Laserfiche WebLink
important part of the bioiogical system within a lake. However, too great an abundance of algae <br />adversely affects both the ecology of the lake as well as the suitability of the lake far use by <br />people. <br />Phosphorus is the plant nutrient that most often controls the amount of algal production in a lake. <br />This is because, comparcd with other plant nutrients phosphorus in a lake is generally lowest <br />relative to demand by algae. If phosphon.ts concentrations are low, algal growth will be low. <br />Conversely, high phosphorus concentrations often foster high algal productivity. <br />Under enriched conditions (i.e., high phosphorus concentrations in the water coluznn), <br />populations of certain types of algae can exploc�e during the summer growing season. One of the <br />most common nuisance algal types are blue-green algae or cyanobacteria. They are particularly <br />problemacic for several xeasons, including: <br />• They decrease water clarity, which affects the perceived suitability of the lake for <br />direct contact recreation such as swimming <br />• They form objectio�able surface scum. The decomposition of surface scum often <br />forms a pattern on the water's surfacc much like spilled paint and generates strong <br />odors that negatively impact the recreational use an aesthetic appeal of the lake <br />• The ecology of bluegreea algae is such that most of the population dies off naturally. <br />Decomposition of this organic mass depletes the lake of oxyJen. The resulting lower <br />dissolved oxygen concentration can threaten the survaval of desirable game fish, make <br />the lake more suitable for rough f sh, and trigger other undesirable coz►ditions, such as <br />release of phosphorus held in the bottom sediments of the lakc <br />• Excessive algal growth can cause taste and odor problems in drinkin� water if the <br />]ake is used as a source of raw watcr. This can substantially increase treatment costs <br />for the water prior to distribution <br />• On occasion, bluegreen algae can secrete toxins poisonous to warm blooded animals. <br />Whiie few human deaths have bcen rcported, thcrc are many documented case5 of <br />wildlife and domestic animal dcaths as a result of ingestion of these toxins <br />Ciry of Roseville 33 <br />Parks Nnturc�l Resoeerce h1a��age»ietzt <br />