Data from: Buried alive: the behavioural response of the mussels, Modiolus modiolus and Mytilus edulis to sudden burial by sediment

Sedimentation in the sea occurs through natural processes, such as wave and tidal action, which can be exacerbated during storms and floods. Changes in terrestrial land use, marine aggregate extraction, dredging, drilling and mining are known to result in substantial sediment deposition. Research suggests that deposition will also occur due to the modern development of marine renewable energy. The response to individual burial under three depths of sediment, three sediment fractions and five burial durations was investigated in two mussel species, Modiolus modiolus and Mytilus edulis in specialist mesocosms. Both mussel species showed substantial mortality, which increased with duration of burial and burial by finer sediment fractions. M. modiolus was better able to survive short periods of burial than M. edulis, but at longer durations mortality was more pronounced. No mortality was observed in M. modiolus in burial durations of eight days or less but by 16 days of burial, over 50% cumulative mortality occurred. Under variable temperature regimes, M. edulis mortality increased from 20% at 8°C to over 60% at 14.5 and 20°C. Only M. edulis was able to emerge from burial, facilitated by increased byssus production, laid mostly on vertical surfaces but also on sediment particles. Emergence was higher from coarse sediment and shallow burials. Byssus production in M. edulis was not related to the condition index of the mussels. Results suggest that even marginal burial would result in mortality and be more pronounced in warm summer periods. Our results suggest that in the event of burial, adult M. modiolus would not be able to emerge from burial unless local hydrodynamics assist, whereas a small proportion of M. edulis may regain contact with the sediment water interface. The physiological stress resulting in mortality, contribution of local hydrodynamics to survival and other ecological pressures such as mussels existing in aggregations, are discussed.

海洋中的沉积作用由波浪、潮汐作用等自然过程形成，风暴与洪水期间该过程会加剧。现有研究表明，陆地土地利用变化、海洋集料开采、疏浚、钻探及采矿活动，均会引发大规模沉积物堆积；而现代海洋可再生能源开发也会导致沉积事件发生。本研究在专业中型实验生态系统（mesocosms）中，针对厚壳贻贝（Modiolus modiolus）与紫贻贝（Mytilus edulis）两种贻贝，探究了其在三种沉积物埋藏深度、三种沉积物粒级及五种埋藏时长下的单次埋藏响应。两种贻贝均出现显著死亡率，且死亡率随埋藏时长增加、细粒沉积物埋藏而升高。厚壳贻贝的短期埋藏存活能力优于紫贻贝，但埋藏时长延长后，其死亡率增幅更为明显。厚壳贻贝在8天及以内的埋藏周期中未出现死亡，但埋藏16天时累积死亡率超过50%。在可变温度条件下，紫贻贝的死亡率从8℃时的20%升至14.5℃与20℃时的60%以上。仅紫贻贝可通过增加足丝（byssus）分泌实现从埋藏环境中挣脱，其分泌的足丝大多附着于垂直表面，也可附着于沉积物颗粒；从粗粒沉积物与浅埋藏环境中成功挣脱的个体比例更高。紫贻贝的足丝分泌量与其自身的条件指数无显著关联。研究结果显示，即便轻微的沉积物埋藏也会导致贻贝死亡，且该效应在温暖夏季会更为显著。成年厚壳贻贝无法自行从埋藏中挣脱，除非借助当地水动力条件辅助；仅有少量紫贻贝可重新接触到沉积物-水界面。本文还探讨了引发死亡的生理胁迫机制、当地水动力对贻贝存活的贡献，以及贻贝集群生存等其他生态压力因素。