Performance Verification Statement for the YSI Inc. Model 6025 Chlorophyll Probe.

Abstract

Instrument performance verification is necessary so that effective existing technologies can be recognized and so that promising new technologies can become available to support coastal science, resource management, and ocean observing systems. The Alliance for Coastal Technologies (ACT) has therefore completed an evaluation of in situ fluorometers designed for measuring chlorophyll. Chlorophyll measurements are widely used by resource managers and researchers to estimate phytoplankton abundance and distribution. Chlorophyll is also the most important light-capturing molecule for photosynthesis and is an important variable in models of primary production. While there are various techniques available for chlorophyll determinations, in situ fluorescence is widely accepted for its simplicity, sensitivity, versatility, and economical advantages. As described below in more detail, field tests that compare manufacturer’s chlorophyll values to those determined by extractive HPLC analysis were designed only to examine an instrument’s ability to track changes in chlorophyll concentrations through time or depth and NOT to determine how well the instrument’s values matched those from extractive analysis. The use of fluorometers to determine chlorophyll levels in nature requires local calibration to take into account species composition, physiology and the effect of ambient irradiance, particularly photoquenching. In this Verification Statement, we present the performance results of the YSI Model 6025 Chlorophyll Probe evaluated in the laboratory and under diverse field conditions in both moored and profiling tests. A total of nine different field sites or conditions were used for testing, including tropical coral reef, high turbidity estuary, open-ocean, and freshwater lake environments. Because of the complexity of the tests conducted and the number of variables examined, a concise summary is not possible. We encourage readers to review the entire document (and supporting material found at www.ysi.com) for a comprehensive understanding of instrument performance. However, specific subsection of parameters tested for and environments tested in can be more quickly identified using the Table of Contents below.