Global warming will impact algal blooms: Report
Climate change is expected to influence the rate of phosphorus entering Lake Erie, causing the faster development of harmful algal blooms (HABs) and longer recovery time frames, said a report released last week by the International Joint Commission.
“Years of high precipitation and warmer water temperatures can result in larger discharges of phosphorus from agricultural lands,” a release from the agency said.
Excess phosphorus, the IJC said, comes commercial fertilizer and manure applications in the western basin of Lake Erie, which takes in everything from Point Pelee in Ontario and Huron, Ohio, on the south shore, west to the Detroit River.
That phosphorus can create eutrophic conditions and the nuisance and harmful algal blooms (HABs) in the lake, which can kill off aquatic life and harm humans as well.
Eutrophic conditions are when a body of water, such as Lake Erie, is rich in nutrients, like phosphorus, that supports a dense growth of algae and other organisms, the decay of which depletes the shallow waters of oxygen in summer, which in turn can kill off anything in those waters.
In 2014, Toledo, Ohio, with a population of nearly 300,000, turned off its municipal water supply after tests revealed toxins in the city’s water supply due to a large algal bloom.
A webinar on the report was held last Tuesday with those who worked on it, including American and Canadian researchers, and consulting companies, to talk about harmful algal blooms and outlining recommendations for additional research, monitoring and data needed to implement best management actions to restore health of Lake Erie.
The IJC said the report — Fertilizer Application Patterns and Trends and Their Implications for Water Quality in the Western Lake Erie Basin — was completed after an extensive analysis of existing data.
A release from the agency said its science advisory board’s science priority committee completed the assessment to “better understand the influence of past, current and possible future non-point agricultural runoff of phosphorus into western Lake Erie, and their potential to cause eutrophic conditions and nuisance and harmful algal blooms (HABs).”
The area under study included the western basin of the lake and the St. Clair-Detroit River system, which feeds directly into the lake. Ontario, Ohio and Michigan are in the basin.
The report said commercial fertilizer is the primary source of phosphorus from agricultural sources into the western basin overall and in the U.S., while in Canada manure and commercial fertilizer are relatively equal sources.
“Given that the most recent comparable binational data are from 2006-07 and that there are no well-established methods for distinguishing phosphorus loads from fertilizer versus manure in the laboratory, more specific fertilizer sales and application data as well as manure generation and application data are needed to advance our understanding of specific agricultural sources,” the release said.
The study showed excess phosphorus from fertilizer application that is stored in agricultural soils and nearby ditches, buffer zones and wetlands has the potential to contribute the nutrients for years or even decades.
“Even a small ‘leakage’ of excess phosphorus may be sufficient to contribute to algal blooms,” the report said.
Artificial tile drains also may increase rates of phosphorus entering the lake. It said management practices associated with phosphorus application — including timing, rates, equipment used — may have a bigger influence on phosphorus release from agricultural lands than fertilizer (commercial fertilizer or manure).
“Phosphorus control measures enacted in the 1970s demonstrated that Lake Erie eutrophication could be reversed. The challenge this time is with agricultural non-point sources of nutrients, which will require a different set of responses. Lake Erie has benefitted from bold action in the past and requires similar bold action today to ensure its health and value to the people of the basin into the future,” the report said.