Observations on aquatic macrophytes in 26 northern New Zealand lakes

Abstract

The presence, depth ranges, and estimated abundance of submerged, emergent, and freefloating 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 bv lava flows. Dense fringes of tall emergent sedges 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.

Re‐establishment of native macrophytes in Lake Parkinson following weed control by grass carp

“…The submerged predominantly native macrophyte community recorded in Lake Parkinson during the present study was similar to that found in a number of Northland dune lakes; Lakes Kahuparere, Shag, Swan, Humuhumu, and Kanono (Tanner et al 1986). These larger dune lakes (13-84 ha) showed a greater diversity of charophytes with 4-6 species recorded for each lake.…”

“…Only male plants have been recorded in the country making this species dependent on vegetative propagation from apical and bud-bearing stem fragments (Mason 1960;Johnstone et al 1985). It was probably introduced to Lake Parkinson during the early 1960s (Mitchell 1977) and presumably displaced a native macrophyte assemblage as has occurred in many other North Island lakes (Coffey 1975;Tanner et al 1986). …”

Effects of light on the growth and photosynthesis of Egeria najas planchon

“…Despite the quantitative importance of native submerged species in Brazilian reservoirs, most ecological information concerning these plants is found outside of their natural range of occurrence. This affirmation is corroborated by the great amount of information about the ecology and ecophysiology of E. densa, for example, which has been generated in ecosystems where it was introduced (e.g., Barko and Smart, 1981;Tanner et al, 1986;Nakanishi et al, 1989;Dutartre et al, 1999). Lack of basic information is more prominent for potential nuisance species not found in temperate water bodies, though widespread in tropical reservoirs.…”

“…Shade tolerance and light-related morphological changes in some species may confer competitive advantages in light-limiting situations, thereby influencing macrophyte community composition (Barko and Smart, 1981;Tanner et al, 1986). Dominance of submerged macrophytes or an alternative stable turbid state, dominated by phytoplankton in lakes, is also mediated by light, among other factors (Scheffer et al, 1993).…”

Distribution and conservation status of the dwarf inangaGalaxias gracilis(Teleostei: Galaxiidae) an endemic fish of Northland dune lakes

“…The catchments have been extensively modified, first by logging and second by clearance of the residual native bush and conversion to pasture for grazing. However, the biotas in most of these lakes are relatively unmodified in that native species still dominate the aquatic plant communities (Tanner et al 1986), and most lakes contain no exotic fish species. McLellan (1985) and Irwin (1975).…”