Effects of log booms on physical habitat, water quality, and benthic invertebrates in the lower Fraser River and estuary

Abstract

To facilitate the movement and processing of timber in some regions of the Pacific Northwest, logs are tied together to form large rectangular rafts (often called “booms”) which are transported and stored in aquatic environments. In the lower Fraser River, British Columbia, some reaches have >50% of shoreline with adjacent log booms, yet our understanding of the effects of log booms on habitats and biota is very limited. We compared sites that have never had log booms to nearby ones with active boom storage occurring to examine differences in environmental characteristics. In contrast to reference sites, nearly all active sites had compacted sediments and little vegetation coverage, likely caused by logs “grounding” onto benthic environments due to tidally influenced water level changes. Total benthic invertebrate abundance was higher at reference sites which had relatively more Amphipoda and Trichoperta, but fewer Haplotaxida, compared to active sites whose compacted and more detrital-laden sediments should favour haplotaxids. Water quality variables generally did not differ between reference and active sites. Grounding of log booms and contact with the below substrate is in contradiction of best management practices and has clear effects on the physical habitat and biota of the area underneath booming sites.