Summit under the sea

A scientific expedition on the
Walters Shoal seamount

On 23 April 2017, the iconic research vessel Marion Dufresne left the city of Le Port in Réunion for the Walters Shoal seamount.

The expedition is part of the International Union for Conservation of Nature (IUCN)'s FFEM-SWIO project on international ocean governance.

The oceanographic research vessel Marion Dufresne operated by the French Polar Institute (IPEV) © FabianoDamato MD 3 - InstitutPolaire Français IPEV

Seamounts are known for their diversity and relative abundance of biological resources.

© Expédition MD208-Walters Shoal IUCN/FFEM/Institut Polaire Français IPEV - Sébastien Faninoz (MNHN)

Walters Shoal is a seamount that lies in the international waters of the South West Indian Ocean, 700km off the southern coast of Madagascar.

The site was chosen especially for this expedition because of the shallowness of its summit - 18 meters below the surface - which makes it more vulnerable to overfishing and other types of exploitation.

The majority of seamounts on Earth are found in the high seas.

Global seamount distribution                               © Yesson et al., 2011

Global seamount distribution                               © Yesson et al., 2011

Serious gaps in legal processes and frameworks to protect biological resources in the high seas expose seamount ecosystems to the effects of pollution, degradation and over-exploitation.

"By learning more about seamounts we can better conserve and sustainably manage these ecosystems. But we cannot wait until we have all the scientific information to act. Time is running out." François Simard, Deputy Director and Senior Adviser for Fisheries, IUCN Global Marine and Polar Programme

On arriving at the site, the contours of the seamount are brought into focus on the screen thanks to seabed mapping technology.

Soon the first dives bring back images from the depths. The scientists on board, from the National Museum of Natural History in Paris and the Institut de recherche pour le développement (IRD), collect and study the rich variety of seamount species. The rotation schedule of day and night teams is put in place and the Marion Dufresne will not sleep until the end of the mission!

Between the surface and 50m below the surface, the waters of Walters Shoal are clear and the terrain is relatively flat. The first impression our divers get is that of a seascape usually found in the Mediterranean. No major outcrops and red coralligenous algae as far as the eye can see.

A tentative sampling estimate shows 500 benthic species - species that live on the sea floor - observed during the expedition, of which about 100 are probably new. The scientists are expecting to find a high proportion of endemic species - species that are found exclusively on Walters Shoal. The description and identification of these species will continue in the coming months, notably at the National Museum of Natural History in Paris.

What are the dynamics of this ecosystem? How does the topography of the sea bed interact with the currents around Walters Shoal? What is the connectivity between Walters Shoal and the coastal ecosystems?

These are questions the results of this expedition will help clarify, to contribute to the better management and conservation of seamount ecosystems in areas beyond national jurisdiction, and particularly on Walters Shoal.

The expedition aboard the Marion Dufresne benefited from the experience of 35 scientists from different countries: France, Madagascar, China and South Africa. A great example of international collaboration!

Thank you to all members of the Walters Shoal MD-208 Expedition for this remarkable investment and shared experience!

A documentary based on the expedition will be launched at IMPAC4 (4th International Marine Protected Areas Congress) in Chile, La Serena,
on 7 September.

The Walters Shoal expedition was made possible through the support of the French Global Environmental Facility (FFEM) and of the French Polar Institute IPEV.