Monitoring Water Quality and Submergent Aquatic Vegetation of Lower Green Bay Wetlands and Influences of the Cat Island Chain Re-establishment Project

Abstract

The loss of the Cat Island Chain (CIC) in Green Bay, Lake Michigan has been a suspected factor in the reduction and degradation of important aquatic habitat. The CIC re- establishment project wave barrier (completed in 2012) was designed, in part, to positively impact aquatic habitat by reducing wave-related stress and subsequently improving water clarity and promoting aquatic vegetation (AV) growth. The objectives of this study were to 1) quantify potential effects of the wave barrier on water quality, wave energy, light extinction, and abundance and distribution of AV; 2) assess the existing aquatic seed-bank on the lee side of the barrier; 3) and determine the survival and growth of transplanted AV propagules and Schoenoplectus acutus (hardstem bulrush) plugs on the lee and windward sides of the barrier. Our study found differences in water quality conditions between the windward and leeward sides of the wave barrier changed over time, with poorer water quality conditions varying between the windward and leeward sites based upon temporal changes in climatic variables; however, transplanted propagules and hard-stem bulrush plugs had greater growth and survivability on the leeward side of the wave barrier. Analysis of the existing AV distribution and seedbank also provided evidence of widespread propagule limitation in the leeside aquatic habitat. Overall, the results of the research suggest the potential for increased AV abundance due to the wave barrier, especially with some facilitated vegetation re-establishment efforts; however, further research is needed to better understand this potential and the possible effects of other factors, such as Lake Michigan water levels, sediment resuspension, and the impacts of tributary runoff.