Water chemistry preferences of five nonnative aquatic macrophyte species in Connecticut: a preliminary risk assessment tool

Abstract

Our analysis of 156 lakes and 5 nonnative aquatic macrophyte species suggest that 4 water chemistry variables can be used to assess the risk associated with species invasion in Connecticut lakes. Our analysis showed that water chemistry and longitude explained a significant amount of the total data variance (33%). Additionally, individual species logistic regressions suggest that these species’ distributions were determined by the specific conductance and pH of the water body. Lakes were then placed into one of the following groups: (1) Cabomba caroliniana/ Myriophyllum heterophyllum (CM), (2) Myriophyllum spicatum/Najas minor/Potamogeton crispus (MNP), (3) Mixed (Mixed), or (4) No Invasive (NI). Multivariate analysis of variance suggests that water chemistry of the groups CM and MNP differed significantly (p < 0.001), and the variables that contributed to this difference were specific conductance (F = 22.16), alkalinity (F = 19.40), and pH (F = 18.61). The Mixed and No Invasive groups were not significantly different. Discriminant function analysis was used as a final analytical tool to determine the risk of NI group lakes developing populations of our nonnative species. The results suggest that the 4 abiotic variables could predict the identity of the CM and MNP groups with a high degree of certainty (i.e., 79 and 71% correct, respectively). When the NI group was included in the discriminant analysis, 34% of these lakes were grouped with CM and 14% with MNP. The remaining 52% of NI lakes had water chemistry parameters capable of supporting all species examined in this study. From these findings, water chemistry risk assessment ranges were developed for these common nonnative species in Connecticut.