2005-07-28_AgendaPacket - Laserfiche WebLink

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Observer guidelines: _ in nutrients. reaching the lake==fisheries com- _" , •'Getproper training position'and/or climactic changes. For this ® Have the same prison take all readings :i~ r~asori,`a variety of evaluauon;iechniques cari` vision uar:ies froth person to person be employed such as graphs of individual sam-' • Note in data sheets and database when plirg season readings, trends, trophic status observers change index, and comparing values to established =- •Have the'"riew and retiring observer take standards or benchmarks. ;" . readings at same time and compare them • Do not wear sunglasses while caking readings i. Individual readings over the sampling LZIZe them Or nOt~ algae season can be graphed and analyzed. Causes mer th cli di f d i S az^e important to lake DATA EVALUATION ng over e sum rea ng ec ecreas o Ltke tlrom or not, algae are important to lake may be the result from increase in abundance eCOL0~1. They are the ecology- They are the first link:in the food of free floating algae (phytoplankton), shore- l d ~l"St link in the chain. They contain chlorophyll, a green pig- eve op- line erosion, or erosion. from site ,~ ment that uses the sun's energy to convert ment near the lake, re-circulation of bottom ` ~OOGZ chain. carbon dioxide and water to food and oxy- sediment from motorboat activity or reduced gen. The algae are then eaten by zooplank- zooplankton populations. -=_ ton, small microscopic animals, which are in ~ " turn eaten by larger animals until they end up 2. Trend analysis of annual long-term cum- in the stomach of fish. Some fish, such as met means is -used to determine if a lake's minnows, feed directly on algae. In the end, clarity is improving, getting worseC.or holding _ algae are directly or indirectl}' food for both :' steady. The MPCA requires eight to ter>_years fish and humans. So, how do we know if of data with four or more readings per season `_ __ algal populations have become excessive? to reliably establish a trend- :_. Consider the following suggestions ~ ~ ~" of things you can do to aid in data evahation. 3. The._Trophic Status Index (TSI) is a • Gather both anecdotal and quantitative good estimator of how much produc-=- historic data on the lake and watershed, tiviry or algal growth is occurrirg "" - including existing water quality data, land in the lake. Robert E. Carlson uses, and activities. developed this mathemati- • Compare-current and historic data. cal model in 1970 as a way Collect additional. water chemistry data • to effectively . communi- - -such as total phosphorus and chlorophyll care a lake's productivity. ~ `a', to establish the relationship between It's a quantitative scale of ~ ~- ,~t~`-: -them and determine if the Seechi disk is 0-1.00 or 100 trophic-lev- ~ '" t)'ie best indicator of water quality. - els. An increase` of ten ~ ~'- r • If you don't have a monitoring plan, 'units represents a doubling develop one. of the algal biomass and h_aly • Seek partnerships with groups such as the- ing the transparenry:~ When - local water planner, Soil and Water evaluating this index;.,a difference of District; Department of Natural less the five is not considered significant. .resources, MPCA, etc. If the=difference is greater than five, the=data ~, _ roust be evaluated to determine the reason for. - -_ Data 'evaluation is complicated by -the fact :. ,,. and the relevance of the difference. The fn1-. <~"that water quality is subjective:-.It depends on~~" lowing scale is usedto~interpret producri~ iiy: - v~°hat the water is used for and local percep- , - " tions. For example, a--clear" cold-water lake 0-40 Oligotrophic: Nutrient E~oor, usual- .- - ~~. may be great for trout hslung, but if .you're ly clear, low algae production--.Iahes, common-., arrglirig for largemouth bass, it's not- Also iE ly found in northeastern Minnesota, you live in northeastern Minnesota your per- 40-50 Mesotrophc: Moderately produc- ception ofwater clarity is quite different from rive fakes. someone in souther ri Mirines~ot'a. Another :a., 50-70 Eutophic: Nutrient rich with high complicating facior is thenatnralyear-to-year ~ levels of algae-produ,cti~rt~~ often resultin<„ in' - ~- - _. variation in.,algal populanonsdue to changes ", murky;green water. '' ;-.Page 4 -