Dataset Information

Seamounts are hotspots of pelagic biodiversity in the open ocean.

ABSTRACT: The identification of biodiversity hotspots and their management for conservation have been hypothesized as effective ways to protect many species. There has been a significant effort to identify and map these areas at a global scale, but the coarse resolution of most datasets masks the small-scale patterns associated with coastal habitats or seamounts. Here we used tuna longline observer data to investigate the role of seamounts in aggregating large pelagic biodiversity and to identify which pelagic species are associated with seamounts. Our analysis indicates that seamounts are hotspots of pelagic biodiversity. Higher species richness was detected in association with seamounts than with coastal or oceanic areas. Seamounts were found to have higher species diversity within 30-40 km of the summit, whereas for sets close to coastal habitat the diversity was lower and fairly constant with distance. Higher probability of capture and higher number of fish caught were detected for some shark, billfish, tuna, and other by-catch species. The study supports hypotheses that seamounts may be areas of special interest for management for marine pelagic predators.

SUBMITTER: Morato T

PROVIDER: S-EPMC2906904 | biostudies-literature | 2010 May

REPOSITORIES: biostudies-literature

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Seamounts are hotspots of pelagic biodiversity in the open ocean.

Morato Telmo T Hoyle Simon D SD Allain Valerie V Nicol Simon J SJ

Proceedings of the National Academy of Sciences of the United States of America 20100506 21

The identification of biodiversity hotspots and their management for conservation have been hypothesized as effective ways to protect many species. There has been a significant effort to identify and map these areas at a global scale, but the coarse resolution of most datasets masks the small-scale patterns associated with coastal habitats or seamounts. Here we used tuna longline observer data to investigate the role of seamounts in aggregating large pelagic biodiversity and to identify which pe ...[more]

PMID: 20448197

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Project description:Seamounts have been likened to "oases" of life in the comparative deserts of the open ocean, often harbouring high densities of threatened and exploited pelagic top predators. However, few such aggregations have been studied in any detail and the mechanisms that sustain them are poorly understood. Here, we present the findings of an integrated study of 3 previously unexplored seamounts in the tropical Atlantic, which aimed to investigate their significance as predator "hotspots" and inform their inclusion in one of world's largest marine reserves. Baited underwater video and visual census transects revealed enhanced diversity and biomass of pelagic top predators, including elevated abundances of 7 species of sharks, predatory fish, and seabirds, within 5 km of 2 shallow seamounts (<100 m), but not a third deeper seamount (260 m). Hydroacoustic biomass of low- and mid-trophic level "prey" was also significantly elevated within 2.5 km of shallow seamounts. However, we found no evidence of enhanced primary productivity over any feature, suggesting high faunal biomass is sustained by exogenous energy inputs. Relative biomass enrichment also increased with trophic level, ranging from a 2-fold increase for zooplankton to a 41-fold increase for sharks. Tracking of the dominant predator species revealed that individual sharks (Galapagos, silky) and tuna (yellowfin, bigeye) often resided around seamounts for months to years, with evidence of connectivity between features, and (in the case of sharks) were spatially aggregated in localised hotspots that coincided with areas of high mid-trophic biomass. However, tuna and silky sharks also appeared to use seamounts as "hubs" in more extensive pelagic foraging ranges, which may help explain disproportionately high predator density. Our results reinforce the conservation significance of shallow seamounts for many marine top predators and offer fundamental insights into their functional roles as both prey "oases" and activity hubs for these species.

Project description:With the ongoing crisis of biodiversity loss and limited resources for conservation, the concept of biodiversity hotspots has been useful in determining conservation priority areas. However, there has been limited research into how temporal variability in biodiversity may influence conservation area prioritization. To address this information gap, we present an approach to evaluate the temporal consistency of biodiversity hotspots in large marine ecosystems. Using a large scale, public monitoring dataset collected over an eight year period off the US Pacific Coast, we developed a methodological approach for avoiding biases associated with hotspot delineation. We aggregated benthic fish species data from research trawls and calculated mean hotspot thresholds for fish species richness and Shannon's diversity indices over the eight year dataset. We used a spatial frequency distribution method to assign hotspot designations to the grid cells annually. We found no areas containing consistently high biodiversity through the entire study period based on the mean thresholds, and no grid cell was designated as a hotspot for greater than 50% of the time-series. To test if our approach was sensitive to sampling effort and the geographic extent of the survey, we followed a similar routine for the northern region of the survey area. Our finding of low consistency in benthic fish biodiversity hotspots over time was upheld, regardless of biodiversity metric used, whether thresholds were calculated per year or across all years, or the spatial extent for which we calculated thresholds and identified hotspots. Our results suggest that static measures of benthic fish biodiversity off the US West Coast are insufficient for identification of hotspots and that long-term data are required to appropriately identify patterns of high temporal variability in biodiversity for these highly mobile taxa. Given that ecological communities are responding to a changing climate and other environmental perturbations, our work highlights the need for scientists and conservation managers to consider both spatial and temporal dynamics when designating biodiversity hotspots.

Dataset Information

Seamounts are hotspots of pelagic biodiversity in the open ocean.

Publications

Seamounts are hotspots of pelagic biodiversity in the open ocean.

Similar Datasets

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