Kelp detritus: quantifying carbon contributions and size distribution

To determine the potential of particulate kelp (Macrocystis pyrifera) detritus to serve as a trophic resource for coastal suspension feeders, we quantified the rate of production and size distribution of kelp detritus in relation to water motion, state of blade erosion, and percent cover of the bryozoan Membranipora sp. on blades. We enclosed kelp blades in specially designed bags both in the lab and in the field to collect detritus particles, which we then fractionated by size. Carbon and nitrogen content were quantified for each size fraction. Preliminary results show significant overlap in kelp detritus size distribution with the 0-300 micron size range consumed by suspension feeders. No significant predictors for rates of detritus production were found. The results from this experiment can be used to assess possible trophic consequences of long-term changes in kelp production on benthic and pelagic suspension feeders and coastal food webs.