Abstract
Abstract. With the mining of polymetallic nodules from the deep-sea seafloor once more evoking commercial interest, decisions must be taken on how to most efficiently regulate and monitor physical and community disturbance in these remote ecosystems. Image-based approaches allow non-destructive assessment of the abundance of larger fauna to be derived from survey data, with repeat surveys of areas possible to allow time series data collection. At the time of writing, key underwater imaging platforms commonly used to map seafloor fauna abundances are autonomous underwater vehicles (AUVs), remotely operated vehicles (ROVs) and towed camera “ocean floor observation systems” (OFOSs). These systems are highly customisable, with cameras, illumination sources and deployment protocols changing rapidly, even during a survey cruise. In this study, eight image datasets were collected from a discrete area of polymetallic-nodule-rich seafloor by an AUV and several OFOSs deployed at various altitudes above the seafloor. A fauna identification catalogue was used by five annotators to estimate the abundances of 20 fauna categories from the different datasets. Results show that, for many categories of megafauna, differences in image resolution greatly influenced the estimations of fauna abundance determined by the annotators. This is an important finding for the development of future monitoring legislation for these areas. When and if commercial exploitation of these marine resources commences, robust and verifiable standards which incorporate developing technological advances in camera-based monitoring surveys should be key to developing appropriate management regulations for these regions.
Highlights
The increasing demand for tech metals for consumer and industrial high-technology devices has again stoked interest in the potential use of global deep-sea polymetallic-nodule fields as exploitable sources of these materials in the near future (Yamazaki and Brockett, 2017; Peukert et al, 2018a; Volkmann and Lehnen, 2018)
Schoening et al.: Megafauna community assessment of polymetallic-nodule fields with cameras multaneously driving the technological development of marine mining equipment and the granting of exploration contracts within the Clarion–Clipperton Fracture Zone (CCFZ) (Lodge et al, 2014), has stimulated several recent European research projects (e.g. JPI Oceans MiningImpact 1–2 and MIDAS)
Focused scientific study commenced in the 1980s, with simulated mining studies conducted in both areas, to assess the response of fauna to mining activities (Lam et al, 2006). These studies are summarised in Jones et al (2017), with the “DISturbance and COLonization” (DISCOL) longterm study in the Peru Basin being the most extensively perturbated region of seafloor studied to date (Thiel, 2001)
Summary
The increasing demand for tech metals for consumer and industrial high-technology devices has again stoked interest in the potential use of global deep-sea polymetallic-nodule fields as exploitable sources of these materials in the near future (Yamazaki and Brockett, 2017; Peukert et al, 2018a; Volkmann and Lehnen, 2018). Despite the occurrence of nodule fields in the Atlantic, Pacific and Indian oceans, the majority of research efforts have been focused on the CCFZ, located in the northern– central Pacific, as it has the highest known density of nodules (Mullineaux, 1987; Jones et al, 2017; Simon-Lledó et al, 2019b), and the Peru Basin (southern–central Pacific) (Bluhm, 2001; Purser et al, 2016; Simon-Lledó et al, 2019a) Both regions have been considered to potentially host commercial abundances of nodules at some point in history. This study aims to provide useful information and guidance on how future optical monitoring of these and other remote ecosystems should most effectively and efficiently be conducted, should commercial exploitation of these remote resource fields commence
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