An evaluation of two diffusion culture techniques for estimating phytoplankton growth rates In situ

1982 ◽  
Vol 70 (1) ◽  
pp. 63-72 ◽  
Author(s):  
M. J. Furnas
Keyword(s):  
Growth Rates ◽  
Phytoplankton Growth ◽  
Culture Techniques

Functional Interaction of Phytoplankton and Zooplankton along the Trophic Gradient in Green Bay, Lake Michigan

1991 ◽  
Vol 48 (1) ◽  
pp. 116-122 ◽  
Author(s):  
Paul E. Sager ◽  
Sumner Richman
Keyword(s):  
Growth Rates ◽  
Lake Michigan ◽  
Algal Species ◽  
Phytoplankton Growth ◽  
Calanoid Copepods ◽  
Trophic Gradient ◽  
Functional Interaction ◽  
Trophic Conditions ◽  
Green Bay

The functional interaction of phytoplankton and zooplankton, expressed in terms of the numerical difference between phytoplankton growth rates per day (in situ,14C method) and zooplankton grazing rates per day (in situ feeding experiments), was studied along the trophic gradient in Green Bay, Lake Michigan. Growth–grazing differences increased with trophic conditions, averaging 0.08 for the water column in the meso-oligotrophic northern bay and 0.56 in the eutrophic southern bay for the summers of 1986, 1987, and 1988. Eutrophic conditions produced dominance of growth by large-size cyanobacteria and low grazing rates by microcrustaceans Small and occasionally negative growth–grazing differences in the meso-oligotrophic region were associated with dominance of larger cladocerans and calanoid copepods and small algal species Phytoplankton growth rates in the northern bay averaged about 28% those of the eutrophic region. A unimodal phytoplankton growth response to increased grazing was observed in the northern bay, suggesting variation in positive (growth stimulating) and negative (grazing losses) effects of zooplankton on the phytoplankton.

scholarly journals Disparities between <i>Phaeocystis</i> in situ and optically-derived carbon biomass and growth rates: potential effect on remote-sensing primary production estimates

2014 ◽  
Vol 11 (4) ◽  
pp. 6119-6149
Author(s):  
L. Peperzak ◽  
H. J. van der Woerd ◽  
K. R. Timmermans
Keyword(s):  
Growth Rate ◽  
Quantum Efficiency ◽  
Growth Rates ◽  
Standing Stock ◽  
Phytoplankton Growth ◽  
Ex Situ ◽  
Fluorescent Light ◽  
Limited Growth ◽  
Global Carbon

Abstract. The oceans play a pivotal role in the global carbon cycle. Unfortunately, the daily production of organic carbon, the product of phytoplankton standing stock and growth rate cannot be measured globally by discrete oceanographic methods. Instead, optical proxies from Earth-orbiting satellites must be used. To test the accuracy of optically-derived proxies of phytoplankton physiology and growth rate, standard ex situ data from the wax and wane of a Phaeocystis bloom in laboratory mesocosms were compared with hyperspectral reflectance data. Chlorophyll biomass could be estimated accurately from reflectance using specific chlorophyll absorption algorithms. However, the conversion of chlorophyll (Chl) to carbon (C) was obscured by the observed increase in C : Chl under nutrient-limited growth. C : Chl was inversely correlated (r2 = 0.88) with Photosystem II quantum efficiency (Fv/Fm), the in situ fluorometric oceanographic proxy for growth rate. In addition, the optical proxy for growth rate, the quantum efficiency of fluorescence &amp;varphi; was linearly correlated to Fv/Fm (r2 = 0.84), but not – as by definition – by using total phytoplankton absorption, because during nutrient-limited growth the concentrations of non-fluorescent light-absorbing pigments increased. As a consequence, none of the three proxies (C : Chl, Fv/Fm, φ) was correlated to carbon or cellular phytoplankton growth rates. Therefore, it is concluded that although satellite derived estimates of chlorophyll biomass may be accurate, physiologically-induced non-linear shifts in growth rate proxies may obscure accurate phytoplankton growth rates and hence global carbon production estimates.

scholarly journals Herbivorous protist growth and grazing rates at in situ and artificially elevated temperatures during an Arctic phytoplankton spring bloom

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5264 ◽  
Author(s):  
Susanne Menden-Deuer ◽  
Caitlyn Lawrence ◽  
Gayantonia Franzè
Keyword(s):  
Primary Production ◽  
Growth Rates ◽  
Elevated Temperatures ◽  
Size Fraction ◽  
Temperature Shift ◽  
Phytoplankton Growth ◽  
Grazing Impact ◽  
Large Variability ◽  
Species Specific

To assess protistan grazing impact and temperature sensitivity on plankton population dynamics, we measured bulk and species-specific phytoplankton growth and herbivorous protist grazing rates in Disko Bay, West Greenland in April-May 2011. Rate estimates were made at three different temperatures in situ (0 °C), +3 °C and +6 °C over ambient. In situ Chlorophyll a (Chl a) doubled during the observation period to ∼12  µg Chl a L−1, with 60–97% of Chl a in the >20 µm size-fraction dominated by the diatom genus Chaetoceros. Herbivorous dinoflagellates comprised 60–80% of microplankton grazer biomass. At in situ temperatures, phytoplankton growth or grazing by herbivorous predators <200 µm was not measurable until 11 days after observations commenced. Thereafter, phytoplankton growth was on average 0.25 d−1. Phytoplankton mortality due to herbivorous grazing was only measured on three occasions but the magnitude was substantial, up to 0.58 d−1. Grazing of this magnitude removed ∼100% of primary production. In short-term temperature-shift incubation experiments, phytoplankton growth rate increased significantly (20%) at elevated temperatures. In contrast, herbivorous protist grazing and species-specific growth rates decreased significantly (50%) at +6 °C. This differential response in phytoplankton and herbivores to temperature increases resulted in a decrease of primary production removed with increasing temperature. Phaeocystis spp. abundance was negatively correlated with bulk grazing rate. Growth and grazing rates were variable but showed no evidence of an inherent, low temperature limitation. Herbivorous protist growth rates in this study and in a literature review were comparable to rates from temperate waters. Thus, an inherent physiological inhibition of protistan growth or grazing rates in polar waters is not supported by the data. The large variability between lack of grazing and high rates of primary production removal observed here and confirmed in the literature for polar waters implies larger amplitude fluctuations in phytoplankton biomass than slower, steady grazing losses of primary production.

The Effect of Phosphorus Limitation on Algal Growth Rates: Evidence from Alkaline Phosphatase

1981 ◽  
Vol 38 (11) ◽  
pp. 1421-1427 ◽  
Author(s):  
Ralph E. H. Smith ◽  
Jaap Kalff
Keyword(s):  
Growth Rate ◽  
Alkaline Phosphatase ◽  
Total Phosphorus ◽  
Growth Rates ◽  
Algal Growth ◽  
Phosphorus Limitation ◽  
Phytoplankton Growth ◽  
Limited Growth ◽  
Phytoplankton Communities

The inducible enzyme alkaline phosphatase (APA) was used to quantify phosphorus limitation of freshwater phytoplankton growth in situ. Natural phytoplankton communities from oligotrophic–eutrophic Lake Memphremagog were grown at phosphorus-limited rates of 0.06–0.93 per day in continuous, lake water cultures. APA varied inversely with phosphorus-limited growth rate and was little influenced by the community composition changes that occurred in culture. Compared to cultures, average in situ APA in Lake Memphremagog during the ice-free season was low, and suggested phosphorus-limited growth rates greater than 0.6 per day in even the most oligotrophic parts of the lake. Although algal abundance varies with total phosphorus among most north-temperate zone lakes, including Lake Memphremagog, our data show that average community growth rates are normally high and change relatively little over a fourfold range of total phosphorus concentration.Key words: alkaline phosphatase, phytoplankton, growth rate, phosphorus

Technique d'observation de surface in situ (TOSIS) :

1996 ◽  
Vol 84 ◽  
pp. 17-22
Author(s):  
A. Ranaivoarisoa ◽  
J. M. Olive ◽  
D. Desjardins
Keyword(s):  
Aqueous Solution ◽  
Crack Initiation ◽  
Grain Boundaries ◽  
Growth Rates ◽  
Triple Junction ◽  
Crack Nucleation ◽  
Initiation Time ◽  
Mesoscopic Scale ◽  
Crack Growth Rates

An optical method named In Situ Surface Observation Technique (ISSOT) is presented in this paper. This method is used to detect crack nucleation from a flaw (here a pit) at mesoscopic scale during a triangular push-pull cycling test under the control of charge amplitude in aqueous solution ofMgCl2 at 117°C. It can be found that the crack initiation time determined by using this technique represents 2 % of that estimated from a mechanical criterion. Moreover, the follow of the crack tip evolution by the ISSOT allows to measure average local crack growth rates. It has been shown that the variations of the latter were related to the effects of barriers such as grain boundaries, twin boundaries and grain boundaries triple junction.

scholarly journals Changing trends and emissions of hydrochlorofluorocarbons and their hydrofluorocarbon replacements

2016 ◽  
Author(s):  
Peter G. Simmonds ◽  
Matthew Rigby ◽  
Archibold McCulloch ◽  
Simon O'Doherty ◽  
Dickon Young ◽  
...  
Keyword(s):  
Growth Rates ◽  
Montreal Protocol ◽  
Hfc 134A ◽  
Production And Consumption ◽  
Ozone Depleting Substances ◽  
Phase Out ◽  
Article 5 ◽  
The Impact ◽  
Global Emissions

Abstract. High frequency, in situ global observations of HCFC-22 (CHClF2), HCFC-141b (CH3CCl2F), HCFC-142b (CH3CClF2) and HCFC-124 (CHClFCF3) and their main HFC replacements HFC-134a (CH2FCF3), HFC-125 (CHF2CF3), HFC-143a (CH3CF3), and HFC-32 (CH2F2) have been used to determine their changing global growth rates and emissions in response to the Montreal Protocol and its recent amendments. The 2007 adjustment to the Montreal Protocol required the accelerated phase-out of HCFCs with global production and consumption capped in 2013, to mitigate their environmental impact as both ozone depleting substances and important greenhouse gases. We find that this change has coincided with a reduction in global emissions of the four HCFCs with aggregated global emissions in 2015 of 444 ± 75 Gg/yr, in CO2 equivalent units (CO2 e) 0.75 ± 0.1 Gt/yr, compared with 483 ± 70 Gg/yr (0.82 ± 0.1 Gt/yr CO2 e) in 2010. (All quoted uncertainties in this paper are 1 sigma). About 80 % of the total HCFC atmospheric burden in 2015 is HCFC-22, where global HCFC emissions appear to have been relatively constant in spite of the 2013 cap on global production and consumption. We attribute this to a probable increase in production and consumption of HCFC-22 in Montreal Protocol Article 5 (developing) countries and the continuing release of HCFC-22 from the large banks which dominate HCFC global emissions. Conversely, the four HFCs all show increasing annual growth rates with aggregated global HFCs emissions in 2015 of 329 ± 70 Gg/yr (0.65 ± 0.12 Gt/yr CO2 e) compared to 2010 with 240 ± 50 Gg/yr (0.47 ± 0.08 Gt/yr CO2 e). As HCFCs are replaced by HFCs we investigate the impact of the shift to refrigerant blends which have lower global warming potentials (GWPs). We also note that emissions of HFC-125 and HFC-32 appear to have increased more rapidly during the 2011–2015 5-yr period compared to 2006–2010.

Outbreak densities of the coral predator Drupella in relation to in situ Acropora growth rates on Ningaloo Reef, Western Australia

Coral Reefs ◽  
2018 ◽  
Vol 37 (4) ◽  
pp. 985-993 ◽  
Author(s):  
C. Bessey ◽  
R. C. Babcock ◽  
D. P. Thomson ◽  
M. D. E. Haywood
Keyword(s):  
Western Australia ◽  
Growth Rates ◽  
Ningaloo Reef

Single Crystal Silicon Carbide On Silicon Using A Supersonic Gas Jet Of Methylsilane

1997 ◽  
Vol 483 ◽  
Author(s):  
S. A. Ustin ◽  
C. Long ◽  
L. Lauhon ◽  
W. Ho
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Single Crystal Silicon ◽  
Maximum Growth ◽  
X Ray Diffraction ◽  
Crystal Silicon ◽  
Cross Sectional ◽  
Supersonic Molecular Beam ◽  
Transmission Electron

AbstractCubic SiC films have been grown on Si(001) and Si(111) substrates at temperatures between 600 °C and 900 °C with a single supersonic molecular beam source. Methylsilane (H3SiCH3) was used as the sole precursor with hydrogen and nitrogen as seeding gases. Optical reflectance was used to monitor in situ growth rate and macroscopic roughness. The growth rate of SiC was found to depend strongly on substrate orientation, methylsilane kinetic energy, and growth temperature. Growth rates were 1.5 to 2 times greater on Si(111) than on Si(001). The maximum growth rates achieved were 0.63 μm/hr on Si(111) and 0.375μm/hr on Si(001). Transmission electron diffraction (TED) and x-ray diffraction (XRD) were used for structural characterization. In-plane azimuthal (ø-) scans show that films on Si(001) have the correct 4-fold symmetry and that films on Si(111) have a 6-fold symmetry. The 6-fold symmetry indicates that stacking has occurred in two different sequences and double positioning boundaries have been formed. The minimum rocking curve width for SiC on Si(001) and Si(111) is 1.2°. Fourier Transform Infrared (FTIR) absorption was performed to discern the chemical bonding. Cross Sectional Transmission Electron Microscopy (XTEM) was used to image the SiC/Si interface.

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