July 7, 2014 Hakai Scholar Jennifer Harding's paper, co-authored with Joel Harding and Professor John Reynolds, was published in Freshwater Biology this month and was even featured on the cover. The title of the paper is "Movers and shakers: nutrient subsidies and benthic disturbance predict biofilm biomass and stable isotope signatures in coastal streams".
Abstract: In a 16 stream study of coastal biofilm isotopes and biomass we found that out of several variables considered, salmon density and catchment size were among the most influential. Our combination of within-stream and among-stream comparisons shows a dual role for salmon as both a nutrient subsidy and a mechanism of disturbance for primary productivity in coastal streams in the Great Bear Rainforest.
Even though disturbance by salmon results in a decrease in biofilm during spawning, salmon-derived nutrients from previous years are linked to an increase in both isotopes and algal biomass prior to the arrival of salmon. This means that salmon-derived nutrients are retained in stream catchments from year to year and that these nutrients are an important fertilizer for freshwater primary producers. Changes to upstream catchments could alter the interplay between salmon, biofilm and nutrient cycling controlling stream food webs.