Chesapeake Bay nutrient and plankton dynamics: III. The annual cycle of dissolved silicon |
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| Authors: | Christopher F D&#x;Elia David M Nelson Walter R Boynton |
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| Institution: | Chesapeake Biological Laboratory, Center for Environmental and Estuarine Studies, University of Maryland, Solomons, Maryland 20688, and Division of Environmental Research, Academy of Natural Sciences of Philadelphia, 19th and the Parkway, Logan Circle, Philadelphia, Pennsylvania 19103 USA;School of Oceanography, Oregon State University, Corvallis, Oregon 97331 USA;Chesapeake Biological Laboratory,Center for Environmental and Estuarine Studies, University of Maryland, Solomons, Maryland 20688 USA |
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| Abstract: | Silicic acid (H4SiO4) flux from the sediment, H4SiO4 concentration and river flow were used to obtain an annual dissolved silicon budget for Chesapeake Bay. H4SiO4 concentrations vary seasonally in the estuary: for a 12-year period, mean H4SiO4 concentrations in the mesohaline region were high both in spring and in late summer to early fall, and were low in late spring—occasionally approaching levels potentially limiting to diatom growth. Most of the annual allochthonous H4SiO4 supply to the estuary derives from the three major rivers, but regenerative H4SiO4 flux from the sediment to the water column exceeds the total riverine input by a factor of at least five. Sediment H4SiO4 efflux exhibits seasonality and averages approximately 2–3 mol Si m?2 yr?1. The high rates of sediment dissolution and efflux appear to maintain high levels of H4SiO4 in the mesohaline region, and Si-limitation of diatom growth there seems unlikely. The relative rates of biogenic silica formation and dissolution do not vary synchronously: seasonal variations in diatom productivity, sedimentary release of H4SiO4 and river flow all contribute to the observed late winter and late summer seasonal maxima and late spring minimum in water column H4SiO4 concentrations. If the only source of Si to support sedimentary H4SiO4 efflux is biogenic particulate silica recently deposited from the water column and this silica in turn was produced by diatoms in a ratio of 8C:1 Si, the minimum annual primary production by diatoms is at least 260 g C m?2, approximately half of annual total plankton primary production. This estimate would be revised upwards according to the amount of particulate biogenic silica dissolving in the water column. Burial of biogenic silica amounts to from 2 to 84% of the sediment efflux of H4SiO4, depending on location in the bay. On an annual basis, burial represents from 60 to 100% of fluvial H4SiO4-Si inputs. |
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| Keywords: | Address for reprint requests Chesapeake Biological Laboratory Center for Environmental and Estuarine Studies University of Maryland Solomons Maryland 20688 |
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