I introduce research activity of Theme 4 “Observational research on Arctic Ocean environmental changes”, conducted during the MR16-06 R/V Mirai cruise.
The Arctic Ocean is experiencing the rapid environmental changes in the world oceans such as warming. Ocean acidification, which results from the dissolution of anthropogenic CO2 into surface seawater, is also in progress. In the near-future Arctic Ocean, warming climate would enhance sea ice decrease and permafrost thaw on land, which leads the decrease in salinity and the addition of allochthonous organic matters, respectively. On the other hand, seasonal warming and sea ice melt also occur every year in the present Arctic Ocean. We therefore believe that investigating the impacts of these environmental perturbations in the present Arctic Ocean ecosystem is one of the important issues to better understand the present and future Arctic conditions.
We conducted manipulation experiment using natural plankton community aboard R/V Mirai during the MR16-06 cruise. Two incubation experiments were carried out in the northern Bering Strait (BS) and Canada Basin (CB), where phytoplankton biomass is very high and low, respectively. In the BS experiment, I tested the effects of warming, ocean acidification and organic matter addition on the plankton community. In the CB experiment, warming, ocean acidification and the decrease in salinity (i.e., sea ice melt) were investigated. Samples obtained here will be analyzed in the laboratory after the cruise. In the last year, I also conducted the experiments with the same treatments with CB experiment during the MR15-03 cruise. This and previous studies would clarify the dynamics of lower trophic levels in the changing Arctic Ocean ecosystem.
Koji Sugie (JAMSTEC / A member of Theme 4)
Seawater sampling for incubation experiment using Niskin-X sampling bottles. All equipment for incubation were washed using detergent, diluted hydrochloric acid, and ultra-pure water to avoid inadvertent contaminations.
Sample processing units. Biogeochemical parameters on the filter and filtrates were analyzed in on land laboratory. We used many kinds of filter papers, those of which are suitable for each biogeochemical parameters.