Assembleia de Brachyura (Crustacea, Decapoda) do substrato não consolidado próximo a duas ilhas costeiras do litoral norte paulista
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2020-02-21
Autores
Godoy, Amanda Thaís
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Universidade Estadual Paulista (Unesp)
Resumo
Embora as ilhas Couves e Mar Virado estejam geograficamente próximas, elas possuem características ambientais distintas. A Ilha das Couves, por exemplo, é mais afetada pelas massas de água que chegam em Ubatuba do que a Ilha do Mar Virado. Fatores abióticos presentes na água e/ou sedimento e bióticos, como relações intra e interespecíficas, podem modular a abundância e distribuição dos organismos marinhos. Assim, o objetivo deste estudo foi comparar a diversidade alfa e beta, a abundância temporal e verificar a associação de alguns fatores ambientais (temperatura, salinidade, conteúdo de matéria orgânica e granulometria do sedimento) com a abundância dos Brachyura coletados em áreas de substrato não consolidado próximas a Ilhas das Couves e Ilha do Mar Virado, região de Ubatuba (SP), durante o período de dois anos (janeiro de 1998 à dezembro de 1999). As coletas foram realizadas mensalmente com um barco de pesca camaroeiro equipado com redes de arrasto do tipo double rig. Para a análise dos fatores ambientais, amostras de água e sedimento foram coletadas, utilizando-se a garrafa de Nansen e o pegador de Van Veen, respectivamente. Os índices ecológicos de Shannon (H'), Pielou (J') e Bray-Curtis foram utilizados para comparar a variação na diversidade entre as ilhas e os anos. A abundância total foi calculada e comparada entre os anos e as estações em cada ilha. A associação dos fatores ambientais com a abundância das espécies foi avaliada pela Análise de Correspondência Canônica (CCA). Foram coletados 2221 indivíduos em ambas as ilhas (1084 em 1998 e 1137 em 1999), pertencentes a 42 espécies, 28 gêneros e 13 famílias. Destes, 570 foram capturados na Ilha das Couves (405 em 1998 e 165 em 1999) e 1651 na Ilha do Mar Virado (679 em 1998 e 972 em 1999). Vinte espécies ocorreram em ambas as ilhas, dez ocorreram somente nas Couves e vinte foram exclusivas do Mar Virado. As espécies mais abundantes foram Hexapanopeus paulensis e Achelous spinicarpus na Ilha das Couves e Callinectes ornatus e Hepatus pudibundus na Ilha do Mar Virado. Quando comparada entre as ilhas, houve diferenças estatísticas na equitabilidade (no ano de 1998) e abundância (entre as estações no outono de 1999). Quando comparada entre os anos em cada ilha, o outono da Ilha das Couves foi a única estação que diferiu significativamente (U = 41.5 e p < 0.05). O tipo de sedimento e a temperatura da água de fundo foram as variáveis mais relacionadas à abundância dos braquiúros. Possivelmente, o principal fator que contribuiu para a abundância de C. ornatus e A. spinicarpus foi a temperatura da água de fundo, a qual é modulada pela maneira que cada local é influenciada pelas massas de água. Quanto a H. pudibundus e H. paulensis, o sedimento pode ter sido o responsável pela distribuição em cada ilha. Embora o número de espécies coletadas nas ilhas tenha sido semelhante, a maneira como os indivíduos estão distribuídos em cada espécie foi diferente, resultando na diferença na equitabilidade. A alta abundância de C. ornatus na ilha de Mar Virado pode ter sido o motivo da diferença encontrada no outono de 1999 entre as ilhas. Provavelmente, as características ambientais distintas de cada local influenciaram a composição da comunidade dessas ilhas. Com base no presente estudo, pode-se inferir que o substrato não consolidado no entorno dos ambientes insulares do presente estudo apresentam condições favoráveis para o estabelecimento e abrigo de diversas espécies de braquiúros, provavelmente, devido a combinação de vários fatores bióticos e abióticos.
Although the Couves and Mar Virado Islands are geographically close to each other, they have distinct environmental features. Couves Island, for instance, is more affected by the water masses reaching Ubatuba than Mar Virado Island. Abiotic factors present in water and/or sediment, and biotics, such as intra and interspecific relationships, can modulate the abundance and distribution of marine organisms. Thus, the objective of this study was to compare alpha and beta diversity, temporal abundance and to verify the association of some environmental factors (temperature, salinity, organic matter content and granulometry of the sediment) with the abundance of Brachyura collected in soft bottom areas near to Couves Island and Mar Virado Island, Ubatuba region (SP), during the period of two years (January 1998 to December 1999). The collections were carried out monthly with a shrimp fishing boat equipped with double rig trawls. For the analysis of environmental factors, water and sediment samples were collected, using the Nansen bottle and the Van Veen grab, respectively. The ecological indexes of Shannon (H '), Pielou (J') and Bray-Curtis were used to compare a variation in diversity between regions and years. Total abundance was calculated and compared between years and seasons on each island. The association of environmental factors with species abundance was assessed by the Canonical Correspondence Analysis (CCA). In total, 2221 individuals were collected on both islands (1084 in 1998 and 1137 in 1999), belonging to 42 species, 28 genera and 13 families. Of these, 570 were caught on Couves Island (405 in 1998 and 165 in 1999) and 1651 on Mar Virado Island (679 in 1998 and 972 in 1999). Twenty species occurred in both islands, ten occurred only in Couves, and twelve were exclusive of Mar Virado. The most abundant species were Hexapanopeus paulensis and Achelous spinicarpus in Couves Island; and Callinectes ornatus and Hepatus pudibundus in Mar Virado Island. When compared between islands, there were statistical differences in equitability (in the year 1998) and abundance (between seasons in the autumn of 1999). When compared between years on each island, the autumn of Couves Island was a single season with a significant difference (U = 41.5 and p <0.05). The type of sediment and the bottom water temperature were the variables most related to the amount of crabs. Possibly, the main factor that contributed to the abundance of C. ornatus and A. spinicarpus was the bottom water temperature, which can be modulated by the way in each location is influenced by water masses. As for H. pudibundus and H. paulensis, the sediment may have been responsible for its distribution on each island. Although the number of species collected on the islands was similar, the way that individuals are distributed in each species was different, resulting in a difference in equitability. The high abundance of C. ornatus in the Mar Virado Island may have been the reason for the difference found in autumns of 1999 between the islands. Probably, the distinct environmental features characteristics to each island are driving the community composition of these islands. Based on the present study, it can be inferred that the unconsolidated substrate surrounding the island environments of the present study presents favorable conditions for the establishment and shelter of several species of brachyurans, probably due to the combination of several biotic and abiotic factors.
Although the Couves and Mar Virado Islands are geographically close to each other, they have distinct environmental features. Couves Island, for instance, is more affected by the water masses reaching Ubatuba than Mar Virado Island. Abiotic factors present in water and/or sediment, and biotics, such as intra and interspecific relationships, can modulate the abundance and distribution of marine organisms. Thus, the objective of this study was to compare alpha and beta diversity, temporal abundance and to verify the association of some environmental factors (temperature, salinity, organic matter content and granulometry of the sediment) with the abundance of Brachyura collected in soft bottom areas near to Couves Island and Mar Virado Island, Ubatuba region (SP), during the period of two years (January 1998 to December 1999). The collections were carried out monthly with a shrimp fishing boat equipped with double rig trawls. For the analysis of environmental factors, water and sediment samples were collected, using the Nansen bottle and the Van Veen grab, respectively. The ecological indexes of Shannon (H '), Pielou (J') and Bray-Curtis were used to compare a variation in diversity between regions and years. Total abundance was calculated and compared between years and seasons on each island. The association of environmental factors with species abundance was assessed by the Canonical Correspondence Analysis (CCA). In total, 2221 individuals were collected on both islands (1084 in 1998 and 1137 in 1999), belonging to 42 species, 28 genera and 13 families. Of these, 570 were caught on Couves Island (405 in 1998 and 165 in 1999) and 1651 on Mar Virado Island (679 in 1998 and 972 in 1999). Twenty species occurred in both islands, ten occurred only in Couves, and twelve were exclusive of Mar Virado. The most abundant species were Hexapanopeus paulensis and Achelous spinicarpus in Couves Island; and Callinectes ornatus and Hepatus pudibundus in Mar Virado Island. When compared between islands, there were statistical differences in equitability (in the year 1998) and abundance (between seasons in the autumn of 1999). When compared between years on each island, the autumn of Couves Island was a single season with a significant difference (U = 41.5 and p <0.05). The type of sediment and the bottom water temperature were the variables most related to the amount of crabs. Possibly, the main factor that contributed to the abundance of C. ornatus and A. spinicarpus was the bottom water temperature, which can be modulated by the way in each location is influenced by water masses. As for H. pudibundus and H. paulensis, the sediment may have been responsible for its distribution on each island. Although the number of species collected on the islands was similar, the way that individuals are distributed in each species was different, resulting in a difference in equitability. The high abundance of C. ornatus in the Mar Virado Island may have been the reason for the difference found in autumns of 1999 between the islands. Probably, the distinct environmental features characteristics to each island are driving the community composition of these islands. Based on the present study, it can be inferred that the unconsolidated substrate surrounding the island environments of the present study presents favorable conditions for the establishment and shelter of several species of brachyurans, probably due to the combination of several biotic and abiotic factors.
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Palavras-chave
Spatiotemporal diversity, Community structure, Benthonic assemblages, Richness, Beta diversity, Biodiversidade, CCA, Ilha das Couves, Ilha do Mar Virado