In situ Measurements of Nutrient and Oxygen Fluxes in a Coastal Marine Benthic Community

Hopkinson, CS; Wetzel, R. G.

doi:10.3354/meps010029

Cited by 56 publications

(24 citation statements)

References 29 publications

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“…Under these conditions the availability and production of nitrate may be much reduced and thereby result in a decrease in denitrification. The few recent direct measurements of denitrification cited earlier, those reported here, the common observation of low N: P ratios in coastal waters, and measurements of sediment-water nutrient fluxes (Nixon 198 1;Kemp et al 1982;Hopkinson and Wetzel 1982) all support the belief that nearshore environments are important sinks in the marine nitrogen cycle. However, our experimental results, and the limited historical and comparative studies from heavily impacted natural systems, suggest that the homeostatic capacity of coastal ecosystems can be exceeded by nitrogen inputs of a magnitude experienced by an increasing number of estuaries, bays, and lagoons.…”

Section: Log[nh+ Pm]) -123mentioning

confidence: 69%

Eutrophication and the rate of denitrification and N₂0 production in coastal marine sediments

Seitzinger

Nixon

1985

Limnology & Oceanography

168

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Large (13 m3, 5 m deep) microcosms with coupled pelagic and benthic components were used to measure the effect of nutrient loading and eutrophication in coastal marine ecosystems on the rates of benthic denitrification (N2) and N2O production. After 3 months of daily nutrient addition, average denitrification rates ranged from about 300 µmol N m−2 h−1 in the sediments of the control microcosm to 880 in the most enriched microcosm. which received 65 times the nutrient input of the control. Increases in the production of N2O were more dramatic and increased by a factor of about 100, from 0.56 µmol N m−2 h−1 in the control to 51 in the most enriched microcosm. Although there was a clear increase in the denitrification rate in the more eutrophic systems, the amount of fixed nitrogen removed was a constant or progressively smaller fraction of the nitrogen input. Even in the most enriched microcosm, at least 16% of the N input was removed by denitrification.

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Section: Log[nh+ Pm]) -123mentioning

confidence: 69%

Eutrophication and the rate of denitrification and N₂0 production in coastal marine sediments

Seitzinger

Nixon

1985

Limnology & Oceanography

168

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“…Sedimentation of biogenic particles is the primary source of regenerated material in coastal ecosystems (Hopkinson & Wetzel 1982, Blackburn & Henriksen 1983, Sundback & Snoeijis 1991. The breakdown of these particles releases organic and inorganic forms of nutrients that 'E-mail.…”

Section: Introductionmentioning

confidence: 99%

Comparative effects of benthic microalgae and phytoplankton on dissolved silica fluxes

De¹,

Lb²

1997

Aquat. Microb. Ecol.

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Microalgal effects on dissolved silica fluxes in an estuarine sandflat were investigated over an annual cycle. Benthic microalgal and phytoplankton chlorophyll a were measured at 17 times in Masonboro Sound, NC, USA, between June 1994 and May 1995. Using light and dark benthic chambers, dissolved silica (DSi) concentrations were measured in situ and used to calculate flux rates. Mean annual biomass was 64.6 and 10.0 mg chl a m-' for benthic microalgae and phytoplankton, respectively. Benthic microalgae and phytoplankton (both containing diatoms), alid cultured benthic diatoms were used to calculate Si:chl a weight ratios. Ratios of Si:chl a showed that benthic microalgae contain more silica per unit chlorophyll than phytoplankton, with mean Sl.chl a ratios of 14.3, 10.9, and 2.8:1, for benthic microalgae, cultured benthic diatoms, and phytoplankton, respectively. DSi flux rates were always higher in the dark, while some negative flux rates (into the sediment) were seen in the light. DSi flux rates averaged 81.0 pm01 m-' h-' in the dark and 37.0 pm01 m-' h-' in the light. Lab and field experiments showed that benthic microalgae can take up water column DSi, while typical phytoplankton concentrations exert little control of water column DSi. Temperature was found to be the major regulator of DSi fluxes, with flux rates decreasing with decreasing temperature. Benthic microalgae were significant regulators of light chamber DSi flux at temperatures <2O0C. Due to benthic microalgal uptake and low water column DSi concentrations observed under lower temperatures, nutnent limitation expenments were performed to determine if phytoplankton were silicate-limited. Of the 3 major nutrients. nitrogen, phosphorus, and silicon, only silicon was limiting for phytoplankton growth in every experiment. Benthic microalgae are important regulators of DSi flux, and can regulate water column DSi concentratlons for at least half of the year, possibly limiting phytoplankton growth and species composition in shallow, coastal environments.

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“…Hargrave 1969, measure oxygen uptake rates of sediments 1972; Pamatmat 197 1;Smith 1974Smith , 1987; consists of incubating sediment and follow- Hopkinson and Wetzel 1982). The tech-ing the decrease in the oxygen concentration niques that have been developed to measure of overlying water as a function of time.…”

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confidence: 99%

Oxygen uptake kinetics in the benthic boundary layer

Hall

Anderson

Loeff

et al. 1989

Limnology & Oceanography

135

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A simple, one-dimensional, transport-reaction model of oxygen uptake by sediments during incubation experiments assumes zero-order reaction kinetics for oxygen removal in the pore water of sediments and takes the apparent diffusive limitation posed by the benthic boundary layer into account. Model calculations are in excellent agreement with experimental data obtained during in situ benthic flux chamber experiments in Gullmarsfjorden, Sweden, during fall (water temp, 10°C) and winter (-1'C). The boundary layer "resistance," represented by a mean diffusive sublayer thickness, was estimated with a series of radioactive tracers. The oxygen uptake curve was initially approximately linear but became exponential below -100 PM oxygen. The half-removal time of oxygen below 100 PM corresponds to a boundary layer resistance similar to that obtained with the radiotracers. The nearly constant rate of decrease of oxygen during the initial phase of the incubations suggests that incubation techniques can be used to obtain an approximate measure of the oxygen uptake rate of sediments as long as the concentration remains above the transition where the curve changes from approximately linear to exponential. This procedure, however, underestimates the oxygen uptake rate by 28-34% compared to model results. Model calculations also suggest that oxygen uptake rates can differ substantially between chamber and outside sediments, especially when hydrodynamic conditions influencing the apparent boundary layer resistance are different within and outside chambers.

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In situ Measurements of Nutrient and Oxygen Fluxes in a Coastal Marine Benthic Community

Cited by 56 publications

References 29 publications

Eutrophication and the rate of denitrification and N₂0 production in coastal marine sediments

Eutrophication and the rate of denitrification and N₂0 production in coastal marine sediments

Comparative effects of benthic microalgae and phytoplankton on dissolved silica fluxes

Oxygen uptake kinetics in the benthic boundary layer

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In situ Measurements of Nutrient and Oxygen Fluxes in a Coastal Marine Benthic Community

Cited by 56 publications

References 29 publications

Eutrophication and the rate of denitrification and N20 production in coastal marine sediments

Eutrophication and the rate of denitrification and N20 production in coastal marine sediments

Comparative effects of benthic microalgae and phytoplankton on dissolved silica fluxes

Oxygen uptake kinetics in the benthic boundary layer

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Eutrophication and the rate of denitrification and N₂0 production in coastal marine sediments

Eutrophication and the rate of denitrification and N₂0 production in coastal marine sediments