The climate-change-induced temperature rise in the North Pacific Ocean has impacted flora and fauna from the tiniest phytoplankton to the largest whales. Since pre-industrial times, the oceans’ water temperature from the tropics to the poles has increased by 0.7°C. Scientists predict the water temperature will increase another 1.4°C to 5.8°C by the end of the century.
Melting sea ice and retreating glaciers offer the most visual evidence of these temperature changes, but our warming oceans’ impacts are many and varied. Most changes are subtle and occur slowly over time, but others explode into a mass mortality incident produced by something as seemingly innocent as a bloom of algae.
During the summer of 2015, warm weather across the North Pacific and West Coast of North America produced sea temperatures much higher than average. This warm water spawned massive algal blooms. While much of the algae was harmless, certain phytoplankton species in the bloom produced dangerous neurotoxins. Since plankton forms the base of the ocean’s food chain, this bloom negatively impacted marine life and fisheries from California to Alaska. Biologists identified nine dead fin whales near Kodiak Island in June and believed toxic algae caused their deaths.
During 2015, researchers noted extremely high levels of the algal toxin domoic acid, leading to closures of recreational razor clam harvests in Oregon and Washington. Fisheries managers also closed a large portion of the Washington state Dungeness crab fishery and some of the sardine and anchovy fisheries in California. Biologists measured the highest domoic acid levels ever recorded in Monterrey Bay, California, in May 2015.
Toxic algal blooms directly impact marine organisms, but ocean warming has also created many subtle changes to the biodiversity and population structures of organisms in the oceans, especially in the once ice-dominated areas of the northern Bering, Beaufort, and Chukchi Seas. Warming ocean waters have significantly affected gray whales in recent years. Increasing seawater temperatures in the Bering Sea have reduced winter ice cover in the region, which has led to a reduction in productivity. Primary productivity in the northern Bering Sea declined by 70 percent from 1988 to 2004. This previously ice-dominated, shallow ecosystem favoring large communities of benthic amphipods, the favorite food of gray whales, has been replaced by an ecosystem dominated by pelagic fish (i.e., those that dwell neither on the bottom nor on the surface). Gray whales have responded by migrating farther north, but biologists cannot predict what will happen if amphipod communities disappear from this region.
During the summer of 2018, the waters in the Bering Sea soared nine degrees Fahrenheit (5°C) warmer than average. Gray whales responded by migrating farther north to the Chukchi Sea. Still, amphipods might now be disappearing from this region as well, forcing gray whales to consume less nutritious krill, and krill might not contain the amount of fatty acids the whales need to build adequate blubber. By the spring of 2019, numerous reports noting gray whale carcasses washed up on beaches from Mexico to Canada were alarming whale biologists. By the end of that year, 214 dead gray whales had been sighted. Of these, 122 carcasses had landed on US beaches, 11 on the shores of Canada, and 81 on Mexico’s beaches. In the United States, 48 whales died in Alaska. Since most whales sink to the ocean floor when they die, the recovered carcasses probably represented only a fraction of the number of gray whales that died in 2019. Most of the whales died on their northward migration after a winter of fasting.
The warming ocean impacts the animals living in the sea and birds and animal that depends on the ocean for their food supply or any part of their life cycle. In Prince William Sound, surveys suggest the horned puffin population in that area declined 79% from 1972 to 1998. Biologists believe this decline in numbers is due to significant changes in the food base due to global warming. In the fall of 2016, hundreds of tufted puffins starved to death in the Pribilof Islands. Like the earlier deaths of horned puffins in Prince William Sound, researchers blamed their deaths on a shortage of food linked to higher-than-normal ocean temperatures in the Bering Sea.
In my recent posts on sharks, I noted that sharks have become more common in the North Pacific in the past decade. Pacific cod populations have crashed in recent years, and the numbers of halibut, pollock, crab, and salmon also seem to be on the decline. As the North Pacific warms, will other types of fish and invertebrates move in to fill the void left by the once-dominant species, or will the ocean become a toxic cesspool, lacking any life?
Robin Barefield is the author of four Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter, and Karluk Bones. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska, and listen to her podcast, Murder
