This study is a quantitative assessment of the role fish-induced bio-resuspension plays in the silica cycle of coastal waters. We used new, published and archived oceanographic data to construct a comprehensive silica budget for Saanich Inlet (Vancouver Island, Canada), a highly productive Northeast Pacific fjord, where siliceous diatoms dominate primary productivity. Anoxia in the deep water of the inlet persists during most of the year, precluding animal life, whereas abundant groundfish continuously rework and resuspend bottom sediments in the shallower, oxygenated margins. This resuspension transfers settled biogenic silica fragments from the sediment, where they are immersed in porewater that is rich with dissolved silica, to the overlying water, where the much lower concentrations accelerate their dissolution rate. The budget shows that Saanich Inlet sediments constitute a sink for approximately 250 × 106 mol Si y−1. Most of this Si enters the inlet in advected, siliceous phytoplankton. Sediment resuspension by groundfish in the oxygenated margins of Saanich Inlet generates about 50% of the total flux of dissolved silica from the inlet seafloor. This resuspension also facilitates a massive transport of biogenic silica from the margins to the anoxic basin, where approximately 90% of all the biogenic silica is buried. The excess dissolution caused by fish activity reduces the burial efficiency of biogenic silica in the entire inlet sediments by about 20%. This case study emphasizes the link between the silica cycle and groundfish activity. Based on this study and because biological resuspension occurs in most regions of the ocean, we recommend that it will be taken into account when budgeting the silica cycle, and potentially other geochemical cycles, in marine environments.
Bibliographical noteFunding Information:
We recognize J.M. Rose, D.I. Eerkes-Medrano, M. Kelly, B. Oake, M. van-Gurp, I. Beveridge, T. Ingram, A.S.M. Chang, T. Rivlin and M. Dray for their technical and laboratory assistance. We thank the teams of: the Canadian Scientific Submersible Facility (ROPOS); the research vessels CCGS J.P. Tully and CCGS Vector; and the VENUS Project for their most professional assistance during field sampling and sample processing. We are grateful to the Institute of Ocean Science, Fisheries and Oceans, Canada, for the use of their oceanographic database. We also thank L. Baumer for her help with proof reading and amending the manuscript. We acknowledge the VENUS Project, University of Victoria, for supporting the ship and the submersible time for the field experiments, and also the USGS, CMGP support of JC. We are also thankful to NSERC Canada and the Canada Research Chairs Foundation for their additional funding to VT and PS, to the Rothschild fellowship awarded to GY, and to the Yohay Ben-Nun fellowship and Moshe Shilo Center for Marine Biogeochemistry fund and the Interuniversity Institute, Eilat for their support of TK.
© 2016 Elsevier Ltd
ASJC Scopus subject areas
- Aquatic Science