Exploring the growth of deep-sea bivalves in areas of potential sea-floor mining

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The area of seabed beyond the continental shelves makes up one of the largest of the Earth's ecosystems. However, the deep-sea benthos is very poorly understood, in large part because the relative inaccessibility of the environment. What is known is that deep-sea communities are diverse, heterogeneous in their composition and contain both generalist and specialist organisms, such as those living in particularly challenging locations, like hydrothermal vents. The life histories of most deep-sea animals are enigmatic. For example, knowledge of growth rates for most species is lacking, as is the extent to which these rates might be influenced by distant external factors, such as photic zone productivity and tidal effects. These life history questions are not esoteric because the deep-sea environment is being increasingly impacted by human activities, both indirectly through changes in the climate system, and directly through current and planned exploitation of marine resources. Seafloor polymetallic nodules and hydrothermal vent deposits are a potential future metals resource, of manganese, nickel and cobalt for polymetallic nodules, and copper, lead, zinc, silver, gold and other trace metals for vent deposits. These potential resources exist largely outside of country exclusive economic zones (EEZs), and in deep water (thousands of metres), so there are major issues that need to be solved before they can be exploited, some purely logistical (e.g., development of novel mining machinery), and some policy related. Outside of EEZs all seafloor resources are licenced by the International Seabed Authority, and this first requires adequate investigation of the ecological impacts of mining before this can go ahead. Currently this type of work is being undertaken by various contractors in a number of areas (e.g., the Clarion-Clipperton Zone in the central Pacific) licenced to a number of different countries.Commercial extraction of these seafloor metal resources will impact the deep-sea environment, and questions about the duration of post-mining ecological recovery or the extent of potential set-aside areas are hampered by a general lack of data about deep-sea animals. The project will provide essential new information about the growth of bivalves from a variety of deep-sea environmental settings, principally hydrothermal vents and polymetallic nodule fields, which are targeted for imminent commercial exploitation. Material will come from existing collections, but there is the potential to join a research cruise to collect new specimens from the Clarion-Clipperton Zone nodule fields. Established sclerochronological imaging and geochemical techniques will be used on larger bivalve specimens, however, the small, fragile shells of many deep-sea bivalves will necessitate the modification of some existing methodologies, with the potential to develop new approaches, as appropriate. Mathematical processing (e.g. spectral analysis) of analytical results will be an essential component of the research.