Lake Edward Conservation Club (LECC) – November 2014
2014 Curly Leaf Pondweed (CLP) Monitoring Project
Long-Term Project Objective: To monitor year-to-year changes in CLP growth in Lake Edward. CLP is an aquatic invasive species (AIS) at nuisance levels in other Brainerd area lakes where it is expensive to treat. To help prevent similar large treatment costs for LECC, we’d like to catch CLP growth in small nuisance areas, before it might potentially become a widespread nuisance in Lake Edward. The LECC Board conducted the project in 2014 in response to specific recommendations of AW Research, the DNR, ciBioBase and Dick Osgood at a CLP conference in Brainerd in April 2012. CLP is an exotic species that the DNR identified in Lake Edward during their lake plant surveys in 2004 and 2005. The experiences of experts at the 2012 CLP conference is that some natural event, or series of events, might cause our current low population of CLP to grow to a much larger nuisance level. If that happens, it would likely be a permanent situation. We should monitor CLP growth year-to-year with vigilance. Heavy CLP growth in other lakes has been known to release a lot of phosphorus just at the time that algae begins to grow. In that way, CLP can also substantially reduce water clarity.
Conclusions & Recommendations: CLP should be monitored every year from ice out to mid-June with visual and rake surveys. Snorkeling surveys may also be needed. CLP should be removed by hand wherever feasible, particularly in the SW corner. If CLP growth reaches nuisance levels, the LECC Board should consider developing a chemical treatment plan with DNR assistance. In years of very dense growth, the LECC Board should consider additional plant mapping to help direct other efforts. CLP and native plant growth was delayed and appeared reduced in 2014. So CLP and native plant information from 2014 should provide useful baseline conditions for comparison to future years of likely greater CLP and native plant growth.
Project Technology: ciBioBase has software that converts sonar log records to maps of plant growth density, lake-bottom hardness (composition) and depth. LECC volunteers recorded sonar logs of the entire lake bottom several times using Lowrance depth finders with SD-type memory chips.
Budget: The LECC Board approved expenditure of up to $3,120 of club funding in 2014.
ci BioBase annual software subscription $1,850
Lowrance Elite 7 HDI depth finder $670
GIS map to help guide volunteers where to log $100
Fuel for volunteer’s boats $500
Observations in 2014:
Winter/Spring: The ice was snow covered for most of the winter, resulting in poor under-ice growing conditions for CLP. Spring was cloudy, further limiting light availability for CLP and native plants. June was unusually wet, setting records in much of MN. For the first time since July2011, there are no drought conditions anywhere in MN.
May: We tested the sonar logging process at the end of May. The resulting map showed sparse new growth, but dense areas of previous year’s growth particularly along shorelines. We used a rake head on a rope to look for CLP particularly in the NW bay where the DNR found CLP in 2004 & 2005. We found no CLP with the rake head and observed no new plants in the water column. Water clarity was reduced beginning in May.
Mid-June: The plant map showed more dense growth out to about 15 feet deep. We saw plants in the water column that the DNR identified as clasping-leaf and white stem pondweeds which are native species. I counted 72 visible plants on line 5 and 104 plants on line 4. Dan Swanson from the MDNR accompanied LECC to look for CLP on June 20, a calm sunny day. We used a rake head on a rope and found no CLP in the NW bay, Jolly Rogers harbor and the bar just north of Cozy Bay Resort. We found some CLP near the Cozy Bay boat ramp. Water clarity was reduced all summer.
June 21: We made a Power Point presentation about the project to members at the annual meeting.
July: Just after July 4th, we snorkeled off Cozy Bay Resort’s dock to hand pull over 100 CLP plants. Each of these plants likely rooted from a turion from growth in a previous year. We also counted 65 turions on new plant tips plus a dozen or so turions that came up attached to plant roots. A turion is a wintering bud that becomes detached and remains dormant at the bottom of the water until conditions become right to start a new CLP plant. Turions are known to remain viable for 7 or more years.
Mid-August: Surface water temperature was 74 F during the sonar logging process. The resulting map shows plant growth is denser than it was in June, but still largely medium density except for areas along the shoreline in the SW bay. We searched for visible CLP plants and with the rake head in the NW bay, the large bar in the SW and off the Cozy Bay Resort dock. There were more visible pondweed plants than in June, but no CLP plants were found except by the Cozy Bay dock. The bottom composition map shows more areas of harder bottom than the June and May maps.
Please see the following images as references. Right-clicking on each image will give you the option to save and/or print a copy for your records.
Composition of the bottom of the lake:
Lake depth (topography):
The full vegetation analysis report: