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Nodinaut

NODINAUT - The name Nodinaut refers to the study area in the central Pacific Manganese nodule area and the name of the submarine Nautile which was used during the expedition.

 

Project leader: Joëlle Galéron, Ifremer, Plouzané

Objectives

A scientific cruise was conducted by Ifremer on the French mining claims in the Clarion Clipperton Fracture Zone (North East Pacific Ocean)  in summer 2004 on the French RV L'Atalante with the submsersible Nautile. The objective was to obtain basic knowledge on the natural state of the benthic communities, and on their habitat characteristics, as a baseline for an impact study of potential nodule exploitation. The structure of the benthic communities (taxonomic composition, diversity, abundance, biomass, distribution) was studied together with environmental parameters (geological, physical and chemical) in order to test for influence of habitat characteristics on spatial variability of benthic communities, encompassing all size classes from microbiota to megafauna.

Sampling

To elucidate at which scale habitat variability influences biological diversity, the study considered regional, local, and micro-scales. The  Nautile was used to target measures and sampling of sediment and fauna needed for the study of the influence of habitat variability on biodiversity at local scale and micro-scale. An evaluation of the recovery of the benthic community after dredging of nodules was conducted in real conditions by sampling a dredge trace about 25 years old.

 

The dynamic of the macrofaunal community was tested with an experimental approach, using free devices left on the bottom for one year. Part of the sampling programme of Nodinaut responds to the needs of the international programme “ Biodiversity, species ranges and gene flow in the abyssal Pacific nodule province : predicting and managing the impacts of deep seabed mining ”. 

Participants

Twenty scientists, 14 from Ifremer and 6 from other institutes (University of Hawaï, USA, DZMB-FIS, Germany, NHM, UK, JAMSTEC, Japan, KORDI, Korea, Université du Québec, Canada) participated in the Nodinaut cruise.

Results

We now have a general view of regional (large) scale patterns in benthic community structure and of the environmental parameters driving these patterns. The community structure of abyssal megafauna and macrofauna differs not only due to the availability and quality of food but also heterogeneity in physical and chemical properties of the habitat (nodules and superficial sediment).

Moreover, data from previous French investigations allowed to choose a restricted area where we could investigate the local (small-scale) influence of the presence of nodules on the benthic community structure. Studies undertaken at the local scale (1-5 miles distance) with the manned submersible Nautile allowed to show for the first time that nodule fields constitute a distinct habitat for infaunal communities, and that macrofauna and meiofauna components differ in abundance depending on the presence of nodules.

 

The last issue addressed by the Nodinaut project concerned the potential for recovery of benthic communities after physical disturbance of the sediment-water interface made by a dredge 26 years earlier. Physical and chemical properties of the sediment in the track did not change significantly over this time, indicating an extremely passive environment at this abyssal depth. However, the resilience of the communities at a larger scale in case of industrial nodule mining cannot be evaluated from these results due to two reasons : the size of the disturbed area would be largely more important, and it is necessary to evaluate the species range at a larger spatial scale.

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