Expected outcome of TARA OCEANS

It will take a lot of work during and after the expedition to interpret and understand the information contained in the collected data.

From a purely scientific point of view, this approach should allow us to establish how ecosystems of “small” organisms in the world’s oceans are structured. We will learn which viruses, bacteria, protists and small metazoan organisms live together in given marine environments. Since the ocean is an open system, one could think that all organisms are everywhere. Obviously this is not the case because when a given organism migrates into an unfavorable environment, it dies.

Our approach should tell us a lot about the mechanisms of evolution. In particular, the classical idea of survival of the fittest could be examined. For instance, how viruses and their hosts co-evolve under different physico-chemical pressure is unknown. The Tara Oceans expedition will provide a unique opportunity to better understand such questions.

We clearly need complex modeling, based on bioinformatics analyses of DNA and RNA sequences obtained from organisms collected during the voyage, combined to morphological analyses of these same organisms.  We will also study populations and communities dynamics in relation to their physico-chemical environments. Thus, we will learn much about how ecosystems change and adapt in response to climate change. Since they are at the base of the oceanic food chain, we may be able to predict how marine ecosystems will affect the climate by producing more or less oxygen and absorbing more or less CO2.

Legacy

Given the proposed sequencing effort, this study will provide the most complete census of oceanic protists ever undertaken. Protists constitute the largest biodiversity gap in eukaryotes. Protists are also known – especially  from the fossil record - to react rapidly to global climate change. Many populations of marine protists have extreme turnover rates and build complex nano- and micro- (in)organic skeletal structures which generate some of the largest fluxes of biological material on earth. Their impact on global geochemical cycles and climate is extremely important. Very little is known about the way protists will react to increasing levels of CO2. We will investigate how changes in protist communities and biodiversity will affect primary productivity and carbon flux.

For the first time, these basic questions will be addressed at the level of the entire protistan community, establishing solid foundations for future research in this underexplored field critical for predicting the co-evolution of climate and biota. Furthermore, the hundreds of thousands of marine protists still to be discovered represent a phenomenal repertoire of unknown genes, metabolic pathways, and nanomaterial. Protists have large genomes often much larger than the human genome. This genetic biodiversity predates and exceeds the relatively smaller gene repertoire of plants and animals. Recent sequencing of oceanic metagenomes has revealed a huge unsuspected diversity of microbial species and genes of prokaryotes and viruses. Eukaryotes have not yet been included in these analyses despite their closer relationship to us.

But the most important out come for the future is that this will open the possibility to build models integrating the evolution of pelagic ecosystems with environmental changes.

Eric Karsenti