Elements in aquatic macrophytes, water, plankton, and sediments surveyed in three North Island Lakes

Abstract

Aquatic macrophytes (Elodea canadensis Rich, in Michx., Lagarosiphon major (Ridley) Moss., Potamogeton crispus L., Potamogeton ochreatus Raoul, Pota‐mogeton cheesemanii A. Cunn., and Myriophyllum elatinoides Gaud.) were collected from Lakes Rotoaira, Taupo, and Aratiatia, North Island, New Zealand, in November 1972 and analysed for 26 elements (nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, sodium, chlorine, silicon, aluminium, iron, titanium, vanadium, chromium, manganese, cobalt, nickel, copper, zinc, molybdenum, strontium, barium, lead, boron, gallium, and zirconium). Elodea and Lagaro‐spihon were sampled again in March 1973, July 1974, and August 1974, to provide data on variability within a single stand, and change in element content during different seasons and different stages of growth. Surface water, plankton, and sediment samples were also collected at each sampling site in November 1972 and were analysed for the same range of elements. The average level of phosphorus (2900 μg.g⁻¹), magnesium (5800 μg.g⁻¹), sodium (5800 μg.g⁻¹) , chlorine (13000 μg.g⁻¹), iron (710 μg.g⁻¹), vanadium (9.2 μg.g⁻¹), chromium (5 μg.g ⁻¹), manganese (5800 μg.g⁻¹) and boron (33 μg.g⁻¹) was highest in macrophytes from Lake Rotoaira. The level of some other elements was also highest in water from Lake Rotoaira: potassium (3 mg.litre⁻¹); calcium (10 mg.litre⁻¹); magnesium (5.6 mg.litre⁻¹) sulphur (6.5 mg.litre⁻¹) and silicon (31 mg.litre⁻¹). Lake Rotoaira apparently has a higher nutrient status than Lakes Taupo and Aratiatia, but the maxima also reflect some of the differences in catchment geology between the three lakes.