown to be limiting factors for the species present in the lagoon since Cirripedia seemed to avoid releasing their larvae under unfavorable environmental conditions. The abundance of A. tonsa was always associated with that of Cirripedia larvae, and it was higher at cooler temperatures.

Abstract Here, we report the first record of the marine copepod Oithona attenuata Farran, 1913, in Brazil, from a costal station near Cabo Frio Island, Arraial do Cabo Municipality, Rio de Janeiro State. Specimens were found during March and May 2011 in zooplankton samples obtained from horizontal hauls using a plankton-net with a 100μm mesh size, and mouth opening of 40 cm diameter.

Resumo A Lagoa de Araruama é uma laguna hipersalina habitada por diferentes espécies de peixes, permanentemente ou durante a estação reprodutiva. Nos últimos anos, algumas alterações ambientais têm sido observadas nesse ecossistema, relacionadas ao lançamento de esgoto in natura, como por exemplo decréscimo de salinidade (de 64 para 41 durante os últimos 40 anos) e aumento da disponibilidade de nutrientes. Considerando que ambas as mudanças podem afetar a assembléia do ictioplâncton, o presente estudo teve como objetivo avaliar todas as relações potenciais entre alterações na salinidade e distribuição de larvas de peixes. As amostras de ictioplâncton foram coletadas mensalmente a partir de janeiro de 2010 a março de 2011, em oito estações fixa na Lagoa de Araruama por meio de uma rede WP2 equipada com fluxômetro. Durante este período, baixas densidades de ovos coincidiram com áreas de alta salinidade, sugerindo que os adultos parecem estar evitando liberar os seus ovos em condições ambientais desfavoráveis às larvas. A distribuição desigual de ovos e larvas dentro da lagoa, como revelado pela correlação linear na variação espacial e temporal, sugere que as mudanças na salinidade influenciaram o ritmo reprodutivo das espécies de peixes que dependem da Lagoa de Araruama.

Abstract The Lagoa de Araruama is a hypersaline ecosystem inhabited by distinct fish species, either permanently or during their reproductive season. Over recent years, some significant environmental changes have been observed in this ecosystem related to the sewage runoff, as salinity decrease (from 64 to 41 psu during the last 40 years) and nutrients increase. As both changes are thought to affect the ichthyoplankton assemblage, the present study aimed to evaluate all the potential relationships between salinity disruption and fish larvae distribution. Ichtyoplankton samples were collected monthly from January 2010 to March 2011 at eight sites in Araruama Lagoon by means of a WP2 plankton net equipped with a flowmeter. During this period, low egg densities were coincident with high salinity regions, suggesting that adults are avoiding to release their eggs under less favorable environmental conditions to the larvae. The uneven distribution of eggs and larvae inside the lagoon, as revealed by both spatial and temporal analyses lead us to suggest that changes in salinity have influenced the reproductive rhythms of those fish species that depend upon the Lagoa de Araruama.

Resumo A ressurgência transfere a água rica em nutrientes do fundo dos oceanos para a superfície, o que beneficia a produção primária e, consequentemente, aumenta a produção biológica local. Cabo Frio é favorecido pelo fenômeno e os copépodes são um dos grupos mais beneficiados. Os resultados mostraram que Pacalanus quasimodo foi a espécie mais abundante em relação às demais devido sua resposta rápida à floração. Assim, este estudo tem como objetivo avaliar a herbivoria e dinâmica das populações de copépodes, com ênfase em P. quasimodo. Os resultados mostraram que a temperatura influencia a produção primária, que, por sua vez, favorece a biomassa séston (R2 = 0,65, p = 0,008). A dominância de P. quasimodo deveu-se à disponibilidade de alimento (R2 = 0,83) e a elevada densidade da população leva a um decréscimo da diversidade (R2 = 0,63, p = 0,002). Nossos resultados revelaram que a predação por copépodes carnívoros, como Corycaeus spp. e Oncaea spp., é o principal fator que afeta a dominância de P. quasimodo (R2 = 0,70, p = 0,004; βcopépodes predador = 0,41, p = 0,04).

Abstract Coastal upwelling is known to transfer the nutrient-rich water from the deep ocean to the surface, which benefits primary production and consequently increases local organic production. Cabo Frio is favored by the phenomenon and copepods are one of the groups most benefited. According to the results presented here, the higher abundances of Pacalanus quasimodo relative to other species are due to its rapid response to upwelling-dependent blooms. Therefore this study aims to assess the herbivory and dynamics of many copepod populations with emphasis on P. quasimodo. The results showed that temperature influences primary production, which in turn benefits the seston biomass (R2 = 0.65, p = 0.008). The dominance of P. quasimodo was due to its emphasis on herbivory (R2 = 0.83) and lead to a decrease in the planktonic diversity (R2 = 0.63, p = 0.002). Our results revealed that predation by carnivorous copepods, like Corycaeus spp. and Oncaea spp. is the main opposing factor affecting P. quasimodo dominance. (R2 = 0.70, p = 0.004; βpredators = 0.41, p = 0.04).