Lower Trophic Ecosystem Model Research Articles

Improved state estimations of lower trophic ecosystems in the global ocean based on a Green’s function approach

A lower trophic ecosystem model, which was originally developed for describing the variability in plankton distribution in the western North Pacific, is applied to the global ocean. A realistic time series of dynamically self-consistent circulation fields obtained by a 4-dimensional variational ocean data assimilation experiment is used for the environmental fields in the ecosystem model. An optimization of the bio-ecological parameter values in 40 provinces by a Green’s function approach enables the ecosystem model to represent the observed variabilities of nutrients and surface chlorophyll concentration with a relatively small number (11) of compartments. In addition, artificial trends of the ecosystem variables due to model errors are generally suppressed by the optimization. The obtained parameter values and ecosystem fields are generally consistent with observations in terms of assimilated and non-assimilated metrics. The integrated lower-trophic ecosystem and physical fields in the global ocean offer important information on the mechanisms (such as El Niños) responsible for the seasonal–interannual variability in the lower trophic ecosystem. Our results demonstrate that, with adequate parameter sets capable of modifying indirectly the model and significance of each pathway to reflect the characteristics of local species, a simple ecosystem model can be applied in quantitative analyses to enhance our understanding of the influence of climate variations on the ocean ecosystem.

Behavioral modeling of Pagrus major in the East Seto Inland Sea

Evaluation of the behaviors of fish that belong to higher levels of the food web is important from the viewpoint of resource management and other environmental issues. Especially for adult fish that can swim against the surrounding currents, it is quite important to consider migration effects when modeling fish behavior. In the present study, a model of fish behavior is developed that considers the migration effect by incorporating a preference for various environmental factors. The species to be modeled, Pagrus major, was chosen because its high value as a food makes it representative of an exploited fish species. In the developed model, the direction of the fish movement is determined by the strength of preference for environmental factors of water temperature, salinity, dissolved oxygen, and prey density. The model is coupled with a hydrodynamic model and a lower-trophic ecosystem model, which predict the physical environment and water quality of the target area. Numerical simulations are carried out to reproduce the spatial distribution and seasonal variations of the ecosystem in the East Seto Inland Sea. Proper parameters for fish behavior were obtained through the processes of model tuning. As a result of the simulations, we clarified that the environmental conditions have a sizeable influence on the migration and distribution of Pagrus major. The developed model is also able to reproduce the fish biomass variation in time and space, which will provide more detailed information for resource management of the fish.

Outcome of the ocean sequestration project, and technical evaluation of CCS as mitigation measure of increase atmospheric CO2 and ocean acidification

Abstract IPCC AR4 reported that the emission of the anthropogenic Carbon Dioxide (CO 2 ) increase the CO 2 concentration in atmosphere after the Industrial Revolution, and increasing of CO 2 concentration caused the global warming. Moreover, it is shown that CO 2 dissolution into the ocean causes the acidification in the surface layer. The buffering effect of the ocean can suppress the change of the CO 2 concentration in the atmosphere. However, the rise of the CO 2 concentration in the ocean surface means the pH of seawater decreases. This phenomenon continues until the difference of CO 2 partial pressure between the atmosphere and the ocean disappears if the emission of CO 2 is stopped. But, the acidification of the ocean progresses as long as it keeps CO 2 emission. It is feared that the ocean acidification has crises influence on various organisms and entire ocean ecosystem. Carbon Capture and Storage is one of the mitigation measure technologies of CO 2 emission. Famous carbon storage technology of the CCS using ocean region is Sub-seabed Geological Storage and dilution type Ocean Sequestration. These CCS Technologies has been developed in RITE. Especially, Research and development project of ocean sequestration technology was established the core technologies for example CO 2 injection and dilution technology, prediction of drop and diluted CO 2 and evaluation methods of biological influence of CO 2 . These core technologies were enabled a feasibility study of Ocean Sequestration technology as total system. These studies showed constructions of ocean sequestration system, and estimated sequestration costs and additional CO 2 amount. Furthermore, in this evaluation, the ocean sequestration system without the influence on the marine organism was shown by scientists of the Ocean Sequestration Project of Japan. This evaluation and comparison study for atmospheric CO 2 decreasing measure and ocean acidification mitigation measure was based on above results, and it was carried out using three dimensional numerical model with ocean circulation model (MOM: Modular Ocean Model), global carbon cycle model based on a lower trophic ecosystem model and one box atmospheric model. And the several scenarios were selected for evaluation of CCS efficiency. These scenarios ware targeted over CO 2 emission based on S550 scenario and over emission were allocated to Geological Storage, Ocean Sequestration, other measure and no measure. Simulation results of Ocean Sequestration suggested efficiency for mitigation measure of increase atmospheric CO 2 and Ocean Acidification. However, it was shown that the effect was different according to the ocean. Results of the simulation study showed “Geological storage without leakage is the best as the effect of measures”. And it is suggested that “There is a possibility of suppressing the ocean surface acidification to more effective by combining dilution type ocean sequestration with subseabed geological storage”. The effectiveness of ocean sequestration and geological storage was shown to some degree by this research. It is necessary to re-examine the use of the ocean model of a high resolution and the emission scenario of CO 2 , and to show the result with higher reliability.

Environmental factors which affect growth of Japanese common squid, Todarodes pacificus, analyzed by a bioenergetics model coupled with a lower trophic ecosystem model

Bioenergetics model is applied to Japanese common squid, Todarodes pacificus. The temporal change of wet weight of common squid, which migrates in the Sea of Japan, is simulated. The time dependent horizontal distribution of prey is calculated a priori by 3-D coupled physical–biological model. The biological model NEMURO (North Pacific Ecosystem Model for Understanding Regional Oceanography) is used to simulate the lower-trophic ecosystem including three kinds of zooplankton biomass two of which is used as prey of common squid. A bioenergetics model reproduced appropriate growth curve of common squid, migrating in the North Pacific and the Sea of Japan. The results show that the wet weight of common squid in the northern Sea of Japan is heavier than that migrating in the central Sea of Japan, because prey density of the northern Sea of Japan is higher than that of the central Sea of Japan. We also investigate the wet weight anomaly for a global warming scenario. In this case, wet weight of common squid decreases because water temperature exceeds the optimum temperature for common squid. This result indicates that migration route and spawning area of common squid might change with global warming.