Changes to an urban marina soundscape associated with COVID-19 lockdown in Guadeloupe

Coral reef fish density at a tourist destination responded rapidly to COVID-19 restrictions

Throughout the world, anthropogenic pressure on natural ecosystems is intensifying, notably through urbanisation, economic development, and tourism. Coral reefs have become exposed to stressors related to tourism. To reveal the impact of human activities on fish communities, we used COVID-19-related social restrictions in 2021. In French Polynesia, from February to December 2021, there was a series of restrictions on local activities and international tourism. We assessed the response of fish populations in terms of changes in the species richness and density of fish in the lagoon of Bora-Bora (French Polynesia). We selected sites with varying human pressures-some dedicated to tourism activities, others affected by boat traffic, and control sites with little human presence. Underwater visual surveys demonstrated that fish density and richness differed spatially and temporally. They were lowest on sites affected by boat traffic regardless of pandemic-related restrictions, and when activities were authorised; they were highest during lockdowns. Adult fish density increased threefold on sites usually affected by boat traffic during lockdowns and increased 2.7-fold on eco-tourism sites during international travel bans. Human activities are major drivers of fish density and species richness spatially across the lagoon of Bora-Bora but also temporally across pandemic-related restrictions, with dynamic responses to different restrictions. These results highlight the opportunity provided by pauses in human activities to assess their impact on the environment and confirm the need for sustainable lagoon management in Bora-Bora and similar coral reef settings affected by tourism and boat traffic.

Sons al Balcó: A Comparative Analysis of WASN-Based LAeq Measured Values with Perceptual Questionnaires in Barcelona during the COVID-19 Lockdown

The mobility and activity restrictions imposed in Spain due to the COVID-19 pandemic caused a significant improvement in the urban noise pollution that could be objectively measured in those cities with acoustic sensor networks deployed. This significant change in the urban soundscapes was also perceived by citizens who positively appraised this new acoustic scenario. In this work, authors present a comparative analysis between different noise indices provided by 70 sound sensors deployed in Barcelona, both during and before the lockdown, and the results of a perceptual test conducted in the framework of the project Sons al Balcó during the lockdown, which received more than one hundred contributions in Barcelona alone. The analysis has been performed by clustering the objective and subjective data according to the predominant noise sources in the location of the sensors and differentiating road traffic in heavy, moderate and low-traffic areas. The study brings out strong alignments between a decline in noise indices, acoustic satisfaction improvement and changes in the predominant noise sources, supporting the idea that objective calibrated data can be useful to make a qualitative approximation to the subjective perception of urban soundscapes when further information is not available.

The presence of COVID-19 face masks in the largest hypersaline lagoon of South America is predicted by urbanization level

The inadequate disposal of face masks has caused a widespread presence of COVID-19 litter in the environment. We monitored 10 beach arcs along approximately 15 km of the largest hypersaline lagoon of South America looking for face masks during the lockdown (2021) and in the "new normal" (2022) period. Our working hypothesis is that the probability of finding face masks increases with higher urbanization levels, which was estimated by the Human Modification Metric. Approximately 3 × 10^-3 face masks m^-2 were found on nine of 10 beaches (90 %) during the lockdown. However, this reduced to 1 × 10^-4 face masks m^-2 found in eight beaches (80 %) after the lockdown. The probability of finding a face mask was significantly higher as urbanization increased (z = 2.799; p = 0.005). This situation imposes the need for a better waste management and environmental education actions, targeting the reduction of direct littering on coastal ecosystem.

Controllable acoustic deterrent based on the warning signals generated by nonel detonators

Acoustic deterrents are a practical strategy to mitigate the impact of underwater noise on marine mammals. However, their safety and effectiveness are still debatable. This study proposes a controllable acoustic deterrence method to protect marine mammals threatened by underwater blasting noise. The method creates strong-randomness warning signals using nonel detonators and establishes an escape time for animals protected. Combining the BELLHOP ray-based acoustic model with the marine environmental parameters and animals' auditory characteristics, we built a prediction model to establish a link between the acoustic fields and the adjustable source parameters, and provide a Risk zone and Deterrent zone for animals. The simulation and experimental results demonstrated that the root mean squared error between the simulated and measured sound pressure spectral density levels did not exceed 4.5 dB and the coefficient of determination remained at approximately 0.8, indicating that the new deterrent is an effective method with good controllable performances.

Marine Noise Effects on Juvenile Sparid Fish Change among Species and Developmental Stages

Marine noise is an emerging pollutant inducing a variety of negative impacts on many animal taxa, including fish. Fish population persistence and dynamics rely on the supply of early life stages, which are often very sensitive to disturbance. Impacts of marine noise pollution (MNP) on juvenile fish have rarely been investigated in temperate regions. This is particularly true for the Mediterranean Sea, which is considered as an MNP hotspot due to intensive maritime traffic. In this study, we investigate the relationship between MNP related to boat traffic and (i) assemblage structure and (ii) the density of juvenile fishes (post-settlers at different stages) belonging to the Sparidae family. We quantified MNP produced by boating at four coastal locations in the French Riviera (NW Mediterranean Sea) by linearly combining five variables into a ‘noise index’ (NI): (i) boat visitation, (ii) number of boat passages/hour, (iii) the instantaneous underwater noise levels of passing boats, (iv) continuous boat underwater noise levels and (v) duration of exposure to boat noise. Then, using the NI, we identified an MNP gradient. By using juvenile fish visual censuses (running a total of 1488 counts), we found that (i) the assemblage structure and (ii) the density patterns of three fish species (i.e., Diplodus sargus, D. puntazzo, D. vulgaris) changed along the MNP gradient. Specifically, the density of early D. sargus post-settlers was negatively related to MNP, while late post-settler densities of D. puntazzo and, less evidently, D. vulgaris tended to decrease more rapidly with decreasing MNP. Our findings suggest the following potential impacts of MNP on juvenile sparids related to coastal boat traffic: (i) idiosyncratic effects on density depending on the species and the developmental stage (early vs. late post-settlers); (ii) negative effects on recruitment, due to possible alteration of late post-settlement movement patterns.

Visual surveys provide baseline data on small vessel traffic and waterbirds in a coastal protected area

The coastal waters of southern British Columbia, Canada, encompass habitat of international conservation significance to coastal and marine birds, including sizeable areas designated in the early 1900s as Migratory Bird Sanctuaries (MBS) to protect overwintering waterfowl from hunting near urban centres. Two of these, Shoal Harbour (SHMBS) and Victoria Harbour (VHMBS), have seen significant marine infrastructure development in recent decades and experience considerable vessel traffic. Vessel-related stressors are known to affect waterbirds, but traffic characteristics in coastal urban areas are poorly understood for the smaller vessels not tracked by Automatic Identification Systems (AIS). We conducted a pilot study using shore-based observers to develop small-vessel baselines for the winter months, when regional waterbird numbers are highest. During our surveys we recorded considerable inter-site variability in vessel traffic characteristics, with one site (SHMBS) a source of nearly twice as many vessel transits as the other (VHMBS). Most recorded vessels were small watercraft (mean length 26 ± 17', mode 18'), and vessels at the high-traffic site were both shorter and faster on average. One in six vessels were classified as 'noisy', of interest given that noise is an important component of vessel disturbance of waterbirds and other marine animals. Few vessels (7% of all recorded) were of the type required to carry AIS transponders, which highlights the monitoring gap created by using AIS-based approaches alone in nearshore waters, and allows for correction of AIS-derived vessel counts. Waterbird community composition also varied by locality, with one site dominated by gulls (Laridae), cormorants (Phalacrocoracidae), and seaducks (Tribe Mergini), and the other by gulls, cormorants, and alcids (Alcidae). Our results demonstrate that fine-scale local variability must be taken into account when managing for vessel traffic disturbance of waterbirds, particularly at sites of high human population density and increasing coastal development.

Effects of COVID-19 lockdown on the observed density of coral reef fish along coastal habitats of Moorea, French Polynesia

During the first COVID-19 lockdown in 2020, levels of coastal activities such as subsistence fishing and marine tourism declined rapidly throughout French Polynesia. Here, we examined whether the reduction in coastal use led to changes in fish density around the island of Moorea. Two natural coastal marine habitats (bare sand and mangrove) and one type of man-made coastal structure (embankment) were monitored on the west coast of the island before and after the first COVID-19 lockdown. At the end of the lockdown (May 2020), significantly higher apparent densities of juvenile and adult fish, including many harvested species, were recorded compared to levels documented in 2019 at the same period (April 2019). Fish densities subsequently declined as coastal activities recovered; however, 2 months after the end of the lockdown (July 2020), densities were still higher than they were in July 2019 with significant family-specific variation across habitats. This study highlights that short-term reductions in human activity can have a positive impact on coastal fish communities and may encourage future management policy that minimizes human impacts on coastline habitats.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10113-022-02011-0.

Comparison of the marine soundscape before and during the COVID-19 pandemic in dolphin habitat in Sarasota Bay, FL

During the COVID-19 pandemic, changes in vessel activity and associated noise have been reported globally. Sarasota Bay is home to a large and increasing number of recreational vessels as well as a long-term resident community of bottlenose dolphins, Tursiops truncatus. Data were analyzed from two hydrophones to compare the soundscape during the COVID-19 pandemic to previous years (March-May 2020 and 2018/2019). Hourly metrics were calculated: vessel passes, 95th percentile sound levels [125 Hz and 16 kHz third octave bands (TOBs), and two broader bands: 88-1122 Hz and 1781-17 959 Hz], and dolphin whistle detection to understand changes in vessel activity and the effect on wildlife. Vessel activity increased during COVID-19 restrictions by almost 80% at one site and remained the same at the other site. Of the four sound level measures, only the 125 Hz TOB and 88-1122 Hz band increased with vessel activity at both sites, suggesting that these may be appropriate measures of noise from rapid pass-bys of small vessels in very shallow (<10 m) habitats. Dolphin whistle detection decreased during COVID-19 restrictions at one site but remained the same at the site that experienced increased vessel activity. The results suggest that pandemic effects on wildlife should not be viewed as homogeneous globally.

How the COVID-19 Pandemic Muted and Remixed the World's Acoustics for a While

PURPOSE OF REVIEW

This review aims to analyze the effects of the pandemic on the world's sound environment.

RECENT FINDINGS

The confinements associated with the pandemic led to a reduction in sound levels worldwide and a change in the perception of soundscapes in the absence of traffic noise and human-generated noise.

SUMMARY

In response to the COVID-19 pandemic, many countries and regions around the world adopted a series of interventions in 2020 that have been referred to as "lockdown" or "confinement." These sets of restrictions had a clear and obvious consequence derived from the absence of people in the streets and the reduction of daily activity and commuting, which caused an unprecedented silencing on a large scale. Along with the silence that ensued, the pandemic and the confinements affected acoustics and our relationship with sounds on different scales. In the cities, this phenomenon had a strong reduction in acoustic intensity due to the absence of vehicles on the streets. Perhaps this was more perceptible in our neighborhoods, with notable changes in their soundscapes, first due to the absence of people in the streets and later due to more outdoor activity derived from the fear of the spread of the virus in indoor spaces. The longer periods of time spent in our homes during the lockdowns also highlighted the importance of sound insulation in buildings and the acoustic conditioning of our schools or homes.

Harbours as unique environmental sites of multiple anthropogenic stressors on fish hormonal systems

Fish development and acclimation to environmental conditions are strongly mediated by the hormonal endocrine system. In environments contaminated by anthropogenic stressors, hormonal pathway alterations can be detrimental for growth, survival, fitness, and at a larger scale for population maintenance. In the context of increasingly contaminated marine environments worldwide, numerous laboratory studies have confirmed the effect of one or a combination of pollutants on fish hormonal systems. However, this has not been confirmed in situ. In this review, we explore the body of knowledge related to the influence of anthropogenic stressors disrupting fish endocrine systems, recent advances (focusing on thyroid hormones and stress hormones such as cortisol), and potential research perspectives. Through this review, we highlight how harbours can be used as "in situ laboratories" given the variety of anthropogenic stressors (such as plastic, chemical, sound, light pollution, and invasive species) that can be simultaneously investigated in harbours over long periods of time.