Reports show that more than 80% of people were affected by the record-breaking temperatures that led to July being the hottest month ever recorded. The severe consequences of last month’s heatwaves also pose threats to marine animals and plants. Heatwaves are linked to melting ice glaciers and the expansion of the ocean waters’ volume. As sea levels rise, low-lying coastal areas are left exposed to the risk of flooding and sudden displacement. In this article, we explore the consequences of rising sea surface temperatures on wildlife and coastal communities.
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In July 2023, the average daily ocean surface temperature worldwide reached 20.96C, breaking the previous record of 20.95C reached in 2016.
This year’s unprecedented heatwaves as well as the climate phenomenon of El Niño are two of the main reasons behind the increase in ocean temperatures. Described as a climate phenomenon that warms ocean surface waters in the Eastern Pacific Ocean, El Niño is a weather phenomenon associated with the warming of sea surface temperatures in the central-east equatorial Pacific. This summer’s record-breaking temperatures led to excessive amounts of hot air being trapped in the atmosphere. The Intergovernmental Panel on Climate Change (IPCC) reports that 90% of that hot air is now being absorbed by the ocean, one of the largest carbon sinks in the atmosphere.
Consequences of Rising Sea Surface Temperatures on Marine Biodiversity
Rising sea surface temperatures caused by the recent surge of heatwaves pose huge threats to marine biodiversity.
According to the International Union for Conservation of Nature (IUCN), the recent surge in heatwaves resulted in a rise in ocean temperatures, which comes with consequences such as ocean acidification and a lack of oxygen levels in seawater. Marine mammals suffer from the loss of breeding ground and reproductive failure, resulting in several species being extinct. Acidification and lower pH also lead to shell dissolutions.
According to the US Endangered Species Act (ESA), approximately 2,270 species are currently listed as endangered or threatened globally. Among them are the vaquita, the North Atlantic right whale, and the Yangtze Finless Porpoise.
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According to a 2020 study pubilshed in Nature, warming seawater can cause shifts in spatial distribution of the marine animal’s original habitat, where species move to different habitats due to a change in temperature. This is one of the most common responses of marine mammals to rapidly warming and acidifying ocean waters. An example is the Bryde’s whales shifts to cool waters, despite it being a subtropical species. By moving to new environments that are native to another species, habitats end up being overcrowded. Moreover, alterations in habitats inevitably increase the number of range shifts of a species. More pathogens are developed and propagated when species shift to different habitats, threatening the immunity of marine animals and increasing stress in organisms.
The increase in ocean temperatures can also hinder the reproductive success of marine mammals. For example, female sperm whales have lower conception rates after being exposed to high sea temperatures for extended periods of time.
Apart from mammals, oysters and other biogenic and carbonate reefs are also at risk due to increasing acidification of ocean waters. Ocean acidification is expected to increase dissolution rates of oyster shells, which are essential in maintaining the structure of oyster reefs.
The rising temperatures of seawater also affect coral reefs. Lower pH values in seawater, a direct consequence of high levels of carbon dioxide absorption, leads to coral bleaching as the lack of oxygen destroys their calcium carbonate structure.
Bleaching occurs when a coral slowly becomes transparent due to prolonged exposure to high seawater temperatures. While not fatal, bleaching puts coral in a vulnerable position, as they are more at risk of diseases due to their deformed calcium carbonate structure. The coral’s immune system weakens and can no longer fight potential diseases.
Coral reefs in the Pacific Ocean, Hawaii, and the Caribbean as well as Australia’s Great Barrier Reef are among those most threatened by global warming. The latter experienced a loss of about half of its corals during the massive bleaching events occurring between 2016 and 2017. Indonesia’s coral reefs are also deteriorating due to overfishing and plastic pollution. The mortality rate remains grim, as scientists warn that only 15% of coral reefs in the region have a chance of surviving or growing by 2050 due to worsening pH levels.
Consequences of Rising Sea Surface Temperatures on Coastal Communities
Aside from affecting marine biodiversity, rising ocean temperatures represent a threat to coastal settlements. As ocean temperatures rise, so will sea levels due to a phenomenon known as thermal expansion. As seawater temperature rises, the volume of the ocean expands; with the rapidly deteriorating climate crisis, the volume of the ocean is only destined to increase in the coming years.
The melting of glaciers and ice sheets is another cause of rising sea levels. Between 1994 and 2017, nearly 30 trillion tons of ices from glaciers melted worldwide. The Antarctic ice sheet is the largest ice sheet in the world. If it melts completely, it will add more than a metre of sea level rise by 2100 and more than 15 metres by 2500, scientists predicted.
The rise in sea levels poses threats on low-lying coastal cities all across the globe. In Southeast Asia, countries such as Bangladesh and cities like Bangkok are facing threats of flooding and risk being submerged entirely.
The average elevation of Bangladesh is nine metres above sea level and most of its urban population is situated in low-lying coastal areas. The Brahmaputra River and Padma River may cause significant flooding if the melting of ice sheets intensifies. Moreover, glaciers serve as an important source of water for Bangladesh’s agriculture industry and its population, so their disappearance would also lead to severe water insecurity in the nation.
Bangkok, Thailand’s capital, is another low-lying city positioned only 1.5 metres above sea level, and has already faced the effects of the increased sea levels. In 2011, for example, deadly floods submerged approximately one-fifth of the city.
Apart from Southeast Asia, other cities and regions on the globe are facing threats from the rising sea levels. Amsterdam, the capital of the Netherlands, is also threatened by rising seas, as 26% of the country is located below sea level and the majority of its urban areas are built around large water bodies.The city of New Orleans in the United States is another low lying coastal city that faces flooding threats. Hurricane Katrina in 2005 was a grim reminder of the terrible consequences that the city faces if sea levels continue to rise, as the hurricane had already caused the city to be 80% flooded and submerged.
Conclusion
The consequences of ocean warming are far-reaching and demand our attention. As we have explored throughout this article, the warming of our oceans poses significant threats to marine ecosystems, biodiversity, coastal communities, and the overall health of our planet. From coral bleaching and habitat loss to altered migration patterns and disrupted food chains, the impacts of ocean warming are already being felt.
However, it is not too late to take action. We must prioritise efforts to mitigate climate change, reduce greenhouse gas emissions, and transition to cleaner and more sustainable energy sources. Additionally, we need to implement strategies to protect and restore vulnerable marine ecosystems, such as coral reefs and coastal habitats. Individual actions also play a crucial role. By making conscious choices in our daily lives, such as reducing our carbon footprint, conserving water, and supporting sustainable fishing practices, we can collectively contribute to the preservation of our oceans.
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