Connectivity of Streams and Wetlands to Downstream Waters: An Integrated Systems Framework

Abstract

Interest in connectivity has increased in the aquatic sciences, partly because of its relevance to the Clean Water Act. This paper has two objectives: (1) provide a framework to understand hydrological, chemical, and biological connectivity, focusing on how headwater streams and wetlands connect to and contribute to rivers; and (2) review methods to quantify hydrological and chemical connectivity. Streams and wetlands affect river structure and function by altering material and biological fluxes to the river; this depends on two factors: (1) functions within streams and wetlands that affect material fluxes; and (2) connectivity (or isolation) from streams and wetlands to rivers that allows (or prevents) material transport between systems. Connectivity can be described in terms of frequency, magnitude, duration, timing, and rate of change. It results from physical characteristics of a system, e.g., climate, soils, geology, topography, and the spatial distribution of aquatic components. Biological connectivity is also affected by traits and behavior of the biota. Connectivity can be altered by human impacts, often in complex ways. Because of variability in these factors, connectivity is not constant but varies over time and space. Connectivity can be quantified with field-based methods, modeling, and remote sensing. Further studies using these methods are needed to classify and quantify connectivity of aquatic ecosystems and to understand how impacts affect connectivity.

Featured Collection Introduction: Connectivity of Streams and Wetlands to Downstream Waters

“…These functions are broadly categorized into source, sink, refuge, lag, and transformation (Leibowitz et al. ).…”

“…Leibowitz et al. () provide a framework to understand hydrological, chemical, and biological connectivity, focused on the mechanisms by which wetlands and headwater streams connect to and contribute to rivers. Fritz et al.…”

“…Key considerations in our synthesis of aquatic connectivity are ecosystem functions within watershed components (e.g., streams, wetlands) that alter fluxes of materials or movements of organisms between them (Leibowitz et al. ). These functions are broadly categorized into source, sink, refuge, lag, and transformation (Leibowitz et al.…”

“…; Leibowitz et al. ). Recent research has quantified the connectivity and cumulative effects of many individual nonfloodplain wetlands within watersheds.…”

“…) as have metrics for quantifying it (Leibowitz et al. ). For the purposes of this featured collection, we define connectivity as follows: Connectivity is the degree to which components of a watershed are joined and interact by transport mechanisms that function across multiple spatial and temporal scales, and is determined by the characteristics of both the physical landscape and the biota of the specific system .…”