New Zealand Journal of Marine and Freshwater Research abstracts
Impact of land use on the faecal microbial quality of hill-country streams
A. Donnison
C. Ross
AgResearch Limited
Private Bag 3123
Hamilton, New Zealand
B. Thorrold
Dexcel Limited
Private Bag 3221
Hamilton, New Zealand
Abstract Faecal contamination of rural streams is of
increasing concern in New Zealand. This study assessed hill-country streams
in the Whatawhata district that were impacted by pastoral farming, indigenous
forest, or Pinus radiata forest; by measuring Escherichia coli
bacteria at 14 sampling sites fortnightly for 2 years. E. coli concentrations
were highest in streams flowing through grazed pasture. In both years there
was a noticeable seasonal pattern in all streams irrespective of land use,
with highest bacterial concentrations in summer and autumn and lowest in
winter and early spring. There was no obvious correlation between E. coli
concentration and rainfall or stream flow. In those streams impacted by a
change in land use from pastoral to pines during the study, E. coli
concentration fell rapidly and remained at levels lower than those in streams
impacted by either indigenous or 7-year pine forests. As E. coli was
detected in all but two samples, the water in these streams is not suitable
for human consumption. The pastoral streams consistently failed to meet stock
drinking-water guidelines (median concentration not greater than 100 E.
coli 100 ml-1) and the forest streams failed to do so in summer.
Twenty-eight percent of pastoral samples, 25% of indigenous forest samples,
14% of 7-year pine forest samples, and 5% in New Pines stream samples (after
planting) had E. coli concentrations associated with a high level
of risk for contact recreation (>500 E. coli 100 ml-1)
and the high concentrations usually occurred in summer.
Keywords Escherichia coli; streams; hill-country;
grazed pasture; forest
M04120; Online publication date 24 November 2004 Received 11 June 2004;
accepted 6 September 2004
New Zealand Journal of Marine and Freshwater Research, 2004, Vol. 38:
845–855
0028–8330/04/3805–0845 © The Royal Society of New Zealand 2004
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