Map of life expectancy at birth from Global Education Project.

Tuesday, June 14, 2005

And another damn thing to worry about . . .

People in New England are well aware, and folks elsewhere may have heard, that we are in the middle of the most severe so-called "red tide" event since we started keeping track -- which for practical purposes is only a few decades. Red tides are blooms -- i.e., population explosions -- in coastal waters of algal species which happen to be harmful in some way. These species are generally unicellular, and they don't necessarily turn the water red. They may be invisible to the eye. Hence scientists now prefer to call these events Harmful Algae Blooms, or HABS.

Our problem here at the moment is a dinoflagellate that causes a human disease called paralytic shellfish poisoning. The organism is consumed by filter feeding shellfish, and the poison it produces concentrates in their tissues. The shellfish generally aren't harmed but people who eat them can be. (Birds and whales can also be harmed by the toxin.) As a result of the current HAB, the New England coast from the Canadian border to the east side of Martha's Vineyard has been closed to shellfishing. Species that cause HABs elsewhere can be even more harmful. For example, HABs in the Gulf of Mexico kill fish and even emit toxins into the air where they cause respiratory distress in humans.

According to the Woods Hole Oceanographic Institute, HABs appear to have been growing more frequent around the world, although it is hard to sort out the effect of more knowledge and better monitoring from the actual trend. The question is to what extent human activity may be responsible. Algae blooms occur naturally, and weather is a key variable. (The Woods Hole page includes links to a lot of info including a depiction of the life cycle of the dinoflagellate.) However, where human activity increases the amount of organic nitrogen in the water, algae blooms are enhanced.

We pump in nutrients from sewage, runoff of fertilizer from farms, lawns and golf courses, and from aquaculture. Destruction of coastal wetlands also affects the amount and proportions of terrestrial nutrients that makes it into the ocean. The folks at Woods Hole don't have much to say about this. Some HABs observed in recent years are clearly not associated with pollution but with weather events or natural cycles, but others may have been caused or enhanced by pollution. We just don't know enough, although the hypothesis has very strong face validity.

For this and other very good reasons -- such as eutrophication of ponds and damage to streams -- we need to stop gratuitously spreading concentrated organic nitrogen compounds all over the place. Organic farming techniques, that use compost instead of concentrated nitrogen compounds, result in far less runoff. Spreading fertilizer on lawns is completely frivolous. I'll withold any sweeping comment on golf courses, but they can be managed in a more ecologically friendly way than they are generally.

We always need to remember that what we do in our own town and own backyard affects the whole world.

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