Coral reefs are among the most productive and biologically diverse ecosystems on Earth, providing habitat and shelter for countless marine species. In Sri Lanka, the reefs have immense ecological and economic significance. With over 180 species of hard corals, these reefs support diverse families like Acroporidae, Faviidae, Poritidae, Pocilloporidae, Agariciidae, and more, making them integral to marine biodiversity. However, they face unprecedented challenges due to climate change, overfishing, and pollution.
Recent reports from the Indian media highlight severe coral bleaching in the Lakshadweep Sea and the Gulf of Mannar. Sri Lankan researchers and scientists are increasingly concerned about the impact of rising sea temperatures. The lack of immediate action poses a serious threat of catastrophic consequences. With thermal stress predicted to reach up to 60% in southern Sri Lanka by 2024, it is crucial to understand how these factors jeopardize coral reefs. Their degradation threatens Sri Lanka's economy, nature, and climate, emphasizing the urgency to act before it's too late.
Coral Reefs and Their Importance
Sri Lanka's coral reefs play a critical role in supporting both the nation's economy and natural environment. Economically, the reefs are indispensable for fisheries and tourism. Fishery resources linked to coral reefs contribute significantly to local livelihoods, providing employment for coastal communities. Tourism, particularly in regions like Hikkaduwa, is heavily reliant on the reefs for snorkeling and diving attractions, bringing millions in foreign exchange revenue. Reefs also offer crucial coastal protection by acting as natural barriers, reducing wave energy and mitigating shoreline erosion.
From an ecological perspective, our coral reefs are vital for sustaining marine biodiversity. These reefs are home to hundreds of species of fish, mollusks, and crustaceans, with many species depending on coral structures for food and shelter. Moreover, they support complex food webs and provide breeding grounds for commercially important fish. Coral reefs also play a role in carbon sequestration, helping regulate carbon dioxide levels in the atmosphere and thus mitigating climate change effects.
Furthermore, coral reefs contribute to water quality by filtering out particulates and pollutants, creating cleaner environments for marine life. Their limestone structures promote a unique chemical balance that is crucial for the ocean's overall health. The diverse coral families, including Acroporidae, Faviidae, and Pocilloporidae, contribute to the structural complexity that supports these ecological functions.
In sum, the coral reefs are not just marine ecosystems but also life-support systems that strengthen economic stability and ecological resilience. The imminent threats of bleaching and reef degradation risk undermining these benefits, necessitating immediate conservation efforts. The sustained loss of coral reef coverage in Sri Lanka could significantly impact food security, economic growth, and coastal protection, affecting millions of people directly and indirectly in the coming decade.
Current threats to Sri Lanka's coral reefs
Sri Lanka's coral reefs are increasingly under threat due to escalating environmental challenges. Recent reports indicate severe coral bleaching in the Lakshadweep Sea and the Gulf of Mannar. According to NARA, prolonged exposure to high ocean temperatures has led to worrying coral bleaching events. Water temperatures have risen to 31°C, which is dangerously high compared to the optimal range of 27-28°C.
When temperatures rise beyond these limits, corals expel the microscopic algae living within their tissues. These algae, known as zooxanthellae, provide essential nutrients to the corals, which are left weakened and vulnerable without them. The stark white coloration that remains is a sign of bleaching, an event that often leads to coral death if thermal stress persists. In some areas, the heatwave lasted two weeks, long enough to jeopardize the reef ecosystem.
Projections from coralreefwatch.noaa.gov predict up to 60% bleaching thermal stress for southern Sri Lanka by April 2024. This alarming prediction aligns with studies suggesting that the country's coral reefs could lose around 4% of their coverage in the next 30 years, with losses as high as 17.76% along the west coast. This degradation will be exacerbated by additional stressors like pollution, overfishing, and sedimentation.
“The chart shows sea surface temperature (SST) data for Southern Sri Lanka, tracking the risk of coral bleaching. We can see a significant spike in SST around May 2024, crossing the bleaching threshold and entering Alert Level 2, suggesting a severe bleaching event.”
Source : NOAA Coral Reef Watch (CRW) website (www.coralreefwatch.noaa.gov)
The consistent rise in SSTs puts the delicate fringing reef ecosystems at risk. Without comprehensive monitoring and urgent action, these ecosystems could face irreversible damage. This endangers not only marine life but also the local economies and communities that rely on coral reefs for sustenance and protection.
Statistics as of 07 May 2024
Source NOAA Coral Reef Watch (CRW) website (www.coralreefwatch.noaa.gov)
Analyzing environmental factors
Several interlinked environmental factors contribute to the degradation of Sri Lanka's coral reefs. The phenomenon of marine heat waves, characterized by prolonged periods of abnormally high ocean temperatures, has severely impacted coral health. The Indian Ocean Dipole (IOD), a climatic phenomenon affecting the entire region, plays a significant role in sea surface temperature (SST) fluctuations. When the IOD index increases, it correlates strongly with higher SSTs, particularly along the southern coast of Sri Lanka.
Data collected between 2005 and 2021 reveal worrying trends. The Multiscale Ultrahigh Resolution (MUR) Level 4 SST dataset shows that different coastal regions in Sri Lanka are experiencing higher temperature anomalies. Regions along the southern coast, such as Hikkaduwa and Mirissa, are especially vulnerable due to their proximity to the warm currents affected by the IOD. Positive SST anomalies have been more frequent and intense since 2014, suggesting a persistent upward trend.
Monthly temperature variations also indicate that the First Inter Monsoon (IM-1) and April are critical periods when SSTs reach their peak. Conversely, the North West Monsoon (NWM) and January record the lowest temperatures. Unfortunately, when temperatures stay high for extended periods, as observed recently, coral bleaching becomes inevitable. Corals lose their essential symbiotic algae, turning white and losing their primary source of nutrition.
In addition to heat stress, changes in ocean currents and wind stress curls impact nutrient distribution, further stressing corals. Coastal development, pollution, and sedimentation from inland agriculture exacerbate these conditions, leading to localized coral mortality. This complex interplay of environmental factors heightens the vulnerability of Sri Lanka's reefs.
Despite the significant impact of these factors, there is a scarcity of studies focusing specifically on Sri Lanka's fringing reef ecosystems. Understanding these regional patterns and trends is crucial for predicting future threats and designing effective conservation strategies. Without immediate intervention and research, the continued rise in temperatures could devastate these vital marine ecosystems, altering our coastal environment irreversibly.
Sri Lanka's coral reefs are woven into the fabric of our coastal communities, offering sustenance, protection, and joy to countless lives. They are vibrant ecosystems where families depend on the bounty of the sea, divers marvel at the colorful fish, and fragile marine life finds shelter. But with each passing day of rising temperatures and unchecked pollution, these reefs teeter on the brink of collapse. If action isn't taken swiftly by policymakers, scientists, and local communities alike, what will remain of these vibrant underwater worlds? Will future generations ever see the reefs flourish again, or will they only be a fading memory?