Posted on March 10, 2022
VICKSBURG, Miss. — Since 2019, U.S. Army Engineer Research and Development Center (ERDC) Research Biologists Dr. Burton Suedel and Justin Wilkens have been working with the U.S. Army Corps of Engineers (USACE) Honolulu District to answer questions about whether dredging-induced sediment plumes could affect corals.
USACE dredges Honolulu Harbor approximately once a decade, and as part of that effort, they address any concerns local, state and federal agencies may have about operations impacting sensitive aquatic resources.
“This entire study was a demonstration of effective collaboration and communication,” Suedel said. “We teamed with the University of Hawaii’s Dr. Robert Richmond and his graduate students and collaborated with the district and their stakeholders throughout the entire project.”
“I believe we enhanced our capabilities by working with Dr. Richmond and his team,” Suedel continued. “It’s a very small circle of investigators conducting corals research, and when you come in from outside you have to establish rapport, and Dr. Richmond is an internationally renowned expert in the coral field.”
Suedel and Wilkens first met with the district and the USACE Pacific Ocean Division, followed by a variety of stakeholders, including the U.S. Environmental Protection Agency, the U.S. Fish and Wildlife Service, the National Oceanic and Atmospheric Administration, Hawaii Department of Transportation-Harbors and others to discuss the dredging plans.
“From those conversations, we came up with an idea to simulate, under controlled laboratory conditions, the settling of sediment onto the coral as a result of dredging so we could learn more about the potential impacts,” said Wilkens. “We involved the stakeholders and built consensus throughout the process. That kind of coordination went a long way towards establishing transparency.”
Kate Bliss, a division regulatory and environmental program manager who worked with the team, thinks the collaborative study went as smoothly as possible.
“When we developed the experimental design, we submitted it to the stakeholders for comments, which wasn’t required, then when we received comments back, we had a meeting to discuss major concerns,” Bliss said.
The ERDC Environmental Laboratory has unique facilities and capabilities ― such as the fish larvae and egg exposure system (FLEES), which simulates a dredging plume. One of Wilkens’ responsibilities was to move the FLEES to Hawaii and set it up for the study.
“The FLEES can be adapted for a multitude of scenarios and conditions ― it can generate information across districts,” Wilkens said. “It’s a custom-built system ― there are just a couple like it at universities — but it’s more or less a one-of-a-kind capability. We’ve used it for fingerling fish, fish larvae, oysters and soft-shell clams. It’s a highly adaptable system; it was just a matter of teaming up with coral experts at University of Hawaii.”
The team thought it would be valuable to generate as much data as possible to address input from stakeholders, so they used both fine-grained sediment from the inner Honolulu Harbor and more course-grained, sand-like material from the entrance channel for the laboratory testing on the corals.
“We had one shot to get this right, and we nailed it — the experiments were very dependent upon what concentrations of sediments we used and how long we exposed the animals,” Suedel said, referring to the coral. “If you don’t expose the corals to the sediment the right way, too little sediment and they don’t respond, and too much sediment would have killed them. It’s a balancing act to simulate the dredging plume and challenging to do considering we’d never done these experiments before.”
After consultation and collaboration with the stakeholders and Richmond, Suedel and Wilkens decided to test three coral species representing different growth morphologies, or shapes —branching, domed or plating ― that are commonly found in Honolulu Harbor.
“By examining the different morphological types of corals, we could get a better understanding of how the dredging plume would affect not just specific coral species or communities, but the coral colony itself,” Richmond said.
During the actual laboratory testing, Wilkens conducted both virtual and in-person tours for stakeholders.
“We had experiments in progress, and I carried a camera in the laboratory and described in detail how the sediment was introduced to the corals,” Wilkens said.
This past September, Suedel and Wilkens flew out to Honolulu and met with the stakeholders to discuss the preliminary results of experiments.
“We received positive feedback,” Wilkens said. “We’re working on the technical report with Richmond that stakeholders will have the chance to review and comment on before it’s published.”
“I was very pleased that every element of the collaboration was truly a partnership,” Richmond said. “I feel very comfortable with the quality of the data, the quantity of the data and the value of the data.”
