Q&A
UB coral researchers Mary Alice Coffroth and Howard Lasker. Photo: Douglas Levere
From CHARLOTTE HSU
Posted on September 16, 2022 This summer, coral researchers from around the world gathered to share their latest findings at a conference dedicated to reef science, conservation and management. One question looms large in the field: As warming waters, ocean acidification and other pressures threaten corals, what will reefs look like in the coming years? “Much of the conference focused on the future of coral reefs,” says UB scientist Howard Lasker, who attended the 15th International Coral Reef Symposium in July in Bremen, Germany, with fellow UB coral scientist Mary Alice Coffroth. Both are research professors of geology in the College of Arts and Sciences. “While it has been a constant theme that we need to reduce CO2 emissions, the focus of much of the work has been on the science behind approaches to facilitate the survival and recovery of reef corals,” adds Lasker. As part of the symposium, Lasker was honored at a reception for newly named Fellows of the International Coral Reef Society (ICRS), which is sponsoring the conference. According to the organization, “ICRS Fellow status is awarded in recognition of scientific achievement, conservation or stewardship, and service to ICRS over a significant period of time.” Before the conference, Coffroth participated in the fourth in a series of workshops hosted by the National Science Foundation-funded Coral Bleaching Research Coordination Network. The event aimed to write an outlook on the future of coral bleaching research. He also attended the first workshop in 2019 to help develop recommendations for experimental coral bleaching design protocols. Lasker and Coffroth have been studying coral reefs for several decades. Their work has spanned a period where large-scale bleaching events and other risks linked to climate change have put many reefs at risk. The pair recently took time to share with UBNow some of their latest research, focused on “soft corals” in the Caribbean, with implications for understanding the future of reefs.
How has the world’s perception of the threats facing reefs changed since you started studying corals?
Lasker: When I started studying reefs in the 1970s, we were all focused on complex and fascinating questions about how reefs work. The role of corals, fish, hurricanes, sea urchins and other organisms was being studied in systems that seemed to have existed “forever” and which we expected would continue “forever”. While some researchers were already raising the alarm about human impacts, many, including myself, thought these concerns about particular places with particularly large human populations or particularly careless approaches to reef use. We have consistently seen the effects of humans spread throughout the world’s oceans, and the effects of ocean warming are not paying attention to local politics. Now he is the rare scientist who does not need to include our changed environments in his research.
What are soft corals and why are they important?
Lasker: When people hear the word coral, they usually think of stony coral. These are corals that produce hard skeletons. Stony corals—called sclerotized corals in the vernacular of researchers—make up the framework of the reef. Soft corals, also known as octocorals, are the lovers of the sea and the sea plumes seen waving back and forth in reef videos. Their name, octocorals, comes from each polyp having eight tentacles. Like their scleractinian cousins, they create three-dimensional structure in the reef, which is used by fish and other small organisms. Unlike their scleractinian cousins, they do not have a solid skeleton and when they die they disintegrate into sand. Octocorals have always been present on reefs, but as hard corals have steadily declined in abundance, octocorals have become increasingly important on reefs. And in some places, octocorals, as opposed to hard corals, have actually increased in abundance. Octocoral forest on the south coast of Agios Ioannis, Virgin Islands. A few stony corals are visible in the foreground, but on this reef and many reefs in the Caribbean, they no longer dominate the reef, says UB coral researcher Howard Lasker. Photo: Howard Lasker
Dr. Lasker, some of your recent work has documented the rise of soft coral “forests” on Caribbean reefs. Can you talk about these findings?
Stony corals, also called hard corals, have been in decline for at least the last 50 years, and unfortunately, many reefs are only a pale shadow of the reefs they were 50 years ago. Octocorals have been more resistant to the stresses that have killed stony corals, and some reefs have changed from a mixture of hard corals and octocorals to mostly octocorals. The upright, tree-like structure of soft corals creates a “forest” that provides many, but not all, of the ecosystem services that hard corals provide. We studied this transition with the goal of understanding why octocorals were resilient and the important question of whether we can expect it to continue.
Dr. Lasker, you co-led a team monitoring reefs in the US Virgin Islands when two major hurricanes hit in 2017. What did you notice over the next few years?
The first thing to understand is that coral reefs have always been affected by hurricanes, just as fire has been an important component of forest dynamics. Historically, hurricanes have caused damage, from which reefs recover over years and decades. The difference now is that stony corals have been reduced to such low numbers that they are not recovering. What we discovered in the Virgin Islands is that while octocorals were adversely affected in our study areas, the damage was not as great as we had feared and, more importantly, over the next year we saw the development of new colonies which in time will lead to recovery of octocoral.
Dr. Coffroth, you recently studied soft corals and their algal symbiosis during a bleaching event. What were some of the most useful findings?
Reef corals and octocorals form a symbiosis with unicellular algae that live in the coral tissue. These algal symbionts, in the family Symbiodiniaceae, use energy from the sun to produce nutrients that are passed on to the coral, and the coral in return provides the algal symbionts with nitrogen, CO2, and a safe place to live. This symbiosis is a true mutuality where both partners benefit. Much of the normal coloration of corals and octocorals is due to the brown algal symbionts they host. During times of stress, such as high temperatures, stony corals and octocorals can lose the algal symbiosis on which they depend. Then the coral appears white, and this is called coral bleaching. We have found that, in many cases, octocorals do not bleach as easily as stony corals, and if they do, they generally recover. Since there are many species of symbiotic symbiotic algae that have different physiologies, we sought to determine whether the symbionts harboring Caribbean octocorals were more thermotolerant. Our laboratory studies have shown that the types of symbionts found in Caribbean octocorals can grow at temperatures where many stony corals experience bleaching. This suggests that at least part of the resilience observed in octocorals may be due to this symbiosis. Flasks containing algal symbionts isolated from stony corals and octocorals. These intracellular symbionts provide corals with nutrients from photosynthesis. Scientists cultivate these algal symbionts to study a variety of topics, including the symbionts’ thermal tolerance and their ability to adapt to a changing climate. Photo: Douglas Levere
What role will soft corals play in the future of coral reefs?
Lasker: This is the big and unknown question. If conditions continue as they are, octocoral forests may persist. They will not build the reef like stony corals, and in the long run this will lead to changes in the reef. Reef scientists refer to this as “reef flattening,” which occurs as the dead skeletons of stony corals erode. However, in the short term, octocoral forests will provide habitat for fish and other organisms, and if conditions improve, their effects could even facilitate the recovery of stony corals. However, this requires a great improvement in environmental conditions. If environmental conditions continue to deteriorate due to rising sea temperatures, overfishing, land use policies and other anthropogenic impacts, then octocorals will suffer as well.
Is there anything else you would like to add?
Lasker: If humans do not reverse CO2 emissions and eliminate other stressors on reefs, then the fate of reefs is rather bleak. Some researchers are working to find and propagate more resilient corals, but that too requires us to halt the decline in environmental conditions. We can’t just turn back the clock and recreate the reefs of 50 years ago, but we may be able to set the stage for recovery if we can reverse CO2 emissions, eliminate overfishing and adopt land use policies that will not further degrade the reefs.
