Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study shows eutrophic lakes may not recover for a millennium

14.06.2005


Although it has taken just 60 years for humans to put many freshwater lakes on the eutrophication fast track, a new study shows their recovery may take a thousand years under the best of circumstances.



Writing in today’s (June 13) online edition of the Proceedings of the National Academy of Sciences (PNAS), University of Wisconsin-Madison limnologist Stephen R. Carpenter reported results of a study that showed that the buildup of phosphorus in soils in lake watersheds is likely to be the source of serious chronic environmental problems for hundreds of years.

"If these results are correct, and I suspect that they are, things could get considerably worse," says Carpenter, a UW-Madison professor of zoology and one of the world’s leading authorities on freshwater lakes. "The buildup of phosphorus in watersheds is very threatening. Sooner or later it is going to hit the lakes and it is going to pose problems."


Eutrophication occurs when nutrient-rich soil washes into lakes and streams. It stimulates the growth of algae and has transformed many of the world’s lakes from clear freshwater reservoirs to soupy, weed-choked pools. It contributes to oxygen depletion, which leads to fish kills, and can stimulate the growth of toxic algae.

According to the study, industrial agriculture, with its reliance on phosphorus-rich fertilizers, is the primary source of much of the excess nutrients responsible for fouling lakes. In rich farming areas, like southern Wisconsin, the routine application of chemical fertilizers and phosphorus-laden manure, has resulted in the gradual accumulation of phosphorus in the soil, which, ultimately, has nowhere to go but into the streams, lakes and rivers of the watershed where it is applied. "There’s a huge amount of phosphorus in the watershed that hasn’t washed into the lake yet," says Carpenter, meaning the problem is likely to persist for centuries.

The new study models phosphorus loading into Lake Mendota, an urban lake in Madison, Wis., that still has nearly 80 percent of its watershed in the rich, dark soils of Wisconsin farm country. It ranks as one of the most studied lakes in the world, and in recent decades has experienced a steady decline in water quality due to accelerated runoff and the resulting eutrophication.

But the lake is similar in most respects to lakes anywhere in the world, Carpenter says, and the results of the new study are generally applicable to lakes anywhere.

"The global pattern is the same," he says. "We are releasing far more phosphorus to the soil than would be released by weathering." Restoring water quality is unlikely unless soil erosion is greatly reduced, phosphorus inputs are checked, and new technologies are developed for reducing phosphorus content of over-enriched soils, the report says.

"This type of eutrophication is not reversible unless there are substantial changes in soil management," Carpenter writes in PNAS. The amount of phosphorus that runs into the lake in any given year is small, the Wisconsin scientist notes, but a little bit of the nutrient is all that is needed to send aquatic ecosystems into overdrive.

Carpenter’s model also shows that, unchecked, phosphorus pollution could put Lake Mendota on a fast track to extreme degradation. "There is a potential shift to an extremely degraded state that could occur even if we shut off the phosphorus tomorrow. It would have water quality as bad as the worst lakes in the world."

Lakes that are that highly eutrophic, Carpenter notes, have a higher incidence of toxic algae blooms, which would make the lake unfit for swimming or exposure to domestic animals and pets.

"And the odor cannot be underestimated. Lake Mendota has a certain smell about it on some summer days now," Carpenter explains, "but we’re going to smell a lot more of that."

Steps that can be taken immediately, Carpenter says, include eliminating the importation of chemical phosphorus to watersheds and limiting feed for cattle and other farm animals to feed that is grown in the watershed. At present, a significant amount of feed for farm animals is imported into the Lake Mendota watershed.

Last year, the City of Madison implemented a ban on chemical phosphorus for lawn products, but farmers still apply phosphorus fertilizers, even when soils have a reservoir of the nutrient.

The biggest help, Carpenter says, would come from reducing soil erosion rates. However, developing larger buffers around lakes and streams, restoring wetlands and encouraging the use of new manure storage and handling processes are also steps that can be taken to reduce phosphorus runoff.

"Anything we can do to reduce the erosion of phosphorus is going to be beneficial," Carpenter says.

Stephen R. Carpenter | EurekAlert!
Further information:
http://www.wisc.edu

More articles from Studies and Analyses:

nachricht Win-win strategies for climate and food security
02.10.2017 | International Institute for Applied Systems Analysis (IIASA)

nachricht The personality factor: How to foster the sharing of research data
06.09.2017 | ZBW – Leibniz-Informationszentrum Wirtschaft

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Salmonella as a tumour medication

HZI researchers developed a bacterial strain that can be used in cancer therapy

Salmonellae are dangerous pathogens that enter the body via contaminated food and can cause severe infections. But these bacteria are also known to target...

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

3rd Symposium on Driving Simulation

23.10.2017 | Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

 
Latest News

Microfluidics probe 'cholesterol' of the oil industry

23.10.2017 | Life Sciences

Gamma rays will reach beyond the limits of light

23.10.2017 | Physics and Astronomy

The end of pneumonia? New vaccine offers hope

23.10.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>