Expedition sets off to investigate unknown life forms in the Pacific Ocean

- It is very fascinating to study life that thrives under extreme conditions. It can teach us about the biological variety diversity on our planet, expanding our understanding of the origin and evolution of life, says Professor Ronnie N. Glud of the University of Southern Denmark (SDU).

Together with Dr. Karl Attard and Technician Anni Glud, he will leave for the South Pacific in a few days’ time to take part in an expedition to the deep, clear water off Rapa Nui (previously also known as Easter Island).

The goal of the expedition is some newly discovered colonies of microbes and corals that live at depths down to 200 - 250 meters. The microbial communities are apparently dominated by cyanobacteria, which form large "mats" of biomass at the seabed.

Extreme lighting conditions

The bacteria are phototrophic; i.e. they use light as a source of energy. Being phototrophic in 200 m deep water is quite an achievement, because the light level is extremely low and has a very special spectral composition.

The corals are also phototrophic (or more precisely; they live in symbiosis with other organisms that are phototrophic), so they are also adapted to this particular habitat.

- Both bacteria and the organisms that live in symbiosis with the corals apparently exploit the blue-violet light that prevail at these water depths. We suspect that they have special pigments that enable them to capture the energy of the unusual light - we look forward to studying this further, says Ronnie N. Glud.

Measuring biological activity at the seabed

The team want, among other things, to investigate how much oxygen the special phototrophic communities produce with the limited amount of light during the daytime and how much oxygen they consume at night.

This will give them an indication of how efficiently these communities grow and to what extent they can form the nutrition for higher life forms in the otherwise extremely nutrient-poor environment.

The team from SDU will apply a very special instrument that can measure the oxygen transport between the phototrophic communities and the bottom water without disturbing them or changing the physical and chemical conditions at the seabed.

The rain brings nutrients

The bacterial mats not only need light to thrive - they also need nutrients. Although land is some distance away, this is probably one source of nutrients.

- When it rains on land, the rainwater sinks into the underground and from here the nutrient-enriched water seeps out of the seabed sustaining the bacterial growth at the seabed - at least that's one hypothesis that we will try to investigate, explains Ronnie N. Glud.

The research team will leave for Rapa Nui on December 2nd, and the expedition is expected to last 2-3 weeks.

Cooperation with Chile and the Netherlands

The expedition is carried out in collaboration with researchers from the Chilean University of the Universidad Católica del Norte and the University of Amsterdam, the Netherlands.

The team has complementary expertise that will provide the researchers with a comprehensive understanding of the special, biological communities.

The expedition includes a dive team that, with special gas mixtures, can dive to depths exceeding 100 m. This ensures that researchers can place their instruments correctly at the seabed and to recover relatively undisturbed samples for further studies in the laboratory.