Possible consequences of containing microplankton for physiological rate measurements

Venrick, Elizabeth L.; Beers, John R.; Heinbokel, J. F.

doi:10.1016/0022-0981(77)90080-6

Cited by 173 publications

(78 citation statements)

References 25 publications

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“…On long time scales, changes in uptake rate due to die1 periodicity were evident in our results. Bottle confinement effects have been shown to lead to serious underestimates of rate processes (Venrick et al 1977) but the constant rates of chl a and POC & PON synthesis indicate no such artifacts in our experiments. Olson & Chisholm (1983) have shown that cell division patterns of nitrogenlimited phytoplankton cultures may be entrained by NH: pulses.…”

Section: Simultaneous Uptake Of Nitrogen Compoundscontrasting

confidence: 46%

Time course of uptake of inorganic and organic nitrogen by phytoplankton in the Strait of Georgia: comparison of frontal and stratified communities

Price¹,

Cochlan²,

Harrison³

1985

Mar. Ecol. Prog. Ser.

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In both frontal and stratified water of the Strait of Georgia, changes in dissolved nitrogen concentrations provided evidence for the simultaneous uptake of ammonium, nitrate and urea by a summer phytoplankton community. Chlorophyll a specific uptake rates of ammonium and urea were ca 2 and 2.4 times greater in stratified water than in frontal water, whereas chlorophyll a specific nitrate uptake rates were ca 1.6 times greater in frontal water. Ammonium and urea regeneration rates, calculated using a mass balance approach, were similar in frontal water, but urea regeneration rates were 2 to 5 times greater in the stratified water during the first 12 h of the experiment. Increases in particulate nitrogen could not be accounted for by corresponding decreases in total concentration of dissolved inorganic nitrogen and urea, or by 15N accumulation in the particulates. In frontal water the change in total dissolved inorganic nitrogen and urea consistently overestimated the change in particulate nitrogen, and in stratified water the change in total dissolved inorganic nitrogen and urea consistently underestimated the change in particulate nitrogen. These data suggest that the plankton community In frontal water was losing nitrogen in the form of dissolved organic nitrogen. By contrast, the plankton community in stratified water took up nitrogen compounds which were not measured as part of the total dissolved inorganic and urea nitrogen, but were most likely dissolved organic nitrogen compounds. Results stress the importance of determining uptake rates of all 3 nitrogen substrates (NHfi, N O and urea) using 15N isotopes and by simultaneously measuring the change in concentration of these compounds throughout the incubation period.

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Section: Simultaneous Uptake Of Nitrogen Compoundscontrasting

confidence: 46%

Time course of uptake of inorganic and organic nitrogen by phytoplankton in the Strait of Georgia: comparison of frontal and stratified communities

Price¹,

Cochlan²,

Harrison³

1985

Mar. Ecol. Prog. Ser.

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“…Several aspects of this technique may be detrimental to the growth of microflagellates, including prefiltration of the inocula and long duration of the experiment. Microflagellates can be damaged during pre-filtration (Bloem & Gilissen 1985, Goldman & Dennett 1986) and they also are sensitive to containment (Venrick et al 1975, Fahnenstiel & Scavia 1987. We believe that future work in marine environments using a variety of techniques will not find a consistent dichotomy in growth rates.…”

Section: Discussionmentioning

confidence: 96%

Taxon-specific growth and loss rates for dominant phytoplankton populations from the northern Gulf of Mexico

Fahnenstiel¹,

McCormick²,

Lang³

et al. 1995

Mar. Ecol. Prog. Ser.

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Taxon-specific growth and sedimentation rates of dommant phytoplankton were measured during 2 cruses (summer 1990 and spring 1991) in the northern Gulf of Mexico as part of the NOAA Nutrient-Enhanced Coastal Ocean Productivity (NECOP) program. Microzooplankton grazing rates also were measured during the summer cruise. During each of the cruises, a series of stations from the Mississippi River mouth to the hypoxia region (located ca 50 to 100 km west) were sampled to examme variability of growth and loss processes along a strong environmental gradient. Significant taxa-and group-specific differences were noted for both growth and loss rates Growth rates ranged from <0.1 to 3.0 d-I with highest rates in the plume region during the summer cruise, where surface rates were close to or exceeded previous urnax values for several taxa. For all taxa, growth rates were lower in the hypoxia region (mean = 0.5 d l ) than in the plume region (mean = 1.1 d l ) ; soluble nitrogen concentrations explained over 50 % of the variability in growth rates. Diatom growth rates were similar to non-diatoms in the plume region, but were significantly lower in the hypoxia region, which suggests that silica limitation may exist in this region. The fate of phytoplankton appeared to be controlled by size and by the degree of silicification. Significant mcrozooplankton grazing loss rates were noted only for small taxa (<20 pm). For microflagellates, microzooplankton grazing rates averaged 82 % (range 42 to 214 %) of the growth rate; sedimentation rates were always < I % of the growth rate. Sedimentation was an important loss for several diatoms, with significant taxon-specific and seasonal differences noted. Large colonial diatoms, such as Skeletonema costatum and Thalassiosira rotula, exhibited the highest sedimentation rates in the plume region dunng the spring cruise(0.2 to 1.0 d l ) , whereas the lowest rates (<0.01 d l ) were noted for Rhizosolenia fragilissirna and Ceratulinapelagica in the hypoxia region dunng the summer cruise. Our results suggest that in the northern Gulf of Mexico, phytoplankton rate processes proceed very rapidly, with growth rates primarily controlled by the supply of nitrogen via the Mississippi River and the fate controlled primarily by size and density (silicification).

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“…The enzyme assay was started by addition of multiple concentrations of substrate analog (2.5, 5.0, 10.0, 20.0, 40.0 mM, final concentration) usually within 2-3 hours of sampling, and incubation time was kept relatively short (within 45 min.) in order to minimize bottle effect 46) or nonlinear metabolic responses 16) . No illumination or shaking was provided during the incubation.…”

Section: Standardization Of Enzyme Assay and Estimation Of Apamentioning

confidence: 99%

Extracellular Proteolytic Activity in the Surface Sediment of a Eutrophic Inlet.

2001

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The potential aminopeptidase activity (APA) in surface sediment (0-1 cm), and important ecological factors of a eutrophicated inlet were monitored for one and a half years on a weekly to biweekly basis to elucidate the fluctuations in extracellular hydrolysis of protein during an annual cycle, and main regulating factors on an annual and/or a seasonal basis. APA was estimated in sediment slurry prepared with unamended bottom water, as the V max of the rate of the enzymatic hydrolysis of a coumarine derivative fluorophore at in situ temperatures. APA varied 5-6 fold during the study period with highest values (225-275 nmole AMC h -1 g -1 dry weight) during September-October or early June when the temperature was 22-28°C and dissolved oxygen concentrations (DO) (2-4 mg L -1 ) in overlying bottom water were high, and much lower values (ca. 50 nmoles AMC h -1 g -1 dry weight) in July-August or December-February. On an annual basis, APA correlated only marginally (p < 0.05; r = 0.25) with the protein content of the surface sediment and not at all with any other variables. However, it showed highly significant correlations (p < 0.001) with temperature (r = 0.81), and protein content (0.65) in mid December-early June, when temperatures were relatively low (ca. 12-22°C) and DO was abundant (ca. 2-6 mg L -1 ) in overlying bottom water.

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Possible consequences of containing microplankton for physiological rate measurements

Cited by 173 publications

References 25 publications

Time course of uptake of inorganic and organic nitrogen by phytoplankton in the Strait of Georgia: comparison of frontal and stratified communities

Time course of uptake of inorganic and organic nitrogen by phytoplankton in the Strait of Georgia: comparison of frontal and stratified communities

Taxon-specific growth and loss rates for dominant phytoplankton populations from the northern Gulf of Mexico

Extracellular Proteolytic Activity in the Surface Sediment of a Eutrophic Inlet.

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