Environmental Influences on Regional Deep-Sea Species Diversity

Abstract

▪ Abstract Most of our knowledge of biodiversity and its causes in the deep-sea benthos derives from regional-scale sampling studies of the macrofauna. Improved sampling methods and the expansion of investigations into a wide variety of habitats have revolutionized our understanding of the deep sea. Local species diversity shows clear geographic variation on spatial scales of 100–1000 km. Recent sampling programs have revealed unexpected complexity in community structure at the landscape level that is associated with large-scale oceanographic processes and their environmental consequences. We review the relationships between variation in local species diversity and the regional-scale phenomena of boundary constraints, gradients of productivity, sediment heterogeneity, oxygen availability, hydrodynamic regimes, and catastrophic physical disturbance. We present a conceptual model of how these interdependent environmental factors shape regional-scale variation in local diversity. Local communities in the deep sea may be composed of species that exist as metapopulations whose regional distribution depends on a balance among global-scale, landscape-scale, and small-scale dynamics. Environmental gradients may form geographic patterns of diversity by influencing local processes such as predation, resource partitioning, competitive exclusion, and facilitation that determine species coexistence. The measurement of deep-sea species diversity remains a vital issue in comparing geographic patterns and evaluating their potential causes. Recent assessments of diversity using species accumulation curves with randomly pooled samples confirm the often-disputed claim that the deep sea supports higher diversity than the continental shelf. However, more intensive quantitative sampling is required to fully characterize the diversity of deep-sea sediments, the most extensive habitat on Earth. Once considered to be constant, spatially uniform, and isolated, deep-sea sediments are now recognized as a dynamic, richly textured environment that is inextricably linked to the global biosphere. Regional studies of the last two decades provide the empirical background necessary to formulate and test specific hypotheses of causality by controlled sampling designs and experimental approaches.

Broad-scale patterns in local diversity of marine benthic harpacticoid copepods (Crustacea)

“…A positive link with productivity has often been considered as the major cause of deep-sea diversity patterns, although the direct evidence for this is currently scarce and ambiguous (Levin et al 2001). Tietjen (1989) Along with the depth-related effect of productivity, our regressions for α diversity also include depth per se as an independent term (Table 2, Models 1, 2, and 6), indicating the existence of some other depthrelated factor(s) that increases richness.…”

“…For example, in a large-scale study, Rombouts et al (2009) found a significant inverse relationship of marine epipelagic (0−200 m) copepod diversity with chl a content, indicating that diversity is high in oligotrophic regions. There are a number of hypotheses to explain the 'decrease phase' of the diversity−productivity relationship, and some of these hypotheses are applicable to marine meiofauna (see Rosenzweig 1995, Levin et al 2001 for a review).There is some additional, though indirect, evidence for negative effects of productivity in the intertidal and subtidal zones. A positive relationship between total meiofaunal abundance and the input of organic matter has been reported repeatedly (De Troch et al 2006, Mokievsky et al 2007, Lampadariou et al 2009).…”

Relationship of benthic foraminiferal diversity to paleoproductivity in the Neogene Caribbean

“…8. Combination of the TROX model (trophic condition and oxygen concentration of Jorissen et al, 1995;Jorissen, 1999) and the parabolic curve of Levin et al (2001) explaining the relationship of local species diversity and productivity (modified after Gooday, 2003). Diversity is low in highly oligotrophic areas such as the Arctic Ocean where food supply (flux of organic carbon to the seafloor = productivity) is very low and thus incapable of sustaining large number of species.…”

“…A present day analogue for describing the relationship of diversity and paleoproductivity noted in the Caribbean can be explained by combining the TROX model (trophic condition and oxygen concentration of Jorissen et al, 1995;Jorissen, 1999) and the parabolic curve of Levin et al (2001), which explains the relationship of local species diversity and productivity (Gooday, 2003;Fig. 8).…”

“…The late Miocene-early Pliocene gradual constriction to complete closure of the CAS also ended the input of highproductivity Pacific waters, leading to decreased paleoproductivity in the Caribbean (Jain and Collins, 2007). Deep-sea benthic foraminiferal diversity is largely controlled by changes in trophic conditions (the availability of food), oxygen concentration and current velocity (Mackensen et al, 1990(Mackensen et al, , 1995Schmiedl et al, 1997;Levin et al, 2001;Gooday, 2003). All are known to induce varied changes in surface-water productivity (Thomas and Gooday, 1996).…”