Potential habitat for chum salmon (Oncorhynchus keta) in the Western Arctic based on a bioenergetics model coupled with a three-dimensional lower trophic ecosystem model

AbstractChum salmon (Oncorhynchus keta) are predominantly located in the Bering Sea during summer and fall. However, several studies have recently reported a different tendency as follows. Observed densities of chum salmon were higher in the vicinity of the Bering Strait and the Chukchi Sea than the eastern Bering Sea in September 2007, and Japanese chum salmon migrated to northern areas in the Bering Sea during summer 2009. The sea surface temperature (SST) in the Arctic marginal seas has increased since the mid-1960s, and especially since 2000. We speculated that the SST increase directly promoted salmon northing from the Bering Sea to the Western Arctic. In this study, we estimated the potential habitat for chum salmon in the Western Arctic using a bioenergetics model coupled with a three-dimensional lower trophic ecosystem model (3-D NEMURO). “Potential habitat” was defined as “an area where chum salmon could grow (i.e., the growth rate was positive)”. In the bioenergetics model, the growth rate of an individual chum salmon was calculated as a function of water temperature, salinity, and prey density, which were obtained from the 3-D NEMURO model results. To evaluate the habitat responses under a global warming scenario, we used the modeled monthly change of water temperature between 2005 (averaged from 2001 to 2010) and 2095 (averaged from 2091 to 2100) under the IPCC SRES-A1B scenario. Our calculations, following the global warming scenario, suggested that the potential habitat for chum salmon would expand to the north due to the increase in water temperature and prey density. In contrast, south of 71°N during summer, the potential habitat would shrink regionally because the water temperature exceeded the optimal condition

Effect of Aquaculture on Material Cycles in Otsuchi Bay, Japan

A numerical physical-biological coupled model is developed for the study of coastal material cycles including aquaculture. The model calculates spatial distributions of PON (Particulate Organic Nitrogen), POP (Particulate Organic Phosphorus), DON (Dissolved Organic Nitrogen), DOP (Dissolved Organic Phosphorus), Chl-a, zooplankton, NO_3-N, NH_4-N and PO_4-P using simulated current. It also takes into consideration the effects of shellfish feeding and excretion, seaweed photosynthesis, and the loading of DIN from rivers. The model is applied to Otsuchi Bay, in Iwate Pref., in Japan. The model elucidated the cycling of nitrogen among ecological compartments. If the amount of cultured shellfish is extremely increased, the feeding by shellfish is large enough to change the lower trophic level ecosystem, reducing concentration of phytoplankton and POM (Particulate Organic Matter) around the cultured region, while phytoplankton increases far from the culture due to the increase of recycled nutrient by the excretion of shellfish

Biochemical properties of warm eddies reproduced by western Arctic marine ecosystem model

第2回極域科学シンポジウム/第34回気水圏シンポジウム 11月17日（木） 統計数理研究所 セミナー室

Dosimetric Comparison between Dynamic Wave Arc and Co-Planar Volumetric Modulated Radiotherapy for Locally Advanced Pancreatic Cancer

Introduction: Dose reduction to the duodenum is important to decrease gastrointestinal toxicities in patients with locally advanced pancreatic cancer (LAPC) treated with definitive chemoradiotherapy. We aimed to compare dynamic wave arc (DWA), a volumetric-modulated beam delivery technique with simultaneous gantry/ring rotations passing the waved trajectories, with coplanar VMAT (co-VMAT) with respect to dose distributions in LAPC cases. Material and Methods: DWA and co-VMAT plans were created for 13 patients with LAPC. The prescribed dose was 45.6 or 48 Gy in 15 fractions. The dose volume indices (DVIs) for target volumes and organs at risk were compared between the corresponding plans. Gamma passing rate, monitor unit (MU), and beam-on time were also compared. Results: DWA significantly reduced the duodenal V39Gy, V42Gy, and V45Gy by 1.1, 0.8, and 0.2 cm3, and increased the liver mean dose and D2cm3 of the spinal cord planning volume by 1.0 and 1.5 Gy, respectively. Meanwhile, there was no significant difference in the target volumes except for D2% of PTV (111.5% in DWA vs. 110.5% in co-VMAT). Further, the gamma passing rate was similar in both plans. MU and beam-on time increased in DWA by 31 MUs and 15 seconds, respectively. Conclusion: DWA generated significantly lower duodenal doses in LAPC cases, albeit with slight increasing liver and spinal cord doses and increasing MU and the beam delivery time. Further evaluation is needed to know how the dose differences would affect the clinical outcomes in chemoradiotherapy for LAPC

Association of mast cell-derived VEGF and proteases in dengue shock syndrome

Background: Recent in-vitro studies have suggested that mast cells are involved in Dengue virus infection. To clarify the role of mast cells in the development of clinical Dengue fever, we compared the plasma levels of several mast cell-derived mediators (vascular endothelial cell growth factor [VEGF], soluble VEGF receptors [sVEGFRs], tryptase, and chymase) and -related cytokines (IL-4, -9, and -17) between patients with differing severity of Dengue fever and healthy controls. Methodology/Principal Findings: The study was performed at Children\u27s Hospital No. 2, Ho Chi Minh City, and Vinh Long Province Hospital, Vietnam from 2002 to 2005. Study patients included 103 with Dengue fever (DF), Dengue hemorrhagic fever (DHF), and Dengue shock syndrome (DSS), as diagnosed by the World Health Organization criteria. There were 189 healthy subjects, and 19 febrile illness patients of the same Kinh ethnicity. The levels of mast cell-derived mediators and -related cytokines in plasma were measured by ELISA. VEGF and sVEGFR-1 levels were significantly increased in DHF and DSS compared with those of DF and controls, whereas sVEGFR-2 levels were significantly decreased in DHF and DSS. Significant increases in tryptase and chymase levels, which were accompanied by high IL-9 and -17 concentrations, were detected in DHF and DSS patients. By day 4 of admission, VEGF, sVEGFRs, and proteases levels had returned to similar levels as DF and controls. In-vitro VEGF production by mast cells was examined in KU812 and HMC-1 cells, and was found to be highest when the cells were inoculated with Dengue virus and human Dengue virus-immune serum in the presence of IL-9. Conclusions: As mast cells are an important source of VEGF, tryptase, and chymase, our findings suggest that mast cell activation and mast cell-derived mediators participate in the development of DHF. The two proteases, particularly chymase, might serve as good predictive markers of Dengue disease severity

Coupling of an individual-based model of anchovy with lower trophic level and hydrodynamic models

Anchovy (Engraulis japonicus), a small pelagic fish and food of other economic fishes, is a key species in the Yellow Sea ecosystem. Understanding the mechanisms of its recruitment and biomass variation is important for the prediction and management of fishery resources. Coupled with a hydrodynamic model (POM) and a lower trophic level ecosystem model (NEMURO), an individual-based model of anchovy is developed to study the influence of physical environment on anchovy's biomass variation. Seasonal variations of circulation, water temperature and mix-layer depth from POM are used as external forcing for NEMURO and the anchovy model. Biomasses of large zooplankton and predatory zooplankton which anchovy feeds on are output from NEMURO and are controlled by the consumption of anchovy on them. Survival fitness theory related to temperature and food is used to determine the swimming action of anchovy in the model. The simulation results agree well with observations and elucidate the influence of temperature in over-wintering migration and food in feeding migration

Lagrangian ensemble model of Copepoda (Neocalanus cristatus) in the northwestern subarctic Pacific

A Lagrangian ensemble model describing the population dynamics of Neocalanus cristatus was developed. To describe the ecology of N. cristatus, life stage must be included in the model. For this purpose, a new zooplankton compartment, divided into nine life stages, was added to the North Pacific Ecosystem Model for Understanding Regional Oceanography (NEMURO). In addition, we introduced Lagrangian particles for the copepod population. Each Lagrangian particle represented a population of the same cohort of copepods with information on representative age, developmental stage, growth rate, structural weight, and food satiation. The new model revealed that surviving cohorts are only matched with the phytoplankton bloom after the nauplii stages. The model showed that the existing phytoplankton concentration when copepodites of N. cristatus appear in the surface water determines the development pattern of copepodite stages. The timing of the seasonal phytoplankton bloom depends on climate change, and a sensitivity analysis showed that the multiple spawning strategy through time has an important role in matching the unstable seasonal bloom cycle on a daily basis. The model including the cohorts can collaborate closely with weekly or monthly observations to reveal the rapid response of the marine ecosystem

Estimation of particulate organic carbon flux produced from eelgrass, Zostera marina L., in a subarctic estuary of Hokkaido, Japan

Akkeshi Lake is a typical subarctic estuary located in Hokkaido, Japan; it is covered with eelgrass, specifically Zostera marina. The oyster Crassostrea gigas is cultured throughout the lake, except for on the intertidal sand flats, where the Manila clam, Ruditapes philippinarum, is cultured near the mouth of the lake. To estimate the particulate organic carbon (POC) flux of various sources, including eelgrass, flowing out from Akkeshi Lake to Akkeshi Bay and to evaluate the role of eelgrass in carbon transport, we developed an ecosystem model that includes phytoplankton, zooplankton, dissolved inorganic matter (DIM), dissolved organic matter (DOM), particulate organic matter (POM), eelgrass, epiphytic algae, oysters and the Manila clam, and separated POM into eight classes according to its sources. Eelgrass and epiphytic algae are the most important sources of POC in Akkeshi Lake, especially in the litterfall season. The total POC inflow/outflow quantities to/from Akkeshi Lake during nine months from April to December was -4648 tons; according to its sources, -4414 tons (outflow) came from eelgrass and epiphytic algae, -551 tons (outflow) from oysters and the Manila clam, 145 tons (inflow) from phytoplankton and zooplankton, 383 tons (inflow) from outside sources (i.e., open sea) and -211 tons (outflow) from the river. The total POC production was approximately 75727 tons, 89% of which was from eelgrass and epiphytic algae; 7% was from oysters and the Manila clam; 3% was from phytoplankton and zooplankton; and 1% was from river