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PHYTOPLANKTON DEPOSITION TO CHESAPEAKE BAY SEDIMENTS DURING WINTER-SPRING
Citation:
Hagy, J.D., III, J., Boynton, AND Jasinski. PHYTOPLANKTON DEPOSITION TO CHESAPEAKE BAY SEDIMENTS DURING WINTER-SPRING. ESTUARINE, COASTAL AND SHELF SCIENCE. Elsevier Science Ltd, New York, NY, 62(1-2):25-40, (2005).
Impact/Purpose:
to estimate chl-a and carbon deposition to sediments
Description:
The often rapid deposition of phytoplankton to sediments at the conclusion of the spring phytoplankton bloom is an important component of benthic-pelagic coupling in temperate and high latitude estuaries and other aquatic systems. However, quantifying the flux is difficult, particularly in spatially heterogeneous environments. Surficial sediment chlorophyll-a(chl-a), which can be measured quickly at many locations, has been used effectively by previous studies as an indicator of phytoplankton deposition to estuarine sediments. In this study, surficial sediment chl-a was quantified in late spring at 20-50 locations throughout Chesapeake Bay during 8 years (1993-2000). A model was developed to estimate chl-a and carbon deposition to sediments using these measurements, while accounting for chl-a degradation during the time between deposition and sampling.
Bay-wide, the accumulation of chl-a on sediments by late spring averaged 171 mg m-2, from which the chl-a and carbon sinking fluxes, respectively, were estimated to be 353 mg m-2 and 26.5 g C m-2. These deposition estimates were approximately 50% of estimates based on a sediment trap study in the mid-Bay. During 1993-2000, the highest average chl-a flux was in the mid-Bay (248 mg m-2), while the lowest was in the lower-Bay (191 mg m-2). Winter-spring average river flow was positively correlated with phytoplankton biomass in the lower Bay water column, increased chl-a deposition to sediments and down-Bay translation of chl-a
deposition. However, in most of the correlations, data from one or more years diverged strongly from patterns apparent in other years. A comparison of the carbon flux associated with the deposition of the spring bloom with annual benthic carbon budgets indicated that the spring bloom did not contribute a disproportionately large fraction of annual carbon inputs to Chesapeake Bay sediments. Regional patterns in chl-a deposition did not correspond with the strong regional patterns that have been found for net plankton metabolism during spring.