Phytoplankton primary productivity around submarine groundwater discharge in nearshore coasts

Marine Ecology Progress Series

Jun Shoji¹  Saori Nishi¹  Shinji Ohsawa¹  Osamu Tominaga¹  Katsuhiro Kitagawa¹  Ryo Sugimoto¹  Shiho Kobayashi¹  Makoto Yamada¹  Hisami Honda¹  Makoto Taniguchi¹ 

关键词: In situ primary productivity;    Submarine groundwater discharge;    222Rn;   

DOI  :  10.3354/meps11980

学科分类：海洋学与技术

来源: Inter-Research

【 摘 要 】

ABSTRACT: Nutrients supplied from submarine groundwater discharge (SGD) are generally thought to enhance primary production in coastal seas. However, there is little evidence for a direct association between SGD and phytoplankton primary productivity. To elucidate the response of in situ primary productivity to SGD, we conducted comparative experiments at 3 coastal sites in Japan with different SGD types (Site A: Obama Bay; Site B: coast along the western foot of Mt. Chokai; Site C: Beppu Bay) during the summers of 2013-2015. At Site A, which is characterized by seepage-type SGD, we found a significant positive relationship between in situ primary productivity and ²²²Rn concentration. This was likely driven by nutrient-limited water column conditions. On the other hand, at the volcanic coastal Sites B and C, which are dominated by spring-type SGD, no clear relationships between in situ primary productivity and ²²²Rn concentration were found. Although significant relationships between nutrient concentrations and ²²²Rn concentration suggest that SGD acts as a primary nutrient source in these regions, the non-trivial influence of light availability complicates those relationships. Furthermore, lower biomass-specific primary productivity around submarine springs at both sites suggests that submarine springs have negative impacts on phytoplankton growth rates around vent sites, possibly due to changes in local environmental conditions. Our study clarified that the mechanism by which SGD affects phytoplankton production differs from one ecosystem to another because of variable hydrogeographical properties, such as the type of groundwater discharge (i.e. spring or seepage).

【 授权许可】

Unknown