Seawater carbonate chemistry, mortality and hatching rate, size and mass of Clupea harengus during experiments, 2011

Due to atmospheric accumulation of anthropogenic CO2 the partial pressure of carbon dioxide (pCO2) in surface seawater increases and the pH decreases. This process known as ocean acidification might have severe effects on marine organisms and ecosystems. The present study addresses the effect of ocean acidification on early developmental stages, the most sensitive stages in life history, of the Atlantic herring (Clupea harengus L.). Eggs of the Atlantic herring were fertilized and incubated in artificially acidified seawater (pCO2 1260, 1859, 2626, 2903, 4635 µatm) and a control treatment (pCO2 480 µatm) until the main hatch of herring larvae occurred. The development of the embryos was monitored daily and newly hatched larvae were sampled to analyze their morphometrics, and their condition by measuring the RNA/DNA ratios. Elevated pCO2 neither affected the embryogenesis nor the hatch rate. Furthermore the results showed no linear relationship betweenpCO2 and total length, dry weight, yolk sac area and otolith area of the newly hatched larvae. For pCO2 and RNA/DNA ratio, however, a significant negative linear relationship was found. The RNA concentration at hatching was reduced at higher pCO2 levels, which could lead to a decreased protein biosynthesis. The results indicate that an increased pCO2 can affect the metabolism of herring embryos negatively. Accordingly, further somatic growth of the larvae could be reduced. This can have consequences for the larval fish, since smaller and slow growing individuals have a lower survival potential due to lower feeding success and increased predation mortality. The regulatory mechanisms necessary to compensate for effects of hypercapnia could therefore lead to lower larval survival. Since the recruitment of fish seems to be determined during the early life stages, future research on the factors influencing these stages are of great importance in fisheries science.由于人为源二氧化碳（CO₂）在大气中的累积，表层海水的二氧化碳分压（partial pressure of carbon dioxide, pCO₂）升高，pH值下降。这一过程被称为海洋酸化（ocean acidification），可能会对海洋生物与生态系统造成严重影响。本研究旨在探究海洋酸化对大西洋鲱（Clupea harengus L.）生活史中最为敏感的早期发育阶段的影响。研究人员将大西洋鲱的受精卵置于人工酸化海水（pCO₂分别为1260、1859、2626、2903、4635 µatm）以及对照组（pCO₂为480 µatm）中培育，直至鲱鱼幼鱼大量孵化。研究团队每日监测胚胎发育情况，并对新孵化的幼鱼进行采样，以分析其形态计量学指标，并通过测定RNA/DNA比值评估其健康状态。升高的pCO₂既未对胚胎发生过程产生影响，也未改变孵化率。此外，研究结果显示pCO₂与新孵化幼鱼的总长度、干重、卵黄囊面积及耳石面积均无线性相关关系。然而，pCO₂与RNA/DNA比值之间存在显著的负线性相关关系：在较高pCO₂水平下，幼鱼孵化时的RNA浓度有所降低，这可能会导致蛋白质生物合成能力下降。研究结果表明，升高的pCO₂会对鲱鱼胚胎的代谢产生负面影响，进而可能抑制幼鱼后续的躯体生长。这将对幼鱼造成不利影响，因为个体更小、生长更迟缓的个体因摄食成功率更低、被捕食致死率更高，其存活潜力更低。因此，为抵消高碳酸血症（hypercapnia）带来的胁迫效应所需的调控机制，可能会降低幼鱼的存活率。由于鱼类种群补充量似乎在早期生活阶段就已确定，因此未来针对这些阶段影响因素的研究，在渔业科学领域具有重要的学术价值。