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In hypersaline environments the zooplankton community is generally poor in density and richness, even so these organisms are fundamental to the base of the local food chain. This study aims to evaluate the spatial and temporal variation of the zooplankton community of Araruama Lagoon, considering the abiotic data of salinity and temperature as well as the biotic data of zooplankton density and composition. Six samples were performed in 12 collection stations from horizontal surface halls with 200 μm mesh nets with a 60 cm diameter opening and an attached flowmeter. A total of 34 holoplanktonic taxa and five groups of meroplankton were identified. In relation to the spatial and temporal variation of the zooplankton of the lagoon, the parameters evaluated showed significant results for both factors. The variations also showed greater richness, diversity and density of species in the collection stations closer to the sea, where salinity was lower. There was a predominance of holoplankton during the study, differing from the results previously found in the 90’s. Em ambientes hipersalinos a comunidade zooplanctônica geralmente é pobre em densidade e riqueza, mesmo assim esses organismos são fundamentais para a base da cadeia alimentar local. O presente estudo tem como objetivo avaliar a variação espacial e temporal da comunidade zooplanctônica da Lagoa de Araruama, considerando os dados abióticos de salinidade e temperatura e os dados bióticos densidade e composição do zooplâncton. Foram realizadas seis amostragens em 12 estações de coleta a partir de arrastos de superfície horizontais, utilizando redes de malha de 200 μm com uma abertura de 60 cm de diâmetro e um medidor de vazão acoplado. Foram identificados um total de 34 táxons holoplanctônicos e cinco grupos de meroplâncton. Em relação a variação espacial e temporal do zooplâncton da lagoa, os parâmetros avaliados apresentaram resultados significativos para ambos os fatores. As variações também apresentaram maior riqueza, diversidade e densidade de espécies nas estações de coleta mais próximas do mar, onde a salinidade foi mais baixa. Houve predominância do holoplâncton durante o estudo, diferente dos resultados encontrados na década de 90.

Cladocera represent an important zooplankton group because of their seasonal prominence in terms of abundance and their contribution in controlling primary production (phytoplankton). On a global scale, there are few studies on Cladocera in hypersaline environments. The present work aims to evaluate the spatio-temporal variation of the Cladocera assemblage across a salinity gradient in the habitats of the Araruama Lagoon. Samples were collected in random months over a period of four years at 12 fixed stations in the Araruama Lagoon using a WP2 plankton net equipped with a flow meter. Our results do not reveal significant influence of the tide and seasonal variation as factors affecting the Cladocera assemblage. Five Cladocera species were found in the Araruama Lagoon, only in stations 11 and 12 where they reached an average of 1,799 ± 3,103 ind. m-3. The mean of the Shannon Diversity Index was 0.45 ± 0.2. The species that stood out in terms of frequency and abundance were: Penilia avirostris (frequency of occurrence: 71%), followed by Pseudevadne tergestina (41%). The same species also stood out in terms of relative abundance, Penilia avirostris (87%) and Pseudevadne tergestina (11%). The absence of Cladocera in the innermost parts of the lagoon suggests that their entrance to these locations is possibly inhibited by the salinity and temperature gradient of the lagoon, being the main factors influencing the dynamics of the Cladocera assemblages. Resumo Os cladóceros representam um importante grupo de zooplâncton, devido ao seu destaque sazonal em termos de abundância e à sua contribuição no controlo da produção primária (fitoplâncton). Em escala global, há poucos estudos com Cladocera em ambientes hipersalinos. O presente trabalho tem como objetivo avaliar a variação espaço-temporal da assembleia de Cladocera em um gradiente de salinidades da Lagoa de Araruama. As amostras foram coletadas em meses aleatórios, durante um período de quatro anos, em 12 estações fixas na Lagoa de Araruama, utilizando uma rede de plâncton WP2 equipada com um fluxômetro. Os nossos resultados não revelam uma influência significativa da maré e da variação sazonal como fatores que afetam a assembleia de Cladocera. Cinco espécies de Cladocera foram encontradas na Lagoa de Araruama. A assembleia apresentou maior densidade absoluta estações 12 e 11, atingindo uma a média de 1.799 ± 3.103 inds-3. A média do Índice de Diversidade de Shannon foi de 0,45 ± 0,2. As espécies que se destacaram em termos de frequência e abundância foram: Penilia avirostris (frequência de ocorrência: 71%), seguida de Pseudevadne tergestina (41%). As mesmas espécies também se destacaram em termos de abundância relativa Penilia avirostris (87%) e Pseudevadne tergestina (11%). A ausência de Cladocera nas partes mais interiores da lagoa sugere que a sua entrada nestes locais é possivelmente inibida pela salinidade e gradiente de temperatura da lagoa, sendo os principais fatores que influenciam a dinâmica da assembleia de Cladocera.

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.

Monstrilloid copepods are protelean parasites with a complex life cycle that includes an endoparasitic juvenile phase and free-living early naupliar and adult phases. The monstrilloid copepod genus Caromiobenella Jeon, Lee and Soh, 2018 is known to contain nine species, each one with a limited distribution, except for two species, members of this widespread genus are known exclusively from males. Hitherto, members of Caromiobenella have not been recorded from tropical waters of the South Western Atlantic (SWA). The nominal species Monstrilla brasiliensis Dias and Suárez-Morales, 2000 was originally described from female specimens collected in coastal waters of Espírito Santo and Rio de Janeiro (Brazil), but the male remained unknown. The failure to reliably link both sexes of monstrilloid species is one of the main problems in the current taxonomy of the group, thus leading to a separate treatment for each sex. New zooplankton collections in coastal waters and intertidal rocky pools of the SWA yielded several male and female monstrilloid copepods tentatively identified as Monstrilla brasiliensis. Our results of both morphologic and molecular (mtCOI) analyses allowed us to confirm that these males and females were conspecific. We also found evidence suggesting that Caromiobenella is not a monophyletic taxon. Our male specimens are morphologically assignable to Caromiobenella, therefore, females of the nominal species Monstrilla brasiliensis, are matched here with the aforementioned males and, thus, the species should be known as C. brasiliensis comb. nov. (Dias and Suárez-Morales, 2000). This finding represents the third documented discovery of a female of Caromiobenella, the first record of the genus in the Southwestern Atlantic, and the first documented record of monstrilloids from coastal tidepools. With the addition of C. brasiliensis, Caromiobenella now includes 10 valid species worldwide. This work represents the second successful use of molecular methods to link both sexes of a monstrilloid copepod. The male of C. brasiliensis is herein described, and a key to the known species of Caromiobenella and data on the habitat and local abundance of C. brasiliensis are also provided.

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 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.

The paper describes the first occurrence of Pleopis schmackeri (Poppe, 1889) (Branchiopoda, Onychopoda) in Rio das Ostras, Rio de Janeiro, Brazil is described. This marine cladoceran species occurred in zooplanktonic samples obtained on July, 2003 with mean density of 10 ind.m-3. Its presence may be related to two hypotheses, due to ballast water and through the Brazilian current, which gets closer to the coast Winter.

This scientific communication represents the record of Pontella marplatensis (Ramirez – 1966), in the station near Cabo Frio Island (Arraial do Cabo RJ – Brazil). This species of marine copepod ocurred in the zooplankton sample on September 15, 2010, obtained through horizontal drag with mesh net of 100 µm and 40 cm in diameter.