Community change in the variable resource habitat of the abyssal northeast Pacific

Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, California 95039, USA.
Ecology (Impact Factor: 4.66). 05/2008; 89(4):991-1000. DOI: 10.1890/06-2025.1
Source: PubMed


Research capable of differentiating resource-related community-level change from random ecological drift in natural systems has been limited. Evidence for nonrandom, resource-driven change is presented here for an epibenthic megafauna community in the abyssal northeast Pacific Ocean from 1989 to 2004. The sinking particulate organic carbon food supply is linked not only to species-specific abundances, but also to species composition and equitability. Shifts in rank abundance distributions (RADs) and evenness, from more to less equitable, correlated to increased food supply during La Niña phases of the El Niño Southern Oscillation. The results suggest that each taxon exhibited a differential response to a sufficiently low dimension resource, which led to changes in community composition and equitability. Thus the shifts were not likely due to random ecological drift. Although the community can undergo population-level variations of one or more orders of magnitude, and the shape of the RADs was variable, the organization retained a significant consistency, providing evidence of limits for such changes. The growing evidence for limited resource-driven changes in RADs and evenness further emphasizes the potential importance of temporally variable disequilibria in understanding why communities have certain basic attributes.

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Available from: Henry A Ruhl, Sep 23, 2015
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    • "The impact of POC on deep-sea animals has been a long-term area of research (Smith, 1987; Wigham et al., 2003a; Robison et al., 2005; Smith et al., 2009; Lampitt et al., 2010; Tecchio et al., 2013). Food supply is known to influence organism abundance , food web structure, and the diversity of communities (Smith and Druffel, 1998; Bett et al., 2001; Smith et al., 2002, 2009; Wigham et al., 2003b; Ruhl and Smith, 2004; Sweetman and Witte, 2008; Ruhl, 2008; Tecchio et al., 2013). However, the impacts of atypically large food influxes (i.e. "
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    ABSTRACT: The seafloor community on an abyssal plain in the NE Pacific (Station M, ∼4000 m depth) was studied between 2006 and 2012 using remotely operated vehicles (ROVs) as part of a continuing 24-year time-series study. New patterns continue to emerge showing that the deep-sea can be dynamic on short time scales, rather than static over long periods. In just over two years the community shifted from a sessile, suspension-feeding, sponge-dominated community to a mobile, detritus-feeding, sea cucumber-dominated assemblage. In 2006 megafaunal diversity (Simpson’s Diversity Index, SDI) was high, yet the community was depauperate in terms of density compared to later periods. Over an 18-month period beginning in spring 2011, the densities of mobile organisms increased by nearly an order of magnitude while diversity decreased below 2006 levels. In late 2012 four sea cucumbers (two Peniagone spp., Elpidia sp. A, and Scotoplanes globosa) were at the highest densities recorded since investigations began at Station M in 1989. For a group of 10 echinoderms investigated over the entire study period, we saw evidence of a long-term cycle spanning two decades. These changes can be tied to a variable food supply originating in shallow water. Large variations over decadal-scales indicate that remote abyssal communities are dynamic and likely subject to impacts from anthropogenic changes like ocean warming, acidification, and pollution manifested in the upper ocean. The degree of dynamism indicates that one-time or short-term investigations are not sufficient for assessing biological community structure in conservation or exploitation studies in the deep sea.
    Progress In Oceanography 05/2014; 124. DOI:10.1016/j.pocean.2014.04.007 · 3.03 Impact Factor
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    • "The projected changes in % biomass are greatest in the abyssal (>3000 m) and hadal zones (>6000 m) as a result of both higher relative changes in low-food conditions and the spatial co-occurrence of these areas with areas of change. These changes are likely to have a major impact as food supply to the benthos is already very low (Smith et al., 2008a; Jamieson et al., 2010) and limiting for benthic communities (Ruhl, 2008). These reductions will likely cause major changes in ecosystem structure, functioning and services across the largest habitat in the world (Smith et al., 2008a). "
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    ABSTRACT: Seafloor organisms are vital for healthy marine ecosystems, contributing to elemental cycling, benthic remineralization, and ultimately sequestration of carbon. Deep-sea life is primarily reliant on the export flux of particulate organic carbon from the surface ocean for food, but most ocean biogeochemistry models predict global decreases in export flux resulting from 21st century anthropogenically induced warming. Here we show that decadal-to-century scale changes in carbon export associated with climate change lead to an estimated 5.2% decrease in future (2091–2100) global open ocean benthic biomass under RCP8.5 (reduction of 5.2 Mt C) compared with contemporary conditions (2006–2015). Our projections use multi-model mean export flux estimates from eight fully coupled earth system models, which contributed to the Coupled Model Intercomparison Project Phase 5, that have been forced by high and low representative concentration pathways (RCP8.5 and 4.5, respectively). These export flux estimates are used in conjunction with published empirical relationships to predict changes in benthic biomass. The polar oceans and some upwelling areas may experience increases in benthic biomass, but most other regions show decreases, with up to 38% reductions in parts of the northeast Atlantic. Our analysis projects a future ocean with smaller sized infaunal benthos, potentially reducing energy transfer rates though benthic multicellular food webs. More than 80% of potential deep-water biodiversity hotspots known around the world, including canyons, seamounts, and cold-water coral reefs, are projected to experience negative changes in biomass. These major reductions in biomass may lead to widespread change in benthic ecosystems and the functions and services they provide.
    Global Change Biology 12/2013; 20(6). DOI:10.1111/gcb.12480 · 8.04 Impact Factor
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    • "The increase in the density of some taxa, and the decrease in others, led to the community shifts observed at the abyssal Porcupine Abyssal Plain (PAP) (Billett et al., 2010) and the Pacific Station M (Ruhl, 2007, 2008). Besides changes in biodiversity and community composition, median body sizes are negatively correlated with higher density (Ruhl, 2008). Changes in the biology and ecology of megafauna also occur spatially and are associated with changes in particle flux quality. "
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    ABSTRACT: We investigated the effects of contrasting surface primary production on the benthic invertebrate megafauna at four sites on the Mid-Atlantic Ridge. The sites, designated NW, NE, SE, were located to the west and east of the Ridge axis and to the north and south of the Charlie–Gibbs Fracture Zone. Benthic megafauna were sampled in 2007 and 2009 with a semi-balloon otter trawl, at a target depth of 2500 m. The total biomass and density of major taxonomic groups did not differ significantly between sites, despite those to the north being characterised by greater surface productivity than those to the south. However, the density and biomass of individual taxonomic groups, as well as diversity and body size, all showed significant differences between sites. Diversity was highest at the SE, and lowest at the NE site. Most species were larger to the north. Community composition was significantly different between all sites, with the greatest number of unique species found at the SE, and noticeably fewer unique species at the northern sites. There was no clear correlation between the surface productivity and community structure, suggesting complex ecological controls on the communities. It is speculated that, in addition to the energy supply, drivers such as strong currents and sediment characteristics, play an important role in shaping the communities at the different sites. To what extent the ridge acts as a dispersal barrier for benthic invertebrate fauna remains unclear. However, high numbers of species unique to the southern site suggest a limited dispersal between the northern and southern areas.
    Deep Sea Research Part II Topical Studies in Oceanography 12/2013; 98. DOI:10.1016/j.dsr2.2013.02.003 · 2.19 Impact Factor
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