Studying Coral Reefs

Afreen Hussain collects samples from a coral nursery during her Fulbright-Kalam Climate Fellowship in Hawaii. Photograph courtesy Afreen Hussain.

Coral reefs support an estimated 25 percent of all marine life by serving as spawning and feeding grounds. Among the most biologically rich and diverse ecosystems on the planet, coral reefs in many regions have been damaged by a process called bleaching. Rising ocean temperatures are considered the most likely cause. Warmer seas cause algae that live symbiotically with the coral to leave their host. The algae provide both nourishment and color to the coral. Without them, the coral bleach out. According to the U.S. National Oceanic and Atmospheric Administration, corals can survive a bleaching event, but they are under more stress and are subject to mortality.

Coral reefs provide many benefits and resources like food sources for local communities; compounds used in medicines, including some that treat cancer; and natural barriers against hurricanes, typhoons and other storms.

Afreen Hussain is a coral ecologist who assesses the impact of climate change and human disturbances on coral communities in order to create a path toward sustainable management and conservation of highly vulnerable coral reefs. Hussain, who is working on a Ph.D. in marine science at the Council of Scientific and Industrial Research (CSIR)-National Institute of Oceanography, Goa, studies coral patches along the west coast of India.  In 2019, she was a Fulbright-Kalam Climate Fellow at the United States Geological Survey (USGS) National Wildlife Health Center in Hawaii.

Excerpts from an interview. 

You study the disease of aquatic organisms, particularly coral reefs. Can you tell us what are some of the problems that coral reefs experience due to climate change and increased temperatures?

Coral reefs are the most diverse, complex and unique of all the marine ecosystems and are therefore known as “rainforests of the ocean.” Although they occupy less than 1 percent of the benthic environment, coral reefs support about 25 percent of all marine life, including over 4,000 species of fish. They offer significant ecological, economic and societal benefits to millions of people, valued at about $9.8 trillion each year. Over the past few decades, coral reefs have been under major threat due to the combined effects of natural and anthropogenic, or human, stressors at regional and global scales, primarily from global climate change, increasing levels of CO2, unsustainable fishing practices, coral diseases and land-based pollution. According to the World Resources Institute report, Reefs at Risk Revisited, 75 percent of the global reefs are currently at risk due to global and local stressors. If these stressors are left unchecked, the percentage of threatened reefs will increase to 90 percent by 2030.

What is coral bleaching and what are the long-term consequences of bleaching?

The increase in sea surface temperature during the past few decades has caused unprecedented mass coral bleaching worldwide. The health of a coral depends on the delicate relationship between the coral host and the symbiotic intracellular photosynthetic algae, called zooxanthellae, which is the major source of nutrition in corals. During periods of environmental pressure like heat stress, high UV, or ocean acidification, the symbiotic zooxanthellae are expelled from the coral host leading to the process of coral bleaching or whitening of corals. This leads to a deficit of nutrition in bleached corals and eventually coral mortality. Bleached corals are also prone to infections by diseases and infiltrating algae. Decline in corals after a bleaching event has long-term ecological, economic and social impacts. It affects local fisheries, dents the tourism industry and leads to changes in the benthic habitat. Therefore, owing to their significance and the looming threat of climate change, it is very important to understand the mechanism of coral bleaching and predict how and whether the corals will adapt to climate change.

How will your work help understand the problems that coral reefs have been facing due to changing climatic conditions?

For my Ph.D. work, I assessed the bleaching pattern of corals on the west coast of India and identified coral species that are more susceptible to bleaching. I also worked on a prediction model for monitoring coral bleaching based on sea surface temperature data. This information is very crucial for policymakers and reef managers to prepare for upcoming bleaching events by reducing the amount of anthropogenic pressure on the reefs during periods of heat stress. This would include a reduction in tourism and fishing activities so that the corals get a conducive environment to recover from bleaching. 

Other objectives included identifying and assessing the spread of coral diseases and recognizing their possible pathogens in the reefs. This aids in categorizing the potential source of pathogens and creation of strategies like wastewater treatment to reduce the risk of coral diseases.

The other major stress is the human impact on the reefs, mainly through unsupervised diving, snorkeling and boat anchoring on reefs. Physical damage to the sensitive coral colonies due to boat anchor drops or tourists stamping on corals had led to widespread damage in shallow reefs. I identified reef spots that are more prone to physical damage owing to the dominance of certain coral morphology (plate-like or branching corals), which would be helpful in sustainable ecotourism by avoiding vulnerable reef spots.

Can you tell us about your experience as a Fulbright-Kalam Climate Fellow in Hawaii?

The research that I conducted as part of the Fulbright-Kalam Climate Fellowship at the USGS National Wildlife Health Center was to investigate the role of heat shock proteins under heat stress in a model coral organism—Aiptasia. Despite the growing research in the field of coral-symbiosis relationships, the cellular and molecular mechanisms of bleaching remain poorly understood. Therefore, the study aimed to investigate the histological and cellular changes in Aiptasia pulchella under heat stress. The results obtained from this study would provide further insights into the cellular and histological basis of coral bleaching and create the foundation for more research about mechanisms of heat tolerance conferred by heat shock proteins in corals.

The Fulbright-Kalam Climate Fellowship has been a great opportunity for both my professional and personal growth. It has been an intellectually stimulating experience and helped develop my scientific research skills as I got to learn from subject experts.

I used the time in the U.S. to develop as a researcher, as well as to learn about American culture and history. The Fulbright orientation seminar in Philadelphia was a great platform to connect with Fulbrighters from across the globe. That’s when I embraced the legacy of being a Fulbrighter and my responsibility towards society.

I consider myself very lucky to be placed in the beautiful, friendly state of Hawaii, where I met amazing people and explored my love for marine life. Being surrounded by beautiful reefs, I took the opportunity to fulfil my dream of diving with manta rays and sea turtles. In a nutshell, Fulbright gave me wings to explore new avenues in life, and helped me make lifelong connections.

Natasa Milas is a freelance writer based in New York City.

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