Abstract
Vulnerable marine ecosystems (VMEs) are considered hotspots of biodiversity and ecosystem functioning in the deep sea, but are also characterised by a high vulnerability to disturbance and a low recovery potential. Since 2006, a series of United Nations General Assembly resolutions have been developed, attempting to ensure the protection of VMEs in international waters. In the Northwest Atlantic Fisheries Organisation (NAFO) Regulatory Area, large areas of seabed have been closed to bottom-contact fishing to protect VMEs. However, knowledge of the influence of VME-indicator taxa on macrofaunal assemblages, and the appropriateness of current fishery closures for protecting macrofaunal biodiversity in this area is limited. Here we investigate relationships between the prevalence of VME-indicator taxa (poriferans [sponges], gorgonian corals and pennatulaceans [sea pens]) and an extensive suite of peracarid crustacean biodiversity metrics in the NAFO Regulatory Area. We also examine whether the current NAFO VME closures protect areas of significantly elevated peracarid diversity. Of the VME-indicator taxa analysed, poriferans were found to have by far the greatest influence over peracarid assemblages. Assemblage structure was altered, and peracarid abundance, biomass, richness, diversity, and variability were enhanced in areas of elevated poriferan biomass, whilst assemblage evenness was slightly depressed in these areas. These findings reaffirm the perception of poriferans as crucial components of VMEs. In contrast, gorgonian coral density had little influence over the faunal assemblages investigated, perhaps reflecting their relatively low prevalence in the study area. Similarly, pennatulaceans were found to influence peracarid assemblages only weakly. This too may reflect a moderately low density of Pennatulacea in the study area. Our results highlight that the application of taxon distribution model outputs to ecological investigations and management decisions in data-limited environments should be treated with caution. Finally, our results indicate that the current system of fishery closures in the NAFO Regulatory Area may not be optimal in terms of providing adequate protection to VMEs against the impacts of bottom trawling.
Highlights
This study aims to investigate the influence of poriferan grounds, gorgonian forests and pennatulacean fields on macrobenthic peracarid crustacean assemblages, as well as to determine whether or not the current fishery closures enforced by Northwest Atlantic Fisheries Organisation (NAFO) protect areas of significantly enhanced peracarid biodiversity compared to other areas in the study region
Striking was the clear dominance of poriferan grounds over the coral habitats analysed in terms of their influence on peracarid assemblages
Our results suggest that species distribution models are not yet dependable enough to be applied as the sole source of information for ecological investigations or management decisions in the NAFO Regulatory Area
Summary
The concept of a “Vulnerable Marine Ecosystem” (VME) centres upon the presence of distinct, diverse benthic assemblages that are limited and fragmented in their spatial extent, and dominated (in terms of biomass and/or spatial cover) by rare, endangered or endemic component species that are physically fragile and vulnerable to damage (or structural/biological alteration) by human activities (Fuller et al, 2008; Rogers et al, 2008; FAO, 2009; Parker et al, 2009; Rogers and Gianni, 2009; Auster et al, 2011; Hansen et al, 2013). Starting in 2004, a series of United Nations General Assembly (UNGA) resolutions of increasing strength and urgency were adopted: UNGA 59/25 (2004), UNGA 61/105 (2006), UNGA 64/72 (2009), UNGA 66/68 (2011), and UNGA 71/123 (2016) These resolutions called for states and Regional Fisheries Management Organisations (RFMOs) to formally recognise the immense importance and value of deep-sea ecosystems and the biodiversity that they contain by adhering to the precautionary principle and ecosystem approach when harvesting biological products from the deep sea. A SAI is defined as any disturbance to a VME that impairs the ability of affected VME constituent populations to replace themselves, degrades the long-term productivity of the habitat, and causes a significant loss of species richness, habitat diversity and structure whilst occurring at an interval that is, on average, shorter than the recovery time for the habitat in question (Hogg et al, 2010)
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