Deep-diving marine scientists from the California Academy of Sciences capture rare look at hurricane impact on coral reefs

SAN FRANCISCO (November 15, 2016) – While residents and visitors affected by Hurricane Matthew took stock of the extreme damage caused by the early-October storm, scientists from the California Academy of Sciences trained their eyes on storm impacts below the ocean’s surface—surveying coral reefs as deep as 420 feet.

Sailing southeast from Miami on the heels of Matthew’s calamitous path through the Bahamas, highly trained Academy scientific divers aboard the MV Umbra charted a plan to visit coral reef sites impacted by the storm. The research team—led by Academy Ichthyology Curator Dr. Luiz Rocha and Steinhart Aquarium Director Bart Shepherd—is interested in virtually unknown mesophotic “twilight zone” reefs that thrive in the otherworldly half-light between 200 and 500 feet below the ocean’s surface. And this was a rare opportunity to compare the impacts that large tropical storms have on both deep and shallow coral reef ecosystems.

When public health and land-based destruction are of highest concern, underwater environmental impacts of tropical storms often remain unseen. The rare photos and video the team managed to capture have helped to clarify the impacts of tropical storms at various depths, and the role that twilight zone reefs play in the larger marine ecosystems. Indeed, the team discovered that powerful storms can impact even the deepest coral reef ecosystems, choking live corals with sand, silt, and land-based debris like tree branches. The researchers will continue to explore the possibility that little known twilight zone reefs might, in some cases, function as refugia for life in the ultra-vulnerable shallows.

Hurricane Matthew “changed our plans”

The Academy’s long-planned marine expedition to the Bahamas (October 9–22)—part of a larger initiative to explore, explain, and rehabilitate global coral reefs*—intended to focus on the region’s invasive lionfish and their impact on endangered fishes. After nearly cancelling the trip due to the hurricane, last-minute storm predictions changed research plans for the two-week expedition. The scientists knew hurricane forecasts, while catastrophic for communities in the storm’s path, might provide a rare opportunity to look at extreme weather impacts on coral reef ecosystems.

Tropical coral reefs are one of Earth’s most studied and best-understood marine ecosystems, but this knowledge is almost entirely limited to shallow reefs accessible through conventional scuba diving. Twilight zone divers on Academy expeditions can explore deep global reefs that are virtually unknown, helping to bring these dark, mysterious ecosystems to light. Mesophotic reefs aren’t often a focus of exploration, particularly so soon after a major tropical storm has passed through.

“Hurricane Matthew threw our expedition objectives out the window,” says co-leader Luiz Rocha, who worked quickly to restructure diving plans around the storm set to hit the Bahamas days before the team’s arrival. “Surveying deep reefs so soon after they’ve been hit by a powerful storm isn’t usually a safe option—we knew this was a unique scientific opportunity. As we grapple with new climate realities on global coral reefs, understanding severe storm impacts from shallow to deep reefs will help us come up with bold conservation interventions.”

This was the first time Rocha, like many expedition members, had executed dives in a recent hurricane’s wake. “It was a fascinating trip, but,” Rocha adds, “very difficult to coordinate. We usually take months to create our research plans. Just days before leaving, we decided to accept the weather card we’d been dealt to explore how hurricanes impact reefs beyond our typical view.”

Path of the storm

Matthew originated as a tropical wave off the northwest coast of Africa in late September, developing into a hurricane as it reached the eastern Caribbean. Intensifying rapidly, the Category-4 hurricane made landfall in Haiti on October 4—killing more than 1,000 people (to date), leveling structures, and exacerbating an ongoing humanitarian crisis.

Matthew then moved on from Haiti and eastern Cuba, churning through the Bahamas from October 5–6 at both Category 3 and 4 strength. 125 mph winds tore at remote land masses and whipped seas above reef sites the Academy team pinpointed for dives less than one week later, once weather conditions in the Bahamas stabilized in the wake of the fast-moving storm.

Tumbling corals and clouds of silt

“It was a rough crossing from Miami to the Bahamas,” says expedition co-leader Bart Shepherd, also an architect of the Academy’s major initiative to research and rehabilitate global reefs. “Twilight zone dives are long and extremely challenging, so our team aboard the Umbra tried to rest as we approached our first dive sites. It certainly wasn’t easy.”

Over the course of two weeks, eight dives told different storm stories. Deep dives near Cay Sal revealed healthy swaths of colorful corals and diverse aquatic life, from groupers and snappers in the clear shallows to small, darting reef fishes significantly deeper. Academy scientists recorded the life and conditions on the bottom (as well as the slow trip back to the surface), taking photos and video and making notes in waterproof notebooks. Some reefs appeared to have avoided the worst of Matthew’s rough ocean conditions—probably, the scientists say, due to each site’s location relative to nearby landmass and path of the storm.

Several of the team’s mesophotic dive sites revealed serious environmental impacts in Matthew’s wake. Sites near Egg Island, Rum Cay, Plana Cay, and Cat Island afforded the team a rare look into murky, sand-filled conditions that threaten vulnerable reefs in the wake of tropical storms. Near reef sites that were particularly impacted by the storm, large swaths of beach from nearby islands appeared to have washed away. On one occasion near Ragged Island off the southern coast of the Bahamas, high winds, rough seas, and poor visibility prevented the team from attempting any exploration whatsoever.

“On reef dives with visible storm impacts, we saw vertical reef walls covered in sand and silt,” says Shepherd. “Corals are living creatures that need access to clean, clear water in order to thrive. Thick coats of sand and silt stirred up by storms can smother them. In some sites, we even witnessed broken corals and sponges from rough conditions in the shallows tumbling down to mesophotic depths. I saw a tree branch with leaves still attached smothering a large coral.”

Reefs have survived natural disturbances—like powerful hurricanes—for millennia. When storms are added to a growing list of modern threats to coral reef ecosystems, Rocha says, “the situation looks bleak, but there’s a light at the end of the tunnel. Reefs adapt to changing conditions quickly and will likely survive, albeit in a new state, as they have in the past. On the bright side of this expedition, our team saw almost no invasive lionfish. This was an unexpected finding given the high densities observed elsewhere in the Caribbean.”

Exploration and restoration efforts continue in global reefs

The Academy’s commitment to studying and rehabilitating global coral reefs will continue alongside several visionary partners in years to come. This December, the institution’s twilight zone divers are set to join forces with shallow coral reef experts—including new curator Dr. Rebecca Albright (coral reef biologist), and longtime invertebrate curators Drs. Terry Gosliner, Rich Mooi, and Gary Williams—in Palau.

The multidisciplinary team will monitor coral health, identify new species, and take stock of fish and invertebrate diversity and abundance. Select live specimens will be safely transported from mesophotic depths back to the Academy for use in public engagement and education in Twilight Zone: Deep Reefs Revealed.

Meanwhile in Curacao, Academy partner SECORE International is hard at work applying a visionary restoration approach—in the form of reef-attaching “seeding units”—to restore dwindling reefs with sexually reproduced corals around the world. Already global leaders in this field, the Academy and SECORE will continue to develop and apply science-based technologies to increase survival of coral reefs on a global scale.

Together with a growing network of partners, the Academy’s unique mix of scientific expertise, world-leading ocean exploration skills, on-the-ground conservation efforts, world-class aquarium and coral-culturing facilities, and innovative educational platforms will give critical marine ecosystems the science-based help—and global attention—they deserve.

*The first phase of the Academy's global coral reef initiative is made possible through the support of visionary donors. The Academy gratefully acknowledges the partners listed below.

• William K. Bowes, Jr. Foundation
• Eva and Bill Price
• Diana Nelson and John C. Atwater
• Dalio Ocean Initiative​
• Jennifer Caldwell and John H. N. Fisher
• Charlotte and Nick Giovanni
• Hellman Foundation
• Laura and Peter Fenton