Unexpectedly rapid increases in the acidity of the Arctic Ocean, affecting the Arctic food chain, reported Sunday are part of a larger problem of acidification in the most fertile regions in the global oceans. Carbon dioxide emissions from fossil fuel burning have raised atmospheric CO2 levels, increasing the acidity of the oceans because CO2 reacts with water to form carbonic acid. Approximately 1/3 of all CO2 emissions to date have been taken up by the oceans, raising the acidity of the water. Because cold water takes up more CO2 than warm water, cold nutrient rich polar regions and tropical and temperate upwelling regions that support most of the ocean's biological activity are acidifying fastest. Cold, acidic waters, will dissolve the shells of sensitive marine organisms, breaking the food chain, in the most fertile, oxygen generating, areas of the oceans.
The sea butterfly Limacina helicina, at the bottom of polar food chains, is very sensitive to acidity.
Many marine shells are made up of a metastable form of calcium carbonate, aragonite, that forms and dissolves quickly. Many of these organisms have evolved in very chemically stable, slightly alkaline marine waters around pH 8.1. Because the activity of the carbonate ion in solution drops very rapidly with increasing acidity above pH 8.1, organisms with aragonite shells that don't control acidity internally cannot survive in acidic water. The sea butterfly's shell formation speed slows dramatically at pH7.78 pdf
The sea butterfly is food for a wide range of fish, birds and marine mammals in the polar regions.
The "shelled pteropod" species produce a calcium carbonate shell; the only shelled pteropod in Arctic waters is Limacina helicina, a species that can occur in high densities in both Arctic and Southern Ocean. Limacina helicina is also an important component of marine food webs.
For example in the Southern Ocean it is frequently very abundant (up to 2681 indm−3) and is a major dietary component for zooplankton and higher predators such as herring, salmon, whale and birds (Hunt et al., 2008; Karnovsky et al., 2008).
Shelled pteropods may also play a geochemical role in the oceans, as significant contributors to the export of carbonate (order 10% of the global CaCO3 flux, Berner and Honjo, 1981) and carbon to the deep ocean (Collier et al., 2000).
The naturally high dissolved CO2 levels in the polar regions, which are the most biologically productive regions in the oceans, make the Arctic Ocean and the Southern Ocean more susceptible to the effects of ocean acidification than the temperate and tropical seas and areas of the oceans. However, ocean circulation brings cold polar waters upward in certain areas, making them sensitive to acidification too.
The uptake of C02 by photosynthesis to from organic carbon chains and in calcium carbonate shells has maintained stable levels of upper ocean acidity for the past 500 million years, excepting periods of mass extinctions, when the chemistry was acidified by rapid increases in atmospheric CO2 levels.
However, the deeper ocean below a certain depth dissolves calcium carbonate for 2 primary reasons. The acidity of the deep ocean is increased by the oxidation to CO2 of organic matter that rains down form the near surface. Increasing pressure also promotes the dissolution of calcium carbonate shells. An oxygen minimum zone forms where most of the organic matter is oxidized. Deep water is more acidic and contains less oxygen than the surface ocean.
The most biologically productive marine areas in the temperate zones and tropics are areas of deep water upwelling. This water is richer in nutrients but more acidic and lower in oxygen than in less productive waters. The Pacific Ocean, which is on the upwelling end of the thermohaline circulation (the great ocean conveyor of salt and heat that begins with downwelling near Greenland in the north Atlantic ocean) is therefore more affected by acidification than the Atlantic and Indian oceans. Tropical coral reefs in the Pacific near Panama are small and tend to fall apart because the water is upwelled and acidic.
Even the Great Barrier reef is suffering. Growth has slowed to record low rates.
Coral growth in Australia's Great Barrier Reef has slowed to its most sluggish rate in the past 400 years.
By J. Freund FishOutofWater
The decline endangers the species the reef supports, say researchers from the Australian Institute of Marine Science.
They studied massive porites corals, which are several hundred years old, and found that calcification has declined by 13.3% since 1990.
Global warming and the increasing acidity of seawater are to blame, they write in Science journal.
By burning, in a few hundred years, fossil fuel carbon that took nature hundreds of millions of years to sequesterwe are recreating a natural disaster, Dr. Ken Caldeira told Congress.
Ken Caldeira's testimony to the House of Representatives.
Twenty years ago, I was studying what happened to ocean chemistry when the dinosaurs became extinct, over 60 million years ago.
When the meteorite hit that killed off the dinosaurs, gases were released that made the oceans acidic. Coral reefs disappeared, along with many other organisms that make their shells or skeletons out of calcium carbonate. It took a few tens of thousands of years for ocean chemistry to recover, but it took coral reefs about two million years to become common once again.
Unfortunately, unless we reduce carbon dioxide emissions, it looks like our effect on the oceans will be similar to the effect of the meteorite that wiped out the dinosaurs, except we are taking a few decades to do what the meteorite did in an afternoon.
Off of the west coast where acidic cold water upwells the volume of acidic oxygen depleted water is growing rapidly with bizarre effects.
Humboldt, or jumbo squid (Dosidicus gigas) have indeed made their return to California waters, and in a big way. They are now being caught on party boats from San Diego to Fort Bragg. Special evening trips that specifically target the squid are catching behemoths ranging from 12 to 40 lbs.
Good numbers of Humboldt squid have been showing up off the California coast in recent years. Although there are no bag limits at this time, anglers should be conservation-minded and take only what they can comfortably use. One large jumbo squid can easily feed an entire family for quite a long time.
By California DFG FishOutofWater
As far as what impact the Humboldt squid may be having on other game fish populations, the jury is still out. The squid's major prey items include lantern fishes; however, lantern fishes are prey to a lot of other game fishes, so it may be more of a competition aspect rather than strictly a predator-prey aspect. Humboldt squid are more efficient predators in low oxygen environments than fish predators and can out-compete these species. However, they also feed on a wide range of species from northern anchovy, Pacific sardine, Pacific mackerel, juvenile rockfishes, and squid species (including themselves, hence their reputation) so there is great potential to directly affect game fish populations.
According to Senior Marine Biologist and DFG squid expert Dale Sweetnam, "Researchers have been observing the expansion and shallowing of oxygen minimum zones off the West Coast in recent years. It is that environment that Dosidicus flourishes in and is probably the reason that they are still out and about and in no hurry to leave."
Expanding low oxygen zones make are a danger to marine life and ultimately all animals that respire oxygen. Schemes to fight global warming and ocean acidification by fertilizing the ocean would make low oxygen zones grow faster. Similarly, efforts to engineer solutions to global warming will not solve the ocean acidification problem.
Dr. Ken Caldeira presented this figure to Congress that showed why we need to reduce CO2 to 350 ppm. Present levels of CO2 are already causing enough acidity to damage corals in the Galapagos islands, endangering the whole unique ecosystem that Darwin discovered.
Orange & Red zones are deadly to coral & acid sensitive life.
By Ken Caldeira to Congress FishOutofWater
The figure shows that if we allow CO2 levels to reach 450PPM as planned (not 350) Galapagos corals will be in the red zone. If that happens the Galapagos ecosystem will likely be irreversibly damaged. Damage in the Galapagos Islands is already being observed at 380PPM.
Some 175 years after the wildlife of the Galapagos helped inspire Charles Darwin to develop his theory of evolution, scientists are measuring the impact of global warming on the rich but fragile biodiversity of the islands. The volcanic archipelago, about 600 miles west of the Ecuadorean coast, is home to scores of endemic species that closely depend on one another for survival.
Scientists say abrupt and frequent changes in sea temperatures and the death of coral reefs near the islands show that global warming is taking its toll on local sea life.
"The coral reefs create a habitat; they are like a forest, like the Amazon. They are home to scores of species. ... If the corals die we lose thousands of species that are associated to the coral," said German marine biologist Judith Denkinger.The Galapagos-based scientist said the harm that pollution and climate change are causing marine life could trigger a domino effect and hurt on-shore species as well.
"Everything is intertwined. You can't say this is land, this is sea, they are both one," Denkinger said, sitting on a rock by the sea and surrounded by growling sea lions.
Everything is intertwined. We must save our seas and all the creatures that depend on us. 350.
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