Author(s)

Brock Christopher Ramshaw^1,2*, Evgeny Alexandrovich Pakhomov^2,3,4

¹101-108 Esplanade W, North Vancouver, Canada.
²Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada.
³Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, Canada.
⁴Hakai Institute, Campbell River, Canada.

Stable isotope analysis was used to determine the relative dietary importance of kelp-derived detritus to plankton and benthic organisms along a gradient of kelp abundance driven by recovering sea otter populations along the west coast of Vancouver Island (WCVI), Canada. The study used region-specific kelp isotope values (δ¹³C and δ¹⁵N) and season-specific phytoplankton isotope values to model dietary contributions of kelp-derived detritus (KDD). In general, KDD contributions were moderate to high in most plankton size fractions during the summer and decreased during the winter, particularly in the kelp sparse region. Hypothesized regional and spatial (distance from the coast) differences in kelp detritus contributions to zooplankton were not evident. Modeled estimates of the KDD contribution to benthic invertebrates were high (>40%) and independent of the organism size, among regions and between seasons, with the exception of Astraea gibberosa in the kelp abundant region. Local oceanography, natural kelp isotope signature variation, and significant overlap between kelps’ and blooming phytoplankton isotope values led to a large uncertainty in the assessed KDD contributions in benthic organisms. These results highlighted the importance of the KDD as a widespread and stable year-round food source in coastal kelp populated regions.

Kelp-Derived Detritus, Primary Production, Stable Isotopes, Vancouver Island, Particulate Organic Matter, Kelp, Benthic Organisms, Primary Consumers, Food Web

Ramshaw, B. and Pakhomov, E. (2021) The Dietary Importance of Kelp-Derived Detritus to Pelagic and Benthic Consumers along the West Coast of Vancouver Island, Canada. Open Journal of Marine Science, 11, 187-213. doi: 10.4236/ojms.2021.114012.