Ecoregions

Gulf of Alaska large marine ecosystem

September 2, 2011, 2:53 pm
Source: NOAA
caption Location of the Gulf of Alaska Large Marine Ecosystem. (Source: NOAA)

The Gulf of Alaska Large Marine Ecosystem (LME) lies off the southern coast of Alaska and the western coast of Canada. It is separated from the East Bering Sea Large Marine Ecosystem by the Alaska Peninsula. Its climate is sub-Arctic. The gelid Subarctic Current, as it bifurcates towards the south, serves as the boundary between the Gulf of Alaska and the California Current LME. For a further description of the Gulf of Alaska’s major currents, see a National Oceanic and Atmospheric Administration (NOAA) report on the major currents of the North Pacific Ocean. The Gulf of Alaska Large Marine Ecosystem is sensitive to climate variations on time scales ranging from the interannual to the interdecadal. This Large Marine Ecosystem is treated in detail by Brodeur et al., 1999. That article contains a map of large-scale near-surface circulation in the North Pacific Ocean.

Productivity 

caption Source: NOAA

The climate of the North Pacific is known to change sharply over periods of decades, centuries and millennia, in concert with climatic processes in other parts of the world, such as in the North Atlantic. This has an effect on plankton biomass production and plankton species composition. The Gulf of Alaska Large Marine Ecosystem is a Class I, highly productive (more than 300 grams of carbon per square meter per year) ecosystem based on SeaWiFS global primary productivity estimates. It presents a significant upwelling phenomenon linked to the presence of the counterclockwise gyre of the Alaska Current National Oceanic and Atmospheric Administration, 2002); this gyre is known as the Alaska Gyre. The Large Marine Ecosystem’s cold, nutrient-rich waters support a diverse ecosystem. Large-scale atmospheric and oceanographic conditions affect the productivity of this Large Marine Ecosystem. There is speculation about what causes changes in the eastern bifurcation of the Subarctic Current into the Alaska Current, and the possible effects of these changes on biological production in this LME. Changes in zooplankton biomass have been observed in both the Gulf of Alaska Large Marine Ecosystem and the California Current Large Marine Ecosystem directly to the South. These biomass changes appear to be inversely related to each other (Brodeur et al., 1999). A well-documented climatic regime shift occurring in the late 1970s caused the Alaska gyre to be centered more to the east (Lagerloef, 1995). Brodeur and his co-authors hypothesize changes in the future production of salmons as a consequence of long-term shifts in the plankton biomass in the last decades. More information is available on climate variability and climate change and its effect on the abundance and production of marine organisms.

Fish and Fisheries 

caption Chart: Gulf of Alaska Large Marine Ecosystem. (Source: NOAA)

The statistics of many agencies tend to apply to all of Alaska, which makes a specific statistical breakdown for the Gulf of Alaska Large Marine Ecosystem difficult to obtain. Catch composition in this LME is characterized by a strong prevalence of the freshwater and diadromous group, and rich salmon fishery. The Gulf of Alaska LME supports a diverse ecosystem that includes several commercially important fisheries such as crab, shrimp, pollock, Pacific cod, mackerel, sockeye salmon, pink salmon and halibut. See FAO 2003, figure 15, for catch percentages in FAO’s 12 species groupings from 1990 to 1999. The catch trends for those ten years are rather stable. Production was 650,000 metric tons in 1990 and was about the same in 1999. For data on king crab landings, tanner crab, and shrimp landings in this LME. (Our Living Oceans, 1999) For an article about the walleye pollock in the Gulf of Alaska. (Duffy Anderson et al., 2002)

For more information on the production dynamics of Alaska salmon in relation to oscillating periods of “warm” and “cool” regimes. (Francis, 1993; Francis and Hare, 1994; Hare and Francis, 1995). There is fishing on an industrial scale in the Gulf of Alaska. The trawlers in this LME are also harvesting untargeted species, some of which are not recovering. NOAA Fisheries in Alaska has more information about trawl surveys conducted through 2002. For detailed fish catch statistics for this LME, see data collected by the University of British Columbia Fisheries Center . FAO also has compiled statistics for the last decade. Click on the figure below for more details. A recent summary of the Gulf of Alaska Groundfish Fishery Management Plan is available. For more information on NOAA's effort to ensure sustainable fish harvests, see Alaska Fisheries Science Center web site . For more information on fisheries, catch statistics, regulations and restricted fishing areas, see the National Marine Fisheries Service’s Alaska Regional Office .

Pollution and Ecosystem Health 

caption Source: NOAA

For information on the coastal condition for all of Alaska. (EPA, 2001). For statistics on harbor seals and harbor porpoises in this LME, see Our Living Oceans, 1999. Pollution problems affecting the Gulf of Alaska LME include predation by invasive species, discharges of oil products, and industrial and agricultural contaminants that enter the LME through a variety of pathways (ocean currents, prevailing winds). Prince William Sound is routinely crossed by large oil tankers. In 1989 the Exxon Valdez, off of the Port of Valdez, the terminus of the Trans-Alaskan Pipeline, spilled 11 million gallons of North Slope crude oil. This was the largest tanker oil spill in US history and it contaminated 1500 miles of the Gulf of Alaska’s coastline. More than 10 years later there are concerns on the lingering effects of the oil spill and the pockets of residual oil in the environment, especially in the Western portion of Prince William Sound. The effects of the oil spill interact with the effects of other kinds of changes and perturbations in the marine ecosystem. More common than spills, however, are smaller discharges of refined oil products, crude oil and hazardous substances. The Gulf Ecosystem Monitoring Program has more information about pollution issues.

Socioeconomics

Several native communities rely for their subsistence on the harvesting of marine resources (fish, shellfish, marine mammals, birds). The economy of the coastal communities is based on commercial fishing of pink and red salmon, fish processing, timber, minerals, agriculture and tourism. Shellfish fisheries developed in the 1960s in the Gulf of Alaska (Our Living Oceans, 1999). Conflicts have emerged between coastal and offshore interests. In 1998, there was an increase of visitors to over 1 million a year. The livelihood of 70,000 full-time residents living in the area was directly affected by the Exxon Valdez oil spill. They had to overcome the effects of the oil-related fish mortalities. Others using the area seasonally for work or recreation were also affected.

Governance

Both the USA and Canada border the Gulf of Alaska Large Marine Ecosystem, which means that there are separate databases of information about government action and management plans. Public perception of the condition of the coastal waters and public health in this LME might differ. Moreover, statistics of many USA agencies tend to apply to all of Alaska. The North Pacific Fishery Management Council, in conjunction with NOAA has produced a Gulf of Alaska Groundfish Fishery Management Plan . The transboundary management of Pacific salmon (sockeye, chum, pink, chinook, coho, and steelhead salmon) has created a problem between the USA and Canada. The Pacific Salmon Treaty (1985) was meant to facilitate the management of these salmon stocks by preventing overfishing and providing for optimum production, but there have been disagreements concerning the equitable sharing of the salmon catch. Quotas are difficult to establish, given the fluctuations of salmon from one year to the next.

Further Reading

 

Disclaimer: This article contains information that was originally published by the National Oceanic and Atmospheric Administration (NOAA). Topic editors and authors for the Encyclopedia of Earth have edited its content and added new information. The use of information from the National Oceanic and Atmospheric Administration (NOAA) should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

 

 

 

Glossary

Citation

(2011). Gulf of Alaska large marine ecosystem. Retrieved from http://www.eoearth.org/view/article/153189

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