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Pesticides and Water Quality

Aquatic Invertebrates and the Food Pyramid

Aquatic invertebrates

Aquatic invertebrates are tiny organisms such as insects or crustaceans, that live in creeks, rivers, and other waterways. Because of their small size, they are hardly ever noticed, but they serve an important role in the ecology of waterways. These invertebrates are the primary consumers in an aquatic ecosystem, feeding on algae and other plants which are the producers in the food pyramid.

Secondary consumers, such as fish, feed on the primary consumers. Tertiary consumers, such as birds or mammals, then prey on the secondary consumers.

Disruption of the food pyramid by pesticides

Many people do not realize the impact that pesticides have on fish and other organisms in our creeks and rivers. Residue from a pesticide application may be washed into storm drains during irrigation or rain. In many cities, the stormwater leads directly into our creeks and rivers.

Diazinon, chloryprifos, and pyrethroids have been identified as imparing water quality because they occur at levels toxic to Ceriodaphnia and Hyalella, tiny aquatic animals which are representative of the many invertebrates in water. This sets off a chain reaction and disrupts the food pyramid. When these organisms die, secondary consumers like fish starve or must look for a new location to reside. The lack of secondary consumers then affects the tertiary consumers, causing them to starve or forcing them to move to new locations.

>> Move your cursor over the illustration to see how a disruption to aquatic invertebrates, such as Ceriodaphnia, would affect the entire food pyramid.

Illustrations by Celeste Rusconi.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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