Scientists say nitrogen may be one reason that algae blooms did not return to Missisquoi Bay on Lake Champlain last summer.
Scientists looked at changes in water temperature and clarity, phosphorus levels and rain amounts.
But none seemed to be linked to the decline in algae except possibly the decreased amount of nitrogen, a plant fertilizer, found in the bay.
In the past, phosphorus, which is found in manure and synthetic fertilizer, has been blamed for fueling the toxic algae blooms.
If nitrogen, also found in fertilizer for annual crops such as corn, is found to be causing the algae blooms, it could change the way the region is trying to reduce lake pollution.