Effects of invasive macrophytes on littoral-zone productivity and foodweb dynamics in a New Zealand high-country lake

Abstract

AbstractInvasion of littoral zones by adventive macrophyte species can facilitate major changes in the ecology of lakes. In Lake Wanaka, a large alpine New Zealand lake, the macrophytes Lagarosiphon major and Elodea canadensis (Hydrocharitaceae) have invaded parts of the lake where they form tall dense plant beds throughout mid-depths (2–7 m) of the littoral zone. We investigated differences in plants, benthic invertebrates, fish, and food webs characterizing native and exotic plant beds in mid-depths of the littoral zone. The 3× higher plant biomass and 2× higher plant surface area in exotic than in native plant beds (quillworts, milfoils, and charophytes) contributed to greater standing stocks and productivity of epiphyton in the exotic plant beds. Invertebrate communities were less dense (1890/m2 vs 4030/m2) and less diverse (richness = 9 vs 12) in native than in exotic plant beds because of differences in biomass, productivity, and physical structure of native and exotic plant communities. Invertebrat...