EXBODI / The engines of marine biodiversity
30 September 2011
End of the Exbodi cruise, 26 days at sea, New Caledonian EEZ, the Loyauté Ridge, and the southern slope of the South Province, number of stations = 172; explored depths: between 250 and 1150 m. One lost dredge! Collections: about 500 specimens of fish, about 2700 cnidarians; about 78 lots of fossil corals - 2500 species, about 45 lots and 73 species of sponges; not even counting all the lots of mollusks, crustaceans, and echinoderms whose final number is not yet established!
One of the objectives of our research is to understand the mechanisms that are at the origin of the biodiversity. New Caledonia is very rich in marine organisms, but what are the mechanisms that generate that diversity? We approach the issue with a genetics angle, studying the connectivity level, for different organisms, between geographically isolated areas.
For example, New Caledonia is located on the Norfolk Ridge. South of the island, a chain of seamounts exhibits a high biodiversity, now well studied. The New Hebrides and the Loyauté chains are located near this Norfolk Ridge. What is the connectivity level between the populations that inhabit these different chains and, within each, between the different seamounts? Are the populations of the oceanic slope of Grande Terre connected to the seamount populations?
To answer these questions, we use taxa that are species-rich and are collected in large numbers. These model systems", with diverse evolutionary histories and reproductive strategies, are used to study the diversity of animals from deep-sea benthic ecosystems. To that end, several species of fish, gastropod mollusks, galatheid squat-lobsters, and gorgonians are the subjects of in-depth studies.
For example, gorgonians of the genus Chrysogorgia are very abundant and diversified, with about sixty species currently described in the world. New Caledonia alone harbours 15 of these species, a greater number than in Western Atlantic! The samples collected during the Exbodi cruise complement lots from the TERRASSE cruise (2008). These data will complement our knowledge in the regional biogeography, and will allow the study of the connectivity of the populations at the scale of the New Caledonian EEZ.
All the results of the Tropical Deep Sea Benthos program, a joint endeavor by IRD and MNHN, as well as the connectivity studies, can be used by the Marine Protected Area Agency to set up proper conservation strategies.