Laserfiche WebLink
<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Total Phosphorus <br /> <br />Phosphorus is an important plant and animal nutrient and through measuring its <br />concentration in the water we can make inferences about the structure of the aquatic <br />ecosystem. Phosphorus is often the limiting nutrient in aquatic systems and its addition <br />from natural or man-made sources can greatly increase the plant growth (productivity) of <br />a stream or lake (Schindler, 1977). As the productivity increases more organic matter <br />accumulates within the stream. Detritivores, breaking down this organic matter, can use <br />up the available oxygen in the stream. This condition is called anoxia and can result in <br />massive die offs of fish and other large organisms living within the stream. <br /> <br />An increase in phosphorus also causes a change in the algal community. When <br />there is an abundance of phosphorus, nitrogen becomes the limiting nutrient and algae <br />which are able to extract nitrogen from the atmosphere grow more rapidly. These are <br />known as blue-green algae and often times form smelly mats on the surfaces of water that <br />are polluted with excess phosphorus. They also produce toxins which, in large enough <br />concentrations, can be harmful to humans and wildlife. <br /> <br />Ninety-eight percent of the phosphorus found in the Mississippi river comes from <br />agricultural runoff, from commercial fertilizers and manure. However, dissolved <br />phosphorus concentrations in groundwater are generally highest in urban portions of <br />Minnesota (Andrews et. al., 1996). This is a result of fertilizers added to lawns and <br />gardens as well as on-site septic system inputs. <br /> <br />The phosphorus levels measured at Trott Brook are high compared to data from <br />other pristine streams. There is a clear trend of increase in phosphorus as one moves <br />down stream, with a doubling of phosphorus concentration between the upstream and <br />downstream sites. This could be due to the annual fall decay of plant material which may <br />cause rapid release of phosphorus (Carpenter, 1980). However, this increase is not <br />inconsistent with anthropogenic pollution. A more intensive monitoring scheme may help <br />identify if this is a natural or anthropogenic effect as well as identify potential pollution <br />sources. <br /> <br />5 <br />