Environmental and Geomorphological Effects on the Distribution of Deep-Sea Canyon and Seamount Communities in the Northwest Atlantic

Kristen Mello-Rafter,Jennifer A Dijkstra,Derek Sowers,Les Watling,Mashkoor Malik,Larry A Mayer

doi:10.3389/fmars.2021.691668

Abstract

Deep sea canyons and seamounts are topographically complex features that are considered to be biological hotspots. Anthropogenic pressures related to climate change and human activities are placing the species that inhabit these features at risk. Though studies have examined species composition on seamounts and canyons, few have compared communities between them, and even fewer studies have examined how species’ abundances correlate with environmental conditions or geomorphology. Consequently, this study compares species composition, community structure, and environmental variables between Northwest Atlantic continental margin canyons and seamounts along the New England Seamount Chain. Geoforms were also related to the occurrence of phyla and biodiversity. Overall, there was a significant difference in species composition between canyons and seamounts with sponges, corals, sea urchins and seastars contributing heavily to observed differences. Environmental conditions of temperature and salinity and the seafloor property slope contributed significantly to communities observed on seamounts, while substrate, depth and salinity contributed significantly to canyon communities. Abundances were significantly higher in canyons, but taxonomic richness, evenness, and diversity were all greater on seamounts. In an era where climate change and human activity have the potential to alter environmental parameters in the deep sea, it is important to examine factors that influence the spatial distribution of deep-sea benthic communities.

Highlights

Biological communities in the deep sea can be heavily impacted by commercial fishery trawling (Althaus et al, 2009; Hiddink et al, 2017), are predicted to experience climate-related stress (Lazier, 1988; Dickson et al, 2002; Levin and Le Bris, 2015; Danovaro et al, 2017), and face future potential threats from deep sea mining
This study demonstrates that there are significant differences in species composition between canyon and seamount communities that are driven by the abundances of sponges, sea urchins and corals
Abundances of sponges and the coral Corallium spp. were higher on seamounts than in canyons, while abundances of the cup coral Desmophyllum dianthus were much greater in canyons

Summary

Introduction

Biological communities in the deep sea can be heavily impacted by commercial fishery trawling (Althaus et al, 2009; Hiddink et al, 2017), are predicted to experience climate-related stress (Lazier, 1988; Dickson et al, 2002; Levin and Le Bris, 2015; Danovaro et al, 2017), and face future potential threats from deep sea mining. Recent studies indicate that water column properties of the deep-sea are changing in response to a changing climate The deep sea has been warming over the past decades and it is predicted this trend will continue with on-going changes in climate (Bindoff et al, 2019). The proposed rate of warming of 0.01–0.1◦C per decade (Purkey and Johnson, 2010) in the deep ocean (1,000– 4,000 m) may accelerate due to climate change (BritoMorales et al, 2020). In addition to warming, dissolved oxygen (DO) has declined over the past few decades and this trend is predicted to continue (Joos et al, 2003; Schmidtko et al, 2017). Anthropogenic stressors associated to changes in climate may lead to changes in the distribution and abundance of deep-sea benthic communities

Methods

Results

Conclusion