Alarm bells ring in Lakshadweep : record bleaching threatens Coral Reefs

By Vivek Saini

Rising ocean temperatures, fueled by climate change, are causing coral reefs worldwide to bleach. In Lakshadweep, A new study revealed a record-breaking coral bleaching event, with marine heatwaves triggering widespread loss of vibrant colours in the Lakshadweep Sea. Survey results from various islands showed a considerable percentage of complex coral species undergoing severe bleaching – a concerning phenomenon highlighting the global threat posed by rising ocean temperatures, a consequence of climate change, to coral reefs worldwide. Coral reefs, the breathtaking underwater rainforests teeming with life, face an existential crisis.  

In early May 2024, the record’s fourth global coral bleaching event was confirmed. This large-scale phenomenon, triggered by rising ocean temperatures linked to climate change, seriously threatens the health and future of coral reefs worldwide. Coral reefs, these stunning underwater vistas and teeming ecosystems, support a quarter of all marine life and provide vital coastal protection. The beauty and diversity of these reefs, with their vibrant colours and intricate structures, are a testament to nature’s artistry. The bleaching threat disrupts this natural masterpiece, leaving reefs pale and vulnerable to disease and death.

Lakshadweep’s Coral Reefs Face Unprecedented Bleaching Event

In a stark reminder of the global threat to coral ecosystems, the idyllic Lakshadweep islands hit the headlines in early May 2024 with news of a record-breaking coral bleaching event. Researchers from the ICAR-Central Marine Fisheries Research Institute (CMFRI) confirmed widespread bleaching, with a significant percentage of hard coral species suffering from severe discolouration. This alarming development underscores the critical impact of rising sea temperatures, a direct consequence of climate change, on these vibrant underwater ecosystems.

Lakshadweep’s coral reefs have faced bleaching events in 1998, 2010, and 2016. However, the scale and intensity of the current event are unprecedented. The Degree Heating Week (DHW) indicator measures accumulated heat stress on coral reefs and has surged above 4°C-weeks in Lakshadweep. According to Dr R.K. Sreenath, a senior scientist at CMFRI who is leading the research, heat stress levels pose a severe threat, potentially leading to widespread coral mortality if water temperatures don’t cool.

This news from Lakshadweep is a microcosm of a global crisis. The event serves as a chilling reminder of the “fourth global coral bleaching event” confirmed earlier this year. Rising ocean temperatures disrupt the crucial symbiotic relationship between coral polyps and the algae (zooxanthellae) living within them. Stressed by excessive heat, coral polyps expel the algae, losing vibrant colours and a vital food source. This bleaching leaves coral reefs vulnerable to disease and starvation, jeopardising their survival. The Lakshadweep case highlights the urgency of addressing climate change and the need for immediate action to protect our precious coral reefs. The following sections of this article will delve deeper into the causes and consequences of coral bleaching and explore ongoing efforts to safeguard these vital underwater ecosystems.

The Symbiotic Dance – Coral and Algae

Coral reefs, often mistaken for living plants, are complex ecosystems built by tiny coral animals called polyps. These polyps secrete a hard calcium carbonate skeleton, forming the intricate structures we associate with reefs. However, these reefs’ breathtaking colours and vibrant life would only exist with a crucial partnership with microscopic algae called zooxanthellae.

Zooxanthellae, belonging to the group dinoflagellates, live within the coral polyps in a symbiotic relationship, meaning both organisms benefit from the association. Think of it as a win-win situation. Zooxanthellae use sunlight to photosynthesise, like plants, producing organic compounds like sugars as a food source. In return for a haven within the coral polyps and access to nutrients released by the coral, the zooxanthellae share a portion of these sugars with their coral host. This exchange gives coral reefs their characteristic colours – the zooxanthellae contain pigments like chlorophyll and carotenoids, contributing to the vibrant hues of coral. This mutually beneficial partnership is a natural wonder and the key to coral reefs’ survival. Understanding the importance of this relationship is crucial in our urgent efforts to protect these fragile ecosystems.

The recent confirmation by the National Oceanic and Atmospheric Administration (NOAA) of the fourth global coral bleaching event underscores the critical importance of this delicate relationship. Rising ocean temperatures, a consequence of climate change, disrupt this symbiosis. When stressed by excessive heat, coral polyps expel the zooxanthellae living within them. This expulsion robs the coral of its vibrant colours and disrupts its food source, jeopardizing its health and survival. The intricate dance between coral and algae creates a thriving ecosystem. These algae, known as zooxanthellae, provide the coral sustenance and help remove waste products. In return, the coral polyps provide the zooxanthellae with a protected environment, essential nutrients, and carbon dioxide for photosynthesis. This mutually beneficial partnership is the foundation for coral reefs’ rich biodiversity and productivity. Understanding the importance of this relationship is crucial in our efforts to protect these fragile ecosystems.

Rising Temperatures – A Stressful Disruption

Vibrant coral reefs, teeming with life, face a growing threat: coral bleaching. This widespread phenomenon, triggered by rising ocean temperatures due to greenhouse gas emissions and other human activities linked to climate change, disrupts the delicate balance between coral and the algae they rely on. The primary cause of rising ocean temperatures is the increase in greenhouse gases in the atmosphere, such as carbon dioxide and methane. These gases trap heat from the sun, leading to a rise in global temperatures. This, in turn, warms the oceans, putting coral reefs at risk. Let’s delve deeper into how heat stress leads to coral bleaching.

Thermal Thresholds and Coral Stress: Like most living organisms, Coral polyps thrive within a specific temperature range. Excessively high water temperatures exceed their thermal tolerance, causing stress. This stress can damage the photosynthetic machinery within the zooxanthellae, disrupting their ability to produce food.

Expulsion as a Defense Mechanism: Stressed coral polyps expel the zooxanthellae residing within their tissues in a desperate attempt to protect themselves from further harm. Think of this as a self-preservation tactic. While this expulsion might offer temporary relief from heat stress, it comes at a significant cost.

Consequences of Bleaching: The loss of zooxanthellae through bleaching has two significant implications for coral. Firstly, it robs them of their vibrant colours. As mentioned, the pigments responsible for the stunning hues of coral reefs are primarily located within the zooxanthellae. Without these colourful algae, bleached coral appears pale and skeletal. Secondly, and more importantly, the expulsion disrupts the coral’s food source. Previously, coral received a portion of the sugars produced by the algae through photosynthesis. Without the zooxanthellae, the coral loses this vital source of nutrition, making it more susceptible to starvation and disease.

Bleaching’s Devastating Impact – From Reefs to Marine Life

Coral bleaching isn’t just an aesthetic concern; it’s a tragedy unfolding beneath the waves. Imagine a thriving underwater metropolis losing its vibrant colours and vital resources. That’s the heart-wrenching reality for coral reefs impacted by bleaching. Let’s dive into the cascading effects of coral bleaching, a story of beauty turned to devastation.

Coral’s Fragile Health: Bleached coral is weakened and stressed. Without the zooxanthellae providing them with food, they become more susceptible to starvation and disease. Additionally, the loss of pigments disrupts the coral’s ability to protect itself from harmful ultraviolet radiation. In severe bleaching events, prolonged stress can lead to coral mortality, leaving behind a barren and fragile ecosystem.

Loss of a Marine Oasis:

Jen McWhorter, Oceanographer at Ocean Chemistry and Ecosystems Division,  NOAA, while responding to CFC over email, states that coral loss leads to a loss of structure and habitat for other species. Coral reefs can be thought of as the ‘rainforest’ of the sea, supporting some of the highest biodiversity in the ocean. When corals die, it is not just a loss of coral; it affects many other species, such as fish and invertebrates, to name a few.

The intricate habitat crumbles when coral bleaches and dies. This is particularly concerning for species that depend on specific coral structures, like the branching corals that have been severely impacted in the Great Barrier Reef. Coral reefs, teeming with life, provide crucial habitat for a quarter of all marine species. They are like underwater cities, providing shelter, food, and breeding grounds for diverse organisms. Fish, invertebrates, and even some algae depend on the complex structure and diverse food webs created by healthy coral reefs. When coral bleaches and dies, this intricate habitat crumbles. Fish populations decline, and the overall biodiversity of the marine environment suffers. But it’s not all doom and gloom. Whether we live near the coast or not, we can contribute to conserving coral reefs. We can make a difference by reducing our carbon footprint, supporting sustainable fishing practices, and advocating for policies that protect coral reefs. Imagine a domino effect – losing healthy coral disrupts the food chain, impacting countless marine creatures.

Economic and Social Impacts: The recent bleaching event on the Great Barrier Reef, estimated to have killed 90% of branching coral, is a stark example of the economic consequences of coral bleaching. Tourism relies heavily on the beauty and biodiversity of coral reefs. Similarly, fisheries depend on the healthy ecosystems reefs provide for fish populations. The decline of these vital ecosystems can lead to job losses, reduced tourism revenue, and disruptions in the food supply chain for coastal communities. Beyond their ecological importance, healthy coral reefs benefit coastal communities. They act as natural breakwaters, protecting coastlines from erosion and the damaging effects of storms and waves. This is where the role of policymakers and marine conservation organisations becomes crucial. They play a significant part in implementing measures to reduce greenhouse gas emissions, protect marine habitats, and promote sustainable fishing practices, all of which are essential for the survival of coral reefs.

Additionally, coral reefs are a significant source of income for coastal communities, supporting tourism and fisheries. Bleaching events threaten these economic benefits, impacting livelihoods and local economies. Imagine the loss of tourism revenue or the decline in fish populations – these are just some ways bleaching events can disrupt the lives of people who depend on healthy coral reefs.

A Race Against Time – Hope for the Future

The escalating threat of coral bleaching paints a concerning picture, but it’s not all doom and gloom. Scientists, conservationists, and even local communities are actively engaged in a race against time to protect coral reefs and foster resilience. Let’s explore some of these efforts that offer a glimmer of hope for the future.

Protecting Existing Reefs:

• Marine Protected Areas (MPAs): Establishing and enforcing MPAs is a crucial strategy. These designated zones act as havens for coral reefs, safeguarding them from destructive human activities like overfishing, pollution runoff from land, and destructive fishing practices. By controlling these stressors, MPAs allow coral populations to recover naturally and build resilience against environmental threats like rising water temperatures. Research from the Great Barrier Reef Marine Park Authority (GBRMPA) demonstrates that well-managed MPAs can see significant increases in coral cover, with some studies suggesting up to 20% growth within a decade.
  
• Coral Reef Restoration Techniques: Beyond protection, active restoration efforts are underway. Techniques like coral gardening and coral transplanting are showing promise. Coral gardening involves nurturing coral fragments in controlled environments, like underwater nurseries, until they are mature enough to be transplanted onto degraded reefs. Coral transplanting involves strategically placing healthy coral fragments directly onto damaged areas to accelerate recovery. These techniques offer a way to heal the wounds inflicted on coral reefs directly.
  

Combating Climate Change:

• Global Climate Action: The most significant long-term solution lies in addressing the root cause – climate change. International cooperation and ambitious efforts to reduce greenhouse gas emissions are crucial to prevent further ocean warming and mitigate future bleaching events. Jen further highlights this point: “Depending on the climate pathway we take, or the amount of greenhouse gas emissions driving increases in global average warming, will directly reflect the frequency and severity of coral reef mortality events. Therefore, the lowest possible climate scenario offers the highest chance of survival for global coral reefs.” While restoration efforts play a role, prioritizing emission reduction offers the greatest hope for our coral reefs. In her opinion, “restoration efforts are important and can offer assistance with recovery at a small scale between mortality events. Still, they should not distract from reducing carbon emissions.”

Investing in Innovation:

• Assisted Evolution: Scientists are exploring innovative solutions like assisted evolution to help corals adapt to a changing climate. This approach involves selecting and breeding corals that naturally exhibit heat tolerance. By creating offspring with these resilient traits, researchers hope to develop coral strains that are more resistant to future warming events.

These efforts highlight the ongoing fight to protect coral reefs. While challenges remain, the dedication and innovation showcased offer a beacon of hope. By supporting these initiatives, advocating for sustainable practices, and making conscious choices in our daily lives, we can contribute to a future where these vibrant ecosystems continue to thrive.

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