Effect of the herbicide triclopyr on the abundance and species composition of benthic aquatic macroinvertebrates in the Ahuriri River, New Zealand

Abstract

Abundance and species composition of aquatic benthic macroinvertebrates were compared between an area sprayed with the herbicide Grazon (active ingredient triclopyr), and an upstream control site (no triclopyr). Five Surber samples were collected from each of three riffles in control and treatment sites on eight occasions over a 1-month period. Aquatic invertebrate species composition was similar in treatment and control sites, and did not change over time. The five taxa that made up 91-95% of all invertebrates by abundance did not vary significantly in treatment compared to control riffles. Abundance of three of the 15 most common taxa (>10 individuals per riffle) differed significantly between treatment and control sites over time. However, none of these fluctuations correspond to the presence of known concentrations of triclopyr in water samples, and it is unlikely that the declines resulted from triclopyr. These results are discussed with reference to known lethal concentrations of triclopyr for some invertebrates, and to the effect of floods on invertebrate populations.

Effectiveness of braided, gravel-bed river restoration in the Upper Waitaki Basin, New Zealand

“…Other applied research and monitoring has included evaluation of effects of residual Grazon on river water quality and aquatic life after spraying (it was found to have insignificant effects when applied appropriately; Maloney, 1995); research on prey switching from rabbits to native birds after rabbit control operations (Sanders, 1997); effects of wetland water levels on Black Stilt populations (Sanders, 1999a); effects of substrate manipulation on bird feeding behavior and success (Sanders, 1999b and; bird population surveys and changes (Maloney, 1999;Maloney et al, 1997); and evaluation of the return of native birds and use of restored areas where willows were removed . In recent years, geographic information systems (GIS), global positioning systems (GPS), and mapping of riparian and wetland vegetation, aquatic, and invertebrate species have been used more extensively to assess the distribution of species, communities, and the health of ecosystems in the basin.…”

Reviews of Environmental Contamination and Toxicology

“…Direct injection treatment resulted in sediment residues of triclopyr of 26-70 Ilg kg -I within hours after application, depending on proximity to the injection site. Triclopyr BEE at 3 L ha-I was aerially applied by helicopter to an 8-km reach of the Ahuriri River upstream of Lake Benmore in New Zealand for control of Russell lupines (Maloney 1995). The total area of the river surface treated was 61.5 ha.…”

SQMCI: A biotic index for freshwater macroinvertebrate coded‐abundance data

“…At 29 Northland stream sites, Collier (1995) found significant positive correlations between MCI and shade and the percentage of native forest in the catchment area in native forest, but significant negative correlations with an index of periphyton biomass, and the extent of pastoral development in the catchment. Maloney (1995) used both the MCI and QMCI in a study of the impacts of the herbicide triclopyr on benthic macroinvertebrate communities in the Ahuiriri River, South Island, New Zealand. Stark (1993) investigated the influences of sampling method, water depth, current velocity, and substratum on the MCI and QMCI.…”