Short-Term Behavioural Responses of the Great Scallop Pecten maximus Exposed to the Toxic Alga Alexandrium minutum Measured by Accelerometry and Passive Acoustics

Harmful algal blooms produced by toxic dinoflagellates have increased worldwide, impacting human health, the environment, and fisheries. Due to their potential sensitivity (e.g., environmental changes), bivalves through their valve movements can be monitored to detect harmful algal blooms. Methods that measure valve activity require bivalve-attached sensors and usually connected cables to data transfers, leading to stress animals and limit the use to sessile species. As a non-intrusive and continuously deployable tool, passive acoustics could be an effective approach to detecting harmful algal blooms in real time based on animal sound production. This study aimed to detect reaction changes in the valve movements of adult Pecten maximus exposed to the toxic dinoflagellate Alexandrium minutum using both accelerometry and passive acoustic methods. Scallops were experimentally exposed to three ecologically relevant concentrations of A. minutum for 2 hours. The number of each type of valve movement and their sound intensity, opening duration, and valve-opening amplitude were measured. Four behaviours were identified: closures, expulsion, displacement, and swimming. The response of P. maximus to A. minutum occurred rapidly at a high concentration. The valve activity of P. maximus was different when exposed to high concentrations (500 000 cells L-1) of A. minutum compared to the non-toxic dinoflagellate Heterocapsa triquetra; the number of valve movements increased, especially closure and expulsion, which were detected acoustically. Thus, this study demonstrates the potential for acoustics and sound production changes in the detection of harmful algal blooms. However, field trials and longer duration experiments are required to provide further evidence for the use of acoustics as a monitoring tool in the natural environment where several factors may interfere with valve behaviours.

由有毒甲藻引发的有害藻华在全球范围内呈上升趋势，对人类健康、生态环境以及渔业造成诸多负面影响。双壳类生物对环境变化等外界刺激具有潜在敏感性，因此可通过监测其壳瓣运动来识别有害藻华。传统的壳瓣活动检测方法需将传感器附着于双壳类生物体表，且通常需要通过线缆进行数据传输，这不仅会对受试动物造成应激，还限制了该方法仅能应用于固着类物种。作为一种非侵入式且可长期部署的监测手段，被动声学（passive acoustics）技术可基于水生生物的发声行为，实现有害藻华的实时有效检测。本研究旨在通过加速度计法（accelerometry）与被动声学技术结合，探究暴露于有毒甲藻微小亚历山大藻（Alexandrium minutum）的成年巨扇贝（Pecten maximus）的壳瓣运动响应变化。实验中，受试扇贝被置于三种符合生态场景的微小亚历山大藻浓度环境中暴露2小时。研究人员对不同类型的壳瓣运动次数、发声强度、壳瓣张开时长以及张开幅度进行了测量。本次实验共识别出四种壳瓣运动行为：闭壳、排遗、位移以及游泳。当处于高浓度藻液环境时，巨扇贝对微小亚历山大藻的响应速度较快。当暴露于浓度为500 000 cells·L⁻¹的高浓度微小亚历山大藻环境时，巨扇贝的壳瓣活动模式与暴露于无毒甲藻三角异弯藻（Heterocapsa triquetra）环境时存在显著差异：其壳瓣运动次数显著增加，尤其是闭壳与排遗行为，且该变化可通过声学手段检测到。综上，本研究证实了基于声学检测与生物发声变化的有害藻华监测方法具有应用潜力。但在自然环境中，诸多因素可能会干扰双壳类的壳瓣行为，因此仍需开展野外试验与长期持续实验，为声学监测手段的实际应用提供更多实证支持。