Alaskan Headwater Streams

Project Title: The Functional Significance of Low-Order Streams and Associated Riparian Wetlands in Supporting Fish and Invertebrate Populations in the Kenai Lowlands, Alaska
Funding Agency and Period:  U.S. EPA to Alaska Fish and Game and Baylor; 2006-07
Project Management:  Coowe Walker (Project Director; Kachemak Bay Research Reserve), Ryan King (PI, Baylor subcontract), Dennis Whigham (Smithsonian Environmental Research Center)
Funding Summary: $110,435 ($81,630 federal) 

Project Summary: Riparian wetlands are the primary connection between terrestrial and aquatic ecosystems. This linkage affects light levels, stream temperatures, dissolved nutrient inputs, and organic matter inputs.  The amount and quality of organic matter inputs are particularly important because they fuel the base of food web in stream ecosystems.  Thus, the type of riparian wetland can strongly influence invertebrate and fish productivity in streams.

Forty-two percent of the Kenai Lowlands, which extends across 810,000 acres of the western Kenai Peninsula in south-central Alaska, is occupied by wetlands. Five of the wetland geomorphic settings identified in the Kenai Lowlands (relict glacial lakebeds, relict glacial drainageways, discharge slopes, kettles and late snow fens) are strongly connected to stream headwaters (i.e., riparian wetlands).  There is limited, but increasing evidence, that some of the headwater stream riparian areas in the Kenai Lowlands provide critical habitat for juvenile salmonids.  Many low-order streams on the lower Kenai Peninsula are located on privately owned lands, where development is imminent based upon existing plat maps. The importance of these headwater habitats to salmonid populations, especially as juvenile rearing habitat, must be recognized before development occurs to provide effective management and regulation. 

We have initiated a collaborative effort between Baylor University, Alaska Fish and Game Department, and the Smithsonian Institution to estimate densities of juvenile salmon populations in 40 streams spanning multiple wetland geomorphic classes in the Kenai Lowlands.  We will assess aquatic invertebrate communities, in-stream habitat, water quality, riparian plant communities, and surrounding land uses at representative sites within each geomorphic unit where headwater streams occur. We will also document how riparian vegetation communities influence stream food web structure and affects elemental imbalances between juvenile salmonids and their food using currrent analytical techniques, specifically determination of (1) carbon and nitrogen stable-isotope ratios to identify major food sources to juvenile salmon, and (2) carbon, nitrogen, and phosphorus concentrations and ratios to evaluate elemental imbalances between consumers and their food.  Using samples collected across different wetland geomorphic settings (ecosystems), we will determine if different riparian wetland vegetation along headwater streams differentially support stream food webs.   

Collectively, this study will help determine why juvenile salmon are more abundant in streams with certain types of riparian wetlands and thus are most important as juvenile habitat. These data will also be used to add data to a digital map called the Kenai Lowlands Wetland Management Tool with fish habitat support functions data.  This information will be an important first step for regulators and managers to assess the ecological consequences of development activities in the headwater regions of watersheds on the Kenai Peninsula.  Moreover, methods developed and applied in this study will help train a Baylor graduate student, will serve as a foundation for securing additional funding in Alaska, and will facilitate future research in streams and wetlands in central Texas planned in the coming months with students and faculty at Baylor University.