Located at the interface between the continent and the ocean, New Caledonia's lagoon is particularly sensitive to anthropogenic pressures. In recent years, scientists have observed an increase in sedimentation in the lagoon bordering the Vavouto industrial site. The SELAMIK oceanographic campaign, organised on board the Alis from 3 to 16 March 2022, aims to understand the origin, fate and impact of sedimentation on the functioning of this lagoon.
In the South Pacific, New Caledonia is an archipelago surrounded by one of the world's largest lagoons, with a total surface area of 24,000 km2. The ecosystems of this lagoon are being heavily impacted by the combined effects of climate change and human activity, as their ecological balance is all the more fragile because the volume of water in the lagoon is small and the reef barrier restricts exchanges with the ocean. However, the lagoon plays a recognised role as a nursery for many species and provides numerous services to local populations. It must therefore be protected from the undesirable effects of poorly controlled development. Deforestation and soil erosion are modifying the functioning of this ecosystem and limiting the development of blue economies such as fishing, aquaculture and tourism. Among the other anthropogenic pressures facing the lagoon, the impact of extractive mining is major. Although this activity contributes significantly to New Caledonia's economic development, it also poses numerous risks for society and the environment, particularly for coastal environments.
During the UECOCOT oceanographic campaign that took place in the Voh-Koné lagoon in 2018, scientists noted an increase in sedimentation in this area, associated with a reduction in marine biodiversity. The massive sedimentation observed seems to have had undesirable effects, such as the rarefaction (sea cucumbers) or disappearance (sea urchins, clams) of species that are abundant in neighbouring lagoons. This observation (which has not been documented until now) is at the origin of the SELAMIK project, the aim of which is to understand the contribution of extractive mining activities to the massive hyper-sedimentation of the Voh-Koné lagoon.
More specifically, the aim is to analyse the hydro-sedimentary processes in this lagoon in order to determine the causes of this hyper-sedimentation and to assess the consequences for the functioning of the ecosystem. To do this, the scientists will seek to answer 3 questions:
1. What are the main hydrodynamic forcings in the lagoon?
2. What role does sediment play in regulating the lagoon's physico-chemical balance?
3. What impact do particulate inputs have on microbial communities?
Field operations will include deploying sensors to measure currents, collecting samples of sediment and suspended particles to measure environmental parameters (carbon, particulate organic nitrogen and phosphorus, chlorophyll), metallic elements and microbial diversity.
Contacts
IRD New Caledonia Communication Department :
Karla Bussone | karla.bussone@ird.fr | 26 08 04
Scientific manager of the SELAMIK campaign:
Cristèle Chevalier | cristele.chevalier@mio.osupytheas.fr | 06 87 28 26 14