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Research Publications: UM-SG-RS-2020-11
Title:
Temporal enhancement of denitrification in bioirrigated estuarine sedimentsYear:
2020Authors:
Owens, MS; Cornwell, JCSource:
Aquatic Sciences 82 ( 4 )DOI:
10.1007/s00027-020-00742-yAbstract:
Temporally intensive observations of sediment biogeochemical fluxes were used to examine the effects of water column oxygen depletion and associated loss of sediment bioirrigation on denitrification rates. In the tidal Choptank River, a subestuary of the Chesapeake Bay, coupled nitrification/denitrification was identified as the main pathway for the production of N-2 gas in the sediment. Although denitrification rates were stimulated by high rates of bioirrigation, the overall efficiency of the process sharply declined as temperature increased and bottom water O-2 declined. Consequently, there was a transition from nitrogen remineralization resulting in N-2 gas production in winter to complete recycling of remineralized NH4+ back to the water column in summer. Bioirrigation rate estimates using a bromide tracer showed the same pattern as those derived from combining diffusive pore water O-2 fluxes with intact core incubations. These bioirrigation estimates were consistent with peak abundance of small spionid polychaetes in early spring with populations declining sharply into summer. Following deposition of the spring algal bloom, bioirrigation was more important than diffusive oxygen transport, increasing the depth of habitat for microbial denitrification. Low bottom water oxygen (similar to 3 mg L-1) in summer was accompanied with a loss of bioirrigation and very low denitrification efficiency. Denitrification efficiency was shown to be sensitive to bottom water oxygen concentrations even in the absence of hypoxia or anoxia.Related Research Project(s) Funded by Maryland Sea Grant:
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Featured Fellow
Leone Yisrael is a cephalopod-loving scuba diver, cook, and loves to try new activities. She conducts genetic analysis and fieldwork at the Smithsonian Environmental Research Center through the Coastal Disease Ecology Lab.
Featured Research Project
Developing a habitat model for mysids, an important link in Chesapeake Bay food webs
Mysids are important mesozooplankton prey for many species of fish in Chesapeake Bay and are an important link in transferring energy from lower to upper trophic levels. Mysids also serve as biological vectors for benthic-pelagic coupling due to their diel vertical migration and omnivorous prey-switching behavior, which makes mysids important regulators of food web architecture. Despite their central role in coastal food webs, surprisingly little is known about mysid ecology and dynamics in Chesapeake Bay.
