Effects of Ocean Acidification on Temperate Coastal Marine Ecosystems and Fisheries in the Northeast Pacific

As the oceans absorb anthropogenic CO2 they become more acidic, a problem termed ocean acidification (OA). Since this increase in CO2 is occurring rapidly, OA may have profound implications for marine ecosystems. In the temperate northeast Pacific, fisheries play key economic and cultural roles and provide significant employment, especially in rural areas. In British Columbia (BC), sport (recreational) fishing generates more income than commercial fishing (including the expanding aquaculture industry). Salmon (fished recreationally and farmed) and Pacific Halibut are responsible for the majority of fishery-related income. This region naturally has relatively acidic (low pH) waters due to ocean circulation, and so may be particularly vulnerable to OA. We have analyzed available data to provide a current description of the marine ecosystem, focusing on vertical distributions of commercially harvested groups in BC in the context of local carbon and pH conditions. We then evaluated the potential impact of OA on this temperate marine system using currently available studies. Our results highlight significant knowledge gaps. Above trophic levels 2–3 (where most local fishery-income is generated), little is known about the direct impact of OA, and more importantly about the combined impact of multi-stressors, like temperature, that are also changing as our climate changes. There is evidence that OA may have indirect negative impacts on finfish through changes at lower trophic levels and in habitats. In particular, OA may lead to increased fish-killing algal blooms that can affect the lucrative salmon aquaculture industry. On the other hand, some species of locally farmed shellfish have been well-studied and exhibit significant negative direct impacts associated with OA, especially at the larval stage. We summarize the direct and indirect impacts of OA on all groups of marine organisms in this region and provide conclusions, ordered by immediacy and certainty.

海洋吸收人为排放的二氧化碳（anthropogenic CO2）后酸度逐渐升高，这一问题被称为海洋酸化（ocean acidification, OA）。由于二氧化碳浓度的增长速度极快，海洋酸化可能对海洋生态系统造成深远影响。在东北太平洋温带海域，渔业兼具关键的经济与文化价值，并为当地提供了大量就业岗位，尤其是在农村地区。在不列颠哥伦比亚省（British Columbia, BC），休闲渔业（sport fishing，即recreational fishing）的创收规模超过商业渔业（包括扩张中的水产养殖业）。休闲捕捞与养殖的鲑鱼以及太平洋大比目鱼（Pacific Halibut）贡献了该地区绝大多数的渔业相关收入。该区域因海洋环流的影响，天然水体本身酸度相对较高（pH值较低），因此可能对海洋酸化的冲击尤为敏感。我们通过分析现有数据，结合当地的碳循环与pH值环境条件，聚焦不列颠哥伦比亚省商业捕捞类群的垂直分布特征，以此呈现当前该海洋生态系统的现状。随后，我们依托现有研究成果，评估了海洋酸化对这片温带海洋系统的潜在影响。我们的研究结果凸显了诸多显著的知识空白：在营养级（trophic levels）2至3以上的生物类群（当地大部分渔业收入来源于此层级）中，我们对海洋酸化的直接影响知之甚少，更遑论诸如温度这类随气候变化同步改变的多重胁迫因子的联合影响。现有研究表明，海洋酸化可能通过改变低营养级生物与栖息地环境，对硬骨鱼类（finfish）产生间接负面影响。尤为值得关注的是，海洋酸化可能引发致死鱼类的藻华（algal blooms）暴发，进而对利润丰厚的鲑鱼水产养殖业造成冲击。另一方面，部分本地养殖的贝类已得到充分研究，其表现出与海洋酸化相关的显著负面直接影响，尤其是在幼虫阶段（larval stage）。我们总结了海洋酸化对该区域所有海洋生物类群的直接与间接影响，并按照影响的紧迫性与确定性排序给出了研究结论。