|September 20, 2013|
Seagrass Below Sunken Cruise Ship Worries Biologists
|When Italian salvage workers propped up the Costa Concordia this week, they cleared a major hurdle in the long saga of the cruise ship that sunk off the coast of Giglio in January 2012. Over the next few weeks, crews will attempt to completely remove the ship from the area.|
But beneath the ship may be a bigger problem that worries some biologists. Having run aground in the Tuscan Archipelago National Park, the largest marine conservation area in the Mediterranean Sea, the shipwreck has posed unique challenges to environmental managers.
The salvage team hired by the Costa Concordia cruise line has taken precautions for the sake of the local marine life. The company has allocated $400 million to minimize environmental damage. Since the beginning of the salvage project, workers have transplanted noble pen shells, removed heavy oil and diesel from the ship, put down pollutant-absorbent booms, and created "bubble walls" in the water to reduce noise pollution.
But one challenge remains: the reef's seagrass.
Feathery-looking Neptune grass blankets the seafloor around the ship. Sitting on the ocean floor for more than a year, the wreck has killed an unknown amount of seagrass; the cruise line has not disclosed the exact size of the area impacted.
The Benefits of Seagrass
Silent and often unseen, seagrass plays a crucial role in the marine ecosystem. In a 2009 study the Florida Department of Environmental Protection quantified the importance of seagrass, estimating that one acre has an approximate economic value of $20,500.
"Seagrass meadows function as a nursery for the ocean," says Nicole Paul, resident biologist and operations manager of Florida-based Seagrass Recovery, a company specializing in the restoration of seagrass in damaged areas. According to Paul, "one healthy acre of seagrass can produce ten tons of seagrass blades per year, providing food, habitat, and nursery areas" for marine life.
Recent studies, including one from 2006, have suggested that seagrass plays a vital role in combatting climate change, as well. Collectively, seagrass meadows around the world are estimated to remove approximately 10 percent of the world's annual carbon emissions.
While crews attempt to replant damaged Neptune seagrass beds, there's debate over whether the area will spring back.
The Challenges of Restoring Seagrass
Enric Sala, a marine ecologist and National Geographic resident explorer, is not optimistic about the team's chance of success. If divers successfully replant the seagrass beds, "it would be a first," he says, explaining that prior attempts have not been at such a large scale.
Indeed, an international study in 2006 on seagrass replanting efforts pointed out the complications. "Some species [of seagrass] are so difficult to transplant that restoration is not logistically or economically feasible," the researchers found.
Yet it may not be out of the question. Kevin Hovel, a biology professor at San Diego State University and a participant in numerous seagrass replanting projects, sees possibility at the Concordia site. "There is an element of chance to it," says Hovel, adding that "seagrasses are a pretty sensitive species."
Outside factors can play a role. While Hovel and his team attempted to replant seagrass in the San Diego Bay, a tropical storm decimated their work, tearing up the grass that wasn't fully rooted in the sediment. In the Mediterranean, Hovel says problems with invasive species like algae, which competes with seagrass, could complicate the effort.
The plant's delicacy is a result of its intricate root system. In parts of the ocean, the Mediterranean included, seagrass beds and their roots have been around for thousands of years. In one case, biologists from the University of Western Australia found a seagrass bed in the Mediterranean that was around 200,000 years old. These ancient root systems keep the seagrass hearty, but they pose challenges to workers during the replanting process.
Whether the seagrass in the area bounces back has implications for people on land. The way the plant stabilizes sand can reduce shoreline erosion from waves and storms. "With no seagrass to diminish the force of the currents along the bottom [of the ocean]," says Nicole Paul, "beaches, business, and homes can be subject to greater damage from storms."