File under: The ocean surprises us. Again.
I often think the more we think we know about our oceans, the more we have to learn. Florida State University Professor Amy Baco-Taylor recently discovered an odd chain of coral while surveying the seamounts off the northwestern Hawaiian Islands.
“I’ve been exploring the deep sea around the Hawaiian Archipelago since 1998, and I’d seen enough to know that the presence of these reefs at these depths was definitely unexpected,” the professor of earth, ocean and atmospheric science told Florida State University News.
The scleractinia coral discovered there is a type that forms from small, stony polyps that grow skeletal protection for their soft bodies.
The North Atlantic and South Pacific provide fertile habitats for deep-sea scleractinian reefs, which require high levels of aragonite to support their skeletal growth, and low levels of carbonate dissolution to prevent their carbonate skeletons from dissolving.
The North Pacific has both low levels of aragonite and high levels of carbonate dissolution, so scientists believed the accumulation of these deep-sea coral colonies was highly unlikely in the deep waters of the North Pacific.
“Even if the species could survive in the area,” Baco-Taylor said, “we shouldn’t be finding an accumulation of reef.”
Her research team postulates an abundance of chlorophyll in the region may be providing enough food for the corals to grow despite negative environmental factors.
“There’s still a mystery as to why these reefs are here,” Baco-Taylor said.
The discovery has prompted some to reconsider the effects of ocean acidification on coral colonies. These findings offer a glimmer of hope in the face of widespread panic about the future of the planet’s coral reefs as a result of ocean acidification.
“These results show that the effect of ocean acidification on deep-water corals may not be as severe as predicted,” said David Garrison, a program director in the National Science Foundation’s Division of Ocean Sciences, which funded the research. “What accounts for the resilience of these corals on seamounts in the Pacific remains to be determined.”
But before we get too excited about this surprisingly good news about coral resiliency and what it could mean for commercial species and the fleets that target them, be aware that the next impulse may well be to expand the Papahanaumokuakea Marine National Monument to include these reefs. As the article states, “they exist in areas where destructive trawling is permitted and active.”
In fairness, this FSU news piece was published four days before the Proceedings of the National Academy of Sciences published the results of an international study on the effects of trawling, so they may not have been availed of the latest evidence of the range of effects of trawling gear on the seabed.
The new study finds that different types of trawl gear results in drastically different seabed impacts. This is not news to experienced commercial fishermen, but it bears studying to confirm that the data support the anecdotal evidence.
“There’s a common perception that you trawl the bottom and the ecosystem is destroyed,” Ray Hilborn, a University of Washington fisheries professor and one of four co-authors who designed the study told Phys-Org. “This study shows that the most common kind of trawling, otter trawling, does not destroy the marine ecosystem, and places that are trawled once a year really won’t be very different from places that are not trawled at all.”
Evidence on trawls aside, the coral protection measures in Hawaii have prohibited destructive fishing gear for decades, long before the monument was established.
“Hawaii’s fleets do not use trawls,” replied Sylvia Spalding, communications director for the Western Pacific Fishery Management Council, via email. “In 1983, the Fishery Management Plan for Precious Corals in the Western Pacific, which was developed by the Western Pacific Fishery Management Council, and among other regulations, requires selective gear only, such as harvesting by hand or through the use of underwater submersible vehicles. Additionally, an amendment to the Bottomfish and Seamount Groundfish FMP in 1986 prohibited potentially destructive fishing techniques, including, among others, bottom trawl nets and bottom-set gillnets in the entire US EEZ in the Western Pacific region, an area of approximately 1.5 million square miles comprising about half of the US EEZ.”
The Hilborn-led study is part of a larger effort to document the effects of bottom trawling gear worldwide. Hilborn is leading the Trawling Best Practices Project with co-authors Michel Kaiser of Bangor University in Wales and Simon Jennings of the International Council for the Exploration of the Seas in Denmark.
The team aims to publish a set of fishing-industry “best practices” for the methods, equipment, density and frequency of bottom trawling.
“Understanding how gear impacts the bottom, and species on the bottom, is important for a scientific understanding of the impacts of trawling,” said Holborn.
A deeper understanding of trawl gear effects could also lead to more accurate descriptions of trawl fishing in the scientific community. Like the coral discovery, we may find ourselves pleasantly surprised.