Trask River Watershed Study: Epilithic algal biomass and chlorophyll a concentrations, 2006-2016

These data are a portion of the larger Trask River Watershed Study which was conducted in the East Fork of the South Fork Trask River of the Coast Range of western Oregon. Basin-wide surveys of epilithic benthic communities were conducted over the course of this study. Samples were collected seasonally in spring, early summer, and late summer and were analyzed for standing stocks of epilithic communities and chlorophyll a (photosynthetic pigment abundance). The sampling was conducted before and after forest harvest to provide insights into the effects of these treatments both locally and downstream.

The Trask River Watershed study area consists of 4 large catchments: Pothole Creek, Gus Creek, Rock Creek, and Upper Main Trask. Within each of the four catchments, 2-4 headwater sites and a downstream site were sampled. In general, Trask River Watershed study data were collected during pre-harvest (2006-2011) and post-harvest (2013-2016) periods, from treated and reference headwater watersheds and from downstream sites. Sampling for the data included in this data publication began in June 2006 and concluded in July 2016. Spring sampling was limited due to site access constraints such as snow and flooding. In 2006, only a limited number of samples were collected. Sampling in late summer only occurred at the larger downstream sites. Site reaches were approximately 30 meters in length in headwater streams and 50-100 meters at downstream sites. Sample collection consisted of scrubbing known areas of hard substrates (primarily cobble sized) and washing scrubbed material into containers. Four samples, or replicates, were collected for each headwater site and six at downstream sites. Processing occurred within 1 month of sample collection to prevent degradation of photopigments. Samples were analyzed to determine phaeophytin concentration, chlorophyll a concentration, dry mass, and ash-free dry mass.
These data are a portion of the larger Trask River Watershed Study. The general objectives of the Trask River Watershed Study were to investigate the effects of forest harvest on the physical, chemical and biological characteristics of small headwater streams, and the extent to which alterations in stream conditions caused by harvest along headwater channels influence the physical, chemical and biological characteristics of downstream fish-bearing streams. This sampling was designed to characterize the standing stock abundances and chlorophyll a concentrations of autochthonous benthic periphyton communities, which can be an important source of food for stream-dwelling organisms.