main aim of the ACE-MERTZ DIVA

The main aim of the ACE-MERTZ DIVA project is to shed light on the exceptional biodiversity and the ecosystem functioning of a key Antarctic region: Adélie land shelf. In addition to describing them in great details (from bacteria to higher trophic levels), we will also determine the parameters that are either maintaining or promoting the evolution of these populations. Our data will then be incorporated into both descriptive and predictive models in order to understand how environmental parameters are forcing ecosystems and predict future changes. Indeed, recent studies show that, although subtle, changes have been observed in the area during the last few decades. In particular, a slow but regular decrease in the salinity the deep water masses at the bottom of the Australo-Antarctic basin under the Mertz polynya. The benthic communities from this area could therefore be amongst the the first to be impacted by these changes. In addition to these relatively slow modifications, the area is also under the strong influence of the Mertz glacier which periodically induce abrupt and catastrophic changes of the surface oceanic conditions:

Campagne et al (2015) showed that the glacier calved massive icebergs every 80-90 years, and that the loss of a large portion of its large tongue deeply impacted impacted the polynya downstream. A more compact sea ice cover in the area means that less sea ice is formed locally and therefore the winter convective processes are reduced. Lacarra and collaborators (2014) showed that dense water formation almost completely stopped soon after the 2010 calving. In less than a year, the salinity of the water surrounding most benthic organisms of the area was reduced by more than 1‰. In addition, since the increase in ice cover induce a decrease of the light available for the photosynthetic organisms, we expect a strong decrease in the primary productivity of the area. This could therefore mean less energy available for the higher trophic levels (either planktic or benthic). Changes in species composition, intra and inter-specific interactions can be expected.

The scientific questions we
will address include:

What are the key species of these ecosystems? How species are interacting?
Which parameters are controlling their dispersal in the ecosystems that we will be studying? Are these parameters varying in space and time? If yes, what is the extent of these changes?
Can we predict these changes and their effects on local ecosystems?
Polar environments are in mutation, what is the fate of these hyper-specialized and therefore very sensitive ecosystems?

Despite large-scale international research initiatives (e.g. CAMLR, CEAMARC), these ecosystems remain understudied and largely unknown from the public. The deployment of state-of-the-art instrumentation combined to more traditional methods will allow for obtaining data that are necessary to answer

the questions listed above. In addition, a very ambitious outreach programme will allow for the public to discover these incredible environments and raise population’s awareness about the urgent need to preserve them.