Observations on aquatic macrophytes in 26 northern New Zealand lakes

Abstract

The presence, depth ranges, and estimated abundance of submerged, emergent, and free-floating aquatic species recorded in exploratory surveys of 26 northern New Zealand lakes are presented. Most of the lakes are small and relatively isolated, being formed in the extensive dune complex of the west coast of Northland. Two of the lakes occur in central Northland in valleys dammed by lava flows. Dense fringes of tall emergent sedges (Eleochans sphacelata and Baumea spp. dominant) occurred in most lakes. Native submerged plant communities free of exotic species were recorded in 21 of the surveyed lakes. Chara corrallina and C. fibrosa were the most abundant charophytes. occurring in 21 and 18 lakes respectively. The endangered species Hydatella inconspicua and Myriophyllum robustum were recorded in 5 and 2 lakes respectively. Three exotic species (Elodea canadenis, Egeria densa, and Ceratophyllum demersum), which have come to dominate the submerged vegetation in many other New Zealand lakes, were recorded individually in five lakes. Where present, they formed tall, often monospecific growths which displaced native submerged species from mid depths. Characteristics of the vegetation, apparent changes, and the effects of exotic species introductions are discussed

Keywords:

• Northland lakes
• dune lakes
• aquatic vegetation
• macrophytes
• charophytes
• exotic plants
• adventive plants
• endangered species
• plant surveys
• plant distribution
• plant invasions