Valve gaping behaviour in bivalve molluscs controls the flow of water across gills that provides both food, and oxygen for respiration. Closure of the valves also provides protection from predators and poor-quality water conditions. Research presented here used a flow through seawater system with controlled changes in salinity and temperature, combined with continuous measurement of valve gape using Hall effect sensors, to study how changes in these variables affect the valve movements of the European oyster (Ostrea edulis) held under controlled long day-length conditions. A clear relationship between periods of reduced light intensity and maximum valve gape was recognised in preliminary studies and provided a benchmark against which to compare how changes in environmental conditions linked to climate change may alter the behaviour of these coastal marine bivalves. Oysters collected from the southwest coast of Norway in August 2022 were held for 72 h at full seawater salinity of 33.6 and a temperature of 15.8 ± 0.5 °C prior to exposure to a reduction in salinity down to 18.2 over a 3 h period. Oysters showed an initial reduction in valve gape width as salinity reached 31.4, with valve gape decreasing further as salinity fell to 28.8. All valves were fully closed at salinity 20.5. Oysters remained in this condition throughout the subsequent 21 h exposure period with salinity at 18.2. Thereafter salinity was increased in 3 steps. In the first step, salinity reached 24.2 over 2 h, and was held there over the following 22 h. All oysters commenced re-opening valves between salinity 22.8 and 24.2. When salinity was further increased to 27.3 over the subsequent 24 h, oysters returned to approximately their pre-exposure valve gape widths. When salinity 33.8 was delivered to the tanks there were 2 d during which maximum valve gape was significantly reduced, after which valve gape width returned to a pre-exposure condition. The predicted pattern of valve opening during reduced light intensity periods was maintained when seawater temperature was raised from 15.8 °C up to 20.1 °C in approximately 1 °C steps every 24 h. However, reduction of temperature from 20.1 °C in similar sized increments altered the expected patterns of behaviour. The results indicate that increasing occurrences of fluxes in salinity and temperature due to climate change have the potential to disrupt normal valve gaping behaviour in European oysters, creating an additional challenge to those they already face from invasive species and disease.

双壳类软体动物的瓣膜张开行为控制着流经鳃的水流，为呼吸提供食物和氧气。阀门的关闭还可以防止捕食者和水质较差的情况。这里介绍的研究使用了盐度和温度受控变化的海水系统，并结合使用霍尔效应传感器连续测量阀门间隙，来研究这些变量的变化如何影响欧洲牡蛎（Ostrea edulis）的阀门运动）在受控的长日照条件下进行。初步研究认识到光照强度降低的时期与最大瓣膜张开之间存在明确的关系，并提供了一个基准，用于比较与气候变化相关的环境条件的变化如何改变这些沿海海洋双壳类的行为。2022 年 8 月从挪威西南海岸采集的牡蛎在海水盐度为 33.6、温度为 15.8 ± 0.5 °C 的条件下保存 72 小时，然后在 3 小时内将盐度降低至 18.2。当盐度达到 31.4 时，牡蛎的瓣膜张开宽度最初减小，当盐度降至 28.8 时，瓣膜张开进一步减小。在盐度为 20.5 时所有阀门完全关闭。在随后的 21 小时暴露期间，牡蛎始终保持这种状态，盐度为 18.2。此后盐度分3步增加。第一步，盐度在 2 小时内达到 24.2，并在接下来的 22 小时内保持在该水平。所有牡蛎在盐度 22.8 至 24.2 之间开始重新打开阀门。当盐度在接下来的 24 小时内进一步增加到 27.3 时，牡蛎恢复到大约暴露前的瓣膜张开宽度。当盐度为 33.8 时，有 2 天的时间，最大阀门间隙显着减小，之后阀门间隙宽度恢复到暴露前的状态。当海水温度每 24 小时以大约 1 °C 的幅度从 15.8 °C 升高到 20.1 °C 时，在光强度降低期间阀门打开的预测模式得以维持。然而，以类似幅度的增量将温度从 20.1 °C 降低改变了预期的行为模式。结果表明，气候变化导致盐度和温度变化的增加有可能破坏欧洲牡蛎正常的阀门张开行为，给它们已经面临入侵物种和疾病的挑战带来额外的挑战。