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

Abstract

A B S T R A C TThe 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 0.09m 2 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. R E S U M OA 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 m 2 . Temperatura e salinidade foram coletadas em cada estação com CTD e uma amostra adicional...

Feeding habits of the seahorse Hippocampus patagonicus (Actinopterygii: Syngnathiformes: Syngnathidae) on the southern coast of Brazil

“…In fact, amphipods are one of the most common prey items of many benthic-feeding fishes (Wakabara et al 1982). They are a diverse and abundant group of peracaridean crustaceans that inhabit a variety of benthic substrata (Thomas 1993), and their density and geographic distribution are highly influenced by hydrodynamic conditions (Rodrigues et al 2012, Maria et al 2016.…”

Integrative Approach to Assess Benthic Ecosystem Functioning on the Southwest Brazilian Continental Shelf

“…The relationships between feeding mode and species mobility are complex, and their study helps to understand the functioning of benthic communities. In the São Sebastião and Santos shelves, several studies were conducted with polychaete and crustacean species to identify their trophic guilds and link them with sediment type and organic matter content [23,24]. Five trophic groups are reported for the SBB shelf and recently were associated with four bioturbation categories, for a better understanding of the functional structure of polychaete assemblages in the São Sebastião Channel and vicinities [15].…”

“…Spatial and temporal changes in the communities of macrofauna were intensely studied on the São Paulo State shelf, the central part of the SBB. Based on bottom topography, water circulation, sediment deposition, and sedimentary organic matter content, the area was characterized by three subareas: the northern Ubatuba and São Sebastião shelves [13,25,26], the central Santos shelf [24,29] and the southern Cananeia/Iguape shelf. Since sediment was identified to be the structural driving factor for the macrobenthic communities, a detailed explanation of its distribution in the complex continental shelf of São Paulo becomes necessary.…”

“…Polychaetes show up as the most numerous group collected accounting for 51% of total fauna on São Sebastião shelf [28]. Polychaetes and crustaceans Peracarida were studied to species level in order to understand benthic community structure and function [24,31]. Working Integrative Approach to Assess Benthic Ecosystem Functioning on the Southwest Brazilian… DOI: http://dx.doi.org /10.5772/intechopen.88308 with several benthic marine groups of invertebrates proved to be important for bringing consistency and generality to the results obtained.…”

“…Some discriminant species here are the large carnivores Sigambra sp. and Aglaophamus sp., the subsurface deposit feeders Petersenaspis capillata and Leitoscoloplos kerguelensis (polychaetes) [29], and the burrowers Pseudoharpina dentata, Urothoe sp., and Heterophoxus videns (amphipods) [24]. On the other hand, as a transitional region, the intermediary zone is usually characterized by high values of species richness, diversity, and evenness besides chlorophyll-a content correlated with density, which indicates fresh organic matter input.…”