EUTROPHICATION: HARD TO SAY, BAD FOR LAKES

(reprinted in part from Twin City Times, April, 2000, by Tim Stewart)

Like many things in nature, lakes have a life cycle. They are born from glacial scouring, river damming and other geological phenomena. New-born lakes are clean, pristine and low in nutrients and biomass.

As lakes age, they become the final resting place for many organic and inorganic particles. Many of these particles serve as nutrients for a host of different beasts.

A lake that has been enriched with sufficient nutrients can make a home for complex and valuable food webs. Over many years, lakes become increasing loaded with nutrients and important changes take place. Sediments and organic matter slowly fill the lake basin, making it shallower. As more and more nutrients become available, flora and fauna bloom. Lake food webs become increasing complex.

This is not always a bad thing. Often, a lake that’s been enriched with nutrients can support a variety of species considered beneficial to humans. Lakes that receive enrichment from human activity often react the same way.

Cultural eutrophication (yoo-trif-I-kay-shun) is the term for a lake that has been supplied with nutrients via human activities. These activities include animal farming, sewage and fertilizer run-off. Many lakes in Maine have suffered from this. One well-known, extensively studied example is China Lake.

Sources of nutrient input is often difficult to pinpoint, but it’s usually a combination of factors that are to blame. For some species, such as trout, to survive, they would need clear, nutrient-poor lakes. Enriched lakes have chemical and biological fluctuations which they or similar species cannot tolerate.

New lakes aren’t born everyday. Accelerating the aging process of lakes creates and imbalance in the overall environment. Examples of these environmental imbalances have been seen all too often in other parts of the county.

The issue of cultural eutrophication is complex. Lakes that have been enriched are difficult to clean up because of the slow turnover rate of lake waters. The best way to improve lake water conditions is to prevent lake enrichment in the first place.