In lakes and oceans, the relative amounts of phosphorus and nitrogen are important.
In the Great Lakes, phosphorus is the nutrient that is usually least abundant. Most of it is readily used by the algae, and any additional amount that enters the water is soon used to create more algae. Rivers naturally transport phosphorus that has weathered from rocks or that has been transported out of soils.
In the Pacific Northwest, soils are naturally rich in phosphorus. Thus, erosion from development, logging, landscaping or natural storm events can adversely affect phosphorus levels in lakes, streams and rivers. As can failing septic systems, animal waste, fertilizers, phosphorus soap and sewage overflows. Typically, regulating agencies recommend a reduction of 70% of excess phosphorus levels to maintain the basic health of a lake or waterbody.
Case Study: Lake Erie
In the late 60's and early 1970's, Lake Erie was experiencing massive algae blooms. Hence, the U.S. and Canada entered into a joint agreement to clean up Lake Erie.
The cost of clean up was $ 8 billion dollars (in today's dollars). Most of the money was spent building and upgrading sewage treatment plants. The reversal of phosphorus loading in Lake Erie is considered a world class success story. (It took 20 years for results).
Everything you could possibly want to know about Phosphorus - in layman's terms.
Phosphorus (P) is an element you can find on the periodic table. Remember the good old days back in high school chemistry when you located oxygen (O) and hydrogen (H) on the chart? Almost all of the phosphorus in nature is in the form of phosphate (PO4-3), an ion consisting of four oxygen atoms bound to one P atom.
Sources of phosphorus include the weathering of geologic phosphate material, atmospheric deposition, groundwater, agricultural runoff, urban runoff, domestic and industrial sewage, septic systems and waterfowl waste.
"Phosphorus is the 15th element on the periodic table of the elements. It is a non-metal that is a solid at room temperature. Our interest lies in the fact that it is an essential part of living organisms and is found in nervous system tissue, bones, and cell protoplasm. (Chemistry 2003)
Not only is phosphorus essential for life, but algae and aquatic plants are often limited by the amount of phosphorus available (Cairns 1986; Fritz 1989; Lau and Lane 2002). The biomass of algae and aquatic plants is directly related to the amount of phosphorus available. Therefore, the more phosphorus in the water, the more algae and plants there will be.
The phosphorus levels in surface water can vary and change in response to climatological and soil factors as well as the vegetation in the watershed (Fritz 1989). Different soil types have different amounts of naturally occurring phosphorus in them. A lake in a phosphorus rich region will have a higher concentration of phosphorus in the water column than a lake in a phosphorus poor region. Climate plays a role in the natural phosphorus input to a lake too. Increased precipitation can lead to greater amounts of erosion with more phosphorus rich sediment being introduced into the lake. Dry periods can also increase the phosphorus input to a lake as more dust is present that can blow into the surface water. Also, more shoreline may be exposed by lower water levels providing more soil to be eroded.
However, human activities can change the phosphorus loads through direct inputs to the watershed or by modifying the vegetation and soil in the watershed (Fritz 1989). In fact, the most frequently identified pollutant to surface water is phosphorus (Havens and Schelske 2001). Through phosphorus modelling it is possible to look at the potential effects that land use changes have on the phosphorus inputs to surface water." (Excerpt on phosphorus taken from a study conducted by Kenny Knight, St. Olaf College, 2003).http://www.stolaf.edu/depts/environmental-studies/courses/es-399%20home/es-399-03/Projects/knight-project/index.html
Why be concerned about Phosphorus nutrient pollution in Lakes?
In 2002, a Dane County Wisconsin teen died after ingesting algae producing toxins while swimming in a Wisconsin lake. Public Health Officials issued a warning to swimmers in Dane County Wisconsin. Avoid Blue-Green Algae.
Phosphorus levels combined with a hot spell caused huge algae blooms that produced neurotoxins (affect the nervous system) and hepatotoxins (affecting the liver).
Killing blue green algae does not diminish its impact on public health, as dead cells still contain toxins. The only solution is to prevent algae blooms.
Is this a new problem? No. The federal government formed the "Joint Industry-Government Task Force on Eutrophication" back in 1967.
Want more information about how to interpret data on Phosphorus? (The link to Steve Hood's draft TMDL Study in the post below does not include a guide to assist people with interpreting or reading lake data). For basic information, please see http://dnr.wi.gov/org/water/fhp/lakes/under/phosphor.htm or, http://www.heinzcenter.org/ecosystems/2002report/fr_water/phosph.shtml