Reactions of the Heavy Metal Cycle to Industrial Activities in the Deep Sea: An Ecological Assessment

Abstract

This article focuses on possible geochemical consequences of potential industrial activities in the deep sea, such as manganese nodule mining, for the heavy metal cycle of the deep sea and possible reactions of the benthic ecosystem. The metal fluxes induced by sediment resuspension are compared with fluvial, atmospheric, and hydrothermal metal fluxes into the ocean. The results of geochemical laboratory experiments and analyses of deep-sea benthic organisms are discussed with respect to their ecological importance in case of a seabed disturbance.A limited short-term increase of heavy metal concentrations in the benthic layer will probably cause only negligible harmful effects on the biota. An essential precondition is that the geochemical milieu remains largely unchanged; especially variations of the redox conditions would result in changes in metal speciation, bioavailability, and toxicity.1. Introduction Ferromanganese Nodules as Potential Sources for Heavy Metal Contamination in Deep-Sea EnvironmentsThe deep-sea basins, e.g., the Peru Basin in the southern Central Pacific and the ClarionClipperton-Fracture Zone in the northern Central Pacific, contain metal-rich manganese nodules of potential economic interest (HALBACH et al., 1988). Intense scientific work was carried out in the seventies and eighties to investigate the geochemistry and metal potential of these deposits (e.g., CRONAN, 1977;CALVERT, 1978;PIPER and WILLIAMSON, 1977;EXON, 1983;DYMOND et al., 1984;GLASBY et al., 1986). However, it was soon recognized that mining of these resources would cause a number of rapid changes of the environmental conditions in large deep-sea areas which naturally can happen only in geological time scales (AMOS, 1977;PADAN, 1990;THIEL et al., 1993). Consequently, the potential effects of deepsea mining became subject of scientific activities which lead, e.g., to the publication of a special issue of Marine Mining (Vol. 3, nos. 1/2, 1981) and to the organization of a Dahlem Workshop (1991) that was dedicated to various aspects of the use and misuse of the seafloor (HSÜ and THIEDE, 1992). Some recent articles give overviews on environmental impact investigations during the past 25 years, such as the American DOMES (Deep-Ocean Mining Environmental Studies) and BIE (Benthic Impact Experiment) studies and the Ger-

Risk Assessment and Ecotoxicology Limitations and Recommendations for Ocean Disposal of Mine Waste in the Coral Triangle

“…Studies on metal accumulation in fish are often hampered by the lack of certainty about their history and exposure rates (e.g., Brewer et al, 2007 (Koschinsky et al, 2003).…”

Temporal and Spatial Effects on Some Physiological Parameters of the Bivalve <i>Lithophaga lithophaga</i> (Linnaeus, 1758) from Coastal Regions of Alexandria, Egypt

“…[26] and [27] reported that a single biomarker cannot provide the basic answers as to what is the actual state of health in the natural populations and that, environmental stress may cause changes in cellular function that alter the physiology of organ system in organisms, suggesting that pollutants might influence the metabolism of the whole organism. [28] and [29] discovered a relationship between xenobiotic chemicals accumulated in oyster (Crassostrea virginica) tissue and various measures of physiological condition and that the possibility of variations of metals concentration due to physiological parameters have been taken into consideration such as stress. In the present study, variations of metal concentrations are to be attributed to variation of metal concentrations in the surrounding water.…”

Geographic and bathymetric comparisons of trace metal concentrations (Cd, Cu, Fe, Mn, and Zn) in deep-sea lysianassoid amphipods from abyssal and hadal depths across the Pacific Ocean

“…To our knowledge, the only published records of metal concentrations in deep-sea amphipods are those from benthopelagic amphipods, putatively identified as E. gryllus, collected from the Peru Basin Mn nodule field (Koschinsky et al, 2003). This highlights the paucity of information on regional variation in metal concentrations in deep-sea habitats.…”

“…Within open ocean pelagic and deep-sea habitats, metals can be released into the water via remineralisation of faecal pellets, fluids from hydrothermal vent systems, weathering of mineral deposits, sedimentary diagenic recycling of metals and the input of aeolian material (e.g. dust) which binds to POM that subsequently sinks (Bennett et al, 2008;Chu et al, 2006;German et al, 2010;Grand et al, 2015;Hauton et al, 2017;Koschinsky et al, 2003;Laglera et al, 2017;Ratnarajah et al, 2014;Yucel et al, 2011).…”