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Marine Ecology Progress Series

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MEPS 635:37-54 (2020)  -  DOI:

Sea wrack delivery and accumulation on islands: factors that mediate marine nutrient permeability

Sara B. Wickham1,2,8,*, Nancy Shackelford1,3, Chris T. Darimont2,4,5, Wiebe Nijland1,2,6, Luba Y. Reshitnyk2, John D. Reynolds2,7, Brian M. Starzomski1,2

1School of Environmental Studies, University of Victoria, Victoria, British Columbia V8W 2Y2, Canada
2Hakai Institute, Heriot Bay, British Columbia V0P 1H0, Canada
3Institute of Arctic and Alpine Research, University of Colorado, 4001 Discovery Dr., Boulder, Colorado 80303, USA
4Department of Geography, University of Victoria, Victoria, British Columbia V8W 3R4, Canada
5Raincoast Conservation Foundation, Sidney, British Columbia V8L 3Y3, Canada
6Department of Physical Geography, Utrecht University, 3508 TC Utrecht, The Netherlands
7Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
8Present address: School of Environment, Resources and Sustainability, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
*Corresponding author:

ABSTRACT: Sea wrack provides an important vector of marine-derived nutrients to many terrestrial environments. However, little is known about the processes that facilitate wrack transport, deposition, and accumulation on islands. Three broad factors can affect the stock of wrack along shorelines: the amount of potential donor habitat nearby, climatic events that dislodge seaweeds and transfer them ashore, and physical characteristics of shorelines that retain wrack at a site. To determine when, where, and how wrack accumulates on island shorelines, we surveyed 455 sites across 101 islands in coastal British Columbia, Canada. At each site, we recorded wrack biomass, species composition, and shoreline biogeographical characteristics. Additionally, over a period of 9 mo, we visited a smaller selection of sites (n = 3) every 2 mo to document temporal changes in wrack biomass and species composition. Dominant wrack species were Zostera marina, Fucus distichus, Macrocystis pyrifera, Nereocystis luetkeana, Pterygophora californica, and Phyllospadix spp. The amount of donor habitat positively affected the presence of accumulated biomass of sea wrack, whereas rocky substrates and shoreline slope negatively affected the presence of sea wrack biomass. Biomass was higher during winter months, and species diversity was higher during summer months. These results suggest that shorelines with specific characteristics have the capacity to accumulate wrack, thereby facilitating the transfer of marine-derived nutrients to the terrestrial environment.

KEY WORDS: Sea wrack · Marine-terrestrial subsidy · Spatial subsidy · Ecosystem connectivity · Wrack deposition · Wrack accumulation · Macrophyte · British Columbia · Remote sensing

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Cite this article as: Wickham SB, Shackelford N, Darimont CT, Nijland W, Reshitnyk LY, Reynolds JD, Starzomski BM (2020) Sea wrack delivery and accumulation on islands: factors that mediate marine nutrient permeability. Mar Ecol Prog Ser 635:37-54.

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