Algal bloom research could benefit from mild year

CATAWBA ISLAND - Stakeholders and business owners throughout the area, dependant on the health of Lake Erie and its multi-billion-dollar industry, are not the only ones hoping for yet another season of only mildly harmful algal blooms.

As experts reflect on 2016 — which had a much more mild bloom for Lake Erie compared to recent years, despite following the most severe bloom on record in 2015 — research from those studying the issue closely say the region could benefit from another mild year.

Monitoring over the last year of the various factors that contribute to the harmful algal blooms further reaffirmed what the research has been consistently finding: The severity of blooms is largely driven by the amount of rainfall during the spring months and leading into summer.

Heavy rains and the resulting agricultural runoff overload the lake with nutrients that harmful algae, such as the toxin-producing microcystis cyanobacteria that has been plaguing Lake Erie for nearly a decade, thrive on.

The primary culprit feeding the blooms is phosphorus, especially when drained into the lake at high concentrations in the form of dissolved reactive phosphorus, which is 100 percent bioavailable to algae.

Research from Heidelberg University’s National Center for Water Quality Research and other partners has found the leading source of Lake Erie’s dissolved reactive phosphorus load in the western basin to be runoff from agricultural tile drainage throughout the Maumee River basin.

Record high precipitation during vital months in 2015 ultimately led to the worst harmful algal bloom ever observed, measuring on the severity index at 10.5 on a scale of 1 to 10, according to the National Oceanic and Atmospheric Administration, NOAA.

In contrast, the near-drought conditions in 2016 resulted in a much lower bloom of just 3.2, the lowest since 2012.

NOAA’s forecast projected a severity of 5.5, but within a range of uncertainty between 3 to 7.

Rick Stumpf, NOAA’s lead for the Lake Erie bloom forecast, explained during an annual forum held by the Lake Erie Foundation on Friday part of the reason for that level of uncertainty.

Some of the statistical models used to predict the severity of the bloom factored in a greater level of phosphorus coming specifically from residual internal loading of that left behind already in the lake from the record bloom year before.

The load and impact from that internal “legacy” phosphorus was not as great as some of the models predicted, which could be good news for Lake Erie if phosphorus reduction efforts continue.

“Fortunately, we overestimated. That’s a good thing,” Stumpf said. “That means the lake responds very quickly. If we change these (phosphorus) loads, the lake will respond very quickly.”

If the carryover phosphorus from the year before had been recycled by a new bloom, Stumpf said 2016 could have been “horrific.” Instead, Lake Erie has shown a remarkable ability to recover when the annual phosphorus load is down.

Now,  Stumpf and his fellow researchers hope for another mild year, and not just for the “obvious reason of having a beautiful lake” and the industries that depend on it.

Lake Erie’s western basin has not had back-to-back “dry years” since 2006-07, when the blooms were at their mildest compared to the last decade.

“We’ve had a series of wet spring after wet spring, except for 2012 and this past year,” Stumpf said. “We really need two back-to-back years in order to see how well we understand this loading and how it works.”

jstinchcom@gannett.com

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Twitter: @JonDBN