Monday, October 03, 2011

Nitrogen pollution disrupts Pacific Ocean

Surging nitrates in Asian waters could dramatically affect marine wildlife. So says science journal Nature in a news piece explaining why we should care about human-caused increases in ocean nitrate levels.

Waste from agriculture and burning of fossil fuels are the suspected cause. This is bad news, and could lead to increasing ocean "dead zones" where oxygen is depleted and many of our favorite ocean animals flee or die.

I always wonder about the demand-side effect on nitrogen that might occur in changed ocean ecosystems based on my experience with rivers. In some streams with healthy ecosystems, increased nitrogen causes increased growth of animals like fish. This happens in a "tightly coupled" ecosystem where fertilizer efficiently moves through plants to herbivores to predators. So the demand side of the system sucks up increased nitrogen supplies.

This effect is so pronounced that it's exploited by people in some places by fertilizing streams with nitrogen to increase the growth of desirable fish.

In our oceans, how much of the excess nitrogen would get cycled into fish biomass if the ecosystems were healthy? Is there a demand-side effect that we neglect to include in our analyses? Does anyone out there know the answer? I've seen tidbits of research that suggest it matters, but never a clear and precise study.

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