Lake Production, Succession, and Eutrophication - Hydro-Environmental Analysis: Freshwater Environments - page 458

biomass (and high productivity or eutrophic). Note that there are many examples of systems with
low productivity and high biomass, such as tropical forests, so the two terms are not synonymous.
One of the characteristics of succession, or the aging of lakes, is that productivity generally
increases as age increases. As age increases and productivity increases, the biomass that is produced
and dies increases, contributing to the increase in lake illing. This is in contrast to the successional
paradigm for forest communities discussed earlier, where younger forests are inherently more pro-
ductive than older forests (Ryan et al. 1997).
As with all such paradigms, the use of the term eutrophication or its deinition is not universally
accepted. In 1967, G. Evelyn Hutchinson, often called the father of modern limnology (cited in
Nixon 1995), opened the proceedings of the First International Symposium on Eutrophication with
the following observation: “it would be well at the beginning of this symposium to try to ind out
exactly what we are about to discuss.”
Some of the alternative deinitions of eutrophication are listed as follows:

• Eutrophication—“the process by which a body of water becomes enriched in dissolved

nutrients (as phosphates) that stimulate the growth of aquatic plant life usually resulting in
the depletion of dissolved oxygen.” (Merriam-Webster Dictionary)

• Eutrophication—“Eutrophication is deined as an increase in the rate of supply of organic

matter in an ecosystem.” (Nixon 1995)

• Eutrophication—“The process by which a body of water acquires a high concentration of

nutrients, especially phosphates and nitrates. These typically promote excessive growth of
algae. As the algae die and decompose, high levels of organic matter and the decomposing
organisms deplete the water of available oxygen, causing the death of other organisms,
such as ish. Eutrophication is a natural, slow-aging process for a water body, but human
activity greatly speeds up the process.” (Art 1993)

• Eutrophication—“The term 'eutrophic' means well-nourished; thus, 'eutrophication' refers

to natural or artiicial addition of nutrients to bodies of water and to the effects of the added
nutrients…. When the effects are undesirable, eutrophication may be considered a form of
pollution.” (National Academy of Sciences 1969)

• Eutrophication—“The enrichment of bodies of fresh water by inorganic plant nutrients

(e.g. nitrate, phosphate). It may occur naturally but can also be the result of human activity
(cultural eutrophication from fertilizer runoff and sewage discharge) and is particularly
evident in slow-moving rivers and shallow lakes … Increased sediment deposition can
eventually raise the level of the lake or river bed, allowing land plants to colonize the
edges, and eventually converting the area to dry land.” (Lawrence et al. 1998)

• Eutrophic—“Waters, soils, or habitats that are high in nutrients; in aquatic systems, asso-

ciated with wide swings in dissolved oxygen concentrations and frequent algal blooms.”
(Committee on Environment and Natural Resources 2000)

16.3.2 c uLturaL e utropHIcatIon
As with Thoreau's description of Walden Pond and nearby Flint's pond, the characteristics of the
drainage basin (e.g., the amount of nutrients available to the lake system) and the mean depth of
the lake or reservoir are the primary factors controlling eutrophication (Horne and Goldman 1994).
As also with the farmer on Thoreau's Flint's pond, activities that increase the amount of nutrients
and sediments in the runoff from the drainage basin, accelerate the eutrophication process. This
accelerated eutrophication due to human-related activities is referred to as cultural eutrophication.
The cause of cultural eutrophication, or increased biological productivity, is most frequently due
to enhanced nutrient availability, or nutrient loads. The term nutrient enrichment is in many, if not
most, instances an alternative term for eutrophication (USEPA 2000). There are a variety of activi-
ties that can lead to this increase in nutrient loads, including urban or agricultural development and