Toward the understanding the response of marine ecosystems to the ocean acidification and other environmental stressors
The subarctic region of the western North Pacific is one of the most serious area regarding the progress of the ocean acidification in the world. The pH at the subsurface (~200m depth) has reduced 0.003-0.004/year. The catastrophic reduction of pH at the subsurface in the subarctic North Pacific would give a negative impact on the zooplankton having the carbonate test especially, planktic foraminifera because this depth include the most suitable habitat layer for micro zooplankton. In addition, sea-ice in the Arctic Ocean has been dramatically reduced over the past decade. This reduction causes complex and enigmatic changes in the marine ecosystem throughout the Arctic Ocean, because of simultaneously occurring “disadvantageous” phenomena, such as ocean acidification and “advantageous” phenomena such as improved light conditions for marine organisms.
The 3rd mid-term research plan of this group focused on the subarctic region of the western North Pacific and western Arctic Ocean where there has been the progress of most serious environmental stressors, such as warming, ocean acidification and sea-ice reduction in the world. The aims are to 1) understand the temporal changes in primary production and the biological pump, 2) understand the physiological response of marine phyto- and zooplankton to ocean acidification that is occurring simultaneously with warming and freshening, and 3) develop a model to simulate the primary production, and understand the response of marine ecosystems and the biological pump to the environmental changes caused by ocean acidification and other environmental stressors.
- Three methods have been used: observations from research vessels and satellites; experimental culture and breeding of plankton; and marine ecosystem modeling. The specific research outlines are as follows:
- Estimation of changes in chemical and physical properties (Temperature, Salinity, Macro and micro nutrients, pCO2, pH, Alk) of water mass to understand seasonal and annual changes in the physical and chemical oceanographic environment associated with warming and freshening in the subarctic North Pacific and Arctic Ocean;
- Detection of seasonal and annual changes in primary production biomass, phytoplankton composition, zooplankton biomass and its composition using the time-series data from a mooring system, satellite data and continuous plankton recorder data;
- Understanding changes in the physiological response of diatom, coccolithophores and foraminifera to environmental changes caused by environmental stressors from culture/breeding experiments;
- Understanding changes in processes of the biogeochemical cycles associated with the centennial-millennial time scale climate change
- Development of models for marine ecosystems (developed to describe marine ecosystems with temporally and specially high resolution and/or global scale) in the subarctic North Pacific and Arctic Ocean in order to reproduce the primary and secondary production of the region, and to predict the distribution of possible marine resources.
Achievement at 5 yr later
- Understand the response of marine ecosystems and the biological pump to the environmental changes caused by ocean acidification and other environmental stressors
- Understand the changing process of biogeochemical cycles associated with centennial-millennial time scale climate change