In‐situ measurement of dissolved organic carbon and total organic carbon in fresh surface waters: Lab validation of a portable field meter

Nonliving organic matter, including organic carbon, in freshwater systems provides energy inputs to food webs and supports various ecosystem functions. Unusually high organic carbon levels can occur naturally in aquatic habitats such as wetlands and blackwater rivers and streams. However, values may also be high due to anthropogenic influences. In recent years, increasing levels of organic carbon have been observed and suggested as drivers of brownification and increased observation of foam on surface waters. Total organic carbon (TOC) and dissolved organic carbon (DOC) are not commonly included in field studies of aquatic ecosystems because of sampling logistics and resources required for laboratory measurement. As a potential alternative to laboratory analysis, we evaluated the effectiveness of a portable field meter by comparing laboratory results to data collected in situ. Comparisons were made at 43 surface water sites across northern West Virginia. At each of these sites, a field measurement was recorded using a Real TOC/DOC Field Meter, and a water sample was collected and transported for laboratory measurement using a Shimadzu TOC‐V analyzer. Data from the laboratory and field for each site were compared using bivariate analysis and concordance correlation on matched pairs. Poor agreement existed between field and lab measurements, so a novel data model was created using laboratory‐derived data for further comparison. Substantial accuracy was achieved using the new data model. This suggests that the Real TOC/DOC Field Meter is a viable instrument for field measurement of organic carbon in aquatic ecosystems and may aid in monitoring and management decisions.