A new study of the impact of fertilizer on Lake Erie shows efforts to cut back on the level of phosphorus leaching into the water have been slightly successful, but scientists say further study is needed to understand how new factors, including global warming, could be adding to the problem.

The study from the International Joint Commission (IJC), called Fertilizer Application Patterns and Trends and Their Implications for Water Quality in the Western Lake Erie Basin, pointed to agriculture as the largest single source of excess nutrients in the lake.

"The report today was about the loads of phosphorus related to manure and chemical fertilizers that are being used in the Western part of Lake Erie," explained Jerome Marty, president of the Society of Canadian Limnologists, who took part in a webinar about the study's findings.

The IJC completed the report to "better understand the influence of past, current and possible future nonpoint agricultural runoff of phosphorus into western Lake Erie, and their potential to cause eutrophic conditions and nuisance and harmful algal blooms."

The study concluded more integrated research and monitoring projects are needed to get a clearer understanding of the lake. New technology such as no-till cropping, tile drains and runoff caused by global warming were also pointed to as factors increasingly contributing to poor water quality conditions in the lake but requiring additional research to better understand their impacts.

"For these new stresses, again, we realize we don't have a full understanding of ... these processes and it calls for monitoring," said Marty.

Blue-green algae Lake Erie Toledo Water Problems

A sample glass of Lake Erie water is photographed near the City of Toledo water intake crib on Aug. 3, 2014. (Haraz N. Ghanbari/Associated Press)

One of the main difficulties for researchers was a shortage of good data for different sources of phosphorus. Marty said studies of the Great Lakes can "come in waves" every five years, but noted the state of Lake Erie gives it one distinct advantage.

"In the case of Lake Erie it's the only lake among the five of the lakes that has a priority program that looks at eutrophication, that being the excess of nutrients that's causing what Lake Erie is unfortunately known for because it's getting very green and sometimes it's toxic."

Proper monitoring takes time

One positive raised by the study was a slight sign of progress shown in phosphorus data.

"The report and the presentation showed there is a slight decline in phosphorus loads if we look at the period of time between 1987 and 2012," explained Marty. But, he cautioned, monitoring the lake properly will require an ongoing effort.

"Anything that will be done in the Great Lakes takes time. It's not something we can do one year and stop doing the following year."