What Next, Galapagos?
The immediate impact of the spill has been relatively minor -- only nine animals are known to have died -- but the total damage to the unique plants and animals of the Galapagos might not be known for years. To assess the long-term repercussions, scientists will be keeping a close eye on the islands' complex ecosystem using an array of ground- and satellite-based tools.
Above: The listing hull of the tanker Jessica, which ran aground near San Cristóbal in the Galapagos Islands (), dumping nearly all of its 240,000 gallons of petroleum products into the sea. The streak of petroleum can be seen trailing off to the left in this picture. Photo by Heidi Snell, Charles Darwin Research Station (CDRS).
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"The birds and mammals are the most visible, but they only constitute a small fraction of the ecological system," said Wayne Landis, director of the Institute of Environmental Toxicology and Chemistry at Western Washington University.
"The (chemicals) that are toxic to birds and mammals are also toxic to the invertebrates and algae and other things that are in aquatic systems. So a lot of the damage isn't readily observed in these kinds of spills," Landis said.
Aquatic bugs and algae may not be as noticeable, but because they provide food for larger organisms, impacts on these inconspicuous creatures will ripple through the rest of the ecosystem over time.
Phytoplankton, along with other photosynthetic organisms like aquatic plants, occupy "square one" in the ecosystem's food chain. Because life in the Galapagos depends so heavily on the islands' smallest life-forms, monitoring the health of marine bugs and plankton will be necessary for understanding the full impact of the spill.
A combination of data from NASA's SeaWiFS (Sea-viewing Wide Field-of-view Sensor) satellite and direct measurements at spots around the islands will give scientists a good idea of how these tiny critters respond to the spill.
SeaWiFS can measure phytoplankton levels in the entire Galapagos ecosystem. The satellite's sensors, which have a resolution of about 1 square kilometer, don't count microbes individually. Instead, they measure the color of the water, which varies with the concentration of chlorophyll and other plant pigments. Water with more phytoplankton simply looks greener than water in plankton-poor regions. [more information]
A primary goal of SeaWiFs is to monitor worldwide populations of aquatic microbes. They might be small individually, but taken together the diminutive life forms play an important role in the global carbon cycle. NASA scientists are using SeaWiFS data to discover how marine plankton numbers vary throughout the year.
Above: The streak of diesel and bunker fuel extending from the shipwreck -- which occurred, ironically, near Shipwreck Bay -- is visible in this image taken on Jan. 21 by NASA's SeaWiFS satellite -- just five days after the spill occurred. The streak extends north from the western point of the island shown in the magnified view. The fuel has since drifted as far west as Isabela Island, which is the large L-shaped island on the left. [click the picture to see aof the Galapagos that points out the location of the spill]
In the Galapagos, scientists expect populations of microbes and other invertebrates to recover in the short term. Their rapid life cycles will compensate for any immediate mortality triggered by the spill. But scientists also want to monitor long-term patterns.
Because of the high degree of interdependence between species in an ecosystem, the timing of the recovery of the various species after an incident such as this spill can influence the long-term health of the system.
Left: Petroleum washed up onto a beach in the Galapagos. While some beaches have been afflicted by the spill, the extent of the damage is far less than the 1989 Exxon Valdez oil spill, which coated thousands of miles of coastline. Photo by Heidi Snell, CDRS.
Landis offered the example of a rock that was affected by the Exxon Valdez oil spill in Prince William Sound in 1989. The rock was cleaned bare by recovery crews. Soon after, the native Fucus gardneri (commonly known as "rockweed") recolonized the rock, and everything appeared to be fine. But when scientists checked the rock four years later, it was bare once again.
"The rock was bare not because of the chemical reappearing, but because the organisms had all colonized the rock at the same time, so they all got old and died at the same time," Landis said.
In places where habitat has been destroyed, the timing of recolonization can be particularly tricky.
"There's a whole sequence that ecologists call 'succession' which has to happen," said Mary Wilcox Silver, an ocean scientist at the University of California at Santa Cruz. "Succession" refers to the order and timing with which species must reestablish themselves for a stable ecosystem to develop.
While the short-term survival of more visible animals like birds and sea lions won't guarantee the integrity of the ecosystem as a whole, minimizing the damage to these populations is nevertheless a major concern.
"They both have low populations, and they could be easily wiped out should something like an oil spill occur in their main habitat," Wellington said. The two bird species are "endemic" to the Galapagos; i.e., they are found nowhere else.
Above: The Galapagos Penguin is the only penguin to breed entirely within the tropics and is the only one to be found in the Northern Hemisphere. These two penguins are not coated in bunker fuel -- their coats are naturally black. Image courtesy of the CDRS.
But while few of the birds have been found coated in oil, they may yet suffer some consequences from the spill if the base of their food chain --marine microbes-- is at peril. A systematic assessment of the short-term impact will take about three months, according to the Charles Darwin Foundation, while monitoring for long-term effects is likely to continue for two to three years.
Charles Darwin Foundation Web site -- detailed information about the fuel spill and the Galapagos Islands in general
Oil Pollution -- general information about oceanic oil pollution from the SeaWiFS Web site
More about phytoplankton -- from the SeaWiFS Web site
NASA's SeaWiFS project -- home page
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