Warming and Wildlife » Pacific Marine Life At Risk

At Risk: Pacific Marine Life

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America's Pacific coast is known for its beauty, surf, free-spirit culture and above all, its amazing wildlife. From orcas to sea lions, salmon to seabirds, grey whales to sea otters, the West Coast is a natural playground treasured by residents and visitors alike.

But global warming is casting a shadow over this seascape, threatening much of what makes the Pacific coast special.

Changes in wind patterns that stir ocean currents and increasing sea surface temperatures appear to be wreaking havoc on the Pacific marine food web. It's a complicated, shifting story of life and death on the seas that marine biologists are just beginning to sort out.

Seabird die-offs, a growing low-oxygen dead zone off the coast of the Pacific Northwest, and a plummeting Chinook salmon fishery in California are a few of the most notable events now partially attributed to global warming.

Dead Zone

In 2002, scientists discovered that a sea bottom off of the Oregon coast which had once been brimming with life was now covered with rotting carcasses of crabs, sea stars and sea worms. Most fish had either fled or died. The pattern continued to repeat itself for several years, and a major report on the phenomenon was released in 2006.

The cause: extraordinarily low oxygen levels, the lowest ever recorded. For the first time, shallow parts of the ocean off the Pacific Northwest coast had zero oxygen in the water.

Strong winds had produced unusually intense upwelling in the California Current, bringing a heavy load of nutrients to the surface. This led to blooming algae that died and rotted, then was consumed by bacteria that depleted oxygen from the water.

What's worse? The low-oxygen zone appears to be spreading north and south driven by the close relationship between ocean currents and wind patterns that can be altered by climate warming.

California Chinook Salmon Fishery Closed

Commercial and recreational fisheries for the Chinook salmon in California are closed for the second year in a row due to a collapse in the Sacramento River fall run.

Scientists investigating the recent crash have attributed it to a combination of recent poor ocean conditions on top of long-term degradation of estuarine and freshwater river habitats and reliance on hatchery production, resulting in genetic homogeneity.

The problem seems to have originated with 2004 and 2005 broods that entered the ocean during periods of weak upwelling, warm sea surface temperatures, and low prey density.

Climate indices related to salmon survival have shown much greater fluctuations over the past several decades. Populations in poor physical condition with low genetic diversity are much less resilient to climate variation in the oceans.

As Go Krill…

The small, shrimplike krill may not look like much. But it is an essential strand in the marine food web – most marine species, from fish to whales to sea birds, either consume krill or its predators.

Scientists have described the relationship between krill populations and the dance between sea surface temperature and the upwelling of cooler, more nutrient rich ocean water to the surface. Warmer oceans and less upwelling can lead to less and smaller krill, which results in less food for a variety of marine species.

That appears to explain what happened in the spring of 2005 off the coast of San Francisco. Higher sea surface temperatures and less upwelling reduced krill abundance.

This had a dramatic impact on local seabird populations, and 40,000 Cassin's Auklets abandoned breeding colonies on Southeast Farallon Island, off the California coast. Hundreds of thousands of auklet chicks starved to death that same year at Triangle Island, British Columbia.