Validation of a Most Probable Number-Based Assay in a Freshwater Environment
Abstract
This report describes the results of a study conducted by the Great Waters Research Collaborative (GWRC), which compared two approaches for quantifying organisms 10 and less than 50 m: 1. The microscopy-based method quantifies living organisms that are either moving or fluorescing, and 2. The Most Probable Number (MPN)-based method combines concentrations estimates of viable phytoplankton determined by the MPN assay with microscope counts of living heterotrophic organisms. The GWRC, acting as the Testing Organization (TO), performed side-by-side analyses of ambient water samples collected from Lake Superior Harbor in the fall of 2018 and winter of 2019. The TO found that the Factor of Agreement (FOA) between the two methods was either below or approximately equal to the threshold value at the low end of the methods specified FOA range (target range: 0.5 2.0, no units). As viable organisms would be a subset of living organisms, it would be expected that FOA less than 1. The TO raised several issues that occurred during their testing; particularly, they had challenges implementing the Initial Precision and Accuracy (IPA) tests in a freshwater environment and found high background fluorescence in ambient waters. As second validation in brackish waters is pending.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 20, 2024
- Accession Number
- AD1228522
Entities
People
- Matthew R. First
Organizations
- United States Naval Research Laboratory