Investigating the environmental drivers of deep‐seafloor biodiversity: A case study of peracarid crustacean assemblages in the Northwest Atlantic Ocean

Abstract

The deep‐sea benthos covers over 90% of seafloor area and hosts a great diversity of species which contribute toward essential ecosystem services. Evidence suggests that deep‐seafloor assemblages are structured predominantly by their physical environment, yet knowledge of assemblage/environment relationships is limited. Here, we utilized a very large dataset of Northwest Atlantic Ocean continental slope peracarid crustacean assemblages as a case study to investigate the environmental drivers of deep‐seafloor macrofaunal biodiversity. We investigated biodiversity from a phylogenetic, functional, and taxonomic perspective, and found that a wide variety of environmental drivers, including food availability, physical disturbance (bottom trawling), current speed, sediment characteristics, topographic heterogeneity, and temperature (in order of relative importance), significantly influenced peracarid biodiversity. We also found deep‐water peracarid assemblages to vary seasonally and interannually. Contrary to prevailing theory on the drivers of deep‐seafloor diversity, we found high topographic heterogeneity (at the hundreds to thousands of meter scale) to negatively influence assemblage diversity, while broadscale sediment characteristics (i.e., percent sand content) were found to influence assemblages more than sediment particle‐size diversity. However, our results support other paradigms of deep‐seafloor biodiversity, including that assemblages may vary inter‐ and intra‐annually, and how assemblages respond to changes in current speed. We found that bottom trawling negatively affects the evenness and diversity of deep‐sea soft‐sediment peracarid assemblages, but that predicted changes in ocean temperature as a result of climate change may not strongly influence continental slope biodiversity over human timescales, although it may alter deep‐sea community biomass. Finally, we emphasize the value of analyzing multiple metrics of biodiversity and call for researchers to consider an expanded definition of biodiversity in future investigations of deep‐ocean life.

Marine macroinvertebrate species-area relationships, assemblage structure and their environmental drivers on submarine banks

“…In fact, the timing of spawning events for Pandalus borealis, a locally abundant shrimp species, was found to coincide with the spring bloom (Koeller et al 2009). Further, food availability has been identified as a significant driver of peracarid biodiversity in the Northwest Atlantic in the vicinity of Flemish Cap and the Grand Banks off Newfoundland (Ashford et al 2019). We hypothesized that banks with greater chl a (resource) concentrations year-round would support larger populations and possibly higher alpha diversity within each group.…”

“…Ocean currents (which can transport passive particles such as larvae) can play a significant role in connecting like habitats and establishing similar assemblages of species (Moritz et al 2013). Variation in key habitat properties such as food availability, anthropogenic disturbance, current speed, habitat heterogeneity and temperature often leads to variation in assemblage structure in spite of flow connectivity and the innate dispersal capacity of marine organisms (Edgar et al 2004, Mouquet et al 2006, Rincón & Kenchington 2016, Ashford et al 2019. With a strong along-shelf current (NE−SW) potentially connecting the 10 offshore banks of the Scotian Shelf (SS; ranging in area from 500 to 10 500 km 2 on a ~122 000 km 2 shelf between 43 and 46°N latitude; Fig.…”

Shedding Light on Deep-Sea Biodiversity—A Highly Vulnerable Habitat in the Face of Anthropogenic Change

“…Another obvious threat is fishing activity-bottom trawling is a common fishing method targeting demersal fishes that threatens marine biodiversity by changing the sediment topography, increasing sediment resuspension, and consequently changing nutrient composition (Pusceddu et al, 2014). In addition, removing large mobile predators from the seabed can cause shifts in predator-prey dynamics (Ashford et al, 2019).…”

A Blueprint for an Inclusive, Global Deep-Sea Ocean Decade Field Program

“…At regional levels, Regional Fisheries Management Organizations (RFMOs) and national monitoring programs can provide satellite-derived data on marine vessel movements. These data enable a reasonably accurate assessment of the spatial distribution of fishing pressure (e.g., NAFO data input to benthic studies in the NW Atlantic; Ashford et al, 2018Ashford et al, , 2019.…”