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New Zealand Journal of Marine and Freshwater Research abstractsBacterial populations, heterotrophic potentials, and water quality in three New Zealand riversM. J. SpencerAngela J. Ramsay*Cawthron Institute, P.O. Box 175, Nelson, New ZealandAbstract Thirty sites were sampled in three New Zealand rivers (Waikato, Maitai, and Wakapuaka) during late summer 1977. Samples were collected from just below the surface at mid river or in the tailraces below hydro-electric dams. Parameters measured included bacterial numbers (direct counts), heterotrophic potential (V».«), adenosine triphosphate (ATP), chlorophyll a (Chi a), and concentrations of nitrogen and phosphorus compounds. Bacterial populations per millilitre fluctuated threefold (6.4-19.4 X 105) along the Waikato River and were lower and more consistent in the two South Island rivers (1.46-2.55 X 105). In contrast, V,n.x varied 5000-fold in the Waikato River, from a characteristically oligotro-phic value of 0.0035 Mg. l^.h"1 (Lake Taupo outlet) to a eutrophic value of 18.4 fig. I"1. h"1 at the Mihi bridge. Vmu for the two South Island rivers ranged from 0.0091 to 0.189 j*g. I"' . h-i. Most parameters were significantly correlated with each other for the Waikato River samples. The strongest correlations were between V»«« and bacterial numbers and between Vmax and nitrate nitrogen. In the Maitai and Wakapuaka River series these correlations were also significant, but the only other significant correlations recorded there were between ATP and nitrate nitrogen, and between ATP and bacterial numbers.
N.Z. journal of Marine and Freshwater Research 12 (4): 415-27. December 1978
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