Abstract
Seafloor massive sulfide (SMS) deposites are commonly found at hydrothermal vents and recently gained the special interest of mining industries. These deposits contain valuable metals and methods are currently developed to mine deep sea SMS deposites. However, excavation of SMS deposits potentially pose a threat to benthic life at the mining site itself, and also in the surrounding environment with plumes of suspended sediment and fine-grained SMS debris created during deep sea mining activities being highlighted as one of the major threats to deep-sea benthic fauna. The benthic communities surrounding the vents are, however, poorly known. As they are often exposed to natural plumes studying such communities could provide valuable information on their resilience towards mining related plumes. The Rainbow hydrothermal vent site at the Mid-Atlantic Ridge is a site characterized by one of the largest continuous natural plumes, which is found persisting over an extensive area. Sediment and water samples were taken both upstream and downstream of the Rainbow hydrothermal vent. Approximately 25km away from the vent reference sites were samples as well. In addition to detecting the plume itself, concentrations of major and trace-metals in the sediments were used as tracers for long time sustained plume influence. At all sites we assessed benthic species composition and detected larvae. Metabarcoding methods were used to determine species composition. Benthic species composition in the sediment was shown to differ between all locations and was highly influenced by the plume’s fall out. Arthropoda were more dominant closer to the vent whereas Annelida and Nematoda were more dominant at the reference locations. Conservation and restoration of all these communities after a deep sea mining event will be difficult due to the spatial variation of these benthic communities.
Highlights
Seafloor massive sulfides (SMS) are commonly deposited at and near hydrothermal vent sites through precipitation of metal sulfides as acidic hydrothermal fluids exit the seafloor in these volcanic active regions (Collins et al, 2013)
The aim of the current study is to apply a metabarcoding approach to: (1) detect patterns in the marine benthic communities in- and outside the path of the Rainbow hydrothermal plume whereby trace metal concentrations are used as proxy for influence of the plume; (2) test if larvae of benthic animals can be detected in discrete water samples with a limited volume, and if so, explore patterns in their distribution around the Rainbow vent
The reference locations (38 and 43), which were supposed to be the least affected by the vent plume because of their large distance from the vent are clustered together with sample locations 58, 56, 54, and 36 which are situated further away from the vent site, either upstream or downstream of the plume
Summary
Seafloor massive sulfides (SMS) are commonly deposited at and near hydrothermal vent sites through precipitation of metal sulfides as acidic hydrothermal fluids exit the seafloor in these volcanic active regions (Collins et al, 2013). Over 300 vent sites have been listed by the International Seabed Authority (ISA) ocean wide, of which a third is supposed to have SMS deposits containing valuable metals (Baker and German, 2004). Suspended sediment plumes created during mining activities are highlighted as one of the major potential threats to deep-sea benthic fauna (Nakajima et al, 2015). Background communities nearby natural vents tend to host higher biomass densities compared to the surrounding deep sea, likely due to their high primary productivity input from the central vent area (Galkin, 1997; Sen et al, 2014). Background communities have received considerably less research effort than the vent-communities themselves (Boschen et al, 2013)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
