A joint research effort has created a straightforward model aimed at guiding the intricate decisions involved in managing the water quality and fish populations in Lake Erie and similar environments.
A well-known saying from hockey, often linked to Wayne Gretzky, advises players to skate towards where the puck is going, instead of where it is.
Recent studies indicate that regulations intended to safeguard the water quality in Lake Erie are aligning with this principle when it comes to protecting the lake’s fisheries.
Specifically, the recommended limits on agricultural nutrient runoff into Lake Erie may actually be too strict for certain fish species. However, these limits are considered appropriate for sustaining healthy fisheries through the middle of this century, despite a warming climate, according to new research led by the University of Michigan.
“Aiming for future targets is the right approach to take now,” stated Don Scavia, professor emeritus at the University of Michigan’s School for Environment and Sustainability. “Although the proposed limits may seem excessive at present, it’s essential not to ease them, as it typically takes a decade or more to see changes.”
This is one of several insights derived from the study led by Scavia with collaborators from the U.S. and Asia.
The research team integrated forward-looking climate models and nearly a century of fishery data with a mathematical model incorporating Lake Erie’s nutrient load and a crucial water quality metric—the oxygen levels found in the lake’s depths.
The findings revealed that the interactions are not as simple as one might think. For example, while reducing nutrient levels can enhance water quality, it doesn’t always lead to benefits for all fish species.
“There are trade-offs,” Scavia noted.
Moreover, as temperatures continue to rise, they will become the primary factor affecting oxygen levels in Lake Erie and similar ecosystems worldwide.
This underscores that managing these ecosystems is complex. Today’s solutions must be continuously assessed to remain effective in the future, a challenge often referred to as a “wicked problem” in land management.
Fortunately, the team’s research offers valuable insights on how to tackle these challenges.
It’s complex
Fertilizers used by farmers contain nutrients that not only benefit crops but also nourish aquatic microorganisms, such as algae and cyanobacteria. Runoff from fields, rich in nutrients, contributes to the notorious algal blooms in Lake Erie—as well as in other regions like the northern Gulf of Mexico and Chesapeake Bay.
When these algae and cyanobacteria die, they settle at the bottom of the water and decay, consuming significant amounts of oxygen and creating hypoxic conditions. In aquatic environments, oxygen is vital for survival, making these low-oxygen areas frequently referred to as “dead zones.”
Hypoxia is particularly detrimental to species like lake whitefish, which prefer the cooler bottom waters of Lake Erie, explained Stuart Ludsin, a professor at Ohio State University’s Aquatic Ecology Laboratory.
However, while cyanobacteria in algal blooms flourish in nutrient-rich conditions, so do the plankton that larger fish consume. Additionally, not all fish inhabit areas affected by hypoxia. For instance, yellow perch actually thrive in nutrient-dense waters, Ludsin noted.
Currently, the nutrient input levels benefit species like yellow perch and walleye but can restrict the habitat available for whitefish. Striking the right balance between fishery productivity and water quality is a continually shifting challenge, made even more complex as the lake’s microbial life increases with rising temperatures.
“I don’t want my research to be misconstrued as advocating for pollution to keep fisheries productive,” Ludsin insisted. “If we neglect to address hypoxia and water quality issues amid ongoing climate change, the lake won’t support essential fish populations.”
The core message, he emphasized, is more nuanced.
“We must identify the optimal nutrient levels that will enhance both water quality and the diversity of fisheries,” Ludsin advised.
What constitutes “optimal” should be a collective decision made by the managers and stakeholders of the water system, argued Anna Michalak, founding director of the Carnegie Science’s Climate and Resilience Hub.
By utilizing data and tools like their mathematical model in these discussions, all involved can grasp how prioritizing water quality could come at the expense of fisheries, and vice versa.
“The key takeaway is the need for a systems-level approach to management issues. This implies that there will always be trade-offs based on specific objectives,” stated Michalak, who has been working with Scavia for over ten years on Lake Erie and other aquatic systems.
“We can’t just react to problems as they arise in environmental systems. Adopting a holistic perspective is essential for developing effective solutions.”
While the data and strategies may differ across ecosystems, the team believes this approach can be broadly applied.
“I believe this study establishes a model and foundational knowledge applicable to other systems,” remarked Dan Obenour, an associate professor of environmental engineering at North Carolina State University. Obenour completed his doctorate at the University of Michigan under the guidance of Scavia and Michalak.
The study also demonstrated that the climate-hypoxia model created by the team is both sturdy and dependable over extended periods. Designed to be “embarrassingly simple,” according to Michalak, the model stands ready to assist in informing future best practices.
“This issue is a wicked problem,” Obenour commented. “Determining the optimal management solutions is tough, and even if a consensus is reached, it will inevitably change. We must remain vigilant.”
Researchers from Heidelberg University in Ohio, Shanghai Jiao Tong University, and the Chinese Academy of Sciences also contributed to this project.
