Sampling Program

SUMMARY OF THE 2001 SAMPLING PROGRAM

Purpose - In Lake Condition - Foam - Stream Sampling - Stressed Stream

From drought conditions to higher than normal summer temperatures to increased levels of algae and finally the “foam”, 2001 provided for a very interesting year of water quality monitoring in the Canandaigua Lake watershed.  We would like to thank the East Shore Association for providing $2,000 towards the overall monitoring program in both 2001 and 2002.  Below are a review of the purposes for water quality monitoring and a summary of significant findings from 2001.

Purpose:  A watershed monitoring program is essential for expanding our knowledge about yearly changes in lake condition, to improve our understanding of the ecological impact of invasive organisms, to determine and quantify sources of pollution so that corrective actions can be taken, and to assure that recent, accurate data are available for environmental decision makers as they contemplate future land use policies and provide direction to future scientific research.    

In-lake conditions: Based on year 2001 in-lake monitoring, the physical limnology of Canandaigua Lake was normal.  Temperature profiles documented the typical progression towards thermal stratification during the spring and summer months.  Fall temperature data indicate a gradual loss of heat from the lake surface and suggest an early winter turnover event.  Dissolved oxygen values were near saturation throughout the water column for the months of April to November.  A slight decline in dissolved oxygen was noted just above the thermocline during late summer.  Lake conductivity showed a slight increase from 2000 values. 

Lake water clarity, measured as secchi disk depth, averaged 6.4 m and reached a maximum of 8.9 m.  Clarity continued a declining trend first noted in 1999.  Algal abundance, estimated by the concentration of chlorophyll a, averaged 2.37 ug/L.  Algal abundance has been increasing since 1999 and this year the phytoplankton community was often dominated by the cyanobacterium, Microcystis aeruginosa.  Research elsewhere suggests that zebra mussels selectively filter against Microcystis, possibly helping to explain its dominance this year in Canandaigua Lake.  Shoreline sampling stations consistently had less chlorophyll a when compared to mid-lake stations.

Zebra mussel populations appear to have declined although no direct counts are available for corroboration.  The changes in lake clarity and chlorophyll a, combined with observations of fewer mussels attached to natural bottom substrates and an increased number of mussel shells at the shoreline, suggest the population may have exceeded the lake’s carrying capacity and crashed.  A regular program of monitoring mussel density and shell size frequency analysis should be started in order to scientifically document future population shifts.   Such a program would also increase the likelihood of detecting the invasion of quagga mussels, a taxonomic relative of zebra mussels and, perhaps, more damaging to the lake foodweb relationships.  Quaggas first invaded the Finger Lakes at Seneca Lake in the year 2000.  Samples of mussels should be collected for toxin analyses.

Nutrient levels in lake water were in the normal range.  Total phosphorus (TP) averaged 9.16 ug/L based on all stations over the eight months.  This result was slightly higher when compared to last year (8.85 ug/L).  However, there were only 13 instances when TP exceeded 10.00  ug/L, a 50% reduction from last year.  TP profiles from mid-lake at Seneca Point had an overall mean of  2.90 ug/L while results from mid-lake at Deep Run an overall mean of 7.88 ug/L.  The substantially higher mean at Deep Run results from extremely large TP values at the 50 meter depth during the summer months.  Higher levels of TP are often related to increased loading from tributaries but in this case might be better explained by benthic processes.  Nitrogen supply, analyzed as the combination of nitrate (NO₃) and nitrite (NO₂), was approximately 0.26 mg N/L throughout the sampling period.  The concentrations of nitrate (NO₃) and nitrite (NO₂) have been stable over the last three decades.  Trophic State Index, a combined measure of lake condition, remained in the oligotrophic category.

Foam: Beginning in early August, large linear streaks of foam became a common sight on the lake surface.  They are formed by Langmuir circulation, a process well known on all large water bodies.  What was peculiar about these streaks was their magnitude, persistence and composition.  Some measured miles long, lasted for days and chemical analysis of the surfactant molecules revealed a high fatty acid content.  These organic molecules are thought to be naturally occurring.  Three hypotheses concerning the source of the surfactant molecules are under study: first, that the molecules are released directly from the decay of zebra mussel flesh, second, that the molecules are a product of the decomposers (e.g., bacteria) that are breaking down the zebra mussel flesh, and third, that the molecules are contributed by the increasing large population of Microcystis in the epilimnion.  We are continuing to study the occurrence of foam on the lake with researchers from the state DEC and SUNY College of Environmental Science and Forestry.

Stream Sampling: Due to a prolonged late summer drought, tributaries to Canandaigua Lake were sampled less than anticipated.  Five storm event samples were collected between March 13, 2001 and March 26, 2002.  Stream water was tested for total phosphorus (TP), total suspended solids (TSS) and nitrogen supply (NO₃/ NO₂).  The highest TP concentrations, in rank order, were detected in Sucker Brook, the Vine Valley stream, Naples Creek, Eelpot Creek and the northern West River.  Levels of TSS were greatest in Fisher Gully, Naples Creek, Gage Gully, Eelpot Creek and Menteth Gully.  Average nitrogen supply exceeded 1.5 mg/L only in Gage Gully, Deep Run, Fallbrook Stream and the northern West River.

Year to year comparisons of stream response to storm events over the time period 1997 to 2001 is variable and problematic.  Based on limited sampling at sequential intervals during the storms, it is difficult to generalize on changes in individual stream quality with any degree of confidence.  While one stream might be sampled on the rising limb of the hydrograph (i.e., first flush of material off the subbasin drainage area), another stream might be sampled on the falling limb of the hydrograph simply due to the time constraints of traveling around the lake.  In addition, stream cross-section appears to change due to erosional/depositional processes associated with each storm event. Discharge estimates, therefore, contain a margin of error.  Earlier studies of nutrient loading are particularly suspect where annual stream discharges exceed 100% of the estimated precipitation delivered to that sub-basin.  We are in the process of trying to more accurately estimate discharge to better estimate overall loading.  The real strength of the stream sampling program is that it is able to highlight areas of substantial pollution and also provides long term data that can be used to compare subwatersheds.  We use this data to then determine where we need to intensify sampling efforts to more accurately identify pollution sources in order to come up with management solutions. 

Stressed stream analyses were conducted along Fallbrook Stream and the Vine Valley Stream. A mid-reach segment of Fallbrook Stream appears to be contributing the majority of the pollutants.  A cooperative remediation program is underway that will assist the landowner as best management practices are implemented.  Initial findings from the Vine Valley Stream show that the highest concentrations are occurring in the upper portion of the watershed.  Further research will be conducted to verify this data.  There is also an ongoing remediation program in this portion of the watershed.  Data collected will hopefully document improved water quality conditions. 

Dr. Bruce Gilman

For a copy of the 2001 sampling  report please contact the Council

© Canandaigua Lake Watershed Council 2002

This Page Last Updates On: November 23, 2005