Looking at the soft-bottom around a coastal coral reef: the impact of terrigenous input on Polychaeta (Annelida) community

Fragmentos dos recifes de coral constituem parte do sedimento ao redor dos mesmos, ampliando os limites do recife. Modelos estatísticos foram criados para investigar se a comunidade de poliquetas ao redor do recife Sebastião Gomes (Banco dos Abrolhos, Brasil) é influenciada pelas características do sedimento e/ou pela posição ao redor do recife, que são variáveis relacionadas à influência do aporte terrígeno. Em julho de 2007, período dominado por ventos que ressuspendem o sedimento fino da costa para os recifes, amostras de sedimento foram coletadas em quatro transectos perpendiculares ao recife (S, O, N e L). A espécie de poliqueta mais abundante foi o carnívoro Goniadides carolinae e o modelo selecionado para descrever a distribuição desta espécie foi muito semelhante aos ajustados tanto para a abundância de macrofauna quanto de poliquetas. Estes modelos apresentaram alta abundância em sedimentos carbonáticos grossos na face do recife exposta aos ventos, onde quase não há sedimento terrígeno. Por outro lado, a riqueza de poliquetas não foi influenciada pela posição dos transectos. Sebastião Gomes é um dos muitos recifes costeiros do Banco dos Abrolhos, cuja saúde está prejudicada devido ao aumento de lama relacionada a atividades humanas, como desmatamento e, recentemente, rejeitos da mineração.Erosion on coral reefs produces fragments of the constructor organisms that are scattered all around, thus enlarging the reef boundaries. Statistical modelling approach was used to investigate whether the Polychaeta community around Sebastião Gomes reef (Abrolhos Bank, Brazil) is influenced equally by sediment characteristics and/or by position related to the reef, that are variables related to the terrigenous input influence. In July 2007, a period dominated by winds that resuspend fine sediment from the land to coastal reefs, sediment samples were taken on four transects perpendicular to the reef (S, W, N and E) and a total of 121 species of polychaetes were recorded. The most abundant species was the carnivorous Goniadides carolinae and the model selected for it approximates to the best models fitted for both total macrofauna and polychaete abundance. These models represented higher abundance in coarse carbonate sediments on windward reef faces, where there is almost no terrigenous sediment. On the other hand, the Polychaeta richness did not depend on the transects. Sebastião Gomes reef is one of the many coastal reefs from Abrolhos Bank, whose healthy is probably in danger because of the increase of mud related to human activities, as deforestation and, recently, mining waste

Spatio-temporal and functional structure of the amphipod communities off Santos, Southwestern Atlantic

The amphipod fauna was employed to investigate a bottom environmental gradient in the continental shelf adjacent to Santos Bay. The constant flow of less saline water from the estuarine complex of the Santos and São Vicente rivers besides the seasonal intrusion of the cold saline South Atlantic Central Water (SACW) bring a highly dynamic water regime to the area. Density, distribution, diversity and functional structure of the communities were studied on a depth gradient from 10 to 100 m on two cruises in contrasting seasons, winter 2005 and summer 2006. Twenty-one sediment samples were taken with a 0.09m² box corer. Temperature and salinity were measured at each station and an additional surface sediment sample was obtained with the box corer for granulometric and chemical analyses. Sixty species were collected on each survey and higher density values were found in summer. A priori one-way Analysis of Similarities (ANOSIM) indicated the existence of three different groups of amphipods related to the depth gradient: the Coastal group, the Mixed Zone group and the Deep Zone group. The Coastal Zone in both cruises was inhabited by a community presenting low diversity and density, besides high dominance of the infaunal tube-dweller Ampelisca paria; the area around 30 m presented the highest values of all the ecological indicators and the species showed several life styles; the outer area, situated between 50 and 100 m depth in the SACW domain, presented a community characterized by lower diversity and high biomass and density values. A season-depth ANOSIM showed the influence of depth and season for the Coastal and Mixed Zone groups whereas no seasonal difference was obtained for the Deep Zone group. The synergistic effect of the SACW and depth in the first place, followed by physical changes in substrate, seem to be the main factors controlling the fauna's distribution. In addition, the estuarine waters from Santos Bay apparently had no effect on the establishment of the environmental gradient observed on the adjacent shelf. Diversity, distribution, functional groups and trophic conditions of superficial sediments are discussed in the light of the main oceanographic processes present on the southern Brazilian shelf.A fauna de anfípodes foi empregada para investigar o gradiente ambiental na plataforma continental adjacente a Baía de Santos. A entrada constante de uma água menos salina proveniente do complexo estuarino de Santos e São Vicente e a intrusão sazonal da água fria e salina da Água Central do Atlântico Sul (ACAS) faz com que a área seja um ambiente hidrodinamicamente instável. Densidade, distribuição, diversidade e estrutura funcional das comunidades de anfípodes foram estudadas em um gradiente de profundidade entre 10 e 100 m, em dois cruzeiros realizados em épocas contrastantes, inverno (2005) e verão (2006). Vinte e uma amostras de sedimento foram coletadas com um box corer de 0,09 m². Temperatura e salinidade foram coletadas em cada estação com CTD e uma amostra adicional de sedimento superficial foi obtida com box corer para análises granulométricas e químicas. Sessenta espécies estiveram presentes em ambos os cruzeiros e altos valores de densidade foram encontrados especialmente no verão. A Análise de Similaridade (ANOSIM) realizada a priori indicou a existência de três grupos diferentes de anfípodes relacionados ao gradiente de profundidade: um grupo Costeiro, um grupo da Zona de Mistura e um grupo da Zona Profunda. A zona Costeira, em ambos os cruzeiros foi habitada por uma comunidade que apresenta baixa diversidade e densidade, além de alta dominância do tubícola infaunal Ampelisca paria; a área em torno de 30 m apresentou os maiores valores de todos os indicadores ecológicos e as espécies de anfípodes mostraram grande diversidade funcional; a área externa, entre 50 e 100 m de profundidade e no domínio da ACAS, apresentou uma comunidade caracterizada por baixa diversidade e altos valores de biomassa. A ANOSIM sazonal-profundidade mostrou diferença sazonal significativa para os grupos Costeiros e da Zona de Mistura, enquanto que para o grupo da Zona Profunda não foi encontrada diferença temporal significativa. O efeito sinérgico da ACAS e da profundidade em primeiro lugar, seguido pelas mudanças físicas do substrato, parecem ser os principais fatores controladores da distribuição da fauna. As águas estuarinas provenientes da Baía de Santos aparentemente não tiveram efeito no estabelecimento do gradiente ambiental observado na plataforma adjacente. Diversidade, distribuição dos grupos funcionais, condições tróficas dos sedimentos superficiais, além de outros aspectos ecológicos das comunidades são discutidos à luz dos processos oceanográficos dominantes na plataforma sudeste brasileira

Spatio-temporal and functional structure of the amphipod communities off Santos, Southwestern Atlantic

The amphipod fauna was employed to investigate a bottom environmental gradient in the continental shelf adjacent to Santos Bay. The constant flow of less saline water from the estuarine complex of the Santos and São Vicente rivers besides the seasonal intrusion of the cold saline South Atlantic Central Water (SACW) bring a highly dynamic water regime to the area. Density, distribution, diversity and functional structure of the communities were studied on a depth gradient from 10 to 100 m on two cruises in contrasting seasons, winter 2005 and summer 2006. Twenty-one sediment samples were taken with a 0.09m² box corer. Temperature and salinity were measured at each station and an additional surface sediment sample was obtained with the box corer for granulometric and chemical analyses. Sixty species were collected on each survey and higher density values were found in summer. A priori one-way Analysis of Similarities (ANOSIM) indicated the existence of three different groups of amphipods related to the depth gradient: the Coastal group, the Mixed Zone group and the Deep Zone group. The Coastal Zone in both cruises was inhabited by a community presenting low diversity and density, besides high dominance of the infaunal tube-dweller Ampelisca paria; the area around 30 m presented the highest values of all the ecological indicators and the species showed several life styles; the outer area, situated between 50 and 100 m depth in the SACW domain, presented a community characterized by lower diversity and high biomass and density values. A season-depth ANOSIM showed the influence of depth and season for the Coastal and Mixed Zone groups whereas no seasonal difference was obtained for the Deep Zone group. The synergistic effect of the SACW and depth in the first place, followed by physical changes in substrate, seem to be the main factors controlling the fauna's distribution. In addition, the estuarine waters from Santos Bay apparently had no effect on the establishment of the environmental gradient observed on the adjacent shelf. Diversity, distribution, functional groups and trophic conditions of superficial sediments are discussed in the light of the main oceanographic processes present on the southern Brazilian shelf

Looking at the soft-bottom around a coastal coral reef: the impact of terrigenous input on Polychaeta (Annelida) community

Abstract Erosion on coral reefs produces fragments of the constructor organisms that are scattered all around, thus enlarging the reef boundaries. Statistical modelling approach was used to investigate whether the Polychaeta community around Sebastião Gomes reef (Abrolhos Bank, Brazil) is influenced equally by sediment characteristics and/or by position related to the reef, that are variables related to the terrigenous input influence. In July 2007, a period dominated by winds that resuspend fine sediment from the land to coastal reefs, sediment samples were taken on four transects perpendicular to the reef (S, W, N and E) and a total of 121 species of polychaetes were recorded. The most abundant species was the carnivorous Goniadides carolinae and the model selected for it approximates to the best models fitted for both total macrofauna and polychaete abundance. These models represented higher abundance in coarse carbonate sediments on windward reef faces, where there is almost no terrigenous sediment. On the other hand, the Polychaeta richness did not depend on the transects. Sebastião Gomes reef is one of the many coastal reefs from Abrolhos Bank, whose healthy is probably in danger because of the increase of mud related to human activities, as deforestation and, recently, mining waste