A study of meiofauna in the COMRA's contracted area during the summer of 2005

Polymetallic nodules were discovered on the Pacific Ocean in 1891. They exist at the sediment surface, sometimes in upper layers of sediments, and cover more than 50% of the sea floor at Clarion-Clipperton fracture Zone (CCFZ) in the north Pacific. The huge economic value from nodule mining has brought to many research programs dedicated to resource evaluation and design of collecting tools in the 1970s. China has carried out surveys on polymetallic nodules and sediment in the CCFZ for many years. Since the late 1980s, China has already got 75000 km super(2) exclusive pioneer areas in COMRA's contracted area. One of the potential impacts of nodule mining is the destruction of the fauna attached to the partial covering of surrounding epifauna by sediment blanketing. Meiofauna, the important components of benthic ecosystem, are considered to be energetically important in benthic food web. as they play a critical role in the recycling of nutrients. In order to manage and mitigate these impacts, we need to better understand the composition and the distribution of meiofauna and its relationship to the environment. A quantitative study was carried out on "Dayang Yihao" in July 2005. The meiofauna samples were collected from 12 stations in eastern and western sub-area at COMRA's contracted areas, Samples were collected using a multiple corer with four tubes of 9.5cm in diameter, and only undisturbed cores with clear overlying water were used. Thirteen benthic groups were found from the surveyed area,. The average density of meiofaunal were (104.4 plus or minus 20.48) ind/10cm super(2) and (40.26 plus or minus 25.84) ind/lOcm super(2) in eastern and western sub-area, respectively. The average biomass of nematode were (5.25 plus or minus 0.99) ( mu g times Dry)/10cm super(2) and (1.68 plus or minus 0.77) ( mu g times Dry)/10cm super(2) in each sub-area. The analysis of spatial distribution has shown that the density of meiofauna and the biomass of nematode in eastern sub-area were substantially higher than that in western sub-area. Nematodes, copepods, polychaeta, and ostracoda were found to be the dominant taxa, and nematodes were the predominant one, constituting 93.13% and 91.36% of total density of meiofauna in eastern and western sub-area, respectively. The analysis of vertical distribution has shown that the density of meiofauna decreased with the depth in the sediment. The top 0--2cm layer of sediment accounted for over 75% of meiofauna. The proportion of me