Underwater Visual Records of Marine Megafauna Around Offshore Anthropogenic Structures

Victoria L. G. Todd,Dianne L. McLean,Laura Lazar,Ingrid T. Peters,Sophie E. Cox,Laura D. Williamson,Aimee L. Hoover,Ian. B. Todd,Peter I. Macreadie

doi:10.3389/fmars.2020.00230

Abstract

In oceans and seas worldwide, an increasing number of end-of-life anthropogenic offshore structures (e.g. platforms, pipelines, manifolds, windfarms, etc.) are facing full or partial removal. As part of the decommissioning process, studies on potential importance of subsea infrastructure to marine megafauna (defined as: cetaceans, pinnipeds, sirenians, large fish – such as sharks, rays, billfishes, and tuna, as well as marine reptiles, and seabirds) are lacking. Dedicated scientific Remotely Operated Vehicle (ROV) surveys around offshore installations are rare, but there is a wealth of archived industrial data and noteworthy species sightings posted publicly on various social media platforms. This study used routine, incidentally-collected ROV (n = 73) and commercial diver (n = 9) video recordings spanning 1998–2019 globally. Data were gathered directly from industrial partners (n = 36) and the public domain (YouTube; n = 46) to provide an account of marine megafauna presence and potential feeding behaviour in the near visible vicinity of subsea anthropogenic structures. A total of 79 video clips and 3 still images of marine megafauna near offshore structures were examined, resulting in 67 individual sightings and 16 sub-sightings (in which an individual was recorded within the same day). At least 178 individuals were identified to a minimum of 17 species of marine megafauna, amounting to a total (combined) sighting duration of 01:09:35 (hh:mm:ss). Results demonstrated proximate presence of marine megafauna (many of which are threatened species) to anthropogenic structures, with most animals displaying foraging or interaction behaviours with the structures. Observations included the deepest (2,779 m) confirmed record of a sleeper shark (Somniosus spp.) and the first confirmed visual evidence of seals following pipelines. These ROV observations demonstrate a latent source of easily-accessible information that can expand understanding of marine megafauna interactions with offshore anthropogenic infrastructure. Consequently, other workers in this field should be encouraged to re-analyse archived datasets, commence further collaborative research projects with industrial partners, and/or expand Internet search terms to additional species assemblages, in a bid to quantitatively elucidate relationships between offshore infrastructure and marine species.

Highlights

Since the industrial revolution, many species have been struggling to cope with habitat modifications, climate change, and other detrimental anthropogenic pressures (e.g., Cheung et al, 2009; Dirzo et al, 2014; IPBES, 2019)
The info@ call for new industrial footage elicited zero response from industry; most videos (n = 46) were sourced from the public domain (YouTube), and n = 36 were from archived or obtained directly from colleagues working in the Oil & Gas (O&G) industry
This review evaluated presence and potential behavior of marine megafauna around offshore anthropogenic structures through video sub-surface sightings from opportunistic industrysupplied or openly-available Remotely Operated Vehicle (ROV) and commercial-diver data collected during General Visual Inspection (GVI) or IMR operations

Summary

Introduction

Many species have been struggling to cope with habitat modifications, climate change, and other detrimental anthropogenic pressures (e.g., Cheung et al, 2009; Dirzo et al, 2014; IPBES, 2019). Subsea-anthropogenic infrastructure provides structurally complex hard substrata on an often otherwise featureless sedimentary seafloor (Larcom et al, 2014). These structures can accommodate diverse sessile-invertebrate communities comprising anemones, hydroids, bryozoans, sponges, mussels, barnacles, soft, and even hard corals that can attract motile invertebrates (Guerin, 2009; Langhamer and Wilhelmsson, 2009; McLean et al, 2017; Meyer et al, 2018; Todd et al, 2018, 2019). Anthropogenic infrastructure has large-scale positive and negative social, economic, and ecological impacts. These structures sustain trophic connectivity through nutrient and resource flow, pelagic-larval dispersal, pipeline linkage, and movement of mobile predators (Macreadie et al, 2011; Henry et al, 2018; van der Molen et al, 2018)

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