HANOVER, N.H. -- Unintentional fertilization of lakes by humans might be creating additional challenges for lake managers fighting to control increased algae, according to a new study by researchers at Dartmouth College, York University and the University of Regina.
The study, published in the July issue of the journal Ecology Letters, examines the effects of fertilization on lake algae. Water too rich with nutrients such as phosphorus and nitrogen will breed excessive algae, which in turn consume dissolved oxygen in the water. This can lead to oxygen deprivation and kill other lake organisms, including fish.
In the study's most startling discovery, researchers found algal composition and abundance fluctuated unpredictably from year to year in an experimentally fertilized lake, even though the level of phosphorus fertilization remained constant throughout the experiment.
"By comparing algal variability before and during experimental fertilization, we have shown for the first time that fertilization of lakes changes their fundamental properties to make them more erratic and much less predictable than in the past," said Kathryn Cottingham, lead researcher and Assistant Professor of Biology at Dartmouth. James Rusak of York University in Toronto and the University of Regina in Saskatechewan and Peter Leavitt, also from the University of Regina, were co-authors on the study.
Because algae levels did not have a direct relationship to the amount of added nutrients, lake managers, ecologists and others who monitor the health of lakes might not be able to make accurate predictions for use in planning management and research efforts, according to the study.
The study also shows that the negative effects of fertilization are a long-term problem: algal levels were just as erratic at the end of the study as during the first years of fertilization.