Hydrodynamic Connectivity of Habitats of Deep-Water Corals in Corsair Canyon, Northwest Atlantic: A Case for Cross-Boundary Conservation

Abstract

Deep-water corals are significant ecosystem engineers that provide habitat complexity in the deep sea. They are indicator species of vulnerable marine ecosystems because of their slow growth and longevity, characteristics that can prolong recovery from disturbances such as fishing. For populations with discontinuous distributions, such as aggregations of deep-water corals, population connectivity is critical in regulating persistence and recovery and is one of the recommended elements in the design of area-based conservation measures. In this study, we assessed potential pathways of connectivity in the Corsair Canyon Conservation Area, off Nova Scotia, Canada, for populations of the deep-water corals Paragorgia arborea and Primnoa resedaeformis discovered in 2014 and afforded protection in 2016. Corsair Canyon located in the Canadian EEZ, ∼ 20 km from the border between Canada and the United States, is potentially receiving larvae from either the Canadian or US EEZ. In Corsair Canyon, P. arborea was very abundant at depths 484-856 m and some colonies of P. arborea were > 2 m high. These are the locally densest aggregations of P. arborea we have detected on the continental slope off Nova Scotia. We also recorded P. resedaeformis at similar depths. Colonies of both species were most often seen attached perpendicularly to a rock face, and into the current. We assessed hydrodynamic connectivity between Corsair Canyon and other canyons to the northeast and southwest along the continental slope with known occurrences of the two corals, using the ocean model Finite-Volume Community Ocean Model (University of Massachusetts-Dartmouth). Our results indicate that estimated hydrodynamic connectivity originates consistently from canyons to the southwest of Corsair Canyon, particularly Georges, and Heezen Canyons. Of these, only Georges Canyon is within Canada's EEZ and based on our data has very sparse populations of corals that can supply potential recruits. Predicted connectivity with the Northeast Channel Coral Conservation Area occurs in winter and spring, but the complexity of circulation in those seasons needs to be resolved to confirm the strength of this connection. Our results strongly suggest that cross-boundary coordination is essential in the conservation of aggregations of deep-water corals in the northwest Atlantic, by ensuring larval exchange and connectivity.

Genetic diversity and connectivity of chemosynthetic cold seep mussels from the U.S. Atlantic margin

“…Benthic lander observations combined with conductivity-temperature-depth casts have indicated complex water mass structure, current speeds and directions, tidal forcing, and internal waves within the canyons [77]. Although the exact mechanisms are unclear, it is possible that larvae are entrained within canyon environments within particular months or seasons [78]. G. childressi larvae are known to ontogenetically migrate to the surface, but they have also been collected near the seabed [58,61,73].…”

UK deep‐sea conservation: Progress, lessons learned, and actions for the future

“…Perhaps one of the most challenging aspects of MPA network design is the adequate incorporation of MPA network connectivity (Johnson et al, 2014) and indeed this may well call for trans-national collaboration (Metaxas, Lacharité, & de Mendonça, 2019), although very few have tested this in practice (e.g. Baco et al, 2016).…”

Climate-Change Refugia for the Bubblegum Coral Paragorgia arborea in the Northwest Atlantic

“…Smaller aggregations of Paragorgia spp. are similarly protected in the Corsair and Georges Canyons Conservation Area (Metaxas et al, 2019), in the Gully Marine Protected Area (Breeze and Fenton, 2007), and the Lophelia Coral Conservation Area, at the mouth of the Laurentian Channel (Beazley et al, 2021a).…”

“…Predictive models of species distributions, when presented with associated levels of uncertainty, enable managers to make informed decisions on the trade-offs implicit in marine spatial planning (Lester et al, 2013;Grorud-Colvert et al, 2014;Carr, 2019;Metaxas et al, 2019), while insight into the impacts of climate change on the size and configuration of suitable habitat, can improve network design (Santos et al, 2020). Meanwhile, Lagrangian particle tracking (LPT) models are valuable for assessing connectivity (e.g., Bracco et al, 2019;Kenchington et al, 2019b;Metaxas et al, 2019;Zeng et al, 2019;Wang et al, 2020;Wang et al, 2021), and can provide independent support for the evaluation of species distribution models (Kenchington et al, 2019b;Wang et al, 2021). In LPT models, virtual "particles" are advected by flow fields derived from numerical ocean models.…”