Tiger sharks equipped with cameras and sensors have helped marine scientists identify and measure the largest seagrass ecosystem recorded.
The newly-mapped sea prairie in the Bahamas is estimated to stretch up to 35,500 square miles, equivalent to the size of the state of Maine, and is likely to be one of the world’s largest marine carbon sinks, according to authors of a research paper published in Nature Communications on Tuesday.
“If protected, these seagrasses can play a crucial role in slowing the climate emergency, as the world moves to deploy a diverse range of strategies to capture carbon from the atmosphere,” said Austin Gallagher, lead scientist of the study and the chief executive of nonprofit Beneath the Waves. “This discovery should give us hope for the future of our oceans.”
Marine and coastal ecosystems such as sea grasses, mangroves, and salt marshes capture and store planet-warming carbon dioxide from the atmosphere at a faster rate than the planet’s forests. Scientists estimate seagrasses account for an estimated 17 percent of the total carbon buried in marine sediments every year. That makes conservation of these habitats an essential part of the global effort to reduce greenhouse gas emissions in order to slow the pace of global warming.
The planet’s oceans, and particularly seagrass ecosystems, remain poorly mapped across many regions, mainly because of the difficulties of measuring them with remote sensing devices like satellites, authors said. From space, sea prairies can be easily confused with phytoplankton, algae, or sediments.
Uncertainty around the area of total seagrass coverage in the world makes it much harder to estimate the ocean's capacity to capture carbon, the paper said.
To conduct the research, authors took an innovative approach and brought together scientists, divers, conservationists, local stakeholders, storytellers - and tiger sharks, the largest marine predator found in tropical seas. Researchers soon found sharks presented advantages over satellites and humans.
“Tiger sharks spend about 72 percent of their time patrolling seagrass beds, which can be observed by the 360-degree cameras we deployed, for the first time in marine animals, on the sharks,” said Carlos Duarte, study co-author and a researcher at the King Abdullah University of Science and Technology in Saudi Arabia. “Tiger sharks cover about 70 kilometers in one day, can work with us 24/7 - with no complaint yet on record - and are not constrained, as human divers are, to shallow depths.”
The new area mapped spans 66,000 to 92,000 square kilometers, extending the documented seagrass area globally by 34% relative to current estimates. Researchers also collected sediment cores from the sea prairie and concluded that the Bahamas likely holds up to a quarter of the global stock of seagrass-based carbon.
“The Bahamas may be in the top of rankings on climate vulnerability, but we now have evidence that we top the list of the world’s blue carbon hotspots, too,” Bahamas Prime Minister Philip Brave Davis said in a statement. “Our seagrasses can play a critical role in generating the resources we need to transition to renewable energy and to adapt and become more resilient to the changing climate.”