Evaluation of Submarine Groundwater Discharge(SGD) effects on the fisheries resources based on stable & radio isotopes techniques

基于稳定模型的海底地下水排放（SGD）对渔业资源的影响评价

基本信息

批准号：
22710012
负责人：
UMEZAWA Yu
金额：
$ 2.58万
依托单位：
Nagasaki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Young Scientists (B)
财政年份：
2010
资助国家：
日本
起止时间：
2010 至 2011
项目状态：
已结题

项目摘要

Terrestrial freshwater and associated nutrient fluxes affect primary production at coastal areas. Differently from river water like Chikugo River, however, the contribution of groundwater discharge to coastal ecosystem has not been well evaluated in Ariake Bay. In this study,^<222> Rn was considered as a good indicator of groundwater, because^<222> Rn concentrations in groundwater along the west coast of Ariake Bay were one or three orders of magnitude higher than those in river waters.^<222> Rn distribution standardized based on the accumulated rainfall and water depth at the sampling location successfully indicated a spatial variation of groundwater discharge. Furthermore, total groundwater fluxes were evaluated from the^<222> Rn distributions, because spatial distributions of^<222> Rn were correlated with actual groundwater fluxes measured at 5 different locations. Nutrient fluxes through the groundwater discharge had also spatial variation ; 7. 8 to 510 kg-N day^<-1> for DIN(dissolved inorganic nitrogen), and 0. 5 to 3. 9 kg-P day^<-1> for DIP(dissolved inorganic phosphorus), with the maximum values at Shimabara area, where both groundwater fluxes and nutrient concentrations in groundwater were highest. On the other hand, the impact of groundwater-derived nutrients on marine ecosystem at offshore area was not observed from the researches usingδ^<15> N in nitrate andδ^<13> C andδ^<15> N in organic matter. Along the west coast of Ariake Bay, where there are no big rivers, groundwater can be important nutrient sources to enhance primary production, resulting in good food sources for bivalves and blooming of green macroalgae. However, the influential areas of groundwater-derived nutrients would be limited in shallow coastal areas.

然而，与筑后河等河水不同，陆地淡水和相关养分通量影响沿海地区的初级生产，在本研究中，^<222> Rn 尚未得到很好的评估。被认为是地下水的良好指标，因为^<222>有明湾西海岸地下水中的 Rn 浓度比河水中的浓度高一到三个数量级。^<222> Rn 分布基于采样点的累积降雨量和水深的标准化成功地表明了地下水排放的空间变化。此外，总地下水通量是根据^<222>Rn分布来评估的，因为^<222>Rn的空间分布与相关。在 5 个不同地点测量的地下水养分通量也存在空间变化；对于 DIN（溶解的无机物），为 7. 8 至 510 kg-N day^<-1>。氮），DIP（溶解无机磷）为0. 5至3. 9 kg-P day^<-1>，最大值出现在岛原地区，该地区地下水通量和地下水养分浓度均最高。另一方面，利用硝酸盐中δ^<15>N和δ^<13>C的研究并没有观察到地下水源营养盐对近海区域海洋生态系统的影响。有机质中的 δ^<15> N 沿有明湾西海岸，没有大河流，地下水可以成为提高初级生产力的重要营养源，为双壳类动物和大型绿色藻类提供良好的食物来源。，地下水源养分的影响范围仅限于沿海浅海地区。