Corals and climate change: How sea anemones are paving the way for coral reef conservation on Vassar campus

Courtesy of Rob and Stephanie Levy

The basement of Olmsted Hall is a mysterious location for non-Biology students at Vassar. Without a reason to descend into the exclusive underground floor, it remains off-limits to those without card access. It’s where many science professors conduct their research—including Jodi Schwarz, an Associate Professor of Biology.

With an original undergraduate degree in history, Schwarz has first-hand knowledge of deviating from a predetermined course. Searching for a break from her landlocked schooling, Schwarz decided to partake in a semester at sea. Unknowingly, she committed to a science-focused program. During her time at sea, the Arizona native realized her love for oceanography and marine biology and eventually decided to go back to school to pursue coral reef research.

Coral reefs are imperative for tourism, fisheries and biodiversity. Despite the importance of coral ecosystems, little is known about coral propagation and symbiosis. Schwarz centered her research around these two variables, using a species of sea anemone that is closely related to corals called Aiptasia pallida

“We can work with those animals to try to address some really fundamental questions about corals,” Schwarz told me. “And then once we know more, then we can go test those ideas in corals once we have a better sense of what’s going on.” In particular, sea anemone research provides clues regarding conservation strategies that may protect endangered coral species.

Environmental activists have historically used charismatic megafauna, such as elephants and polar bears, to captivate the attention of the public and initiate conversations about conservation. For example, climate change sympathizers utilize photos of polar bears carefully treading on melting ice to appeal to the public’s heartstrings in an attempt to push an agenda of climate change awareness and action. While individually much smaller than their charismatic comrades, “before” and “after” images of colorful corals being reduced to lonely bleached masses have also encouraged similar responses from the public.

In 2020, the Great Barrier Reef suffered a mass bleaching event that affected large portions of the reef. Bleaching events in 1998, 2002, 2016 and 2017 were all the product of rising ocean temperatures, which are a direct result of greenhouse gas emissions. Readily available images of bustling coral ecosystems complete with colorful fish alongside images of stark-white bleached corals are compelling to say the least, but what is really happening inside of the corals and how do we know?

Schwarz has dedicated her research to discovering more specific details regarding the behavior of these important and alluring animals. Schwarz uses A. pallida because corals are difficult to grow in the lab. Aside from slight differences, sea anemones offer the ideal opportunity to obtain information regarding propagation and bleaching tendencies of coral-like animals. 

Sea anemones reproduce sexually in a process called “spawning,” in which they release a cloud of gametes (eggs and sperm) into the water column in a synchronized fashion. Spawning events only happen once a year for corals, but sea anemones may spawn up to once a month according to the lunar cycle. The scarce nature of spawning events necessitates a highly coordinated cycle, in which the male and female anemones release their gametes in close succession to one another.

Like corals, sea anemones engage in a symbiotic relationship with microorganisms. The bright colors that coral reefs are known for are actually the result of a symbiotic interaction between microorganisms and coral reefs. The organisms integrate themselves into the cells of corals, and make use of the nitrogenous waste secreted by the corals. The corals benefit by then using the sugar that is photosynthesized by their symbionts. 

Schwarz compared the fluctuating density of coral symbiodinium to deciduous trees during autumn, which both follow an annual cycle. The process of symbiodinium fluctuation in coral reefs is not well understood, but we do know that if it is interrupted by an environmental stressor it can be disastrous for the health of coral reefs.   

When corals lose their color, they are actually losing their symbiodinium. While this in itself is not fatal, coral growth and reproduction is hindered without what Schwarz called the “microscopic partners that live inside of them.” Coral bleaching events are often caused by a warming in ocean temperature. Even a few degrees’ change can be catastrophic for coral reef symbionts. Schwarz explained: “When corals are exposed to warm temperature…instead of symbiosis forming it’s the symbiosis falling apart.”

Bleaching events, such as the 2020 occurrence in the Great Barrier Reef, result in symbiont populations being completely depleted. While some species of corals are more susceptible or resilient to bleaching, high enough ocean temperatures are adept at killing the animals themselves. 

This is particularly concerning given the consistently rising ocean temperatures. The ocean is responsible for absorbing 90 percent of the heat accumulated by greenhouse gases, as well as 30 percent of the carbon dioxide emitted by human activity. Ocean acidification, sea level rise and warming waters are certain to instigate ripple effects that impact marine and terrestrial ecosystems alike. The economic and biodiversity implications of coral mortality demand that we take action, but the highly particular environmental requirements for coral growth complicate lab research. 

According to Schwarz, sea anemones and corals are similar enough that “working with sea anemones in the lab is an important way to conserve coral reefs, even though it isn’t clear that there is a direct connection.”

Basic information about spawning and propagation will help the science community better understand how to combat bleaching. Schwarz uses a lunar light to provoke monthly spawning in A. Pallida. Through trial and error, she learned the necessary conditions for sexual reproduction in sea anemones. Given the imminent rise in sea temperature, understanding the conditions under which spawning occurs is vital information for coral reef conservation efforts.

But research can only get us so far in preserving coral reefs. In our discussion, Schwarz recognized the environmental changes that must be made at the global level, such as reducing greenhouse gases, but she also mentioned the environmental responsibilities of local communities. 

Reducing the burden of climate awareness down to the individual, however, is not sufficient for truly mitigating oceanic warming. This is especially important for small coastal communities whose livelihoods depend on the natural resources provided by the ocean. Schwarz confirmed, “All of the stakeholders have to come together and create policy that will allow for sustainable fishing…[and] protection of coral reefs [and] that will create solutions that are compatible for the local cultural and economic setting and context.”

Ultimately, the key to conserving the natural habitats, ecosystems and overall biodiversity in the wild is collaboration and the subsequent creation of solutions that are both rigorous and realistic for the most affected communities. 

Schwarz’s research at Vassar may seem far removed, but her contribution to coral research brings us closer to understanding the inner workings of coral propagation and symbiosis.  

“Science is [not] trying to promote a specific engineering response or technological response or policy level response,” she explained. “Science is just one tiny part of this whole huge network of things that influences whether or not corals are protected.” 

For an up-close-and-personal look at live A. pallida, email Professor Schwarz at joschwarz@vassar.edu.

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