Word: phytoplankton
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Dead zones are created when excess nitrogen and other pollutants in ocean water promote large blooms of algae and phytoplankton on the surface. The nitrogen gets there in a couple of ways: through river water filled with fertilizer from farm runoff and from air polluted with tailpipe and smokestack emissions. When the algae die and sink to the ocean floor, bacteria there break them down, while consuming pretty much all of the available oxygen in the water. The bacteria also proliferate wildly, taking over the ecosystem and exacerbating the oxygen depletion. If conditions like strong currents, which are common...
...reasons the oceans soak up so much carbon is that phytoplankton--microscopic floating plants--love it, feasting on it and taking it out of circulation. The problem is, there are vast regions where the water is iron poor and plankton languish. The amount of iron the plants need and aren't getting is tiny--less than 20 lb. per sq. mi. (3 kg per sq km) by some estimates. If this were pumped as a diluted slurry into the wake of a ship steaming back and forth like a tractor seeding a field, the plankton would bloom and global...
...turns out, is not as pristine as it looks: as it flowed to the sea over many thousands of years, it picked up mineral- rich dust that settled out of the atmosphere. As they melt, the bergs are releasing that highly nutritious dust, which feeds phytoplankton, a microscopic form of oceanic plant life on which shrimplike krill feed. The result, says Smith: "There is an accumulation of organisms around icebergs, and this goes through the food chain up to seabirds." The iceberg ecosystem could extend to seals and penguins as well, although there's no proof of that yet. With...
...only that, but most of the krill surrounding the bergs die natural deaths and float to the bottom of the sea--taking with them the globe-warming carbon dioxide pulled from the atmosphere by the phytoplankton they fed on. That CO2, once absorbed, is kept from doing any more harm. It's not enough to cancel out human-generated greenhouse gases, but it doesn't hurt. [This article contains a complex diagram. Please see hardcopy...
...changes in environmental cues--things like ice cover, temperature and salinity--are reflected in other natural events. The growth rates of algae and phytoplankton change. Salmon are migrating to western Arctic waters from the northern Pacific. There is concern that Atlantic cod will encroach in the east and compete with the smaller Arctic cod, which have thrived in frigid climates with their special proteins that prevent freezing of the blood. Meanwhile, the retracting ice makes it harder for ringed seals to find breeding grounds and for polar bears to hunt...