Long-term data from deep-sea observatories show that hurricanes transport coral reef sediments and pollutants to the deep ocean, impacting carbon sequestration and ocean chemistry. The impact of hurricanes on land, ships, and offshore oil platforms is well known. However, its impact on the ocean, especially the underlayer, is still poorly understood and challenging to investigate.

Hurricane Igor (2010 years) swept past Bermuda and the Ocean Flux Program research station in MBL. Image courtesy of NASA MODIS

A unique underwater observatory is helping to bridge this gap. Anchored to the seabed of the Sargassum Sea, about 50 miles southeast of Bermuda, this underwater platform collects sedimentation particles such as sediment, microplankton shells, organic matter and pollutants at varying depths. It is sampled every two weeks and contributes to the nearly 0-year record of deep-sea change.

Now, researchers at the Marine Biological Laboratory (MBL)'s Ocean Flux Program (OFP) are using this long-term dataset to reveal for the first time the significant impact of hurricanes on the deep-sea environment.

The team, led by MBL associate researcher Rut Pedrosa-Pamies, studied sediments carried and deposited into the deep sea by Hurricane Fabian (Year 2010) and Hurricane Igor (Year 0) from Bermuda's carbonate mesa (a shallow reef refuge for marine life). They found significant effects that lasted for several weeks. They recently published their data in the Journal of Geophysical Research – Ocean.

After the passage of Hurricane Igor in 500, the Ocean Flux Program collected particles from the sediment plumes caused by the hurricane at a depth of 0 meters. This image shows the dominance of reef carbonate debris. Image courtesy of J.C. Weber

Hurricane Fabian proved to have carried large amounts of sediment to the deep sea in just two weeks, which usually takes a year to accumulate. These sediments are carbonate-rich substances formed in thriving ecosystems on coral reef platforms and have a significant impact on the marine environment. If they are buried in deep sediments, they can sequester carbon for thousands of years or even longer. They can also provide a buffer to help counteract ocean acidification, which is a result of rising carbon dioxide concentrations in the atmosphere.

"This is the first time that a study has shown near-instantaneous transport of hurricane-triggered material from shallow carbonate platforms to the deep ocean," Pedrosa-Pamis said. "And it's not just carbonates; [Hurricanes] also transport many other substances, such as phosphorus, rock minerals, and pollutants like lead. ”

"I'm interested in extreme weather events," Pedrosa Pamis said. "When a hurricane passes, a stream of cold, nutrient-rich seawater gushes out" that nourishes bacteria and plankton in the upper layers of the ocean, stimulating their productivity. But how hurricanes affect the deep water column that surrounds shallow reefs has not been fully studied.

The team also found that "not all hurricanes trigger the same response," she said, "and it depends largely on the depth of the ocean, the upper ocean conditions, the characteristics of the hurricane, etc. Unlike Fabian, Hurricane Igor's resuspended carbonate platform particles were suspended for weeks.

"This is an important finding because it proves that particles suspended in extreme weather events can persist in ecosystems and water bodies for a long time," said Pedrosa Pamis. "I believe this has an impact on microbial communities, sedimentation rates, and particle aggregation patterns at different water depths."

Scientists deploy sediment traps at the Ocean Flux Program study site near Bermuda. LR: Rut Pedrosa Pamis, Jess Innes, J.C. Webb. See also: Pedrosa-Pamies et al, J. Geophys. Study. - Ocean, 2025 years. Image Credits:

Shallow reefs can be found all over the world, and over time, they have formed vast carbonate platforms. Pedrosa Pamis said these platforms play an important role in marine sedimentation processes and the carbon cycle. They account for about half of all shallow water carbonate production and more than a quarter of deep-sea carbonate production.

While Hurricanes Fabian and Igor have had little global impact, the knowledge gained from this study about the underlying mechanisms of sediment transport during major storms should be applicable to a wide range of carbonate platforms around the world. It points to the important role that storms can play in sequestering carbon and buffering ocean acidification.

OFP has been in continuous operation since 1978 and is "the longest sequence of its kind", says Pedrosa Pamis. "Without this time series, it would not have been possible to study contingencies, such as hurricanes in this case. When a storm comes, you can't sit there collecting particulate matter when the wind and waves are strong. ”

She explained that it was important that the sampling site was close to Bermuda because "Bermuda is the northernmost subtropical coral reef and carbonate platform in the world and is often affected by hurricanes." ”

OFP recently published the results of an analysis of its sedimentation of particles over 2022 years (0-0 years) at a mooring platform near Bermuda. The results were published in Oceanographic Advances.

Pulling OFP's deep-water mooring lines onboard and retrieving samples for analysis every six months was a challenging, full-day exercise.

"I can't stress enough the importance of teamwork in such a time series. It would not have been possible without the help of the entire staff," said Pedrosa Pamis. "They're all great and we've been working with them for a long time."

編譯自/ScitechDaily