Environmental predictors and turnover of biota along a seamount chain

Abstract

Biological communities on seamounts are widely regarded as being distinct from those in other offshore habitats, but it is unclear what factors drive any differences. We used invertebrate and algal data from the extensive REVIZEE benthic surveys from the continental margin and seamounts in the Southwest Atlantic Ocean off Eastern Brazil to investigate environmental predictors of seamount assemblage composition. We found that seamount summit samples were significantly different from those of the continental shelf for both invertebrates and algae. Invertebrate samples from the shelf showed more spatial variability than those from seamounts, congruent with the increased variability in both sampled sea‐floor habitats and oceanographic conditions recorded along the continental margin. The most important environmental predictors of assemblage composition across all habitats were distance from shore, temperature, dissolved oxygen and particulate organic carbon for invertebrates, and distance from shore, nitrate and phosphate concentrations for algae. Only distance from shore for invertebrates, and distance from shore, nitrate and phosphate concentrations for algae were consistently emphasised in analyses restricted to seamount and island samples. We found no support for the hypothesis that seamount assemblages in this region become less species rich with distance from the continental margin. However, algal samples did form a serial gradient of compositional turnover with distance from shore. In summary, the seamounts shared the same species pool as nearby continental margins but samples contained a different, equally rich, assemblage of species.

Kelps’ Long-Distance Dispersal: Role of Ecological/Oceanographic Processes and Implications to Marine Forest Conservation

“…Many suitable deeper refuges for these species can be identified, such as the Rio Grande rocky parcels at Rio Grande Sul State, southern Brazil, or Vitória Trindade seamounts, Espírito Santo State, southwestern Brazil. In these environments the topography of the seamounts can promote the upwelling of the cold nutrient rich waters, cooling and fertilizing the warmer, oligotrophic shallow waters [110], and in turn provide potentially ecophysiological conditions for the development of kelp spores or germlings [93]. We reinforce that the apparent absence of both species in areas with high habitat suitability is probably a consequence of absence or scarcity of sampling efforts.…”

Science Priorities for Seamounts: Research Links to Conservation and Management

“…At the regional scale, similarities in faunal composition between seamounts and other habitats have been reported for galatheids [17] and molluscs [30] in the South Pacific: in both cases, seamounts share a common regional pool of species with the communities of non-seamount habitats. On seamounts along the Vitoria-Trinidade seamount chain off Brazil, the general invertebrate assemblages differ from those on the shelf, yet there is no gradient in species richness with distance offshore along the linear east-west chain [41]. These recent studies emphasise that it is impossible to generalise about the spatial scales over which faunal assemblages of seamounts are structured.…”

Preliminary observations on the benthic marine algae of the Gorringe seabank (northeast Atlantic Ocean)

“…requienii, Nitophyllum punctatum, Spermothamnion strictum, Ectocarpus siliculosus, Saccorhiza polyschides, Bryopsis hypnoides, Valonia macrophysa and V. utricularis. Reasons for the differing algal assemblages and the separate occurrence of the kelps L. ochroleuca and S. polyschides, respectively, on these seamounts are unclear, but may reflect a gradient of changing algal species assemblages as noted by O'Hara et al (2010) in the southwest Atlantic Ocean.…”