Abstract
Abstract. Mining of polymetallic nodules in abyssal seafloor sediments promises to address the growing worldwide demand for metallic minerals. Given that prospective mining operations are likely to have profound impacts on deep seafloor communities, industrial investment has been accompanied by scientific involvement for the assessment of baseline conditions and provision of guidelines for environmentally sustainable mining practices. Benthic meiofaunal communities were studied in four prospective mining areas of the Clarion–Clipperton Zone (CCZ) in the eastern Pacific Ocean, arranged in a southeast–northwest fashion coinciding with the productivity gradient in the area. Additionally, samples were collected from the Area of Particular Environmental Interest no. 3 (APEI-3) in the northwest of the CCZ, where mining will be prohibited and which should serve as a “source area” for the biota within the larger CCZ. Total densities in the 0–5 cm upper layer of the sediment were influenced by sedimentary characteristics, water depth and nodule density at the various sampling locations, indicating the importance of nodules for meiofaunal standing stock. Nematodes were the most abundant meiobenthic taxon, and their assemblages were typically dominated by a few genera (generally 2–6) accounting for 40 %–70 % of all individuals, which were also widely spread along the CCZ and shared among all sampled license areas. However, almost half of the communities consisted of rare genera, each contributing less than 5 % to the overall abundances and displaying a distribution which was usually restricted to a single license area. The same observations (dominant and widely spread versus rare and scattered) could be made for the species of one of the dominant genera, Halalaimus, implying that it might be mainly these rare genera and species that will be vulnerable to mining-induced changes in their habitat.
Highlights
As mining of mineral resources on land is increasingly burdened with logistic and geopolitical concerns (Petersen et al, 2016), humankind is looking towards the deep seafloor (∼ 4000–5000 m) as a potential source to meet the global demand for metallic deposits
Since the Clarion–Clipperton Zone (CCZ) falls beyond national jurisdiction, the regulatory framework for prospective nodule mining is provided by the International Seabed Authority (ISA), which has so far granted 16 exploration licenses to interested parties
This study reports data for meiofauna across a broad latitudinal and longitudinal range within the CCZ and includes species-level information for a typical subdominant deep-sea genus of nematodes, Halalaimus
Summary
As mining of mineral resources on land is increasingly burdened with logistic and geopolitical concerns (Petersen et al, 2016), humankind is looking towards the deep seafloor (∼ 4000–5000 m) as a potential source to meet the global demand for metallic deposits. One of the requirements of the ISA toward contractors is documentation of the biota in their license area and evaluation of the impact that planned mining activities will have on the environment (Lodge et al, 2014; Vanreusel et al, 2016).
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