Groundfish overfishing, diatom decline, and the marine silica cycle : lessons from Saanich Inlet, Canada, and the Baltic Sea cod crash
Figure S1: Infaunal abundance in the surface sediments of Saanich Inlet margins, Fraser Ridge (British Columbia), and two sites in Bonne Bay (Newfoundland). (12.97Kb)
Figure S2: Infaunal abundance in fish excluding experiments in Patricia Bay, Saanich Inlet. (78.25Kb)
Figure S3: DSi versus time in a benthic chamber during the in situ simulated resuspension experiment conducted in the northern Gulf of Aqaba, Red Sea. (18.48Kb)
Movie S1: An Atlantic cod (Gadus morhua) resuspending sediment while chasing small fish at depth of 440 m in the North Sea. (12.56Mb)
Movie S2: A slender sole (Lyopsetta exilis) at depth of 93 m in Saanich Inlet resuspends sediment when capturing overhead zooplankton and when emerging from the sediment. (30.65Mb)
Movie S3: A spiny dogfish (Squalus acanthias) resuspending sediment while chasing a school of herring at depth of 95 m in Saanich Inlet. (10.87Mb)
Movie S4: Goatfish resuspending sediment while searching for benthic invertebrates in the sandy seafloor in the Gulf of Aqaba. (36.26Mb)
Text S1: Description of a benthic chamber experiment in the northern Gulf of Aqaba and captions for Figures S1, S2, and S3. (84.23Kb)
Snelgrove, Paul V. R.
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KeywordMarine silica cycle; Groundfish activity; Sediments resuspension; Overfishing; Baltic Sea; Saanich Inlet
In this study, we link groundfish activity to the marine silica cycle and suggest that the drastic mid-1980s crash of the Baltic Sea cod (Gadus morhua) population triggered a cascade of events leading to decrease in dissolved silica (DSi) and diatom abundance in the water. We suggest that this seemingly unrelated sequence of events was caused by a marked decline in sediment resuspension associated with reduced groundfish activity resulting from the cod crash. In a study in Saanich Inlet, British Columbia, Canada, we discovered that, by resuspending bottom sediments, groundfish triple DSi fluxes from the sediments and reduce silica accumulation therein. Using these findings and the available oceanographic and environmental data from the Baltic Sea, we estimate that overfishing and recruitment failure of Baltic cod reduced by 20% the DSi supply from bottom sediments to the surface water leading to a decline in the diatom population in the Baltic Sea. The major importance of the marginal ocean in the marine silica cycle and the associated high population density of groundfish suggest that groundfish play a major role in the silica cycle. We postulate that dwindling groundfish populations caused by anthropogenic perturbations, e.g., overfishing and bottom water anoxia, may cause shifts in marine phytoplankton communities.
Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 23 (2009): GB4032, doi:10.1029/2008GB003416.
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