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The Effects of Ship Noise on Marine Mammals—A Review
The number of marine watercraft is on the rise—from private boats in coastal areas to commercial ships crossing oceans. A concomitant increase in underwater noise has been reported in several regions around the globe. Given the important role sound plays in the life functions of marine mammals, research on the potential effects of vessel noise has grown—in particular since the year 2000. We provide an overview of this literature, showing that studies have been patchy in terms of their coverage of species, habitats, vessel types, and types of impact investigated. The documented effects include behavioural and acoustic responses, auditory masking, and stress. We identify knowledge gaps: There appears a bias to more easily accessible species (i.e., bottlenose dolphins and humpback whales), whereas there is a paucity of literature addressing vessel noise impacts on river dolphins, even though some of these species experience chronic noise from boats. Similarly, little is known about the potential effects of ship noise on pelagic and deep-diving marine mammals, even though ship noise is focussed in a downward direction, reaching great depth at little acoustic loss and potentially coupling into sound propagation channels in which sound may transmit over long ranges. We explain the fundamental concepts involved in the generation and propagation of vessel noise and point out common problems with both physics and biology: Recordings of ship noise might be affected by unidentified artefacts, and noise exposure can be both under- and over-estimated by tens of decibel if the local sound propagation conditions are not considered. The lack of anthropogenic (e.g., different vessel types), environmental (e.g., different sea states or presence/absence of prey), and biological (e.g., different demographics) controls is a common problem, as is a lack of understanding what constitutes the ‘normal’ range of behaviours. Last but not least, the biological significance of observed responses is mostly unknown. Moving forward, standards on study design, data analysis, and reporting are badly needed so that results are comparable (across space and time) and so that data can be synthesised to address the grand unknowns: the role of context and the consequences of chronic exposures.
Journal Article
Sea mammals : the past and present lives of our oceans' cornerstone species
\"A richly illustrated introduction to the world's living and extinct sea mammals. From the gregarious sea otter and playful dolphins to the sociable narwhal and iconic polar bear, sea mammals are a large, diverse, and increasingly precious group. In this book, Annalisa Berta, a leading expert on sea mammals and their evolution, presents an engaging and richly illustrated introduction to past and present species of these remarkable creatures, from the blue whale and the northern fur seal to the extinct giant sperm whale, aquatic sloth, and walking sea cow. The book features more than 50 individual species profiles, themed chapters, stunning photographs, and specially commissioned paleo-illustrations of extinct species. It presents detailed accounts of these mammals' evolutionary path, anatomy, behaviour, habitats, and conservation. And because these are key species that complete many food chains and have the widest influence of all sea life, the book also offers insights into a broad variety of marine worlds today and in the future\"--Publisher's description.
Book
Return to the sea : the life and evolutionary times of marine mammals
\"Return to the Sea portrays the life and evolutionary times of marine mammals--from giant whales and sea cows that originated 55 million years ago to the deep diving elephant seals and clam-eating walruses of modern times. This fascinating account of the origin of various marine mammal lineages, some extinct, others extant but threatened, is for the non-specialist. Set against a backdrop of geologic time, changing climates, and changing geography, evolution is the unifying principle that helps us to understand the present day diversity of marine mammals and their responses to environmental challenges. Annalisa Berta explains current controversies and explores patterns of change taking place today, such as shifting food webs and predator-prey relationships, habitat degradation, global warming, and the effects of humans on marine mammal communities\"-- S ource other than Library of Congress.
Book
Vulnerability of Arctic marine mammals to vessel traffic in the increasingly ice-free Northwest Passage and Northern Sea Route
The fabled Northwest Passage and Northern Sea Route that were once the quests of early Western explorers are now increasingly sea ice–free, with routine vessel transits expected by midcentury. The potential impacts of this novel vessel traffic on endemic Arctic marine mammal (AMM) species are unknown despite their critical social and ecological roles in the ecosystem and widely recognized susceptibility to ice loss. We developed a vulnerability assessment of 80 subpopulations of seven AMM species to vessel traffic during the ice-free season. Vulnerability scores were based on the combined influence of spatially explicit exposure to the sea routes and a suite of sensitivity variables. More than half of AMM subpopulations (42/80) are exposed to open-water vessel transits in the Arctic sea routes. Narwhals (Monodon monoceros) were estimated to be most vulnerable to vessel impacts, given their high exposure and sensitivity, and polar bears (Ursus maritimus) were estimated to be the least vulnerable because of their low exposure and sensitivity. Regions with geographic bottlenecks, such as the Bering Strait and eastern Canadian Arctic, were characterized by two to three times higher vulnerability than more remote regions. These pinch points are obligatory pathways for both vessels and migratory AMMs, and so represent potentially high conflict areas but also opportunities for conservation-informed planning. Some of the species and regions identified as least vulnerable were also characterized by high uncertainty, highlighting additional data and monitoring needs. Our quantification of the heterogeneity of risk across AMM species provides a necessary first step toward developing best practices for maritime industries poised to advance into this rapidly changing seascape.
Journal Article
Marine mammals as ecosystem sentinels
The earth's climate is changing, possibly at an unprecedented rate. Overall, the planet is warming, sea ice and glaciers are in retreat, sea level is rising, and pollutants are accumulating in the environment and within organisms. These clear physical changes undoubtedly affect marine ecosystems. Species dependent on sea ice, such as the polar bear (Ursus maritimus) and the ringed seal (Phoca hispida), provide the clearest examples of sensitivity to climate change. Responses of cetaceans to climate change are more difficult to discern, but in the eastern North Pacific evidence is emerging that gray whales (Eschrichtius robustus) are delaying their southbound migration, expanding their feeding range along the migration route and northward to Arctic waters, and even remaining in polar waters over winter—all indications that North Pacific and Arctic ecosystems are in transition. To use marine mammals as sentinels of ecosystem change, we must expand our existing research strategies to encompass the decadal and ocean-basin temporal and spatial scales consistent with their natural histories.
Journal Article
Encyclopedia of whales, dolphins and porpoises
\"In [this book], award-winning author and whale researcher Erich Hoyt takes readers into the field for an intimate encounter with some 90 species of cetaceans that make their homes in the world's oceans. Drawing on decades of firsthand experience and a comprehensive familiarity with the current revolution in cetacean studies, Hoyt provides unique insights into the life histories of these compelling marine mammals. Here are discoveries about cetacean biology and behavior, from the physical differences and adaptations among the baleen and toothed whales to their highly intelligent hunting and feeding methods. The courtship and mating practices, family relationships and the lifelong bonds among some family members are fascinating. The symphonic composer of the whale world is the humpback whale, whose complex 30-minute songs reverberate across the liquid universe of the ocean . Some cetaceans survive deep diving and negotiate lengthy migrations across oceans. This book is a fascinating compilation of the latest data on cetaceans and an impassioned argument for the ongoing need for international protection of at-risk populations and their increasingly damaged habitat.\"-- provided by the Publisher.
Book
Implications for marine mammals of large-scale changes in the marine acoustic environment
The amount of underwater sound from ship traffic, commercial, research, and military sound sources has increased significantly over the past century. Marine mammals and many other marine animals rely on sound for short- and long-range communication, for orientation, and for locating prey. This reliance has raised concern that elevated sound levels from human sources may interfere with the behavior and physiology of marine animals. The dominant source of human sound in the sea stems from propulsion of ships. Shipping noise centers in the 20- to 200-Hz band. Frequencies this low propagate efficiently in the sea, and shipping has elevated the global deepwater ambient noise 10- to 100-fold in this frequency band. Baleen whales use the same frequency band for some of their communication signals, and concern has been raised that elevated ambient noise may reduce the range over which they can communicate. Marine mammals have a variety of mechanisms to compensate for increased noise, but little is known about the maximum range at which they may need to communicate. Some of the most intense human sources of sound include air guns used for seismic exploration and sonar for military and commercial use. Human sources of sound in the ocean can disturb marine mammals, evoking behavioral responses that can productively be viewed as similar to predation risk, and they can trigger allostatic physiological responses to adapt to the stressor. Marine mammals have been shown to avoid some human sound sources at ranges of kilometers, raising concern about displacement from important habitats. There are few studies to guide predictions of when such changes start to lower the fitness of individuals or have negative consequences for the population. Although acute responses to intense sounds have generated considerable interest, the more significant risk to populations of marine mammals is likely to stem from less visible effects of chronic exposure.
Journal Article