The Consequences of Marine Heat Waves: What You Should Know

Daily Current Affairs : 24-July-2023

In recent times, global sea surface temperatures have been soaring, and in April, the average daily temperature reached an alarming 21.1 degrees Celsius, breaking the previous record set in 2016. The persistently high ocean temperatures have given rise to devastating marine heat waves (MHWs) around the world. This essay explores the concept of MHWs, their impact on ocean life, and the repercussions for human societies.

What are Marine Heat Waves?

Marine heat waves are extreme weather events occurring in the oceans. These waves are characterized by a significant rise in the surface temperature of a particular sea region, surpassing the average temperature by 3 or 4 degrees Celsius for at least five consecutive days. MHWs can last for extended periods, ranging from weeks to months or even years.

Impact of Marine Heat Waves on Ocean Life

1. Fish Kills: While a temperature increase of 3 or 4 degrees Celsius may seem insignificant to humans, it can be catastrophic for marine life. For example, MHWs along the Western Australian coast during 2010 and 2011 resulted in devastating fish kills.
2. Destruction of Kelp Forests: Kelp forests, essential habitats that support various marine animals, are particularly vulnerable to MHWs. Studies have shown that MHWs have destroyed kelp forests and fundamentally altered coastal ecosystems.
3. Coral Bleaching: High ocean temperatures in tropical regions, such as the Atlantic and Caribbean, have led to widespread coral bleaching events. Corals, sensitive to water temperature, expel the algae living in their tissues when the water becomes too warm, causing them to turn entirely white. This not only reduces the reproductivity of corals but also makes them more susceptible to fatal diseases. Thousands of marine animals depend on coral reefs for survival, making coral bleaching a grave concern for their existence.
4. Growth of Invasive Alien Species: MHWs create favorable conditions for the growth of invasive alien species, which can disrupt marine food webs and harm native species.
5. Change in Species Behavior: MHWs force marine species to alter their behavior, putting them at greater risk of harm. For instance, MHWs have been linked to whale entanglements in fishing gear, causing additional threats to these magnificent creatures.

Impact of Marine Heat Waves on Humans

1. High Intensity Storms: MHWs, characterized by higher ocean temperatures, can intensify storms like hurricanes and tropical cyclones. As warmer oceans lead to increased evaporation and heat transfer to the air, storms gather more water vapor and heat. Consequently, this results in stronger winds, heavier rainfall, and more devastating flooding when storms reach the land, posing heightened risks to human lives and infrastructure.
2. Loss of Food and Livelihood: Approximately half a billion people depend on coral reefs for sustenance, income, and protection. When MHWs cause the destruction of these reefs, human communities relying on them also suffer the consequences, facing food and economic insecurity.

Important Points:

Impact of Marine Heat Waves on Ocean Life:

• Marine heat waves (MHWs) are extreme weather events with ocean surface temperatures 3-4 degrees Celsius above average for at least five days.
• MHWs have been observed in various regions, leading to devastating effects on marine life.
• Fish kills occur during MHWs, causing significant disruptions in marine ecosystems.
• Kelp forests, vital habitats supporting marine animals, are destroyed during MHWs, altering coastal ecosystems.
• Coral bleaching, a consequence of MHWs, affects coral reefs, reducing their reproductivity and making them vulnerable to diseases.
• Coral bleaching threatens the survival of thousands of marine species dependent on coral reefs.
• MHWs promote the growth of invasive alien species, causing disruptions in marine food webs.
• MHWs force marine species to change their behavior, leading to increased risks for wildlife.

Impact of Marine Heat Waves on Humans:

• Higher ocean temperatures associated with MHWs intensify storms like hurricanes and tropical cyclones.
• Stronger storms lead to more powerful winds, heavier rainfall, and increased flooding, posing higher risks to human lives and infrastructure.
• Approximately half a billion people depend on reefs for food, income, and protection.
• MHWs’ destruction of coral reefs adversely affects human communities reliant on them, leading to food and economic insecurity.

Why In News

In April, the average daily global sea surface temperature soared to an unprecedented 21.1 degrees Celsius, shattering the previous record set back in 2016 when it was 21 degrees Celsius. This concerning escalation highlights the alarming trend of rising sea temperatures, warranting urgent attention to address its potential implications on marine ecosystems and weather patterns.

MCQs about The Consequences of Marine Heat Waves

1. What defines a marine heat wave (MHW)?
   A. An extreme weather event occurring in coastal areas
   B. An increase in ocean surface temperature by 1-2 degrees Celsius for at least five days
   C. A rise in the surface temperature of a particular sea region by 3-4 degrees Celsius above average for at least five days
   D. Unusually warm water currents in the deep ocean
   Show Answer
   Correct Answer: C. A rise in the surface temperature of a particular sea region by 3-4 degrees Celsius above average for at least five days
   Explanation: A marine heat wave is an extreme weather event occurring when the surface temperature of a specific sea region rises to 3-4 degrees Celsius above the average for at least five days.
2. What is the impact of coral bleaching during marine heat waves?
   A. Increased coral reef growth and biodiversity
   B. Enhanced resilience of corals to environmental stress
   C. Expulsion of algae from coral tissues, leading to white appearance and increased vulnerability to mortality
   D. Improved reproductive capacity of corals
   Show Answer
   Correct Answer: C. Expulsion of algae from coral tissues, leading to white appearance and increased vulnerability to mortality
   Explanation: Coral bleaching occurs during marine heat waves when corals expel algae (zooxanthellae) from their tissues due to high water temperatures. This causes the corals to turn entirely white and become more vulnerable to mortality.
3. How do marine heat waves affect human societies?
   A. By reducing the intensity of storms and cyclones
   B. By promoting the growth of beneficial marine species
   C. By threatening food and economic security for communities dependent on reefs
   D. By contributing to lower sea levels
   Show Answer
   Correct Answer: C. By threatening food and economic security for communities dependent on reefs
   Explanation: Marine heat waves threaten food and economic security for human communities that depend on reefs. The destruction of coral reefs during MHWs negatively impacts those relying on them for sustenance, income, and protection.
4. What is the primary reason behind intensified storms during marine heat waves?
   A. Increased wind patterns in the affected regions
   B. Higher atmospheric pressure over oceans
   C. Stronger ocean currents
   D. Higher ocean temperatures leading to more evaporation and heat transfer
   Show Answer
   Correct Answer: D. Higher ocean temperatures leading to more evaporation and heat transfer
   Explanation: Intensified storms during marine heat waves are primarily attributed to higher ocean temperatures, leading to increased evaporation and heat transfer from the oceans to the air. This results in more powerful winds and heavier rainfall.

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