Active Ecological Restoration of Cold-Water Corals: Techniques, Challenges, Costs and Future Directions

Abstract

Cold-water coral (CWC) habitats dwell on continental shelves, slopes, seamounts, and ridge systems around the world’s oceans from 50 to 4000 m depth, providing heterogeneous habitats which support a myriad of associated fauna. These highly diverse ecosystems are threatened by human stressors such as fishing activities, gas and oil exploitation, and climate change. Since their life-history traits such as long lifespan and slow growth rates make CWCs very vulnerable to potential threats, it is a foremost challenge to explore the viability of restoration actions to enhance and speed up their recovery. In contrast to terrestrial and shallow-water marine ecosystems, ecological restoration in deep marine environments has received minimal attention. This review, by means of a systematic literature search, aims to identify CWC restoration challenges, assess the most suitable techniques to restore them, and discuss future perspectives. Outcomes from the few restoration actions performed to date on CWCs, which have lasted between 1 to 4 years, provide evidence of the feasibility of coral transplantation and artificial reef deployments. Scientific efforts should focus on testing novel and creative restoration techniques, especially to scale up to the spatial and temporal scales of impacts. There is still a general lack of knowledge about the biological, ecological and habitat characteristics of CWC species exploration of which would aid the development of effective restoration measures. To ensure the long-term viability and success of any restoration action it is essential to include holistic and long-term monitoring programs, and to ideally combine active restoration with natural spontaneous regeneration (i.e., passive restoration) strategies such as the implementation of deep-sea marine protected areas (MPAs). We conclude that a combination of passive and active restoration approaches with involvement of local society would be the best optimal option to achieve and ensure CWC restoration success.

When Scientists and Industry Technologies Mitigate Habitat Loss: The First Bioconstruction Relocation in the Mediterranean Sea

“…-The use of artificial structures (namely the cause of the disturbance, TAP pipeline), as in cold-water corals or deepsea restoration interventions due to operational issues (O'Connor et al, 2020;Montseny et al, 2021); -The relocation of the portions of the reefs that would have been lost during the laying of the TAP pipeline, following the transplanting fragmented dislodged colonies widespread in coral reef environments (Henry and Hart, 2005;Forrester et al, 2011).…”

“…The experience and methods developed in shallow coral active restoration represent a great opportunity to successfully address the challenges of restoring deeper similar ecosystems, such as cold-water coral habitats (Montseny et al, 2021). The advent of mitigation interventions on deeper ecosystems, broadly known as deep-sea restoration, poses new challenges related to habitat features, operational difficulties, and high costs (Van Dover et al, 2014).…”

Feasibility of the Sabellarid Reef Habitat Restoration

“…1 It, indeed, is a global project launched by the United Nations for the decade 2021-2030 (Decade on Ecosystem Restoration, 2021) 2 and is an integral part of the European Green Deal and the Mission Starfish 2030. 3 So far, some efforts have been made to restore degraded and threatened marine habitats (e.g., Boström-Einarsson et al, 2020;Cebrian et al, 2021;Montseny et al, 2021). In the Mediterranean Sea, several studies focused on the restoration of coralligenous formations (Fava et al, 2010;Forcioli et al, 2011;Montero-Serra et al, 2017;Topçu et al, 2018;Montseny et al, 2019;Pagès Escolà et al, 2020;Casoli et al, 2021), seagrass meadows (Pirrotta et al, 2015;Alagna et al, 2019;Da Ros et al, 2021;Mancini et al, 2021;Piazzi et al, 2021;Ventura et al, 2021), macroalgal forests (De La Fuente et al, 2019;Tamburello et al, 2019), and other vulnerable habitat-forming species (Baldacconi et al, 2010;Musco et al, 2017).…”

Food Preferences of Mediterranean Cold-Water Corals in Captivity

“…CWCs are threatened by several anthropogenic activities (D'Onghia et al, 2016;Ragnarsson et al, 2016;Montseny et al, 2021). Among them, deep-sea fisheries directly affect CWC reefs (D'Onghia, 2019), up to an estimated 95-98% of the total coral cover (Gianni, 2004).…”

“…Considering that the research field on ecological restoration of deep-sea ecosystems is still in its infancy (Da Ros et al, 2019), only few studies focus on CWCs active restoration actions, as reported in the literature (Montseny et al, 2021). The transplantation of nubbins taken from healthy colonies or reared in aquaria into degraded coral grounds is the preferred restoration action (Da Ros et al, 2019 and references therein).…”