Standing stocks and distributional patterns of meiobenthos on the deep seafloor of KODOS area in the Clarion-Clipperton Fracture Zone (NE Pacific)

Abstract

This study was conducted to investigate the community structure and distributional pattern of meiobenthos associated with future deep-sea mining in the KODOS (Korea Deep Ocean Study) area present at the Clarion-Clipperton Fracture Zone (CCFZ) located in the southeastern part of the North Pacific Ocean. This study was carried out as part of baseline environmental study of KODOS long term project in the proposed mining areas for the environmental impact assessment that is comparable to future mining and whose effects are monitored over a period of time. Samples for meiobenthic study were collected at 44 stations (water depth: 4860~5021 m) in KR5 blocks of KODOS area during the cruise of R/V ONNURI (2008~2010, 2012~2014) and R/V KOK (2011). Sediment samples were collected using MC (multiple corer) and acryl subcorers (diameter 3.6 cm). 14 meiobenthos taxa (3-8 taxa at each station) were found. Nematodes were the most abundant taxon (60~86%). Harpacticoid copepods (5~26%), benthic foraminiferans (1~12%) were also dominant groups at all sites. The total meiobenthos density varied from 12 to 150 ind./10cm2 (nematodes: 7~105 ind./10cm2) and biomass were 9~47 &micro g/10cm2 at each station. A total 171 nematode individuals were sorted into 20 families, 50 genra, 73 species in study area. Diversity index of nematode community were 2.04~3.20 (H: 0.50~1.01 at meiobentic higher group level). The study area is characterized by Z) located in the southeastern part of the North Pacific Ocean. This study was carried out as part of baseline environmental study of KODOS long term project in the proposed mining areas for the environmental impact assessment that is comparable to future mining and whose effects are monitored over a period of time. Samples for meiobenthic study were collected at 44 stations (water depth: 4860~5021 m) in KR5 blocks of KODOS area during the cruise of R/V ONNURI (2008~2010, 2012~2014) and R/V KOK (2011). Sediment samples were collected using MC (multiple corer) and acryl subcorers (diameter 3.6 cm). 14 meiobenthos taxa (3-8 taxa at each station) were found. Nematodes were the most abundant taxon (60~86%). Harpacticoid copepods (5~26%), benthic foraminiferans (1~12%) were also dominant groups at all sites. The total meiobenthos density varied from 12 to 150 ind./10cm2 (nematodes: 7~105 ind./10cm2) and biomass were 9~47 &micro g/10cm2 at each station. A total 171 nematode individuals were sorted into 20 families, 50 genra, 73 species in study area. Diversity index of nematode community were 2.04~3.20 (H: 0.50~1.01 at meiobentic higher group level). The study area is characterized by