Will rising pCO2 levels in the ocean affect growth and survival of marine fish early life stages?

知识价值：海洋酸化有可能影响广泛的海洋生物，从而改变我们海洋的组成和功能。与钙化的海洋无脊椎动物不同，人们普遍认为海洋鱼类不会受到未来预计的二氧化碳浓度的影响。虽然在幼鱼和成鱼阶段可能是这样，但在高二氧化碳海洋中，鱼胚胎和幼鱼的命运不太确定，因为这些阶段的二氧化碳敏感性数据基本上无法获得。认识到这一知识差距，并受到最近两项关于小丑鱼和海鲈鱼幼虫的研究结果的启发（Munday等）。Pnas 107 (2010)；Checkley等人。科学324(2009))，研究人员进行了一系列实验，将内陆银鱼（Menidia beryllina）的卵和早期幼虫暴露在二氧化碳浓度升高的环境中，同时严格遵守目前海洋酸化研究的“最佳实践”指导方针。在CO2浓度为1000 ppm时，绿柱头潜蝇孵化后1周的平均存活率（5个实验）明显下降了75%，新孵化幼虫的平均长度下降了22%。结合先前的研究，这些结果表明，鱼类生命早期阶段对预计本世纪发生的二氧化碳增加的敏感性高得惊人。考虑到包括大多数商业鱼类在内的许多鱼类种群的丰度往往受到影响早期生活史生长和生存的过程的调节，海洋酸化可能影响未来鱼类种群的动态，并成为对可持续渔业的又一挑战。研究人员认为，现在迫切需要更好地了解二氧化碳是如何影响海洋中鱼类胚胎和幼虫的生存能力的。这需要新的方法，包括在多个物种之间进行更长期、更大规模的实验。研究人员将全面研究目前和未来的二氧化碳水平（400 - 1000ppm）对三种模式鱼类的卵和幼虫阶段的影响：大西洋银鱼（M. menidia），内陆银鱼（M. beryllina）和羊头鲦鱼（Cyprinodon variegatus）。他们还将调查来自不同纬度的同一物种（menidia）种群。这些物种/种群具有生态重要性，因为它们处于中等营养地位，具有与商业海洋鱼类相当的生活史，在遗传生长能力和假定敏感性方面存在差异，并且非常适合实验室实验。在不同的CO2、温度（21,27°C）和饲喂条件（低、随意）下进行的实验中，将测量生存和生长（基于体重和长度），从而允许将CO2的影响与热应力和食物限制同时考虑。摄食率、总生长效率和耗氧量的量化将表征高二氧化碳环境的生理成本。幼鱼的耳石和骨骼元素的钙化变化将通过重量和Ca45放射性示踪剂方法来确定。最后，幸存的menidia（或M. beryllina）将被饲养到成熟，它们的后代将受到不同水平的二氧化碳的挑战。在几代人的时间里重复这种方法将证明二氧化碳抗性可能通过自然选择进化到何种程度。总的来说，这项研究将在理解海洋酸化如何挑战世界上最宝贵的海洋资源——鱼类方面取得重大进展。更广泛的影响：这项调查将作为石溪大学博士生的论文主题，并将支持一名女性博士后研究员。在支持教育多样性、丰富本科和中学教育和研究方面，各学院有着良好的记录，并将在本项目中继续这些做法。一个新颖的外展项目有可能在项目期间达到100万水族馆的顾客。

Intellectual merit: Ocean acidification has the potential to affect a broad spectrum of marine organisms and thereby transform the composition and function of our oceans. In contrast to calcifying marine invertebrates, marine fish are widely believed to be unaffected by the CO2 concentrations projected for the future. While this may be so for juvenile and adult fish stages, the fate of fish embryos and larvae in high CO2 oceans is less certain as CO2-sensitivity data for these stages are largely unavailable. Recognizing this knowledge gap and inspired by the findings of two recent studies on clownfish and sea bass larvae (Munday et al. PNAS 107 (2010); Checkley et al. Science 324 (2009)), the investigators performed a series of experiments exposing eggs and early larvae of inland silversides (Menidia beryllina) to elevated CO2 levels while strictly adhering to current "best practice" guidelines for ocean acidification research. At 1,000 ppm CO2, average M. beryllina survival ~1wk post-hatch significantly and consistently (five experiments) declined by ~75% compared to current day CO2 levels (390 ppm), while average length of newly hatched larvae decreased by 22%. Together with prior studies, these results suggest a surprisingly high susceptibility of fish early life stages to the CO2 increases that are projected to occur this century. Given that the abundance of many fish stocks, including most commercial species, is often regulated by processes affecting early life history growth and survival, ocean acidification may impact the dynamics of future fish populations and become yet another challenge to sustainable fisheries. The investigators believe that there is now a pressing need to better understand how CO2 affects the viability of fish embryos and larvae in the ocean. This requires novel approaches involving longer-term, larger-scale experiments across multiple species. The investigators will comprehensively examine the impacts of current and future CO2 levels (400 - 1,000 ppm) during the egg and larval stages of three model fish species: Atlantic silversides (M. menidia), inland silversides (M. beryllina) and sheepshead minnows (Cyprinodon variegatus). They will also investigate populations of the same species (M. menidia) from differing latitudes. These species/populations are ecologically important due to their intermediate trophic position, have comparable life histories to commercial marine fish, offer differences in genetic growth capacity and presumed sensitivity, and are highly amenable to laboratory experimentation. Survival and growth (weight- and length-based) will be measured in experiments performed at different CO2, temperature (21, 27°C) and feeding conditions (low, ad libitum), thus permitting the affects of CO2 to be considered in parallel with thermal stress and food limitation. Quantification of feeding rates, gross growth efficiency, and oxygen consumption will characterize the physiological costs of high CO2 environments. Changes in calcification of larval fish otoliths and skeletal elements will be determined from weights and a Ca45 radiotracer approach. Finally, surviving M. menidia (or M. beryllina) will be reared to maturity and their offspring will be challenged with differing levels of CO2. Repeating this approach over several generations will demonstrate the extent to which CO2 resistance may evolve through natural selection. Collectively, this study will make significant advances toward understanding how ocean acidification may challenge the world's most valuable marine resource, fish.Broader Impacts: This investigation will serve as the dissertation topic for a doctoral student at Stony Brook University and will support a female post-doctoral researcher. The PIs have a strong record of supporting diversity in education and in enriching undergraduate and secondary school education and research and will continue these practices for this project. A novel outreach program has the potential to reach one million aquarium patrons during the project.