A comparison of sampling methods for the detection of the invasive alga Didymosphenia geminata in New Zealand rivers / Cathy Kilroy, Matt Dale.

By: Kilroy, Cathy.
Contributor(s): Dale, Matt. (NIWA. Christchurch) | Biosecurity New Zealand.
Material type: materialTypeLabelBookSeries: NIWA client report ; CHC2006-078; NIWA Project ; MAF06509.Publisher: [Wellington, N.Z.] : MAF Biosecurity New Zealand, 2006Description: 37, [5] p. : ill. ; 30 cm.Subject(s): DIDYMOSPHENIA GEMINATA | RESEARCH PROJECTS | SURVIVAL RATES | BIOLOGICAL INVASIONS | DIATOMS | ENVIRONMENTAL CONDITIONS | RIVERS | CHEMICAL CONTROL | SOUTH ISLAND | LAKES | STREAMSHoldings: Electronic Online resources: Click here to access online | Click here to access online Abstract: Regular surveillance for the non-indigenous, invasive diatom Didymosphenia geminata in New Zealand is part of Biosecurity New Zealandgass incursion response to this organism. The sampling method initially used comprised collection of a pooled sample of algae growing on 25 stones at each river site surveyed. This method has been shown to be capable of detecting relatively low densities of D. geminata. However no work has been done to investigate whether alternative methods are more effective. b0s The work described in this report has been undertaken at the request of Biosecurity New Zealand. Its main objective was to trial different sampling methods for D. geminata in order to identify those that minimise the probability of false negatives. Additional aims were: to quantify the sampling effort required to detect D. geminata when it is rare at a site (including a determination of gbsraregcs); to calculate and compare the resources required for each sampling method; to qualitatively assess the relationship between visible D. geminata growth and cell densities in the water and benthos. Outcomes will be used to develop a standardised protocol for detecting D. geminata for surveillance in unaffected catchments, for monitoring affected catchments (e.g., by local authorities) and for other studies that require the ability to detect D. geminata. b0s Our strategy was to undertake the sampling comparisons on rivers where D. geminata was known to be present, but which also included downstream reaches free of the alga. We sampled six sites on each of two rivers in which D. geminata had been recently reported. D. geminata was confirmed in the Ahuriri River 47-48 days before our initial survey, and in the Aparima River 11-12 days before the survey. The main survey was undertaken on 5-8 April 2006. Additional follow-up surveys were undertaken in both rivers. ... - Executive summary.
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"September 2006"

Includes bibliographic references (p. 36-37).

Regular surveillance for the non-indigenous, invasive diatom Didymosphenia geminata in New Zealand is part of Biosecurity New Zealandgass incursion response to this organism. The sampling method initially used comprised collection of a pooled sample of algae growing on 25 stones at each river site surveyed. This method has been shown to be capable of detecting relatively low densities of D. geminata. However no work has been done to investigate whether alternative methods are more effective. b0s The work described in this report has been undertaken at the request of Biosecurity New Zealand. Its main objective was to trial different sampling methods for D. geminata in order to identify those that minimise the probability of false negatives. Additional aims were: to quantify the sampling effort required to detect D. geminata when it is rare at a site (including a determination of gbsraregcs); to calculate and compare the resources required for each sampling method; to qualitatively assess the relationship between visible D. geminata growth and cell densities in the water and benthos. Outcomes will be used to develop a standardised protocol for detecting D. geminata for surveillance in unaffected catchments, for monitoring affected catchments (e.g., by local authorities) and for other studies that require the ability to detect D. geminata. b0s Our strategy was to undertake the sampling comparisons on rivers where D. geminata was known to be present, but which also included downstream reaches free of the alga. We sampled six sites on each of two rivers in which D. geminata had been recently reported. D. geminata was confirmed in the Ahuriri River 47-48 days before our initial survey, and in the Aparima River 11-12 days before the survey. The main survey was undertaken on 5-8 April 2006. Additional follow-up surveys were undertaken in both rivers. ... - Executive summary.

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