Trask River Watershed Study: Benthic macroinvertebrate sampling, 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 benthic macroinvertebrate communities were conducted over the course of this study (2006-2016). Benthic samples were collected in early spring, early summer and late summer using a Surber net (500 micron mesh). This macroinvertebrate sampling was conducted before and after forest harvest and in reference watersheds to provide insights into both local and downstream effects. Specifically, these data from headwaters and downstream sites include biomass, density, and functional feeding group (FFG) densities of aquatic macroinvertebrates and rate of emergence of adult aquatic macroinvertebrates. 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. Beginning in 2007, one downstream site in each catchment was sampled using Surber samplers twice per year, in early summer and during late summer. Within each catchment, 3 headwater streams were consistently sampled each year in early summer. Springtime sampling occurred in some years. In the Pothole basin, a 4th headwater site (PH1) was added in 2010. These macroinvertebrate samples were analyzed for taxonomic composition and densities. Benthic macroinvertebrates were identified to the lowest practical taxonomic level, typically genus, although some individuals could only be consistently keyed to the subfamily, family or order level. Starting in 2009, benthic samples were preserved by freezing, then thawed and macroinvertebrates sorted from organic and inorganic material. These macroinvertebrates were dried and ashed to calculate bulk biomass. Biomass was not measured for individual taxa. Emergence rates of adult aquatic macroinvertebrates were measured for a subset of headwater sites from June through mid-August in 2009-2010 (pre-treatment) and 2013-2014 (post-treatment). These adult specimen were also identified to the lowest practical taxonomic level after collection and preservation.
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. The primary role of this sampling was to characterize the taxonomic composition and densities of macroinvertebrate benthic communities, which can be an important source of food for fish, amphibians, and terrestrial predators.
For more information about these data and this study, see Johnson et al. (2022).