The Blank Can Make a Big Difference in Oceanographic Measurements

Cullen, John J.; Davis, Richard F.

doi:10.1002/lob.200312229

Cited by 129 publications

(127 citation statements)

References 36 publications

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“…Fv/Fm provides a robust and easily measured parameter indicating photosynthetic health (Cullen and Davis 2003;Franklin et al 2009 Their results indicated that an Fv/Fm value of 0.1 equates to a 15% efficiency of PSII, which can be modelled to imply that more than 90% of cells would be photosynthetically non-functional. Rates of recovery here suggest that an Fv/ Fm value of 0.1 and below is a valid indication of nonviable cultures.…”

Section: Discussionmentioning

confidence: 99%

The effect of prolonged darkness on the growth, recovery and survival of Antarctic sea ice diatoms

2011

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While global climate change in polar regions is expected to cause significant warming, the annual cycle of light and dark will remain unchanged. Cultures of three species of Antarctic sea ice diatoms, Fragilariopsis cylindrus (Grunow) Krieger, Thalassiosira antarctica Comber and Entomoneis kjellmanii (P.T. Cleve) Poulin and Cardinal, were incubated in the dark and exposed to differing temperatures. Maximum dark survival times varied between 30 and 60 days. Photosynthetic parameters, photosynthetic efficiency (a), maximum quantum yield (Fv/ Fm), maximum relative electron transport rate (rETRmax) and non-photochemical quenching (NPQ), showed that dark exposure had a significant impact on photoacclimation. In contrast, elevated temperatures had a relatively minor impact on photosynthetic functioning during the dark exposure period but had a considerable impact on dark survival with minimal dark survival times reduced to only 7 days when exposed to 10°C. Recovery of maximum quantum yield of fluorescence (Fv/Fm) was not significantly impacted by temperature, species or dark exposure length. Recovery rates of Fv/Fm ranged from -5.06E-7 ± 2.71E-7 s -1 to 1.36E-5 ± 1.53E-5 s -1 for monthly experiments and from -9.63E-7 ± 7.71E-7 s -1 to 2.65E-5 ± 2.97E-5 s -1 for weekly experiments. NPQ recovery was greater and more consistent than Fv/Fm recovery, ranging between 5.74E-7 ± 8.11E-7 s -1 to 7.50E-3 ± 7.1E-4 s -1 . The concentration of chl-a and monosaccharides remained relatively constant in both experiments. These results suggest that there will probably be little effect on Antarctic microalgae with increasing water temperatures during the Antarctic winter.

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Section: Discussionmentioning

confidence: 99%

The effect of prolonged darkness on the growth, recovery and survival of Antarctic sea ice diatoms

2011

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“…This close coupling of light and iron, which increases the cellular demand for iron under low-light conditions, can diminish lightdependent photosynthesis when iron concentrations are too low to support growth (Hiscock et al, 2008;Moore et al, 2013;Ryan-Keogh et al, 2017b). Iron is also required in the function of both nitrate and nitrite reductase (de Baar et al, 2005), which function to facilitate the assimilation of nitrate and nitrite and their subsequent intracellular reduction to ammonium. In the Southern Ocean, and other HNLC areas, nitrate uptake rates are reported as becoming iron-limited for this reason (Cochlan, 2008;Lucas et al, 2007;Moore et al, 2013;Price et al, 1994).…”

Section: T J Ryan-keogh Et Al: Seasonal Development Of Iron Limitamentioning

confidence: 99%

“…The high productivity characteristic of this region is driven in part by the high macronutrient availability, while phytoplankton growth and productivity are ultimately constrained by the availability of light and iron (de Baar et al, 1990;Martin et al, 1990). The result of this limitation is the prevalence of macronutrients in the surface waters at the end of the growing season, resulting in the paradoxical high-nutrient low-chlorophyll (HNLC) conditions characteristic of the region.…”

Section: Introductionmentioning

confidence: 99%

Seasonal development of iron limitation in the sub-Antarctic zone

Ryan‐Keogh

Thomalla

Mtshali³

et al. 2018

Biogeosciences

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Abstract. The seasonal and sub-seasonal dynamics of iron availability within the sub-Antarctic zone (SAZ; ∼ 40-45 • S) play an important role in the distribution, biomass and productivity of the phytoplankton community. The variability in iron availability is due to an interplay between winter entrainment, diapycnal diffusion, storm-driven entrainment, atmospheric deposition, iron scavenging and iron recycling processes. Biological observations utilizing grow-out iron addition incubation experiments were performed at different stages of the seasonal cycle within the SAZ to determine whether iron availability at the time of sampling was sufficient to meet biological demands at different times of the growing season. Here we demonstrate that at the beginning of the growing season, there is sufficient iron to meet the demands of the phytoplankton community, but that as the growing season develops the mean iron concentrations in the mixed layer decrease and are insufficient to meet biological demand. Phytoplankton increase their photosynthetic efficiency and net growth rates following iron addition from midsummer to late summer, with no differences determined during early summer, suggestive of seasonal iron depletion and an insufficient resupply of iron to meet biological demand. The result of this is residual macronutrients at the end of the growing season and the prevalence of the high-nutrient low-chlorophyll (HNLC) condition. We conclude that despite the prolonged growing season characteristic of the SAZ, which can extend into late summer/early autumn, results nonetheless suggest that iron supply mechanisms are insufficient to maintain potential maximal growth and productivity throughout the season.

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“…Obtaining accurate absolute values of biophysical parameters from the fluorescence transients requires the subtraction of both instrument response function (IRF) non-linearities (Laney, 2003) and, depending on the parameter, sample blanks (Cullen and Davis, 2003). An IRF was only determined following the final cruise, AMT 11 using a chlorophyll a extract and deionised water (Laney, 2003;Suggett et al, 2004;Moore et al, 2005) for all gains and both FRR chambers.…”

Section: Frr Fluorescence and Determination Of Electron Transport Ratesmentioning

confidence: 99%

Photosynthetic electron turnover in the tropical and subtropical Atlantic Ocean

Suggett

Moore

Marañón

et al. 2006

Deep Sea Research Part II: Topical Studies in Oceanography

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Photosynthetic electron transport directly generates the energy required for carbon fixation and thus underlies the aerobic metabolism of aquatic systems. We determined photosynthetic electron turnover rates, ETRs, from ca. 100 FRR fluorescence water-column profiles throughout the subtropical and tropical Atlantic during six Atlantic Meridional Transect cruises (AMT 6, May-June 1998, to AMT 11, September-October 2000. Each FRR fluorescence profile yielded a water-column ETR-light response from which the maximum electron turnover rate ðETR max RCII Þ, effective absorption (s PSII ) and light saturation parameter (E k ) specific to the concentration of photosystem II reaction centres (RCIIs) were calculated. ETR max RCII and E k increased whilst s PSII decreased with mixed-layer depth and the daily integrated photosynthetically active photon flux when all provinces were considered together. These trends suggested that variability in maximum ETR can be partly attributed to changes in effective absorption. Independent bio-optical measurements taken during AMT 11 demonstrated that s PSII variability reflects taxonomic and physiological differences in the phytoplankton communities. ETR max RCII and E k , but not s PSII , remained correlated with mixed-layer depth and daily integrated photosynthetically active photon flux when data from each oceanic province were considered separately, indicating a decoupling of electron turnover and carbon fixation rates within each province. Comparison of maximum ETRs with 14 C-based measurements of P max further suggests that light absorption and C fixation are coupled to differing extents for the various oligotrophic Atlantic provinces. We explore the importance of quantifying RCII concentration for determination of ETRs and interpretation of ETR-C fixation coupling. r

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The Blank Can Make a Big Difference in Oceanographic Measurements

Cited by 129 publications

References 36 publications

The effect of prolonged darkness on the growth, recovery and survival of Antarctic sea ice diatoms

The effect of prolonged darkness on the growth, recovery and survival of Antarctic sea ice diatoms

Seasonal development of iron limitation in the sub-Antarctic zone

Photosynthetic electron turnover in the tropical and subtropical Atlantic Ocean

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