the environment is harsh

1. Humans irrigate to help improve agricultural productivity. Sounds like a good idea.
2. Irrigation is coordinated with the seasons, so those on the California coast irrigate approximately in unison.
3. Irrigation water runs to the ocean, bringing with it salts from the fertilized land.
4. Along the coasts, surface salinity rises to unprecedented levels.
5. Diatoms (aka algae, plant plankton) are drawn to the salty surface water.
6. Diatoms of genus Pseudo-nitzschia reproduce and release domoic acid.
7. Domoic acid concentrates in the fatty tissue of plankton feeders like shellfish.
8. Seals and sea lions eat lots of shellfish.
9. Domoic acid activates certain receptors in the brain causing excess calcium to build up in neurons.
10. Neurons degenerate.
11. Seals and sea lions become lethargic, have seizures and die.  According to the NY Times, "domoic acid poisoning has killed hundreds of the animals across Southern California this spring and thousands since a major outbreak in 2002."

This sucks. It isn't like we released some deadly poison into the sea and we could have known this would happen.  This required changes in salinity, a species of algae, and a deadly neurotoxin.  It is impossible to predict the third order effects of human uses of the environment.  So, we are stuck reacting to environmental damage.  We are stuck undoing the investments we made in whatever is causing the environmental damage.  At best, we can proactively manage the risks we know.  But there are always the unknown unknowns.

The Marine Mammal Center figured this stuff out.  In response, they started treating affected animals.  This includes "control of seizures using agents such as phenobarbital, diazepam, and lorazepam."  That isn't going to make much of a difference.  The most they can help directly is a few dozen animals at a time. It is going to take a big change to fix this problem.  Or maybe the causation is wrong and this wasn't about irrigation run-off at all.  Here's hoping.

Sources:

• "Agricultural runoff fuels large phytoplankton bloom in vulnerable areas of the ocean" (Nature, March 10, 2005) (PDF here).
• "Ocean Animal Emergency" Nova (broadcast Nov. 25, 2008)
• "Domoic Acid", Wikipedia