Head-high waves were breaking over the reef, battering Cliff Kapono every 10 seconds or so as he sat on his surfboard. As the surf pounded and pushed him towards nearby rocks, a rush of sediment-stained floodwaters from Honoli'i Stream threatened to sweep Kapono from Hilo Bay, out to the raging ocean. A stone's throw from his childhood home—and from his office in the MEGA Lab at the University of Hawaii at Hilo—Dr. Kapono battled to keep in position as he measured the salinity of the turbulent mass of water beneath him, tossing him like a piece of driftwood.

"These are some of the most biodiverse coral reefs I've seen," he says from his base in Hilo. "And what's so cool is these corals aren't like the corals you would see in Finding Nemo: the big fan corals, pinks and purples and crazy colors. These are more native, endemic corals—very Hawaiian. To me, they're the working-class coral of the world, and they're in a working-class community in Hawaii.

"It's so non-intuitive to think that we have these thriving corals, because the water is brown a lot because of the runoff," he adds. "I'm just trying to understand why the reef is not completely destroyed like so many other places that have similar point-source pollution in their system."

Ahupua'a

Kapono characterizes the flow of sediment and freshwater into the bay not just in scientific terms and milligrams per liter, but in uniquely Hawaiian terms, using the traditional concept of ahupua'a—wedge-shaped allotments of land that ran from the volcanic peaks to the sea.

"There's a fundamental idea in Hawaiian culture that connects the ridge to the reef, and the watershed is the resource that facilitates that thinking," he explains. "What happens up in the mountains ultimately will get out to the ocean through this conduit. The conduit is introducing a disturbance to the reef. I want to characterize the events when these large amounts of fresh water carrying silt and sediment put these plumes out into the bay. Why is the coral still surviving? Because that same action from a very different perspective is happening to other bays across the world."

(Image credit: Steve Werblow)

Kapono suspects the answer may lie in the coral's microbiome, the teeming mass of bacteria and fungi that coat the reef in a thin but vital layer of mucus that he describes as the reef's immune system. As a PhD candidate and pro surfer on the worldwide circuit, Kapono studied the impact of ocean water on the microbiome of his fellow athletes. Now he's planning to apply the same analytical technology to study changes in the microbiome of the reef itself as it endures and recovers from repeated blasts of sediment.

"I'm interested in monitoring what the resting microbiome is before the disturbance, during the disturbance and after the disturbance to hopefully better understand if the microbiome changes," Kapono explains. "If the microbiome is changing, how quickly can you recover to a healthy microbiome?"

Characterizing

Before he shifts his research to the stage of sampling and analyzing microbiota from the reef, Kapono is characterizing the flow of water and sediment throughout the water column. His tool is a SonTek CastAway-CTD, which measures conductivity, temperature and depth at a rate of 5 Hz, then calculates salinity, sound speed and other parameters.

To take measurements of the water column, Kapono lets the CastAway sink to the reef and reels it back up on a polypropylene line. About the size of a soda can, the CastAway-CTD tags each cast with its GPS location at both the beginning and end of the measurement. So even while drifting rapidly in strong wave- and tide-induced currents, Kapono has been amassing a detailed, three-dimensional database of the movement of the freshwater lens that drifts over the denser saltwater of Hilo Bay during storms.

"The CTD provides me with the opportunity to visualize where the water is flowing," he says. "It's a really powerful little tool. It allows me to get a lot of data relatively quickly. Ultimately the outliers will expose themselves and the inconsistencies will be normalized if I get enough data over a longer period of time."

Dr. Xue Fan, Senior Applications Engineer at SonTek, notes that Kapono is applying the CastAway to exactly the sort of rigorous challenge it was designed to tackle.

"Our goal with the CastAway was to create an instrument that could deliver publishable data in just about any conditions," Fan says. "The idea of Cliff being able to take measurements in storm conditions demonstrates that the operation is simple enough to collect reliable data even in rough water."

Fan adds that the CastAway is part of a suite of Xylem instruments that can also help Hawaii's growing aquaculture industry. The $83-million industry has been dominated by algae production, but ornamental, finfish and shrimp culture have gained significant share in recent years, and renewed interest in traditional Hawaiian fishpond culture mirrors Kapono's connection to ahupua'a. Monitoring water conditions in aquaculture—whether in a restored 1,000-year-old basalt fish pond or a modern runway system—is vital to success, she notes.

Deeper Understanding

Kapono says he is driven to understand the success of the "working class coral" in his backyard and share its secrets. For him, it's a human story, too.

"Within our indigenous perspective as native people from Hawaii, we believe that we have a familial, genealogical tie to the coral reef as humans," he explains. "I hope that nature can inspire what's happening in society. There are some things in nature, like these coral reefs, that are incredibly resilient. Especially now in this time where we're faced with a lot of social inequities and social injustices, hopefully that can inspire us to empower our resiliency as people from all different genders, occupations, races, political and religious beliefs—that a little bit of adversity might actually prove beneficial to our survival.

"It seems like such a beautiful story to tell through science," he adds.

This feature appeared in Environment, Coastal & Offshore (ECO) Magazine's 2021 Autumn edition, to read more access the magazine here.