Agricultural Runoff Leading to Deadly Algal Blooms

Farming is essential to the food supply and economy within Ohio. However, agricultural practices are reaping negative effects on aquatic ecosystems with an excess of phosphorus pollution. Agricultural practices such as; feeding operations, grazing, plowing and fertilizer are responsible for 85% of the phosphorus pollution found within Lake Erie.

This image shows agricultural runoff in action. The waters flowing from these fields contain minerals like phosphorus and nitrogen.


The biggest risk associated with the Lake Erie ecosystem and phosphorus pollution is the formation of deadly algal blooms. Algal blooms are known to create dead zones (areas in the water in which there is no oxygen present) because algae consumes all the oxygen in the water, releasing carbon dioxide. Due to the lack of oxygen, very few fish and wildlife species can survive in dead zones. Algae also prevents light from reaching vegetation at the bottom of the lake, blocking photosynthesis and consequently damaging food sources and nursing grounds for aquatic species.

The photo above illustrates the extent of algae contamination in all of the Great Lakes. It is clear within the photo that Lake Erie has significantly more algae than the surrounding lakes, emphasizing the need for control of phosphorus pollution and in turn, agricultural runoff.

In order to limit the amount of agricultural runoff and number of algae blooms, farming practices must be adjusted. A few techniques that are known to cause less phosphorus pollution are crop rotation, no till agriculture and nutrient/fertilizer management practices. Although new agricultural practices can help, the best way to prevent further growth of algal blooms is through greater education on the risks and causes of blooms.


This diagram shows how phosphorus can be transferred from farmlands to ponds and into waterways.


Algal Blooms 101

Agricultural Runoff, Tox Town

Algal Blooms in the Great Lakes, The University of British Columbia (Picture 2)

Damaging Consequences of Agricultural Runoff, Greentumble

Agricultural Runoff Picture 2

Agricultural Runoff Diagram (Picture 3)



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