Coastal upwelling that brings to the surface both CO₂- and nutrient-rich deep seawater is related to acidification and intense biological productivities in surface waters. However, the impact of biological activities on upwelling-induced acidification from nearshore to offshore areas in an upwelling zone remains insufficiently known. In this paper, we present daily records of high-resolution profiles of carbonate chemistry and hydrographic parameters from the nearshore to the offshore upwelling zone off the east coast of Hainan Island (ECH) in July 2014 (summer season). A three end-member mixing model was adopted to discriminate biological processes from physical mixing and to further semiquantitatively diagnose biological contribution to the upwelling-induced acidification. The results show divergent responses in pH, aragonite saturation state (Ω_Ar) and biomediated nonconservative dissolved inorganic carbon (ΔDIC) at depths of 10 m–30 m between nearshore and offshore regimes under the on-going coastal upwelling, which were attributed to the distinct roles of biological activities in mediating acidification in the upper 30 m across the ECH. Specifically, in the offshore regime, enhanced photosynthesis reduced the upwelling-induced acidification by 40% (i.e., type C: relief role), whereas aerobic respiration increased acidification in the subsurface waters of the nearshore regime by 15% (i.e., type B: aggravation role). This led to the pH and Ω_Ar minimum in upwelled waters along the transect from the nearshore to the offshore. In contrast, the biological contribution was almost negligible over surface waters in the nearshore regime because of the balance between net community productivity and net community calcification (i.e., type A: limited or minor role).

沿海上升流使CO ₂都浮出水面-深层营养丰富的海水与地表水的酸化和强烈的生物生产力有关。然而，生物活性对上升流区中从近岸到近海的上升流诱发的酸化的影响仍然是未知的。在本文中，我们提供了2014年7月（夏季）从海南岛东海岸（ECH）附近到近海上升流区的碳酸盐化学和水文参数高分辨率剖面的日常记录。采用三个末端成员混合模型来区分生物过程与物理混合，并进一步半定量诊断生物学对上升流致酸化的贡献。结果表明在pH值发散的响应，文石饱和状态（Ω_氩）和在持续的海岸上升流作用下近岸和近海区域之间10 m–30 m深度处的生物介导的非保守溶解性无机碳（ΔDIC），这归因于生物活动在介导上游30 m以上酸化中的独特作用ECH。具体而言，在近海环境中，增强的光合作用将上升流诱导的酸化作用降低了40％（即C型：起浮作用），而有氧呼吸使近岸海域地下水的酸化作用增加了15％（即B型：加剧的作用）。这导致pH值和Ω_氩从近岸到近岸的沿上升流水域的最小量。相反，由于净社区生产力与净社区钙化之间的平衡（即，A型：作用有限或次要作用），近岸水域对地表水的生物学贡献几乎可以忽略不计。