This page has been archived and is no longer updated. Eutrophication is characterized by excessive plant and algal growth due to the increased availability of one or more limiting growth factors needed for photosynthesis Schindler , such as sunlight, carbon dioxide, and nutrient fertilizers.
Eutrophication occurs naturally over centuries as lakes age and are filled in with sediments Carpenter However, human activities have accelerated the rate and extent of eutrophication through both point-source discharges and non-point loadings of limiting nutrients, such as nitrogen and phosphorus, into aquatic ecosystems i. However, during the s and s, scientists linked algal blooms to nutrient enrichment resulting from anthropogenic activities such as agriculture, industry, and sewage disposal Schindler The known consequences of cultural eutrophication include blooms of blue-green algae i.
The estimated cost of damage mediated by eutrophication in the U. Figure 1 Aquaculture ponds, such as these channel catfish production ponds, typically contain high concentrations of nutrients, such as nitrogen and phosphorus, due to regular feeding of the fish. Consequently, these ponds are also plagued by recurring cyanobacterial blooms and hypoxia. All rights reserved. John Berry, and Dr. Fernando Bernal-Brooks.
The most conspicuous effect of cultural eutrophication is the creation of dense blooms of noxious, foul-smelling phytoplankton that reduce water clarity and harm water quality Figure 2. Algal blooms limit light penetration, reducing growth and causing die-offs of plants in littoral zones while also lowering the success of predators that need light to pursue and catch prey Lehtiniemi et al.
Furthermore, high rates of photosynthesis associated with eutrophication can deplete dissolved inorganic carbon and raise pH to extreme levels during the day. Dead zones are found in many freshwater lakes including the Laurentian Great Lakes e.
