Potential effects of an invasive bivalve, Nuttallia obscurata: on select sediment attributes within the intertidal region of coastal British Columbia
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| Authors: | Chan, KY; Bendell, LI |
| Year: | 2013 |
| Journal: | Journal of Experimental Marine Biology and Ecology 444: 66-72 Article Link (DOI) |
| Title: | Potential effects of an invasive bivalve, Nuttallia obscurata: on select sediment attributes within the intertidal region of coastal British Columbia |
| Abstract: | On the west coast of British Columbia, Canada, the varnish clam, Nuttallia obscurata, is a rapidly spreading invasive species that can reach high densities (i.e. 800 individuals m(-2)). A field survey (Tier I) and an in situ mesocosm density manipulation experiment (Tier II) were applied to determine the potential effects of this invasive bivalve on select sediment attributes within the intertidal zone. In situ experiments involved seeding 1 m(2) mesocosms with varnish clams at four densities; 0 (control), 200 (low), 500 (mid) and 800 (high). Sediment samples were taken 7 times over a three week period and analyzed for organic matter, ammonium and grain size (gravel, coarse silt, fine silt and silt) at three different depths, 0-3 cm (surface), 3-6 cm (intermediate) and 6-9 cm (bottom). Field surveys demonstrated that at natural densities bivalve distribution was best explained by sediment grain size. Contrary to expectations, the in situ manipulations indicated that at high densities varnish clams did not significantly increase sediment organic matter concentrations. Their ability to deposit feed and re-ingest biodeposits may have prevented accumulations. High densities of varnish clams did however result in significantly higher concentrations of sediment ammonium and percent silt, but mostly within the lower sections of the sediment core. Reworking of the surficial sediments due to intense storm activity likely obscured any differences in determined sediment attributes among the 4 treatments. Nitrogen is a limiting nutrient with ammonium preferentially used by phytoplankton and microphytobenthos. These primary producers form the basis of all marine food webs thus increases in amounts of ammonium to shallow coastal seas as a result of high densities of an invasive bivalve within intertidal zones could result in an increased risk of eutrophication within these sensitive regions. (C) 2013 Elsevier B.V. All rights reserved. |
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