Marine Heat Waves

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Marine heat waves are defined as a duration when the water surface temperature is 90% warmer than prior sea surface temperatures; this may last from days to months. The waves may reach thousands of kilometers, affecting fisheries and marine ecosystems, as well as crops and wildlife on land, and of course, human life. Global warming has caused ocean waters to become warmer; ocean currents move the warm water to colder areas, causing marine heat waves that affect this area mostly in a negative way; such as slowing salmon growth, stressing non-moving creatures, such as oysters and shellfish, and interfering with the natural cycles of seaweeds, modifying their habitats.

However, these variations in ocean temperatures are irregular and scientists had struggled to construct patterns for these heat waves and their impacts due to lack of description for them. Once experts agreed on a definition, they realized that the heat waves occurred 54% more frequently 1925‒2016. Many people did not realize the environmental consequences until it was too late; for example, in 2011, a marine heat wave destroyed a kelp forest, replacing it with turf seaweed off the West Coast of Australia. The ecosystem change became permanent even after the ocean temperatures were back to normal.

Scientists later discovered a connection between climate change and marine heat waves, using satellites and previous data available. The 2016 marine heat wave in tropical Australia was caused by greenhouse gas emissions, resulting from Man’s actions, which cause global warming. These heat waves resulted in an increase by approximately 50 times in the possibility of extensive bleaching of the Great Barrier Reef.

Due to the increase of sea water temperatures caused by global warming, corals expel beneficial algae that live inside their tissues. The decrease of the algae, which are responsible for absorbing greenhouse gases in the ocean could influence the ocean’s ability to absorb these gases. This also leads to the release of carbon dioxide through collapsing seagrass areas. For example, losing seagrass meadows in the Shark Bay area led to an increase in bacteria, a decrease in blue crabs and scallops, negative effects on the health of green turtles, and a decrease in long-term carbon storage where they live.

With the continual rise in ocean temperatures and the occurrence of marine heat waves, the marine ecosystems that numerous people rely on for food and their livelihood will be more unstable and unpredictable. For instance, marine heat waves affect fisheries and aqua-farming businesses, having a large impact on some peoples’ lives as it affects their work and income.

Another example is the North Pacific warm water “Blob”, a large mass of relatively warm water, which led to the shutting down of recreational and commercial fisheries, bringing about the loss of millions of dollars. Over the course of two years, this “Blob” resulted in the emergence of a destructive bacteria epidemic by the coast and altered the weather drastically in the Pacific Northwest.

Researchers should first work on using technology to predict future variations that will lead to warm ocean water, to find out if the temperature will increase and how long these waves will last. Second, they should extend their results to decision and policy makers, so that they know the marine heat waves’ effect on the environment and their duration.

This knowledge will help fisheries and aquafarming businesses know when to open or close, and when to harvest. These forecasts may aid in limiting the dangers; however, they do not solve the main problem of climate change. If this issue remains unresolved, then marine ecosystems will change permanently due to high water temperatures.

References

media.bom.gov.au
nature.com
ncbi.nlm.nih.gov
pbs.org

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