Impact of Climate Change on Marine Ecosystems and Aquatic Life
The melting of glaciers, an abundance of carbon dioxide (CO2), and the overheating of water bodies, among other factors, have made global warming a worldwide concern with catastrophic effects on several parts of the ecosystem. Recently, climate change has accelerated its impact on the marine ecosystem, resulting in significant changes. It is projected that climate change will impact organisms, specifically their individualism, the structure and size of their populations, as well as the structure and operation of ecosystems.
Climate change affects all aquatic ecosystems, including coastal estuarine environments, freshwater bodies, and marine ecosystems. The possible consequences of climate change on marine animals may be direct, such as the impacts of diminishing sea ice and increasing ocean levels on seal haul-out areas or species tracking a certain spectrum of water temperatures within which they can physically exist. The indirect effects may include changes in prey availability, which impact distribution, abundance, migratory patterns, and susceptibility to illness and contaminants.
Effect of Climate Change on Large Marine Mammals
Impact of Climate Change on Hawaiian Monk Seals and Coastal Habitats
Marine mammals are found in just about all ocean habitats, as well as several rivers and inland seas. The Hawaiian monk seal, an endangered species, requires terrestrial habitat for parturition, nursing, molting, and resting that is safe from shark attack and within commuting distance of marine foraging habitat. A concern was raised about the threat of climate change to the small, low-lying Northwestern Hawaiian Islands (NWHI) due to global sea-level rise (Gulland et al., 2022). Simple passive flooding scenarios predicted considerable habitat loss by 2100 based on contemporary Intergovernmental Panel on Climate Change predictions of sea-level rise (Gulland et al., 2022).
Loss of terrestrial habitat has been most conspicuous at the largest Hawaiian atoll, French Frigate Shoals. Then, in a sharp departure from the continued slow erosion, the next two most significant pupping islands at French Frigate Shoals practically perished during the two months in 2018 (Gulland et al., 2022). Trig Island ultimately succumbed to water, while East Island was devastated by Hurricane Walaka. The latter was remarkable, as East Island was supposed to be the most robust in the atoll due to its extremely high elevation. These unplanned occurrences suggest that sea level rise, in conjunction with tides, storms, and potentially other variables, may lead to abrupt changes in coastal morphology.
Rising Sea Levels and Emerging Predator Threats
Pups appear to be more susceptible to a new type of predator due to the loss of beachfront habitat. Galápagos sharks are common across the NWHI, but only in French Frigate Shoals do they feed on young monk seals; this behavior has only recently been seen as Whaleskate Island’s population has declined significantly. In contrast to more normal pupping habitats, the islands in French Frigate Shoals allow these sharks to approach the coastline more closely, allowing them to hunt pups. Far more often, drowning is related to storms or high tides.
Marine Heatwaves and Whale Entanglements
The increasing sea levels have negatively affected a variety of large mammals, such as whales. Between 2014 and 2016, an unusual maritime heatwave in the California Current environment led to the compression of offshore upwelling and a subsequent movement of forage fish inshore (Gulland et al., 2022). Following their meal, large whales, notably humpback whales, ventured closer to the shore than normal.
Meanwhile, a Harmful Algal Bloom (HAB) of Pseudo-nitzschia diatoms, which was also linked with warmer temperatures, led to elevated levels of the biotoxin domoic acid in filter-feeding prey. To minimize human exposure to toxic crabs, the beginning of the Dungeness crab fishery was delayed due to elevated toxin levels. In conjunction with the change in whale distribution, this delay resulted in an abnormally high spatiotemporal overlap between whales and crab gear, eventually leading to a major increase in humpback whale entanglements.
Climate changes have altered the availability of prey, influencing distribution, abundance, and migration. Significant changes in the seasonal migrations and distribution patterns of North Atlantic right whales coincided with the resumption of the population, which had decreased almost a decade ago. Changes in the number and distribution of their primary food, the late-stage copepod Calanus finmarchicus, caused by rapid warming in the Gulf of Maine, were also linked to the occurrence of these alterations (Baumgartner et al., 2017).
Unexpectedly, relatively significant numbers of right whales appeared in eastern Canadian seas, putting them susceptible to ship strikes and entanglement in snow crab gear. Sharp et al. (2019) report that in recent decades, entanglement in fishing gear and vessel impacts have been the leading causes of mortality for North Atlantic right whales. Initially, efforts to lessen the risk of vessel strikes looked beneficial, but steps to prevent entanglement have not.
Although the proximate causes of death (entanglement and ship hit) were not novel, climate change seems to have been the driving force behind the shift in the foraging pattern. This resulted in an unexpected increase in the quantity and location of right whale corpses between 2017 and 2019. (Gulland et al., 2022). In addition to making the right whales more susceptible to entanglement and ship collisions in recent years due to changes in foraging areas, climate change appears to have reduced their foraging prospects. This is evident in terms of prey availability and quality, which in turn affects their health and reproduction.
Arctic Ice Loss and Its Effects on Polar Bears, Walruses, and Manatees
The decreasing sea ice has an impact on polar bears. Polar bears are dispersed among 19 essentially distinct subpopulations in the Arctic. The population of two sub-populations has remained steady over the long term (approximately three generations); one has grown, while four have declined. At the same time, data are insufficient to determine long-term patterns for the other 12. (Gulland et al., 2022). Five sub-populations have remained stable over the short term (approximately the most recent generation), two have increased, and four have decreased (Gulland et al., 2022). Of the two subpopulations that the United States and Canada share, the Southern Beaufort Sea subpopulation saw both long-term and short-term reductions, with decreases in size, body condition, and reproduction associated with a drop in sea ice.
The degree of ice retreat is linked to the greater dependency of Southern Beaufort Sea bears on land during the summer, which increases their likelihood of encountering humans and other animals. Additionally, it increases the danger of exposure to viruses found on land. Given the extended ice-free months, some signs that bears in this subpopulation are increasingly spending a lot of time on land. The floating ice they cross to gain greater proximity to their prey also recedes from the coast. Polar bears must thus swim farther, which increases their danger of drowning.
Due to the offshore retreat of summer sea ice in the Chukchi Sea to locations too deep for walruses to feed, many have relocated to coastal regions where they recover between feeding expeditions. In midsummer, in the lack of summer sea ice, hundreds of animals have been recorded congregating on U.S. and Russian coastal haul-outs (Gulland et al., 2022). Many of these haul-outs are located near towns where human activity, such as gunshots or the presence of animals like polar bears and wild dogs attracted to the haul-out locations, poses a danger of triggering stampedes that end in the trampling and killing of walruses.
Local communities and management authorities collaborate to prevent such incidents. Those species that remain on the ice when it advances across deep water northward of the continental shelf risk starvation. The decrease in seasonal sea ice extent may have a severe impact on walrus prey.
The Indian manatee, for which the consequences of climatic changes have been anticipated and hypothesized, but not clarified. Die-offs caused by hazardous algal blooms, cold exposure, and starvation often occur, although the connection between these events and climatic changes remains uncertain [89]. The Manatee ecosystem in the temperate-tropical region of the southeastern U.S. is vulnerable to warming, increased storm intensity, rising sea levels, and shorter winter freeze spells. As sub-tropical animals located in the northernmost sections of the species’ territory, manatees in U.S. waters are frequently subjected to water temperatures below 20°C, placing them at risk of cold-induced illness and death (Hardy et al., 2019). Their over-winter existence in Florida depends on proximity to warm-water refugia supplied by natural artesian springs, canals, and drainage ditches with restricted mixing of top and bottom waters.
The recent northward migration of manatees in response to warmer summers has increased the distance between certain warm-water refugia and the species’ feeding grounds. Additionally, natural springs are diminishing due to rising sea levels and groundwater depletion. The intention to shut down coal-fired power plants for political, environmental, and socio-economic factors will further reduce the supply of artificial warm-water refugia. Thus, despite global warming trends and as contradictory as that might seem, manatees that migrate north during warmer, prolonged summers are expected to become more vulnerable to winter cold spells as their proximity to warm-water refuges diminishes.
Understanding and Stewardship of the Biosphere
Biosphere stewardship presents an innovative approach to sustainability, involving multiple stakeholders. Despite the necessity of individual ecological stewards, biosphere stewardship stresses the value of communal action and, by extension, governance. Biosphere stewardship refers to unique governance structures that can successfully approach transformations in sustainability.
Biosphere stewardship entails transforming local-to-global social-ecological change pathways to enhance ecological integrity and human well-being. The concept of earth stewardship requires cooperation across multiple scientific and social disciplines, including climate science, oceanography, ecology, environmental science, political science, sociology, and anthropology. Together, people must appreciate the causal linkages between human behavior, institutional interplay, and the stability and change of climatic, ecological, and earth systems.
Individuals, corporations, and governments must adopt a new philosophy of environmental citizenship to practice earth stewardship. This must be predicated on thoroughly comprehending the repercussions, costs, and possibilities connected with choices that affect the planet’s trajectory. This, in turn, necessitates efficient communication of concerns and opportunities as well as a better harmonization of incentives with societal norms that promote sustainable human behavior. As discussed in the paper about the roots of recent global change, it is easier to formulate local-to-global trajectories that are more sustainable. These solutions should enhance the resilience of ecosystems and human well-being while maintaining the flexibility to learn and adapt to inevitable challenges.
References
Baumgartner, M. F., Wenzel, F. W., Lysiak, N. S., & Patrician, M. R. (2017). North Atlantic right whale foraging ecology and its role in human-caused mortality. Marine Ecology Progress Series, 581, 165-181. Web.
Gulland, F. M. D., Baker, J. D., Howe, M., LaBrecque, E., Leach, L., Moore, S. E., Reeves, R. R., & Thomas, P. O. (2022). A review of climate change effects on marine mammals in United States waters: Past predictions, observed impacts, current research and conservation imperatives. Climate Change Ecology, 3. Web.
Hardy, S. K., Deutsch, C. J., Cross, T. A., de Wit, M., & Hostetler, J. A. (2019). Cold-related Florida manatee mortality in relation to air and water temperatures. PLOS ONE, 14(11), e0225048. Web.
Sharp, S., McLellan, W., Rotstein, D., Costidis, A., Barco, S., Durham, K., Pitchford, T., Jackson, K., Daoust, P., Wimmer, T., Couture, E., Bourque, L., Frasier, T., Frasier, B., Fauquier, D., Rowles, T., Hamilton, P., Pettis, H., & Moore, M. (2019). Gross and histopathologic diagnoses from North Atlantic right whale Eubalaena glacialis mortalities between 2003 and 2018. Diseases of Aquatic Organisms, 135(1), 1–31. Web.