Behavioral responses of brown shrimp (Crangon crangon) to reduced seawater pH following simulated leakages from sub-sea geological storage of CO2

Large-scale storage of CO2 within sub-sea geological formations is a viable option for reducing the volume of this greenhouse gas released directly to the atmosphere from anthropogenic activities. Risks to benthic marine life following possible leakage of gas through the seabed from this carbon capture and storage (CCS) initiative are not yet well established. This study examined behavior (activity patterns) in brown shrimp (Crangon crangon), exposed to a range of reduced seawater pH conditions (7.6, 7, or 6.5) simulating leakage scenarios of varying scales. Brown shrimp have an endogenous rhythmicity associated with their activity, which dictates they are most active during hours of darkness, presumably as protection against vision-dependent predators. This endogenous rhythm in activity continues to be expressed when shrimp are held under constant low-light conditions in the lab and provides an ecologically relevant endpoint to measure when examining the influence of reduced pH on the behavior of these animals. No marked differences in activity pattern were observed between control shrimp maintained at pH 8.1 and those at pH 7.6. However, changes in activity were evident at pH 7 and pH 6.5, where significant shifts in timing and intensity of activity occurred. There was an unexpected increase in activity within periods of expected light, probably signaling efforts by shrimp to migrate away from reduced seawater pH conditions. The loss of this important member of the benthic community due to migration may have important consequences for many of the resilient species that remain.

将二氧化碳大规模封存于海底地质构造中，是减少人为活动直接向大气排放该温室气体体量的可行方案。该碳捕集与封存（Carbon Capture and Storage, CCS）项目若发生气体经海底泄漏的情况，可能对底栖海洋生物（benthic marine life）造成风险，但目前此类风险尚未明确。本研究以褐虾（Crangon crangon）为研究对象，观测其在一系列梯度降低的海水pH条件（7.6、7、6.5）下的行为（活动模式），以此模拟不同规模的泄漏场景。褐虾的活动存在内源性节律（endogenous rhythmicity），该节律决定其在黑暗时段活动最为活跃，推测这一行为是为了躲避依赖视觉的捕食者。当褐虾在实验室中处于持续弱光环境时，这种内源性活动节律仍会稳定表达，因此可将其作为生态学相关的观测终点，用以评估海水pH降低对该物种行为的影响。在pH为8.1的对照组褐虾与pH为7.6的实验组褐虾之间，未观测到活动模式存在显著差异。但在pH为7和pH为6.5的条件下，褐虾的活动模式出现了明显变化：活动的时序与强度均发生了显著偏移。在本该处于光照的时段内，褐虾的活动出现了意料之外的提升，这可能预示着褐虾正试图逃离低pH海水环境。因迁移而流失的这一底栖群落关键物种，可能会对留存下来的众多耐受物种产生重要影响。