The carbon cycle group History The carbon cycle group was formed in 1989 at the University of Science and Technology, by Yngve Børsheim and professor Sverre Myklestad. At that time a new method for the analysis of dissolved organic carbon (DOC) in seawater had been introduced, and some of the results obtained with the new method were rather controversial. We undertook a journey round the world to visit the leading scientists in the field of carbon cycle and seawater analysis, visiting researchers in Bermuda, Woods Hole (Massachusetts, USA), (Maryland , USA), and finally the scientists who started it all, Yoshimi Zuzuki and his senior colleague, the now late Yokio Sugimura. Loaded with information we convinced the research council of Norway to finance a project on DOC, and in 1990 we purchased a new DOC analyser. After ten years of almost continuous use that machine was still operating, along with a second machine that was purchased in 1999. When Sverre Myklestad retired in 2001, the group dissolved, but after Yngve Børsheim moved to Bergen, the research on the role of DOC in the global carbon cycle continues within the cooperation between the Institute of Marine Research and the Bjerknes Centre for Climate Research.

Concentration of DOC in the upper 200 meters at Station M in the Norwegian Sea, shown as mM C (colour-bar).

Results In the first years it was important to resolve the question of what was the true concentration of DOC in seawater, and how much it varied. We established a sampling program from a very exotic platform in the Norwegian Sea. This station is a weather ship that is located at the position far out in the ocean round the year. The position is 66N,2E, and the ship leaves this position only once a month to go ashore for a switch of crew. The main purpose of the ship is meteorological observation, but she also carries equipment for taking water samples at all depths down to the bottom of the sea 2300m below the surface. We analysed profiles taken every month for three years, and we could then conclude that below 1000m depth, the concentration of DOC was constant, whereas in surface water, where light is available and photosynthesis takes place, there is a distinct annual variation. In spring the concentration rises steadily, parallel with the spring bloom of phytoplankton, and this increase continues through summer, and in September the concentration starts to decline, until winter concentrations are reached some time in January. We demonstrated a similar yearly cycle in an inshore environment, the Trondheim fjord close to our laboratory. Previously it was believed that the concentration of DOC was rather constant, but our results showed that a lot of the material that was produced by photosynthesis during the productive season in fact was released as DOC. This conclusion is supported by very recent results from another nearshore location, the marine lagoon Hopavågen that has been an importent site for marine fertilization studies. The consumers of DOC are the bacteria, or more precise, the heterotrophic bacteria. Obviously they were not able to degrade the DOC at the rate it was produced. This lead us to the second stage in our projects, the rate of production and consumption of DOC. These rates are necessary to establish to incorporate the flow of energy through DOC in models of ocean productivity, and also in models that are constructed to simulate the role of the ocean in the regulation of the concentration of carbon dioxide in the atmosphere.