Boat noise interferes with Lusitanian toadfish acoustic communication

Time-series variation in the locomotor behavior and vocal traits of Japanese medaka (Oryzias latipes) acutely exposed to organophosphorus pesticide chlorpyrifos

Organophosphorus pesticides (OPs), such as chlorpyrifos (CPF), are the most commonly used pesticides worldwide. Considering that OPs will eventually enter aquatic ecosystems due to runoff from agricultural lands, accidental leakage, and other unforeseen emergencies, monitoring water pollution of those substances is crucial for environmental protection and public health. In this study, Japanese medaka (Oryzias latipes) were exposed to CPF (0.03, 0.06, and 0.12 mg/L) for 6 h, and the time-series variations in their locomotor behavior and vocal traits were investigated. Compared with that measured before exposure, significantly changed locomotor behavior and vocal traits in Japanese medaka exposed to CPF could be observed at 4 h after exposure and thereafter, and the pattern of behavioral changes depends on the CPF concentrations. Exposure to CPF also changed the frequency-sound pressure level curve of Japanese medaka at 6 h after exposure, especially at 0.12 mg/L. Moreover, CPF exposure could significantly inhibit the acetylcholinesterase (AChE) activity in the brains and eyes of medaka, which exhibited significant correlations with the variation of locomotor behavioral and vocal traits. Considering that inhibiting the AChE activity is the primary mechanism underlying the neurobehavioral toxicity of all OPs, our finding suggested that simultaneously monitoring changes in the locomotor behavioral and vocal traits has a high potential to reflect the pollution of organophosphorus substances.

Urbanisation and boating are the main contributors to underwater soundscapes in three temperate estuaries

Anthropogenic noise has been identified as one of the most harmful forms of global pollutants impacting both terrestrial and aquatic ecosystems. As global populations continue to increase, coastlines are seeing substantial increases in the level of urbanisation. Although measures are in place to minimise stress on fauna, they rarely consider the impact of anthropogenic noise. In Australia, New South Wales (NSW) estuaries have seen extensive increases in urbanisation in recent years. Yet, there remains minimal baseline data on their soundscapes to determine if noise pollution is a threat. This research provides a first assessment of baseline sounds across a temporal and seasonal scale. Recreational boating was the primary soundscape contributor in estuaries, and estuaries with higher urbanisation levels contained higher sound levels. This research provides useful information for managers of NSW estuaries and is of global relevance in an era of increasing generation of anthropogenic noise in estuarine and coastal systems.

Addressing underwater noise: Joint efforts and progress on its global governance

Underwater noise generated by human activities has become a major reason of concern over the past decades as human exploitation of world seas became more intense. A key to reduce human-generated acoustic pressure on aquatic ecosystems depends on an approach based on international cooperation. Over the past years, scientists worldwide worked together to assess trends in underwater noise levels in order to develop mitigation measures that would allow the effective protection of endangered species without reducing the possibilities for a sustainable use of seas. This review focused on international programmes dedicated to underwater noise monitoring, mapping and to programs dedicated to mitigate noise and its effects on marine fauna. All together this review shows the existence of a growing, general, international consensus on the fact that anthropogenic underwater noise should be significantly reduced by setting appropriate mitigation measures and effective regulatory actions.

Noise-induced masking of hearing in a labyrinth fish: effects on sound detection in croaking gouramis

An increasing level of anthropogenic underwater noise (shipping, drilling, sonar use, etc.) impairs acoustic orientation and communication in fish by hindering signal transmission or detection. Different noise regimes can reduce the ability to detect sounds of conspecifics due to an upward shift of the hearing threshold, a phenomenon termed masking. We therefore investigated the masking effect of white noise on the auditory thresholds in female croaking gouramis (Trichopsis vittata, Osphronemidae). We hypothesized that noise would influence the detection of conspecific vocalizations and thus acoustic communication. The auditory evoked potentials (AEP) thresholds were measured at six different frequencies between 0.1 and 4 kHz using the AEP recording technique. Sound pressure level audiograms were determined under quiet laboratory conditions (no noise) and continuous white noise of 110 dB RMS. Thresholds increased in the presence of white noise at all tested frequencies by 12-18 dB, in particular at 1.5 kHz. Moreover, hearing curves were compared to spectra of conspecific sounds to assess sound detection in the presence of noise in various contexts. We showed that masking hinders the detection of conspecific sounds, which have main energies between 1.0 and 1.5 kHz. We predict that this will particularly affect hearing of female's low-intensity purring sounds during mating. Accordingly, noise will negatively affect acoustic communication and most likely reproductive success.

Boat noise impacts Lusitanian toadfish breeding males and reproductive outcome

Anthropogenic noise is a growing threat to marine organisms, including fish. Yet very few studies have addressed the impact of anthropogenic noise on fish reproduction, especially in situ. In this study, we investigated the impacts of boat noise exposure in the reproductive success of wild Lusitanian toadfish (Halobatrachus didactylus), a species that relies on advertisement calls for mate attraction, using behavioural, physiological and reproductive endpoints. Two sets of artificial nests were deployed in the Tagus estuary and exposed to either ambient sound or boat noise during their breeding season. Toadfish males spontaneously used these nests to breed. We inspected nests for occupation and the presence of eggs in six spring low tides (in two years) and assessed male vocal activity and stress responses. Boat noise did not affect nest occupation by males but impacted reproductive success by decreasing the likelihood of receiving eggs, decreasing the number of live eggs and increasing the number of dead eggs, compared to control males. Treatment males also showed depressed vocal activity and slightly higher cortisol levels. The assessment of oxidative stress and energy metabolism-related biomarkers revealed no oxidative damage in noise exposed males despite having lower antioxidant responses and pointed towards a decrease in the activity levels of energy metabolism-related biomarkers. These results suggest that males exposed to boat noise depressed their metabolism and their activity (such as parental care and mate attraction) to cope with an acoustic stressor, consistent with a freezing defensive response/behaviour. Together, our study demonstrates that boat noise has severe impacts on reproductive fitness in Lusitanian toadfish. We argue that, at least fishes that cannot easily avoid noise sources due to their dependence on specific spawning sites, may incur in significant direct fitness costs due to chronic noise exposure.

Boat noise impacts early life stages in the Lusitanian toadfish: A field experiment

Marine traffic is the most common and chronic source of ocean noise pollution. Despite the evidence of detrimental effects of noise exposure on fish, knowledge about the effects on the critical early life stages - embryos and larvae - is still scarce. Here, we take a natural habitat-based approach to examine potential impacts of boat noise exposure in early life stages in a wild fish population of the Lusitanian toadfish (Halobatrachus didactylus). In-situ experiments were carried out in the Tagus estuary, an estuary with significant commercial and recreational boat traffic. Nests with eggs were exposed to either ambient (control) or boat noise (treatment), for 1 fortnight. Eggs were photographed before being assigned to each treatment, and after exposure, to count number of eggs and/or larvae to assess survival, and sampled to study development and oxidative stress and energy metabolism-related biomarkers. Data concerns 4 sampling periods (fortnights) from 2 years. Results indicate that offspring survival did not differ between treatments, but boat noise induced a detrimental effect on embryos and larvae stress response, and on larvae development. Embryos showed reduced levels of electron transport system (ETS), an energy metabolism-related biomarker, while larvae showed higher overall stress responses, with increased levels of superoxide dismutase (SOD) and DNA damage (oxidative stress related responses), ETS, and reduced growth. With this study, we provided the first evidence of detrimental effects of boat noise exposure on fish development in the field and on stress biomarker responses. If these critical early stages are not able to compensate and/or acclimate to the noise stress later in the ontogeny, then anthropogenic noise has the potential to severely affect this and likely other marine fishes, with further consequences for populations resilience and dynamics.

Boat noise affects meagre (Argyrosomus regius) hearing and vocal behaviour

Aquatic noise has increased in last decades imposing new constraints on aquatic animals' acoustic communication. Meagre (Argyrosomus regius) produce loud choruses during the breeding season, likely facilitating aggregations and mating, and are thus amenable to being impacted by anthropogenic noise. We assessed the impact of boat noise on this species acoustic communication by: evaluating possible masking effects of boat noise on hearing using Auditory Evoked Potentials (AEP) and inspecting changes in chorus sound levels from free ranging fish upon boat passages. Our results point to a significant masking effect of anthropogenic noise since we observed a reduction of ca. 20 dB on the ability to discriminate conspecific calls when exposed to boat noise. Furthermore, we verified a reduction in chorus energy during ferryboat passages, a behavioural effect that might ultimately impact spawning. This study is one of few addressing the effects of boat noise by combining different methodologies both in the lab and with free ranging animals.

Fish sounds and boat noise are prominent soundscape contributors in an urban European estuary

Passive acoustic monitoring is a valuable tool for non-intrusive monitoring of marine environments, also allowing the assessment of underwater noise that can negatively affect marine organisms. Here we provide for the first time, an assessment of noise levels and temporal soundscape patterns for a European estuary. We used several eco-acoustics methodologies to characterize the data collected over six weeks within May 2016 - July 2017 from Tagus estuary. Biophony was the major contributor dominated by fish vocalizations and the main driver for seasonal patterns. Maritime traffic was the major source of anthropogenic noise, with daily patterns monitored using 1584 Hz third-octave band level. This indicator avoided biophony and geophony, unlike other indicators proposed for the EU Marine Strategy Framework Directive. Furthermore, the frequency overlap between anthropophony and biophony demands precautionary actions and calls for further research. This study provides an assessment that will be useful for future monitoring and management strategies.

Sex Associated Effects of Noise Pollution in Stone Sculpin (Paracottus knerii) as a Model Object in the Context of Human-Induced Rapid Environmental Change

Simple Summary

In this comprehensive multidisciplinary study, we applied a novel multilevel approach to stone sculpins Paracottus knerii Dybowski, 1874, as model organisms and test for the first time the hypothesis of sex-dependent differences in response to long-term noise exposure in fish. The results testify that the stone sculpin females appeared to experience excessive stress, while the males showed adaptive recalibrations. These effects may be explained by a unique adaptive strategy of offspring care in the stone sculpin males and their biological role in reproductive behavior within the species. The findings obtained may help to elucidate the links between noise exposure in the context of human-induced rapid environmental change (HIREC), long-term sex-related changes in fishes, and the possible further evolutionary success of a species. Such HIREC modeling not only provides information about the potential consequences under anthropogenic pressure but also can help identify the natural mechanisms of stress resistance in different species, including those related to sex, and also contribute to the development of effective environmental management practices.

Abstract

This work simulates the consequences of HIREC using stone sculpins as model organisms. Sex-dependent effects of long-term noise exposure at mean sound pressure levels of 160–179 dB re 1 μPa (SPL_pk–pk) were measured. We applied a multilevel approach to testing the stress response: a comparative analysis of the macula sacculi and an assessment of hematological and molecular stress responses. Noise exposure resulted in hair cell loss, changes in some cytometric parameters in blood, and an increase in the number of functionally active mitochondria in the red blood cells of males and its decrease in females, demonstrating a mitochondrial allostatic load and depletion of functional reserve. Finally, a statistically significant decrease in the telomerase activity of the auditory epithelium and a shortening of telomere length in the brain as molecular markers of stress were observed after noise exposure only in females. No significant decrease in telomerase activity and shortening of telomere length in nerve target tissues were observed in stressed males. However, we recorded an increase in the telomerase activity in male gonads. This sex-dependent difference in load may be associated with accelerated cellular aging in females and lower stress-related long-term risk in males. In this article, we discuss possible reasons for these noise-induced stress effects.