A recently released Ohio Environmental Protection Agency study shows problematic levels of nitrates and phosphorus in Sandusky Bay tributaries.
Such concentrations of nutrients can cause algae growth and low oxygen levels in the waterways.
"These types of impairments are fairly typical in most parts of the state, but especially in Northwest Ohio," Ohio EPA spokeswoman Dina Pierce said.
The flat, agricultural landscape of the area creates more opportunity for manure and septic runoff to enter streams and rivers. The result is damage to the ecosystem, she said, especially to sensitive fish, invertebrate and water insect populations.
Research done in 2009 on Green Creek, Pickerel Creek, Raccoon Creek, Beaver Creek, Mills Creek, South Creek, Muskellunge Creek, Pipe Creek and the Sandusky River from Fremont to the bay revealed two-thirds of the tributaries are not meeting Ohio water quality standards.
Mills and South creeks have been negatively impacted by livestock access to the streams, and Buck Creek has been negatively affected by crop production and pesticides.
Researchers found Bark Creek has problems associated with failing home septic systems and the lack of sewer systems around it.
On the bright side, researchers also found upgrades to Bellevue and Clyde wastewater treatment plants have led to improved water quality to both Mills and Raccoon creeks. But further reductions in nutrient discharges are needed, the agency said.
Having recorded the health of waterways and sources of pollution, the Ohio EPA can now work with local governments and residents to improve the water quality of the tributaries. Such improvements could include creating buffers between farm fields and streams, fencing livestock out of streams and replacing or repairing septic systems.
Pierce said the agency will soon meet with community members to get feedback on the study and ongoing work to improve the waterways.
The Ohio EPA noted the study area does include eastern Sandusky County where state health officials identified a childhood cancer cluster. The Ohio EPA said the study results do not indicate water quality problems associated with known causes of cancer.