Author: R. Smith, M. Clymer
Author Affiliation: LCWC
Journal: Unpublished Report, 19 January 2019
An unprecedented dense growth of the highly invasive Eurasian watermilfoil (Myriophyllum spicatum) reached monoculture levels in Cedarville and Sheppard bays within the Les Cheneaux Islands (LCI) in 2011 and 2012. Dense patches of Eurasian watermilfoil (EWM) grew in over ten percent of other LCI waters during that time. The objective of this six-year study was to learn how EWM and other rooted aquatic plants (macrophytes) responded to the record EWM density of that period. Beginning in 2013, EWM density fell precipitously in both bays and remained at low levels for the remainder of the study. Based upon point-intercept analysis, growth density of other macrophytes common to these bays decreased, remained constant, or increased during the study period. Possible explanations for the dramatic EWM decline include: natural EWM life cycle, natural pathogens, allelopathic agents, water level/temperature, or a combination of these.