From Coastlines to Coral
BY JANE CARRICK
Like many of the extraordinary women featured on this site, I fell in love with the ocean early on and fell hard. Declaring myself a future marine biologist by the time I was about 9 years old, I spent summers exploring the barnacle-ridden rocky tidal pools at Wingaersheek Beach in my home state of Massachusetts or catch-and-releasing crabs and invertebrates that were unfortunate enough to pass by my grandparents’ dock in Chesapeake Bay. I was happiest when I was saltiest, and that hasn’t changed.
My path took some detours along the way—I worked in a biomedical research lab and a medical office for a total of about 3 years after college—but I ultimately knew that my early avowal to marine biology was the correct one. I managed to parlay my curiosity of the ocean into a career exploring and trying to conserve critical marine habitat by eventually going back to school to earn my masters degree at University of Miami with marine ecology and coral restoration guru Dr. Diego Lirman. These days, you can find me SCUBA diving the tropical reefs off the coast of Miami, working hard alongside the same dedicated team of coral restoration scientists to bring back local populations of endangered reef species.
Restoration involves taking small wild fragments of coral, growing and maintaining them in underwater nurseries, and later fragmenting and transplanting them back onto degraded reefs where they used to exist naturally. It’s a fairly simple concept but a complicated one in practice. Early on, I was a little overconfident because under my belt I had 10 years of SCUBA know-how, an (expired) instructor certification, and extensive scientific diving training from the University of Miami. But I was quickly humbled when I realized all the moving parts and underwater task loading that is required to make a restoration expedition run smoothly. Being able to communicate worldlessly underwater with your teammates, identify different species in the wild, collect, fragment, and transplant corals while taking care to not damage any part of the reef, and to do all this efficiently while not losing any of your equipment (which sometimes floats!) and practice safe diving in all sorts of ocean conditions, all the while being able to adapt and change plans promptly underwater in response to unforeseen obstacles is challenging and exhausting. That said, it is the most exciting and satisfying work that I have ever been lucky enough to perform.
Beyond the in-water work, the science of restoration is multilayered as well. We maintain multiple underwater nurseries with thousands of corals from over 100 distinct genotypes and 7 species. We need to make every coral count, so planning and sound science is critical. Our lab, as well as many others, have spent years studying the details of how to make restoration efficient and successful. Since the field of coral restoration gained momentum about 15 years ago, questions have popped up, like how much genetic or species diversity makes restoration successful, how close or far apart corals should be outplanted, what role is played by environmental conditions like structural complexity (rugosity) of the reef, light, temperature, proximity to other marine habitats, latitude, depth, fish abundance, and these are just scratching the surface. We don’t just restore corals, but also study how to restore corals.
My own work is centered on how to do this in a way that can restore one particularly important ecosystem service that natural reefs provide: coastal protection. I’ve thought a lot about my early exposure to the ocean from the vantage of beaches and shorelines. These dynamic interfaces are where most of us get to first learn about our oceans. Changing from season to season or even hour by hour, so many different forces act upon our coasts: tropical storms, tides, currents, wind, waves, and the creatures that live there are all architects of the coast. So much so that we humans, like the mid-Atlantic barnacles and crabs I persecuted as a child, have learned to adapt to the ever-changing shapes of our shoreline. We have raised our houses with stilts, we have replenished our beaches with sand from foreign countries, and we have continuously built right up to water’s edge because, despite their unpredictability, coasts are our thresholds to the sea. With more than 40% of the global population living within 100 km of the shore now, it’s pretty clear that we value being near the ocean. We are a coastal species.
But the coasts are not only valuable to us—they’re where we launch our shipping vessels, reel in our catches, relax in the sun, and head out to snorkel or SCUBA dive--they are also increasingly vulnerable. Tropical storms, including hurricanes/cyclones, are expected to become more intense with warming ocean temps and sea level rise. Meanwhile, humans historically (and presently) destroy the coastal defenses that Nature has curated for millions of years--perhaps most of all, coral reefs.
A little background. Healthy and structurally complex coral reefs tend to act as submerged breakwaters and are our first line of defense from energetic waves coming towards shore. In fact, a coral reef can reduce wave energy by an average of 97%, which can translate to major benefits to the coastline in terms of reduced erosion and protection from storm surge and wave-driven flooding. We know this and yet we still are systematically decimating reefs and other protective habitats to our own detriment, in some cases replacing them with man-made structures which are costly, tend to break down over time, and restore few to none of the natural ecosystem services and natural beauty we’ve lost.
There have been plenty of studies on how coral restoration can recover lost ecosystem services, like fish biomass. But it’s been very difficult to study how restoration could potentially recover the coastal protection benefits that we see with natural healthy reefs. In theory, restoring corals to a reef should create more structure and cause waves to lose energy as they pass over the coral. But the questions we ask ourselves now become: how large does a restoration area need to be in order to see a benefit? How far away from shore should we restore in order to see an effect on the shoreline? What are the trade-offs when compared to man-made coastal protection benefits and what could the synergies be if we combined man-made with natural solutions?
Some of these questions we attempt to answer by bringing our restoration expertise into the UM SUSTAIN (SUrge STructure Atmosphere INteracation) wave tank facility. SUSTAIN is a MASSIVE (23 m long x 10 m wide x 2 m tall) fully programmable tank, capable of generating wind and waves up to a Category 5 hurricane, making it the largest indoor wave facility of its kind. Using coral skeletons from our restoration work, I build to-scale coral reef “thicket” models to simulate a restoration thicket. With SUSTAIN’s physical oceanography team, we then program waves to run across the models towards an artificial shoreline and measure what the wave height and energy looks like both before and after the thicket models. The difference in those numbers—which can be significant in different conditions-- are direct benefits provided by a model restored reef.
But, because restoration plots can take years to grow and may continue to face the same threats as natural reefs, we wanted to take it a step further and see whether we could harness some of the benefits of man-made (or “gray”) infrastructure and combine them with the benefits of coral restoration (or “green infrastructure”). To do this, we merged minds with talented engineers from UM to design a hybrid reef breakwater, made of a trapezoidal cement breakwater underneath and live restoration corals on the breakwater surface. The idea is that the sub-structure can break a wave by changing the water depth and the surface corals create friction that further reduces a wave’s energy.
A laboratory setting is an excellent way to study complex interactions, because we can fully program the wave tank to our specifications, run controls, and more easily deploy instruments. But we must also know whether our laboratory findings hold true in a real-world setting, by measuring waves on a restoration reef. To do this, we repeat the tank experiments at in situ well-developed reefs and around existing breakwaters to determine what percentage of wave energy is reduced. This way, we can validate our tank experiments and learn how to best design restoration projects to protect South Florida’s coasts.
I’m thrilled to share my work on this blog. I’d be remiss though, if I said I did it alone. In fact, this project is a highly interdisciplinary one, with a team of scientists from 5 different departments, all studying the same problem from their own unique perspectives (marine ecology, restoration science, physical oceanography, environmental engineering, as well as urban planning and communications). It’s been my pleasure and my challenge to manage this team, funded by an internal UM grant source, and I am continually grateful that I’ve found my role in work that merges my love and respect for coastal places with my deep-seated urge to spend as much time underwater as possible. If you leave with one take-away, please let it be this: marine science is evolving. Increasingly intricate problems like coastal resilience and coral reef conservation now require complex approaches that bring together practical applications with theoretical science, laboratory and modeling studies with in situ investigations, and teams of thinkers from many diverse backgrounds. Keep your mind open, work hard, and stay happy and salty!