The Ocean as a natural heritage

The Tree of Life The Tree of Life describes the relationships of all living organisms, including bacterial (Eubacteria and Archaea) and eukaryotic organisms on earth in an evolutionary context. Whereas this was initially the task of biologists (taxonomists and systematicists), it has become a joint venture with evolutionary biologists and bioinformaticians. Highthroughput DNA sequencing ( Wikipedia - High-throughput screening) has revolutionised the field. Comparing gene sequences has revealed completely new domains (and phyla), but has also made clear that morphologically similar but genetically different species abound and that the census to date represents serious underestimates.

THE ORIGIN OF LIFE

Microbial life originated in the ocean an estimated 3.6 billion years ago, and eukaryotic life some 2.1 to 3.0 billion years ago. A wide diversity of multicellular life appeared some 1.26-0.95 billion years ago. Land became colonized by green plants 0.60 billion years ago and man has joined life on earth a mere 200,000 years ago. The long evolution on Planet Ocean has generated a wealth of biodiversity at the gene, species and ecosystem level. Some aspects have received a disproportionate level of attention with concentration on a top down approach where organisms close to man such as whales, fish and shellfish have been prioritized. In contrast others have been neglected, such as the microbes and viruses. Genomics helps with this.

GENOMICS AND THE TREE OF LIFE

A total of 212,000 species have been identified in the ocean , but the tally on species diversity is expected to reach millions, possibly even more than on land. However, we know very little about most species identified, let alone those yet to be discovered. Building the ultimate Tree of Life is a huge challenge, and several conditions have to be met.

LOSS OF BIODIVERSITY

Why do we prepare seemingly endless lists of species of marine organisms? It is foremost an attempt to understand the functioning of the biosphere and hence to help manage the services and goods delivered. Organisms occupy habitats and form an integral part of ecosystems, whose function and dynamics are determined by the variety, abundance and activities of these organisms. The diversity shift is monitored through taxonomic experts and compiled in a global database Census of Marine Life – CoML. There is growing evidence for the loss of population diversity, where smaller or more delicate (e.g., deep-sea and polar) populations are the first victims

MICROORGANISMS AND THE GLOBAL BIOLOGICAL PUMP

A millimeter of beauty. The radiolarian Sphaerozoum is a colonial nanophytoplankter.

Genomics has already provided a breakthrough in assessing the diversity, importance and functioning of the smallest creatures in the ocean—the picoplankton, creatures of less than 2 μm. This thriving community is ecologically overwhelming with an estimated contribution to primary productivity of on average 50% to 90% ; it essentially drives biogeochemical processes. The ocean stores huge amounts of carbon in living creatures and dead organic matter. This process is intimately linked to the cycling of oxygen and the life cycle of living organisms. They shuttle carbon, oxygen and nitrogen between the ocean surface, the abyss and again to the surface. Microorganisms, such as the picoplankton play a crucial role in this system through CO₂ sequestration, control of the ocean’s acidity, productivity and dynamics. Rapid changes in global climate tend to modify or even offset this balance. The slow down of global ocean currents (the so called conveyer belt) through changes in atmospheric heat distribution, will affect the biochemical and physiological capacities of marine organisms. Such changes can be monitored through metagenomic approaches. The biological pump described above is of crucial importance for life on earth. Continuous monitoring needs to be provided through permanent off-shore stations with remote sensing to evaluate marine biomass production at all levels and then combined with confirmatory experiments at the laboratory and field scale.

References

Metagenomics Scanning electron micrograph of a virus attached to the surface of an Emiliania huxleyi cell. The virus particle on the right hand cell is approx. 180 nm in diameter. Dr Keith Ryan, Marine Biological Association & Dr Willie Wilson, Plymouth Marine Laboratory Metagenomics, or the study of DNA recovered from the natural environment focuses on the DNA of many tiny organisms, which cannot be identified and cultured in the laboratory. It has enabled us to start reconstructing the function of microbial communities. The number of novel discoveries through a metagenomic approach is impressive and includes the discovery of a number of novel biochemical pathways (e.g., , ) and novel organisms (e.g., , ) with exploitation potential.