Tsunami May Have Dealt Blow to Marine Life
Jan. 5, 2005 — -- The devastation from the South Asian tsunami has been horribly apparent on land, but what about under water?
Human carnage and suffering are obviously foremost on most minds now, but researchers are just beginning to assess damage to marine life, including mangroves and coral reef communities, which are vital to fishing industries and tourism. The United Nations has assigned $1 million to fund a task force to survey environmental damage.
If past studies from other events, such as hurricanes, are any indication, experts say the impact on marine life could be vast and lasting.
"I think there is going to be significant impact," said Tom Hourigan, a coral reef expert with the National Marine Fisheries Service headquarters in Silver Spring, Md. "Even hurricanes can have an impact on marine life, and the scale of this is much greater."
Coral reef communities may have been torn up in chunks in some areas and suffocated by piles of mud and debris in others. Nurseries for young fish and turtles in mangroves and marshland may have been wiped out, possibly jeopardizing future fishing crops for decades to come.
And while most large marine animals likely escaped to deeper waters as the towering waves struck, debris such as fishing gear and sharp, rusting metal poses future risks for the animals.
"There are many different components to how the tsunami may have damaged marine life," said Rusty Brainard, a fisheries expert with the National Marine Fisheries Service in Honolulu.
Vital Coral Reefs Vulnerable
Among the most vulnerable and vital marine life affected are coral reefs. These intricate communities are made up of limestone, built by colonies of coral polyps and algae. The structures support more species per unit than any other marine environment, including endless species of fish, sea horses, sea turtles and sponges.
They are vital for local fishing communities that catch fish living around them, as well as for a tourism industry that features the reefs to attract snorkelers and divers.
The reefs were already stressed in many parts of South Asia and Thailand by warmer waters stemming from the El Niño weather event in 1998. Now researchers shudder to imagine what further damage the tsunamis have wrought.
"As the tidal waves came in, they brought a lot of force and probably broke a lot of the corals. Then as they went out again, they probably dragged a lot of debris back in and along the coral reefs," said Hourigan.
Indeed, initial reports to Marcos Noordeloos of the WorldFish Center, based in Penang, Malaysia, said some reefs off the coast of Thailand were "in bad shape," and, according to one report, "destroyed." So far, reports suggest the damage is inconsistent, said Noordeloos, with some reefs escaping damage and others showing minor and major damage.
"It will be a while -- months, at least -- before we get a picture of the damage to coral reefs," he said.
Another likely possibility is some coral reefs are now suffocating under mounds of silt, sand and other debris. Coral reef communities depend on clear water for survival and the debris-laden waters around South Asia could lead to their slow demise.
The shallow environments of mangroves and sea grass are also likely to have been damaged. Brainard explains these areas are partially enclosed bodies of water around the coastline that often host the most delicate forms of marine life, such as young fish.
"The nursery habitats for fish stocks and young fishes were probably wiped out," he said. "That could mean the next couple years could have low fish levels, which could lead to lower fish levels for the next couple decades."
Trouble Ahead for Larger Marine Animals?
Larger marine animals may have been less vulnerable to the destruction. Greg Bossart, a marine mammal expert at Harbor Branch Oceanic Institution in Fort Pierce, Fla., says if these larger marine animals were in deep waters, they likely escaped immediate trouble.
"As long as they were in deep enough waters, I would bet most dove out of the way of the tsunami," he said. "Animals are more sensitive to things like this than ourselves. They can sense pressure changes from the waves."
At least one humpback dolphin and her calf off the coast of Thailand weren't so fortunate. They were tossed into a small lagoon and remained trapped there for 10 days. Local fishermen and soldiers came to the rescue Wednesday afternoon after two previous attempts failed. Bossart says the dolphins were likely swimming in shallow waters when they were caught up by the waves, but he thinks most dolphins were likely able to dive from trouble.
There could be more threats to come, however. Brainard points out that the heaps of debris that were cast into the ocean by the tsunami now pose an ongoing risk to marine life, both large and small.
Fishing gear cast from storm-struck fishing boats can take years to deteriorate. Once underwater these nets snarl species such as dolphins and endangered leatherback turtles.
"Any air-breathing marine animal is especially vulnerable," Brainard said.
Other debris, such as buses, cars and other metal objects swept away by the tsunami, will leach into the waters and may foster green algae blooms, which thrive on iron. Such algal blooms can then crowd out other communities, including corals. Finally, any large object in coastal waters can further erode the bottom and cause further damage.
"Anything on the ocean bottom can be moved by currents and waves," said Brainard. "That can act like an underwater bulldozer."
Lynne Zeitlin Hale, director of the Nature Conservancy's Global Marine Initiative, points out that many local research facilities and researchers, themselves in Sri Lanka, Thailand and Indonesia have suffered like everyone else in the area, so this could further slow efforts to assess damage.
"Many local researchers have lost equipment and their boats. Their labs are a mess," she said. "We know there has been lots of damage. But quantifying it is going to take time."