Potential for acoustic masking due to shipping noise in the European lobster (Homarus gammarus)

Low-frequency noise impairs righting reflex behavior by disrupting central nervous system in the sea slug Onchidium reevesii

Anthropogenic noise has significantly increased due to human activities, posing a threat to the health and survival of marine organisms. However, current studies have often emphasized its effects on the physiological aspects of marine organisms, while ignored the relationship between the neuroendocrine system and behavior. This study aimed to evaluate the righting behavior and relevant physiological functions of the central nervous system (CNS) in sea slug (Onchidium reevesii) exposed to low-frequency noise and subsequent noise removal. The duration of the sea slugs' righting reflex increased with longer noise exposure time. The degree of neuronal cell damage and apoptosis were significantly increased and relevant gene expressions were affected (Glu, AChE, FMRFamide and CaMKII) (P < 0.05). After the removal of noise, the righting reflex speed gradually recovered, and the degree of neuronal cell damage, apoptosis and the expression levels of genes continued to decrease. Pearson correlation analysis showed that the righting time was positively correlated with CNS tissue and DNA damage, apoptosis rate, and negatively correlated with the expression levels of genes. Therefore, low-frequency noise exposure causes damage to the CNS of sea slugs, subsequently impairing their normal behavior. Sea slugs exhibited partial recovery within 384 h after removing noise. These findings provide valuable insights into the effects of low-frequency noise on the CNS and behavior of marine invertebrates.

Impact of small boat sound on the listening space of Pempheris adspersa, Forsterygion lapillum, Alpheus richardsoni and Ovalipes catharus

Anthropogenic stressors, such as plastics and fishing, are putting coastal habitats under immense pressure. However, sound pollution from small boats has received little attention given the importance of sound in the various life history strategies of many marine animals. By combining passive acoustic monitoring, propagation modelling, and hearing threshold data, the impact of small-boat sound on the listening spaces of four coastal species was determined. Listening space reductions (LSR) were greater for fishes compared to crustaceans, for which LSR varied by day and night, due to their greater hearing abilities. Listening space also varied by sound modality for the two fish species, highlighting the importance of considering both sound pressure and particle motion. The theoretical results demonstrate that boat sound hinders the ability of fishes to perceive acoustic cues, advocating for future field-based research on acoustic cues, and highlighting the need for effective mitigation and management of small-boat sound within coastal areas worldwide.

Acoustic scaling in the European spiny lobster (Palinurus elephas)

Sound is an important cue for arthropods. In insects, sound features and sound-producing apparatus are tightly correlated to enhance signal emission in larger individuals. In contrast, acoustic scaling in marine arthropods is poorly described even if they possess similar sound-producing apparatus. Here, the acoustic scaling of the European spiny lobster is analyzed by recording sounds in situ at 1 m from a wide range of body sizes. The dimensions of associated sound-producing apparatus increased with body size, indicating sound features would also be influenced by spiny lobster size. Indeed, temporal sound features changed with body size, suggesting differences in calling songs could be used for spiny lobster acoustic communication. Source levels (peak-peak) ranged from 131 to 164 dB re 1μPa for smaller and larger lobsters, respectively, which could be explained by more efficient resonating structures in larger animals. In addition, dominant frequencies were highly constrained by ambient noise levels, masking the low-frequency content of low intensity sounds from smaller spiny lobsters. Although the ecological function of spiny lobster sounds is not clear yet, these results suggest larger body sizes benefit because louder calls increase the broadcast area and potential interactions with conspecifics, as shown in the insect bioacoustic literature.