Freshwater Scientist and Practitioner Perceptions of Blackwater Streams and Rivers in the United States

Blackwater streams and rivers exist in many ecoregions in the United States, with concentrations in the Coastal Plains, Northern and Southern Appalachians, and the Upper Midwest. In the global literature, they are characterized as being low-gradient, sandy bottom streams with low pH, low conductivity, low suspended solids, low oxygen levels, and high dissolved organic carbon (DOC). However, an exploratory analysis of existing data suggests that this characterization may not adequately represent their diversity in the United States. Comprehensive protection of blackwater streams and rivers in the U.S. has been impeded by the lack of an operational framework for their identification and classification. This is important as these systems represent a unique habitat that harbors plant and animal species specifically adapted to this extreme environment. As part of an effort to increase knowledge on the extent and diversity of blackwater streams and rivers in the U.S., we examined data collected from several thousand streams as part of the National Rivers and Streams Assessments conducted by U.S. EPA, states and tribes. Field forms used in the survey include the option to identify systems as having the appearance of “blackwater”. For sites having this designation, planned analyses include statistical comparisons of in situ water chemistry and physical habitat among blackwater and non-blackwater streams. The purpose of this exercise is not to develop a definitive list of blackwater sites or criteria for their identification, but rather to better understand what freshwater scientists and practitioners generally identify as “blackwater” in a field setting. This information will help ensure that planned efforts to develop a framework for the identification and characterization of blackwater streams and rivers of the United States adequately addresses the pool of systems field scientists perceive as “blackwater”.

Impact/Purpose

Blackwater streams and rivers found in the United States are concentrated in certain regions, and they tend to share certain physical and chemical characteristics. However, because there is currently no national framework for identifying and classifying such streams in the U.S., protection of these special systems has been impeded. Our initial work on this topic relies on field data collected as part of the National Rivers and Streams Assessments, in which crews are able to designate sites as “blackwater”. This information provides us with a first step in evaluating features that crews may be using to identify these systems. By comparing sites with and without the designation, we can better direct our efforts to develop a system of identification and classification of blackwater streams and rivers.

Citation

Blocksom, K., J. Flotemersch, AND R. Mitchell. Freshwater Scientist and Practitioner Perceptions of Blackwater Streams and Rivers in the United States. 12th National Monitoring Conference, Virtual, OR, April 19 - 24, 2021.