Volunteer-collected water quality data can be used for science and management

Abstract Hoyer, MV, Canfield, DE Jr. 2021. Volunteer-collected water quality data can be used for science and management. Lake Reserv Manage. 37:235–245. This study addresses concerns that comparison studies between professional and volunteer-collected data have been of limited scope, conducted under experimental conditions, and that results may not be applicable to existing large-scale, long-term volunteer monitoring datasets. Historical (2008 to 2019) phosphorus, nitrogen, chlorophyll, and Secchi data collected by 5 Florida organizations charged with monitoring water quality were compared with Florida LAKEWATCH volunteer-collected data from 216 lakes. The state organizations had National Environmental Laboratory Accreditation Conference (NELAC)-certified laboratories and LAKEWATCH used modified procedures needed to accommodate a volunteer program. The lakes are located in central Florida, range in trophic status from oligotrophic to hypereutrophic, and provided approximately 650 independent overlapping annual geometric mean pairs for comparison. Paired t-tests comparing logarithmic transformed annual geometric mean data pooled from all professional organizations with similar overlapping volunteer-collected data showed significant (P < 0.05) differences for phosphorus, nitrogen, and Secchi depth but not for chlorophyll. The significant differences when reported arithmetically were only 1.1 µg/L, −1.1 µg/L, and 0.1 m, respectively. Regression analyses on the same data showed strong significant (P < 0.05) relations with coefficient of determinations (R2 ) of 0.91, 0.98, 0.79, and 0.78 for phosphorus, nitrogen, chlorophyll, and Secchi depth, respectively. Slopes for each paired regression were not significantly different from 1. These results demonstrate that volunteer-collected data were equivalent to data collected professionally, that the quality of volunteer data can be similar to that produced by NELAC-certified laboratories, and thus that data are adequate for both research and management.