Effects of invasive Typha on aquatic environments and biota

Abstract

Invasive cattail hybrids, Typha X glauca, pose a significant threat to the biodiversity of northern Michigan coastal wetlands. Typha quickly dominates the environment, leading to a decrease in local plant diversity. In this study, we examined whether the presence of invasive Typha led to a decrease in aquatic macroinvertebrate abundance and diversity, changes in chlorophyll-a content, and/or changes in nutrient levels at a coastal wetland in St. Ignace, MI. We collected and compared samples from three plots where Typha was absent and three plots where Typha had already invaded and established itself. Typha-invaded waters showed a significantly lower abundance (Z=-3.38, p=0.001) and diversity (t=4.55, df=22, p<0.000) of aquatic macroinvertebrates. Contrarily, we observed no significant difference in chlorophyll-a content (Z=0, p=1), nitrate (t=-0.478 df= 4 p=0.658), ammonium (t=-.336 df=4 p=.754), phosphate (t=-0.79 df= 4 p=0.474, and total phosphorus (t= -.085 df=4 p=.936). Our results suggest that Typha invasion is detrimental to the fitness of many different macroinvertebrate taxa by dramatically altering the environment while leaving the nutrient levels and abundance of algae unchanged.