Differences in meiofauna communities with sediment depth are greater than habitat effects on the New Zealand continental margin: implications for vulnerability to anthropogenic disturbance.

Norliana Rosli,Daniel Leduc,P. Keith Probert,Katrin Berkenbusch,Malcolm R. Clark,Ashley A. Rowden,Carlos Neira

doi:10.7717/peerj.2154

Abstract

Studies of deep-sea benthic communities have largely focused on particular (macro) habitats in isolation, with few studies considering multiple habitats simultaneously in a comparable manner. Compared to mega-epifauna and macrofauna, much less is known about habitat-related variation in meiofaunal community attributes (abundance, diversity and community structure). Here, we investigated meiofaunal community attributes in slope, canyon, seamount, and seep habitats in two regions on the continental slope of New Zealand (Hikurangi Margin and Bay of Plenty) at four water depths (700, 1,000, 1,200 and 1,500 m). We found that patterns were not the same for each community attribute. Significant differences in abundance were consistent across regions, habitats, water and sediment depths, while diversity and community structure only differed between sediment depths. Abundance was higher in canyon and seep habitats compared with other habitats, while between sediment layer, abundance and diversity were higher at the sediment surface. Our findings suggest that meiofaunal community attributes are affected by environmental factors that operate on micro- (cm) to meso- (0.1–10 km), and regional scales (> 100 km). We also found a weak, but significant, correlation between trawling intensity and surface sediment diversity. Overall, our results indicate that variability in meiofaunal communities was greater at small scale than at habitat or regional scale. These findings provide new insights into the factors controlling meiofauna in these deep-sea habitats and their potential vulnerability to anthropogenic activities.

Highlights

Continental margins comprise a variety of topographically-defined habitats such as canyons, seamounts and slopes, as well as chemically-defined habitats such as cold seeps and hydrothermal vents (Levin et al, 2010)
Results of DistLM analyses showed that abundance in the 0–1 cm sediment layer was significantly correlated with profile curvature and water depth
Knowledge of the benthic communities associated with distinct habitats in the deep sea has increased significantly during the last decades, as we have a better understanding of how substrate type and availability, biogeochemistry, nutrient input, productivity, hydrographic conditions and catastrophic events shape community patterns on regional scales (Levin et al, 2010; Vanreusel et al, 2010)

Summary

Introduction

Continental margins comprise a variety of topographically-defined habitats such as canyons, seamounts and slopes, as well as chemically-defined habitats such as cold seeps and hydrothermal vents (Levin et al, 2010). Seamounts, which are defined as elevated features that include knolls, pinnacles and hills where the elevation can be as low as 100 m (Clark et al, 2010; Pitcher et al, 2007), can affect surrounding flow conditions resulting in enhanced currents, eddies, up- and down-welling and closed retention cells (Bashmachnikov, Loureiro & Martins, 2013; White et al, 2007) These modified flow conditions increase vertical mixing, spatial variation in sedimentation processes, and the distribution of food resources (Bongiorni et al, 2013; Levin & Dibacco, 1995; Zeppilli et al, 2013). Vent ecosystems are typically dominated by benthic invertebrate taxa that host symbiotic, chemoautotrophic microorganisms, and the infauna of hydrothermally ‘active’ sediments has been shown to differ from that of ‘inactive’ sediments (Levin et al, 2009)

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