When scientists looked at 13 years of data from 139 lakes in intensively agricultural areas of Iowa, they saw lakes that were surprisingly clear despite extremely high nutrient concentrations. In a study published October 9, 2017 in the journal Inland Waters, scientists from the University of Minnesota Duluth and Minnesota Sea Grant report that the lakes were so excessively fertilized that most of that algae and cyanobacteria containing the green pigment chlorophyll were killed.
Regulatory agencies have often used water clarity as an indicator of water quality. The results of this study suggest that approach may not necessarily work in all regions. Such extreme nutrient levels appear to destroy existing algae and cyanobacteria resulting in an increase in water clarity. The concept is similar to the way applying too much fertilizer on land can damage, if not kill, plants and render soil barren.
The reduction in algae is likely the result of the interplay of phosphorus, nitrogen, the landscape and sunlight, which when combined causes the excessive nitrate particles in the water column to form reactive oxygen species that damage or kill algae by bursting their cell walls and membranes.
Date: October 10, 2017
Image: Google Images
Coordinator: EnvGuide Team
Source: https://www.sciencedaily.com/releases/2017/10/171010105708.htm