Laboratory and field measurements of aquatic productivity made by a minicomputer employing a dual oxygen electrode system

Smith, David F.; Horner, Sally M.

doi:10.1007/bf00393947

Cited by 3 publications

(1 citation statement)

References 13 publications

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“…Of these techniques, the measurement of system respiration has several advantages; it provides a rapid and simple assessment of heterotrophic metabolism which can b e directly related to the oxidation of organic matter. Modern, sensitive electrode systems (e. g. Smith & Horner 1982) and high precision Winkler determinations (Williams & Jenkinson 1982, Griffith 1988 have made oxygen measurements amenable even to open ocean studies.…”

Section: Introductionmentioning

confidence: 99%

Size fractionated metabolism of coastal microbial plankton

Hopkinson¹,

Sherr²,

Wiebe³

1989

Mar. Ecol. Prog. Ser.

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The quantitative significance of microbial heterotrophs in overall plankton metabolism was investigated in estuarine and coastal waters off the Georgia coast (USA). Three size classes were examined: < 208 pm, < 10 pm and < 1 p m Respiration was measured by monitoring the rate of oxygen consumption in water samples incubated at in situ temperatures in the dark. Rates by all size classes of plankton were highest in the upper reaches of the Duplin h v e r estuary during summer (52.4 pg O2 1-l h-') and lowest 10 km offshore during winter (10.1 pg O2 1-l h-'). Respiration by organisms passing a 1 pm screen exceeded rates in 208 pm and 10 pm filtered samples, but this enhancement decreased w~t h increasing distance offshore. This increased bacterial (< 1 pm) respiration could not be attributed to artifacts of the filtration procedure or to bacterial growth. Respiration results were consistent with concurrently conducted studies of bacterioplankton growth and bactivorous microprotozoan grazing. Static models of carbon and nitrogen flow between bacterioplankton and heterotrophic protozoa suggest that the C/N ratio of the bacterial food source could largely dictate organic carbon conversion efficiency of planktonic bacteria, the relative role of bacteria and microprotozoans as recyclers of nitrogen and the rate of organic carbon utilization. The relative importance of bacterial nitrogen remineralization decreases as the C/N ratio of the organic substrate increases. Results of this study are discussed in context of the microbial loop and the trophic flow leading to higher organisms.

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Section: Introductionmentioning

confidence: 99%

Size fractionated metabolism of coastal microbial plankton

Hopkinson¹,

Sherr²,

Wiebe³

1989

Mar. Ecol. Prog. Ser.

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Dissolved gases in seawater and sediments

Key¹

1987

Reviews of Geophysics

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Certainlythe most controversial results derived from the study of any dissolved gas concerned oxygen utilization rates in the North Atlantic.Jenkins (1982) estimated a net oxygen utilization rate (OUR) for the Beta triangle region of the North Atlantic (apices 26.5øN x 38.5øW, 32.5øN X 30.0øW, and 22.5øN X 28.5øW) of 5.7 moles of oxygen consumed m -2 yr -1 for the zone below 100m. He assumed that the oxygen distribution below the euphotic zone was stationary and steady state and therfore that the in situ oxygen consumption must be balanced by physical transport of oxygen into the area. His estimates were based on measured distributions of dissolved oxygen and the trac-

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An In Situ System for Evaluating Effects of Toxicants on the Metabolism of Littoral Communities

Lindblad¹,

Kautsky²,

Kautsky³

1988

Functional Testing of Aquatic Biota for Estimating Hazards of Chemicals

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A portable in situ continuous-flow apparatus for measuring metabolic activities of littoral ecosystems is described. Oxygen, temperature, light, and flow rate are continuously monitored by a microcomputer that redirects the water flow through the measurement chamber from acrylic jars containing the communities. The apparatus is especially designed for experimental purposes, since it is possible to alter the incoming waters by adding various toxicants. The application of the method is presented by an example showing the response of a filter-feeding community to cadmium. The community showed statistically significant changes in respiration (oxygen) and excretion (nitrogen or phosphorus) as a result of treatment. Calculated ratios—such as the oxygen/nitrogen ratio, oxygen/phosphorus ratio, and perturbation index (PI), which is the relative change due to treatment, taking into account changes in the controls—were more sensitive measurements of sublethal stress than specific values of oxygen, nitrogen, or phosphorus. These indexes are independent of biomass, and PI normalizes synchronic changes in the environment due to light, temperature, and salinity variations, which affect both treated and control systems equally. The design of the system allows the communities to be placed back in the environment after being tested and also allows repeated measurements to be made of possible delayed effects or recovery from perturbations. In this paper, the authors introduce a new measurement of disturbance, the absolute disturbance index (ADI). ADI is the absolute distance between the metabolic activity of an undisturbed system and a disturbed point in a multidimensional space where each dimension represents the PI of a measured parameter.

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Laboratory and field measurements of aquatic productivity made by a minicomputer employing a dual oxygen electrode system

Cited by 3 publications

References 13 publications

Size fractionated metabolism of coastal microbial plankton

Size fractionated metabolism of coastal microbial plankton

Dissolved gases in seawater and sediments

An In Situ System for Evaluating Effects of Toxicants on the Metabolism of Littoral Communities

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