Stunning 3D digital models visualize the surface of coral reefs in painstaking detail

Coral reefs are complex ecosystems, a jumble of microhabitats created by corals and the substrate beneath them: holes, areas that are smooth or rough, regions that have steep or shallow slopes.

Where do coral larvae, called planulae, like to settle? What seascapes help youngsters of different coral species flourish? And do varying species compete for the same microhabitats/spots on the reef?

To study these questions, University at Buffalo scientist Ángela Martínez Quintana has created stunning 3D digital models that visualize the surface of coral reefs in painstaking detail. And these artful re-creations aren't just beautiful: They're also filled with data on the distribution of young corals, known as recruits, that scientists are analyzing.

Field work photos, still images of models, and links to interactive models:

https://www.buffalo.edu/news/releases/2022/04/018.html#models

Martínez Quintana isn't the first researcher to craft such models. But the science she and colleagues are doing with the models, leveraging them to study species distribution in coral reefs, could lead to exciting new tools for studying 3D ecosystems.

As climate change and other pressures kill corals, causing many reefs to lose structural complexity, the work could aid restoration efforts and illuminate how different types of coral might cope with such transformations.

The work is part of a larger National Science Foundation-funded project that explores how and why some groups of corals are holding their own on reefs while others are declining. That research is led by Howard Lasker, PhD, at UB and Peter Edmunds, PhD, at California State University, Northridge.

Reconstructing underwater ecosystems in intricate detail

When I started to do this, I did not know that reefs could be reproduced digitally, and I tried to measure holes and crevices on the reef with a caliper."

Martínez Quintana, a UB PhD student in evolution, ecology and behavior

She quickly realized she would need better tools. Stuart Sandin, PhD, and Nicole Pedersen, both researchers at the Scripps Institution of Oceanography, introduced Martínez Quintana to "structure from motion," a photogrammetry technique that allows for the digital re-creation of 3D structures from sequences of overlapping images. This was the technology she needed.

Diving off the coast of St. John in the U.S. Virgin Islands, Martínez Quintana took close-up videos of coral reefs, focusing on small square areas of the sea floor called quadrats. The footage, consisting of many overlapping still frames, captured the reef's topography in intricate detail, including objects hidden behind other objects, and regions tucked below overhangs.

Martínez Quintana also took copious notes, documenting the precise locations of tiny young corals on the reef.

"These organisms can be just a few millimeters in size, so to find them, I spent hours with my face 10 centimeters from the bottom of the reef," she says.

The result: Beautiful, 3D models that users can rotate, zooming in and out to inspect facets of the reef. The visualizations combine Martínez Quintana's observations of coral recruits' location with data on the topography of the reef and other organisms present, including juvenile and adult corals, and other benthic invertebrates such as sponges.

Studying corals' preferences in a complex, 3D ecosystem

Martínez Quintana constructed many such models, each focusing on structural details of reef surfaces in 50-by-50-centimeter areas.

Analyzing the data stored within them would require additional tools. Martínez Quintana wanted to understand the distribution of young corals in a complex, 3D ecosystem, but conventional research methods focused on the distribution of species across geographic areas in two dimensions.

She was losing too much data. She needed new techniques. For this, Martínez Quintana worked with biogeographer Adam Wilson, PhD, an associate professor of geography in the UB College of Arts and Sciences.

Wilson, a key partner on the research, developed a computational approach to analyze the models, each of which consists of a multitude of points housing information about the underwater landscape. Together, the points form a 3D polygonal mesh. Wilson's approach allows scientists to study the distribution of coral recruits on this mesh surface, with a focus on identifying the characteristics of microhabitats suitable for recruits of different coral species.

"This method has the potential to be revolutionary, since it will allow us to better understand how organisms partition their environment and interact with each other on complex three-dimensional ecosystems. It could be used not only on coral reefs, but also on ecosystems such as the canopy of the rainforest," Martínez Quintana says.

"What's really innovative about Ángela's research is that she's using these 3D models to learn about ecological processes," Wilson says. "She's interested in recruitment and successful growth of young corals on the reef, so she's been mapping where the coral recruits are on that landscape, and then using statistical models and machine learning models to try to infer which microhabitats are suitable for those corals to succeed."

"In developing these 3D models, Ángela has opened up new ways of answering critical questions, which we have not had the tools to address," says Lasker, UB research professor of geology and professor emeritus of environment and sustainability. Lasker is Martínez Quintana's PhD adviser.

Martínez Quintana says 3D models hold huge promise for both research and education.