Retired Limnologists Never Die, They Just Keep Collecting Data
After 50 years of sampling lakes, streams and estuaries, while training budding limnologists on the latest YSI instrumentation on Lake Michigan, I have focused my attention on Willoughby Lake in northern Vermont during my retirement. The lake is the deepest in the state with a maximum depth of 337 ft. ~100 m with clear water and Secchi disc readings upwards of 12 m.
Sampling a lake of this depth without the aid of a ship with winches poses problems if one is limited to the use of hand-hauled sampling devices lowered and raised in from numerous depths. Having a YSI 6600 data sonde has made data collection much easier, more efficient and much more productive with respect to the array of measurements that can be taken with a single deployment.
I established a 60 m deep reference station that is an easy run from our cottage in a 1964 Pen Yan runabout. I routinely log depth profiles of temperature, dissolved oxygen, conductance, pH and chlorophyll. Profiles are taken June through September at least twice per month and more frequently in response to storms, blooms and other interesting phenomena. Vertical plankton tows are also taken and scanned under a microscope.
In addition to my personal sampling, I also work with the Vermont Agency of Natural Resources to supplement data collected through a Lay Monitoring Cooperative. The basic protocol for lake sampling involves the collection of an integrated water sample in a weighted garden hose lowered to a depth twice the Secchi disk reading. Water drained from the hose is sent to the state laboratory for analysis. I coordinate with the lay monitor on Willoughby Lake to take YSI sonde deployments in conjunction with the hose sampling. Data from the sonde yields information on the condition of the water column through the depth of the hose cast, while providing a full profile to the lake bottom at each sampling station.
I use data logged with the sonde in public talks to the local lake association as well as to others around the state. Limnological cruises have been a popular fund raising item at our lake association’s time and talent auction, which have fetched bids of $200 and more for a sampling cruise on the lake. Each bid winner receives a plot of the data collected with YSI 6600 as well as the opportunity to help with the sampling.
Future work will attempt to detect leakage from septic systems near the lake shore. Many cottages were built decades ago with crude systems that have deteriorated over the years. Preliminary sampling with the 6600 sonde attached to the bow of a canoe paddled close to the shore has detected elevated conductance readings in comparison with those observed in the open lake. The integration of the sonde data with continuous GPS readings will make the sampling more efficient and provide specific data on the location of any “hot spots” detected. These data will be plotted on a depth chart of the lake that I have produced.
For further information contact Arthur Brooks, Professor Emeritus University of Wisconsin-Milwaukee via email: email@example.com.
References: Vermont laymonitoring. Photos and depth chart of Willoughby Lake via the Westmore Association.
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