Fig 1.
(a and b.) Location of the study site, Baynes Sound and Lambert Channel (Lat: 49° 31’59.99” N Long: -124 ° 49’ 59.99” W) (a), and study site sampling locations (b).
Sample sites are as follows: 1 Comox Estuary Low Tide, 2 Royston Bay Low Tide, 3 Mud Bay Low Tide, 4 Deep Bay Low Tide, 5/6 Henry Bay Low and High Tide, 7/8 Morningside Beach Low and High Tide, 9/10 Fillongley Park Low and High Tide, 11/12 Gravelly Bay Low and High Tide, 13/14 Metcalfe Bay Low and High Tide, Ferry Terminal Low and High Tide 15/16. Sites 1–6 and 13–16 are within Baynes Sound, whereas sites 7–12 are within Lambert Channel. The shallow underwater plateau is indicated with a red circle [24].
Fig 2.
Principal component analysis for sediment characteristics of the 16 sampling sites.
PC1 Principal component 1, PC2, Principal component 2, OM; organic matter. Location identifiers for sites within the bivariate plot are provided within the text within the Methods section.
Fig 3.
Examples of the types of microplastics recovered from sediments.
Fig 4.
(a and b) Number of microbeads (a) and microfiber and microfragments (b) recovered from the intertidal sediments from the 16 sampling locations within Baynes Sound and Lambert Channel.
Site name identifiers are provided within the text within the methods section.
Fig 5.
Principal component analysis for the microplastic characteristics of the 16 sampling sites.
Those samples most similar at 70% are indicated by the green circles. The presence of microbeads accounts for the greatest amount of variation among all sample sites.
Fig 6.
(a, b and c.) Percent abundance of microbeads a), microfibers b) and microfragments c) from the 5 sediment size fractions for the 16 sampling sites.
Note how grain size grades of <0.63 μm and 250–0.63 μm contain the greatest number of microplastic particles.
Table 1.
% organic matter (%OM), % silt, total number of microbeads recovered from sediment and % microbeads for minimum and maximum polymer densities for the 16 study sites.
Two sites (values bolded, 2, Royston, Low Tide and 5/6, Henry Bay, Low and High Tide contained a percent mass of microbead equal to or greater than either %OM or % silt, two key sediment components which govern trace metal behavior within coastal sediments.
Fig 7.
Sites of greatest microbead accumulation, likely a consequence of the Comox Bar a shallow underwater plateau that extends north of Denman Island which reduces circulation at the north end of Baynes Sound with this portion of the sound behaving like an embayed water body rather than an open channel [24].