Observations on some chemical parameters and the phytoplankton of five west coast dune lakes in Northland, New Zealand

Abstract

In a surver ~t different seasons fro!'l April 1976 to September 1977 an analysis of temperature, cond~cuvlty •. oxygen. ammoma, soluble phosphate. nitrate, and algal taxonomy was carned out m five west coast dune lakes in Northland. Chemical data indicated that the Pouto group lakes (Kanono. Waingata. and Parawanui) did not possess significantly higher nutrient levels than the Kai-iwi group (Taharoa, Waikere). Preserved phytoplankton from Lakes Kanono and Parawanui was mainly diatom-dominated, whereas that from Lakes Waingata, Taharoa, and Waikere consisted almost entirely of desmids and dinoflagellates. Evidence for increasing eutrophication in Lake Kanono came from the presence, though In small quantities, of the diatom Fragilaria crotonensis and blue-green algae including Microcystis aeruginosa and Aphanizomenon jlos-aquae. Some of the lesserknown algae are described and illustrated. Several new records have been made for the freshwater algal flora of New Zealand.

Observations on aquatic macrophytes in 26 northern New Zealand lakes

“…All the remaining lakes are formed in basins or dammed valleys in the extensive sand-dune complex of the west coast. The bathymetry of many of the larger lakes in the present study and limited data on their physical, chemical, and biological features are noted in Cunningham et al 1953: Cunningham 1957Fish 1966;Flint 1970;Irwin 1971Irwin -1982Irwin & Main 1978, 1981Donovan 1973;Green 1975Green , 1976Lam et al 1979;Cassie & Freeman 1980;McLellan 1985. These authors have noted annual water temperatures in the range of 9-25~ and secchi depths of 0.5-9.2 m in these lakes.…”

Ontogenetic habitat shifts by Galaxias gracilis (Galaxiidae) between the littoral and limnetic zones of Lake Kanono, New Zealand

“…Thermal stratification has not been recorded in Lake Kanono during summer months (Cunningham et al 1953, authors unpublished data), but this is probably because the lake is relatively shallow and is quickly mixed by prevailing winds from the west. The lake has a relatively high concentration of silicon (Kokich),3 and its phytoplankton was dominated by diatoms (Cassie & Freeman 1980).…”

Environmental factors associated with the decline of dwarf inanga Galaxias gracilis McDowall in New Zealand dune lakes

“…For example, low silicon concentrations can limit the growth of diatoms (Titman, 1976;Tilman, 1977). Cassie and Freeman (1980) found that the plankton of Lake Kanono, where silica levels were high, was dominated by diatoms, whereas in Lakes Waingata, Taharoa and Waikere, which have lower levels of silica, diatoms were scarce and desmids and dinoflagellates predominated. Fish (1966) noted a change in the species composition of both the phyto-and zooplankton in Lake Waingata from desmids, ciliates, copepods and cladocerans in 1962, to Dinobryon, Ceratium and cladocerans in 1965.…”

“…Water supply to Lakes Kahuparere, Waingata, Rotokawau and Taharoa is primarily from direct rainfall, as the catchment size is small relative to lake surface area, whereas Lake Kanono is fed from a relatively large catchment and water from this is supplemented by groundwater supplies (McClellan, 1985). Summer stratification is rare in the shallow (maximum depth 510 m) dune lakes (Cunningham et al, 1953;Cassie and Freeman, 1980), but occurs in the deeper (maximum depth 420 m) lakes such as Taharoa and Waikere (Kokich, 1991).…”