Effect of ocean acidification on growth and otolith condition of juvenile scup, Stenotomus chrysops@en

Increasing amounts of atmospheric carbon dioxide (CO2) from human industrial activities are causing changes in global ocean carbonate chemistry, resulting in a reduction in pH, a process termed \"ocean acidification.\" It is important to determine which species are sensitive to elevated levels of CO2 because of potential impacts to ecosystems, marine resources, biodiversity, food webs, populations, and effects on economies. Previous studies with marine fish have documented that exposure to elevated levels of CO2 caused increased growth and larger otoliths in some species. This study was conducted to determine whether the elevated partial pressure of CO2 (pCO2) would have an effect on growth, otolith (ear bone) condition, survival, or the skeleton of juvenile scup, Stenotomus chrysops, a species that supports both important commercial and recreational fisheries. Elevated levels of pCO2 (1200-2600 µatm) had no statistically significant effect on growth, survival, or otolith condition after 8 weeks of rearing. Field data show that in Long Island Sound, where scup spawn, in situ levels of pCO2 are already at levels ranging from 689 to 1828 µatm due to primary productivity, microbial activity, and anthropogenic inputs. These results demonstrate that ocean acidification is not likely to cause adverse effects on the growth and survivability of every species of marine fish. X-ray analysis of the fish revealed a slightly higher incidence of hyperossification in the vertebrae of a few scup from the highest treatments compared to fish from the control treatments. Our results show that juvenile scup are tolerant to increases in seawater pCO2, possibly due to conditions this species encounters in their naturally variable environment and their well-developed pH control mechanisms.人类工业活动导致大气二氧化碳（CO₂）排放量持续增加，正引发全球海洋碳酸盐化学组成发生改变，进而造成海水pH值下降，这一过程被称为海洋酸化。由于海洋酸化可能对生态系统、海洋资源、生物多样性、食物网、种群数量造成影响，甚至波及经济发展，因此明确哪些海洋生物对升高的CO₂浓度敏感具有重要意义。过往针对海洋鱼类的研究已证实，暴露于高浓度CO₂环境下，部分鱼类的生长速度会加快，耳石（otolith，耳骨）体积也会更大。本研究旨在探究升高的二氧化碳分压（pCO₂）是否会对幼体铜平鲷（Stenotomus chrysops）的生长、耳石状态、存活率以及骨骼发育产生影响，该物种同时支撑着重要的商业与休闲渔业。经过8周的养殖后，升高的pCO₂浓度（1200~2600 μatm）对幼体铜平鲷的生长、存活率以及耳石状态均无统计学意义上的显著影响。实地监测数据显示，在铜平鲷的产卵场——长岛海湾，由于初级生产力、微生物活动以及人为输入的影响，原位二氧化碳分压已达到689~1828 μatm。上述研究结果表明，海洋酸化未必会对所有海洋鱼类的生长与存活产生负面影响。对实验鱼的X射线分析显示，与对照组个体相比，最高CO₂处理组中少量铜平鲷的脊椎骨出现骨质增生（hyperossification）的比例略高。本研究结果证实，幼体铜平鲷对海水pCO₂升高具有耐受性，这可能与该物种在自然多变环境中所经历的条件，以及其完善的pH调节机制有关。