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Particle delivery to the benthos of coastal Lake Michigan
Author(s) -
Waples James T.
Publication year - 2015
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2015jc011297
Subject(s) - water column , benthos , benthic zone , flux (metallurgy) , nuclide , oceanography , advection , sediment , water mass , bottom water , environmental science , hydrology (agriculture) , sediment trap , particle (ecology) , sediment–water interface , geology , atmospheric sciences , geomorphology , chemistry , physics , geotechnical engineering , organic chemistry , quantum mechanics , thermodynamics
A 2‐D non‐steady state model was applied to measured profiles of 234 Th/ 238 U and 90 Y/ 90 Sr disequilibria in a shallow (22 m) water column of coastal Lake Michigan. Downward fluxes of 234 Th and 90 Y were primarily driven by onshore horizontal advection. Concordance between 234 Th and 90 Y‐derived mass flux estimates from the water column could only be realistically achieved under a nuclide scavenging scenario dominated by direct sorption on bottom or near‐bottom sediment and vertical convection in the water column—not sinking particles. An estimated vertical 234 Th/ 90 Y flux ratio of ∼0.31 in the water column agreed with measured 234 Th/ 90 Y activity ratios on collected ejecta from bottom dwelling dreissenid mussels (0.26 ± 0.05) and not with water column particles (3.3 ± 1.3). A similar 238 U/ 90 Sr parent nuclide activity ratio of 0.30 ± 0.02 suggests that both 234 Th and 90 Y are scavenged in toto below the maximum sampling depth (17 m) and near the sediment/water interface. Determining the mechanism by which particles are transported to the bottom is important for understanding not only how benthos are supplied with water column material, but also how particle fluxes should be measured and calculated.