Here is data for three large ecological disturbances impacting Alaskan waters during the sea otter population decline under investigation. Alaskan officials were unsure whether these events, if any, could be responsible. One of the events is a naturally recurring disturbance, while the other two disturbances are directly caused by humans.
| Natural | Human initiated |
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(cartoon courtesy of Center for Ocean-Atmospheric Predictions Studies)
El Nino is a disruption of the ocean-atmosphere system in the tropical Pacific such that coastal upwelling off the South American coast decreases or stops. While Alaska is many thousands of miles north of South America, El Nino events have ecological impacts worldwide. Within the last 20 years, two of the most severe El Nino events ever recorded occured (1982-83 and 1997-98).
During the 1997-98 El Nino, sea level along the Alaskan coast rose up to 30 cm above normal, and sea surface temperature rose above normal. While data for the 1982-83 El Nino is not as comprehensive, its impact on Alaskan coastal water may be similar.
(www.pmel.noaa.gov/tsunami/Sea_level_1997_98/sea_level_1997_98.html; www.coaps.fsu.edu/lib/climatoons)
Commercial fishing is a large and growing industry in Alaska. In 2002, this industry harvested 5 billion pounds of fish and shellfish, which generated over $900 million. Target species include salmon, herring, halibut, abalone, and sea urchin. Improved technology result in the potential for larger catches. However, there is also increased potential for overfishing because the fishermen are not leaving enough animals in the water to replenish wild stock for next season.
Go to Pacific Northwest Industry for more information.
- How could the fishing industry impact sea otters?
- How can the one-time event of the oil spill have such prolonged affects on the sea otters?
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Approximately 1,000 sea otters were killed as a result of this oil spill. Most of the casualties were along the path of the spill. While clean-up crews worked to remove and recover the oil, they were only able to recover 14% of the 11 million gallons. Scientists speculate that the remaining oil either evaporated, sunk to the bottom of the ocean, dispersed into the water column, or soaked into subsurface caverns and crevices. Due to the dispersing of the oil, the adverse effects from this spill on the remaining sea otter populations was difficult to assess. There is evidence to suggest that the sea otter population within Prince Willliam Sound is recovering. However, regions where the spill was heaviest show no sign of recovery. Meanwhile, the effects and status of sea otters outside of the spill zone is unknown. www.oilspill.state.ak.us/facts/spillmap.html |
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This web site was created by Lynn Tran at the North Carolina State University, Department of Mathematics, Science, and Technology Education on 7/12/03. Faculty advisor Dr. David Eggleston, NCSU, Department of Marine, Earth, & Atmospheric Sciences. Last updated December 29, 2003 .