The genus Tryblionella W. Smith (Bacillariaceae, Bacillariophyta) in southern Brazil salt marshes / O gênero Tryblionella W. Smith (Bacillariaceae, Bacillariophyta) em marismas do Sul do Brasil

Abstract: Tryblionella is a large epipelic genus, widespread from fresh to marine waters. Most of the studies including the genus are based only in light microscopy. Few recent studies are exclusively dedicated to Tryblionella and the ultrastructure of some species is still little known. In this paper we present eleven species of Tryblionella found in epiphyton and microphytobenthos in Patos Lagoon salt marshes. All the species are described, illustrated in light and scanning electron microscopy and comments about their taxonomy, distribution and ecology are provided. Two taxa are reported for the first time in the State of Rio Grande do Sul and one in Southern Brazil. The number of species registered in this study comprises nearly a half of the number of species registered in the country. The high richness observed may be related to the dynamics of the salt marshes, which provides both the mixing of fresh and marine waters communities and the diversity of microhabitats. The great variability among the species analyzed allowed to extend the general concept of Tryblionella, adding features which were not considered in the previous characterizations of the genus.

Resumo: Tryblionella é um gênero de diatomáceas epipélicas, distribuído de águas doces a marinhas. A maioria dos estudos que incluem o gênero baseia-se apenas em microscopia óptica. Poucos estudos recentes são exclusivamente dedicados à Tryblionella e a ultraestrutura de algumas espécies ainda é pouco conhecida. No presente artigo, apresentamos onze espécies de Tryblionella encontradas no epifíton e no microfitobentos nas marismas da Lagoa dos Patos. Todas as espécies foram descritas, ilustradas em microscopia óptica e eletrônica de varredura e comentários sobre a taxonomia, distribuição e ecologia foram fornecidos. Dois táxons foram registrados pela primeira vez para o estado do Rio Grande do Sul e um para a região Sul do Brasil. O número de espécies registradas neste estudo compreende cerca de metade das espécies registradas para o país. A grande riqueza observada pode estar relacionada à dinâmica das marismas, que proporciona tanto a mistura de comunidades de águas doces e marinhas quanto diversidade de microhabitats. A grande variabilidade entre as espécies analisadas permitiu que o conceito geral de Tryblionella fosse ampliado, incluindo características que não haviam sido consideradas nas caracterizações anteriores do gênero.

Evaluation of the Blue Crab Callinectes sapidus Rathbun, 1896 Bycatch in Artisanal Fisheries in Southern Brazil

ABSTRACT We evaluated the incidental catch of the blue crab in artisanal fisheries through the analysis of sex ratio, catch per unit effort, net positioning, and size in which the capture probability was 50% (P50). The specimens were collected from 2011 to 2013 in the estuary of Patos Lagoon, southern Brazil. The analysis showed a higher occurrence of males. Variations in the catch per unit effort showed greatest abundance values close to the mouth of the estuary. Catch per unit effort was similar when comparing fishing seasons and net positions. P50 indicated a low selectivity of the nets since it varied between studied areas but stayed below the size at first maturity. Catches indicated a greater effort on males, since females migrated to spawn in the ocean area adjacent to the estuary during the fishing period studied. The spatial variation of the catch per unit effort showed heterogeneity in fishing catches. Thus, optimal management of the resource should consider the particularities of each area.

Biodegradation of [D-Leu1] microcystin-LR by a bacterium isolated from sediment of Patos Lagoon estuary, Brazil

Background Toxic cyanobacterial blooms are recurrent in Patos Lagoon, in southern Brazil. Among cyanotoxins, [D-Leu1] microcystin-LR is the predominant variant whose natural cycle involves water and sediment compartments. This study aimed to identify and isolate from sediment a bacterial strain capable of growing on [D-Leu1] microcystin-LR. Sediment and water samples were collected at two distinct aquatic spots: close to the Oceanographic Museum (P1), in Rio Grande City, and on São Lourenço Beach (P2), in São Lourenço do Sul City, southern Brazil. Methods [D-Leu1] microcystin-LR was isolated and purified from batch cultures of Microcystis aeruginosastrain RST9501. Samples of water and sediment from Rio Grande and São Lourenço do Sul were collected. Bacteria from the samples were allowed to grow in flasks containing solely [D-Leu1] microcystin-LR. This strain named DMSX was isolated on agar MSM with 8 g L1 glucose and further purified on a cyanotoxin basis growth. Microcystin concentration was obtained by using the ELISA immunoassay for microcystins whereas bacterial count was performed by epifluorescence microscopy. The genus Pseudomonas was identified by DNA techniques. Results Although several bacterial strains were isolated from the samples, only one, DMXS, was capable of growing on [D-Leu1] microcystin-LR. The phylogenetic analysis of the 16S rRNA gene from DMXS strain classified the organism as Pseudomonas aeruginosa. DMXS strain incubated with [D-Leu1] microcystin-LR lowered the amount of toxin from 1 g.L1 to 0.05 g.L1. Besides, an increase in the bacterial countfrom 71×105 bacteria.mL1 to 117×105 bacteria.mL1was observed along the incubation. Conclusions The use of bacteria isolated from sediment for technological applications to remove toxic compounds is viable. Studies have shown that sediment plays an important role as a source of bacteria capable of degrading cyanobacterial toxins. This is the first Brazilian report on a bacteriumof the genus Pseudomonasthat can degrade [D-Leu1] microcystin-LR, the most frequent microcystin variant in Brazilian freshwaters.

Biodegradation of [D-Leu1] microcystin-LR by a bacterium isolated from sediment of Patos Lagoon estuary, Brazil

Background: Toxic cyanobacterial blooms are recurrent in Patos Lagoon, in southern Brazil. Among cyanotoxins, [D-Leu1] microcystin-LR is the predominant variant whose natural cycle involves water and sediment compartments. This study aimed to identify and isolate from sediment a bacterial strain capable of growing on [D-Leu1] microcystin-LR. Sediment and water samples were collected at two distinct aquatic spots: close to the Oceanographic Museum (P1), in Rio Grande City, and on São Lourenço Beach (P2), in São Lourenço do Sul City, southern Brazil. Methods: [D-Leu1] microcystin-LR was isolated and purified from batch cultures of Microcystis aeruginosastrain RST9501. Samples of water and sediment from Rio Grande and São Lourenço do Sul were collected. Bacteria from the samples were allowed to grow in flasks containing solely [D-Leu1] microcystin-LR. This strain named DMSX was isolated on agar MSM with 8 g L−1 glucose and further purified on a cyanotoxin basis growth. Microcystin concentration was obtained by using the ELISA immunoassay for microcystins whereas bacterial count was performed by epifluorescence microscopy. The genus Pseudomonas was identified by DNA techniques. Results; Although several bacterial strains were isolated from the samples, only one, DMXS, was capable of growing on [D-Leu1] microcystin-LR. The phylogenetic analysis of the 16S rRNA gene from DMXS strain classified the organism as Pseudomonas aeruginosa. DMXS strain incubated with [D-Leu1] microcystin-LR lowered the amount of toxin from 1 μg.L−1 to < 0.05 μg.L−1. Besides, an increase in the bacterial count–from 71 × 105 bacteria.mL−1 to 117 × 105 bacteria.mL−1–was observed along the incubation. Conclusions: The use of bacteria isolated from sediment for technological applications to remove toxic compounds is viable. Studies have shown that sediment plays an important role as ...

Evaluation of space adequateness of shrimp farms in Southern Brazil

In Rio Grande do Sul State, there are four marine shrimp (Litopenaeus vannamei) farms in the municipal districts of São José do Norte and Rio Grande, and other four with previous license for operation. Thus, the present study aimed to identify and characterize areas for marine shrimp farming located in the Southern portion of the Patos Lagoon estuary (32º00'S 52º00'W) by employing the analysis of satellite remote sensing (Landsat TM and ETM+/Google Earth), airborne remote sensing (35mm system ADAR 1000), terrestrial remote sensing (RICOH 500SE), and field expeditions, integrating data in a Geographical Information System (IDRISI Andes). As a result, the enterprises were built on coastal fields or in obliterated dune areas, which are favorable for cultivation. The proximity of possible consuming markets and local labor, relatively good access roads and local technical support also favor the projects. However, there must be caution in terms of changes in the original projects, which could cause environmental impacts and noncompliance of environmental norms, such as the occupation of salt marsh areas. Based on the obtained information, instruments can be created to help inherent legal decision-making to manage the activity for futures enterprises.

No estado do Rio Grande do Sul existem quatro fazendas produtoras de camarões (Litopenaeus vannamei) marinhos nos municípios de São José do Norte e Rio Grande, e outras quatro fazendas já possuem licença prévia. Assim, o presente estudo propôs identificar e caracterizar as áreas destinadas a cultivos de camarões marinhos localizadas na porção sul do estuário da lagoa dos Patos (32º00'S 52º00'W), empregando análises de sensoriamento remoto orbital (ETM+/Landsat, Google Earth), aéreo (35mm/sistema ADAR 1000), terrestre (RICOH 500SE) e de saídas de campo, integrando os dados num Sistema de Informação Geográfica (IDRISI Andes). Resultados apontaram que os empreendimentos foram construídos sobre campos litorâneos ou em regiões de dunas obliteradas, regiões estas propícias para o cultivo. A proximidade dos possíveis mercados consumidores e mão de obra local, estradas de acesso relativamente boas e suporte técnico local também favorecem os projetos. No entanto, deve haver cautela em termos de mudanças nos projetos originais, o que poderia causar impactos ambientais e descumprimento das normas ambientais, tais como a ocupação de áreas de marismas. A partir das informações obtidas, podem ser criados instrumentos que auxiliarão na tomada de decisões legais para gerenciar a atividade em futuros empreendimentos.

Diet and feeding strategy of the dusky grouper Mycteroperca marginata (Actinopterygii: Epinephelidae) in a man-made rocky habitat in southern Brazil

A garoupa-verdadeira (Mycteroperca marginata) é uma espécie marinha geralmente associada a fundos rochosos e recifes. O presente trabalho investiga a dieta e estratégia alimentar de uma população da garoupa-verdadeira que habita um longo (4,5 km) par de molhes de pedra na desembocadura do estuário da laguna dos Patos, sul do Brasil. Não há trabalhos anteriores realizados nesse tipo de habitat construído pelo homem e este trabalho fornece uma base de comparação com estudos de dieta de outras populações da garoupa-verdadeira ocorrendo em habitats naturais. De modo similar ao encontrado em estudos prévios realizados em substratos naturais, caranguejos e peixes foram as principais categorias de alimento consumidas (%IRI = 85,1 e %IRI = 12,6, respectivamente), enquanto camarões e moluscos tiveram menor importância na dieta (%IRI = 1,9 e %IRI = 0,4, respectivamente). Como reportado anteriormente para populações de garoupa-verdadeira que habitam recifes e fundos rochosos, o presente trabalho revelou marcadas mudanças na dieta em função do tamanho da espécie. Siri-azul e peixes tornam-se gradativamente mais importantes na dieta de indivíduos maiores (> 500 mm de comprimento total, CT). Finalmente, foi observado que a população de garoupa-verdadeira teve uma estratégia alimentar generalista com uma elevada variação entre indivíduos no consumo de presas. Essa estratégia permaneceu similar ao longo do aumento em tamanho da espécie. Os resultados do presente trabalho sugerem que substratos rochosos estabelecidos pelo homem propiciam locais de alimentação adequados para a garoupa-verdadeira no sul do Brasil e que poderiam ser usados como ferramentas adicionais nos esforços de conservação dessa espécie ameaçada.

The dusky grouper (Mycteroperca marginata) is a marine species usually associated with rocky bottoms and reefs. The present work investigated the diet and feeding strategy of a dusky grouper population inhabiting a 4.5 km long pair of rocky jetties located in the mouth of Patos Lagoon estuary. No prior research has been conducted in such man-made habitat and the current study provides a basis for comparative studies on the diet of the dusky grouper populations inhabiting natural vs. manmade rocky habitats. Similarly with previous studies on natural substrates, crabs and fishes were the main food categories consumed (%IRI = 85.1 and %IRI = 12.6, respectively), whereas shrimps and mollusks had lower importance in the diet (%IRI = 1.9 and 0.4, respectively). As previously reported for dusky grouper populations inhabiting reefs and rocky bottoms, the present work revealed conspicuous size related dietary shifts. Blue crabs and fishes become increasingly important food itemsin the diet of larger individuals (> 500 mm, TL). Finally, it was found that the studied dusky population has a generalist feeding strategy with a high between-individual variation in prey consumption. Such strategy remained similar across the size increment of the species. Our findings suggest that man-made rocky substrates provide suitable feeding grounds for the dusky grouper in southern Brazil and could be used as an additional tool in the conservation efforts of this endangered species.

Age, growth, and reproductive aspects of the dusky grouper Mycteroperca marginata (Actinopterygii: Epinephelidae) in a man-made rocky habitat in southern Brazil

The dusky grouper, Mycteroperca marginata, is an important commercial marine fish that is currently considered an endangered species worldwide and listed as overexploited in Brazil. Although its reproductive biology has been studied elsewhere, no information is available for populations in its southernmost distribution limit on the Brazilian coast. The present work investigates age structure, growth and reproduction of individuals inhabiting a pair of rocky jetties, about 4.5 km long each, located in the mouth of Patos Lagoon in the municipality of Rio Grande, in the southwestern Atlantic Ocean. A total of 130 individuals obtained between February 2007 and May 2009 were analyzed, with total length ranging from 260 to 800 mm. The growth coefficient found in the present study (K: 0.069) was lower than values reported for dusky grouper populations from the Mediterranean Sea (0.087) and southeast Africa (0.09). This difference could be related to higher average water temperatures in these regions compared to the current study site or due to poorer habitat quality in terms of the shelters available for dusky grouper individuals to establish their territories. Microscopic ovarian analyses of individuals during three years of sampling revealed only the occurrence of immature and resting females. The absence of ripe or post-spawning individuals, associated with low GSI values (<0.2) over the studied months, indicates that the dusky grouper did not use this man-made rocky substrate as a spawning site. The current L50 estimate of 451.3 mm indicates that most individuals captured in this area are immature. Such fishing pressure on immature specimens, associated with its slow growth rates and complex reproductive characteristics, threatens sustainability of the current dusky grouper fishery at the study site.

A garoupa-verdadeira, Mycteroperca marginata, é uma espécie de importância comercial que atualmente é considerada como ameaçada mundialmente e sobre-explotada no Brasil. Embora sua biologia reprodutiva tenha sido estudada em outras regiões, nenhuma informação está disponível sobre populações que habitam o extremo sul da sua distribuição na costa brasileira. O presente trabalho investiga a estrutura de idade, crescimento e reprodução de indivíduos que habitam dois molhes de pedra, com cerca de 4,5 km de extensão cada, localizados na desembocadura da laguna dos Patos no município de Rio Grande, no Atlântico Sudoeste. Foram analisados 130 indivíduos obtidos entre fevereiro de 2007 e maio de 2009, com comprimento total entre 260 e 800 mm. O coeficiente de crescimento no presente estudo (K: 0,069) foi inferior aos valores reportados para oMediterrâneo (0,087) e sudeste da África (0,09). Essa diferença pode estar relacionada a temperaturas médias maiores nessas regiões comparadas ao presente local de estudo ou devido a menor qualidade de habitat em termo de abrigos para os indivíduos de garoupa-verdadeira estabelecerem seus territórios. Análises microscópicas dos ovários dos indivíduos durante esses três anos de amostragens revelaram somente a ocorrência de indivíduos imaturos e fêmeas em repouso. A ausência de indivíduos ovados ou em pós-desova, associada com baixos valores do IGS (<0,2), ao longo de todos os meses de coleta, indica que a garoupa-verdadeira não utiliza esse substrato rochoso construído pelo homem como um local de desova. A estimativa de um L50 de 451,3 mm indica que a maioria dos indivíduos capturados nessa região é imatura. Pressão de pesca sobre indivíduos imaturos, associada com a sua lenta taxa de crescimento e complexo modo reprodutivo, ameaça a sustentabilidade da atual pesca da garoupa-verdadeira na área de estudo.

Estimating size at first maturity (L50) from Gonadossomatic Index (GSI) data

Correct estimates of size at first maturity (L50) are useful for fish stock management and different methods have been proposed. In this study we propose the use of a modified logistic to estimate L50, including a variable asymptote (A). We also test the use of the Gonadossomatic Index (GSI) as a flag to establish the reproductive status of each female fish. The method is demonstrated using GSI data for four Neotropical fish species: Characiformes: Astyanax fasciatus (n = 473) and Oligosarcus robustus (n = 297); Siluriformes: Loricariichthys anus (n = 427) and Trachelyopterus lucenai (n = 195). The results were stable enough to propose this method be used for other fish species with different life histories and with a relatively unconstrained sampling programs. Nevertheless, a wide scale test program is desirable to identify any possible bias in this approach.

Estimativas precisas do tamanho de primeira maturação (L50) são úteis para a gestão de estoques naturais, existindo diversos métodos disponíveis na literatura. No presente estudo é proposto um método alternativo através de uma equação logística modificada, incluindo-se uma assíntota variável (A). Testou-se igualmente o uso do Índice Gonadossomático (GSI) como indicativo do status reprodutivo para fêmeas de peixes. O método é demonstrado com dados de quatro espécies de peixes Neotropicais: Characiformes: Astyanax fasciatus (n = 473) e Oligosarcus robustus (n = 297); Siluriformes: Loricariichthys anus (n = 427) e Trachelyopterus lucenai (n = 195). Os resultados obtidos foram suficientemente estáveis para propor-se o emprego do método para outras espécies de peixes com diferentes histórias de vida, mesmo que em programas de amostragem limitados. Sugere-se, entretanto, avaliação da metodologia em larga escala como forma de identificar-se possíveis desvios da abordagem proposta.

Effects of dredged sediment disposal on the coastal marine macrobenthic assemblage in Southern Brazil

The aim of this study was to evaluate the deposition impact of dredged material from Patos lagoon estuary on a benthic macroinvertebrate assemblage structure in an adjacent coastal marine area. Nine sampling stations were chosen at random in the disposal area, and nine others in the same way in an adjacent control area. Samples were collected at a 19 m depth before sediment disposal (11 July 2000), during dredging and disposal operations (25 Oct. 2000), and three months thereafter (24 Aug. 2001). Statistical analysis indicated that sampling periods presented similar characteristics in both the control and disposal sites. Disposal of dredged sediment from Patos lagoon had no detectable detrimental effects upon macrobenthic faunal assemblage at the dumping site. This result is attributed both to adaptation of resident biota to dynamic sedimentary conditions and to the fine estuarine sediment dredged, the dispersion of which in the water column might have minimized sediment deposition and consequent damage to the benthic fauna.

Objetivou-se avaliar o impacto da deposição de material dragado proveniente da região estuarina da lagoa dos Patos sobre a estrutura da associação macrobentônica no sítio de deposição, situado no ambiente marinho costeiro adjacente à desembocadura da laguna. Nove estações de coleta foram sorteadas, tanto no sítio de deposição quanto na área controle adjacente. As amostras, a 19 m de profundidade, foram coletadas antes do início de deposição do sedimento (11/07/2000), durante as operações de dragagem e deposição (25/10/2000) e três meses após o encerramento das atividades de deposição do material dragado (24/08/2001). Análises estatísticas indicaram que áreas controle e sítio de deposição apresentaram características faunísticas similares dentro dos períodos amostrais. Não foram detectados efeitos prejudiciais da deposição do sedimento sobre a associação de macroinvertebrados bentônicos na área de depósito. Este resultado pode ser atribuído às características da biota residente que está, provavelmente, adaptada às condições da dinâmica sedimentar do local e também às características predominantemente finas do sedimento dragado que, ao dispersar-se na coluna d'água, minimizaram a deposição das frações mais finas e um eventual dano ao macrozoobentos.