Size Class Dependent Relationships between Temperature and Phytoplankton Photosynthesis-Irradiance Parameters in the Atlantic Ocean

Robinson, Alex; Bouman, Heather A.; Tilstone, Gavin H.; Sathyendranath, Shubha

doi:10.3389/fmars.2017.00435

Cited by 15 publications

(14 citation statements)

References 122 publications

(231 reference statements)

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“…However, in regions with different underlying physical forcing that experience a smaller range in temperature, such as the Arabian Sea and open ocean gyres, the relationship between temperature and P B m is less obvious (this study; [40,41,105,107,110]). In such regions, chlorophyll-a concentration and the taxonomic and size structure of the phytoplankton community may be better indicators of variability in P B m [38,41,86,107,108]. The initial slope of the P-I curve seems to be more difficult to predict based on empirical relationships with physico-chemical conditions (this study, [41,86]), and it has been suggested that the simplest approach to estimate α B would be to relate α B to the assimilation number [33,110,111].…”

Section: Discussionmentioning

confidence: 91%

“…Over the past three decades, considerable efforts have been made to establish a global database of P-I parameters ( [2,31,33,86]; this study) and to decipher their empirical relationships with physico-chemical and optical properties to enable prediction of photosynthetic parameters on regional and global scales [38,40,41,[105][106][107][108]. The observed relationships between physico-chemical conditions and P-I parameters in the present study confirmed earlier observations that temperature may be a good predictor of the assimilation number (P B m ), especially in coastal regions and temperate oceanic regions where temperature and associated water column stability dictates seasonal changes in the taxonomic and size structure of phytoplankton communities [40,86,109].…”

Section: Discussionmentioning

confidence: 99%

“…Methods designed to assign photosynthetic parameters based on their relationships to other variables amenable to remote-sensing [106,110], could, in the future, lead to a more dynamic assignment of these parameters. Sea surface temperature and phytoplankton community size structure (this study; [33,38,40,41,86,105,107,108]) could be suitable variables for further development of such methods for different ocean basins and biomes.…”

Section: Discussionmentioning

confidence: 99%

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Primary Production, an Index of Climate Change in the Ocean: Satellite-Based Estimates over Two Decades

et al. 2020

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Primary production by marine phytoplankton is one of the largest fluxes of carbon on our planet. In the past few decades, considerable progress has been made in estimating global primary production at high spatial and temporal scales by combining in situ measurements of primary production with remote-sensing observations of phytoplankton biomass. One of the major challenges in this approach lies in the assignment of the appropriate model parameters that define the photosynthetic response of phytoplankton to the light field. In the present study, a global database of in situ measurements of photosynthesis versus irradiance (P-I) parameters and a 20-year record of climate quality satellite observations were used to assess global primary production and its variability with seasons and locations as well as between years. In addition, the sensitivity of the computed primary production to potential changes in the photosynthetic response of phytoplankton cells under changing environmental conditions was investigated. Global annual primary production varied from 38.8 to 42.1 Gt C yr − 1 over the period of 1998–2018. Inter-annual changes in global primary production did not follow a linear trend, and regional differences in the magnitude and direction of change in primary production were observed. Trends in primary production followed directly from changes in chlorophyll-a and were related to changes in the physico-chemical conditions of the water column due to inter-annual and multidecadal climate oscillations. Moreover, the sensitivity analysis in which P-I parameters were adjusted by ±1 standard deviation showed the importance of accurately assigning photosynthetic parameters in global and regional calculations of primary production. The assimilation number of the P-I curve showed strong relationships with environmental variables such as temperature and had a practically one-to-one relationship with the magnitude of change in primary production. In the future, such empirical relationships could potentially be used for a more dynamic assignment of photosynthetic rates in the estimation of global primary production. Relationships between the initial slope of the P-I curve and environmental variables were more elusive.

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Primary Production, an Index of Climate Change in the Ocean: Satellite-Based Estimates over Two Decades

et al. 2020

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“…It thus would appear that the high primary production at the DCM during PEACETIME was due not only to enhanced levels of phytoplankton biomass but also to the presence of a diatom-rich community characterised by high photosynthetic efficiency. These results stress the importance of incorporating the linkage between community structure and photophysiological parameters to improve the application of bio-optical productivity models over diverse ecological and biogeographic settings (Robinson et al, 2018;Uitz et al, 2010;Uitz et al, 2012).…”

Section: Phytoplankton Photophysiology and Productivitymentioning

confidence: 75%

Deep maxima of phytoplankton biomass, primary production and bacterial production in the Mediterranean Sea during late spring

Marañón

Uitz

Boss

et al. 2020

Preprint

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Abstract. The deep chlorophyll maximum (DCM) is a ubiquitous feature of phytoplankton vertical distribution in stratified waters that is relevant for our understanding of the mechanisms that underpin the variability in photoautotroph ecophysiology across environmental gradients and has implications for remote sensing of aquatic productivity. During the PEACETIME (Process studies at the air-sea interface after dust deposition in the Mediterranean Sea) cruise, carried out from 10 May to 11 June 2017, we obtained 23 concurrent vertical profiles of phytoplankton chlorophyll a, carbon biomass and primary production, as well as heterotrophic prokaryotic production, in the western and central Mediterranean basins. Our main aims were to quantify the relative role of photoacclimation and enhanced growth as underlying mechanisms of the DCM and to assess the trophic coupling between phytoplankton and heterotrophic prokaryotic production. We found that the DCM coincided with a maximum in both biomass and primary production but not in growth rate of phytoplankton, which averaged 0.3 d−1 and was relatively constant across the euphotic layer. Photoacclimation explained most of the increased chlorophyll a at the DCM, as the carbon to chlorophyll a ratio (C:Chl a) decreased from ca. 90–100 (g:g) at the surface to 20–30 at the base of the euphotic layer, while phytoplankton carbon biomass increased from ca. 6 mgC m−3 at the surface to 10–15 mgC m−3 at the DCM. As a result of photoacclimation, there was an uncoupling between chlorophyll a-specific and carbon-specific productivity across the euphotic layer. The fucoxanthin to total chlorophyll a ratio increased markedly with depth, as did the biomass contribution of large cells, suggesting a dominance of diatoms at the DCM. The increased biomass and carbon fixation at the base of the euphotic zone was associated with enhanced rates of heterotrophic prokaryotic activity, which also showed a surface peak linked with warmer temperatures. Considering the phytoplankton biomass and turnover rates measured at the DCM, nutrient diffusive fluxes across the nutricline were able to supply only a minor fraction of the photoautotroph nitrogen and phosphorus requirements. Thus the deep maxima in biomass and primary production were not fueled by new nutrients, but likely resulted from cell sinking from the upper layers in combination with the high photosynthetic efficiency of a diatom-rich, low-light acclimated community largely sustained by regenerated nutrients. Further studies with increased temporal and spatial resolution will be required to ascertain if the deep primary production peaks associated with the DCM persist across the western and central Mediterranean Sea throughout the stratification season.

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“…The size-structure of the phytoplankton affects export of large aggregates (Boyd and Newton, 1999), with large cells thought to contribute more to the flux of carbon at depth than smaller phytoplankton, at similar levels of total chlorophyll (Guidi et al, 2009), acknowledging small-celled carbon export can be significant (Richardson, 2019). The photosynthetic rate of phytoplankton, for a given concentration of total chlorophyll, has been shown to depend on size-structure (Platt and Jassby, 1976; Fernández et al, 2003; Morán et al, 2004; Uitz et al, 2008; Álvarez et al, 2016; Brewin et al, 2017b; Curran et al, 2018; Robinson et al, 2018a,b). Biological heating by phytoplankton is influenced by the chlorophyll-specific absorption coefficient, which changes with size (Bricaud et al, 2004; Devred et al, 2006; Uitz et al, 2008; Brewin et al, 2011).…”

Section: Resultsmentioning

confidence: 99%

Factors Regulating the Relationship Between Total and Size-Fractionated Chlorophyll-a in Coastal Waters of the Red Sea

et al. 2019

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Phytoplankton biomass and size structure are recognized as key ecological indicators. With the aim to quantify the relationship between these two ecological indicators in tropical waters and understand controlling factors, we analyzed the total chlorophyll-a concentration, a measure of phytoplankton biomass, and its partitioning into three size classes of phytoplankton, using a series of observations collected at coastal sites in the central Red Sea. Over a period of 4 years, measurements of flow cytometry, size-fractionated chlorophyll-a concentration, and physical-chemical variables were collected near Thuwal in Saudi Arabia. We fitted a three-component model to the size-fractionated chlorophyll-a data to quantify the relationship between total chlorophyll and that in three size classes of phytoplankton [pico- (<2 μm), nano- (2–20 μm) and micro-phytoplankton (>20 μm)]. The model has an advantage over other more empirical methods in that its parameters are interpretable, expressed as the maximum chlorophyll-a concentration of small phytoplankton (pico- and combined pico-nanophytoplankton, Cpm and Cp,nm, respectively) and the fractional contribution of these two size classes to total chlorophyll-a as it tends to zero (Dp and Dp,n). Residuals between the model and the data (model minus data) were compared with a range of other environmental variables available in the dataset. Residuals in pico- and combined pico-nanophytoplankton fractions of total chlorophyll-a were significantly correlated with water temperature (positively) and picoeukaryote cell number (negatively). We conducted a running fit of the model with increasing temperature and found a negative relationship between temperature and parameters Cpm and Cp,nm and a positive relationship between temperature and parameters Dp and Dp,n. By harnessing the relative red fluorescence of the flow cytometric data, we show that picoeukaryotes, which are higher in cell number in winter (cold) than summer (warm), contain higher chlorophyll per cell than other picophytoplankton and are slightly larger in size, possibly explaining the temperature shift in model parameters, though further evidence is needed to substantiate this finding. Our results emphasize the importance of knowing the water temperature and taxonomic composition of phytoplankton within each size class when understanding their relative contribution to total chlorophyll. Furthermore, our results have implications for the development of algorithms for inferring size-fractionated chlorophyll from satellite data, and for how the partitioning of total chlorophyll into the three size classes may change in a future ocean.

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Size Class Dependent Relationships between Temperature and Phytoplankton Photosynthesis-Irradiance Parameters in the Atlantic Ocean

Cited by 15 publications

References 122 publications

Primary Production, an Index of Climate Change in the Ocean: Satellite-Based Estimates over Two Decades

Primary Production, an Index of Climate Change in the Ocean: Satellite-Based Estimates over Two Decades

Deep maxima of phytoplankton biomass, primary production and bacterial production in the Mediterranean Sea during late spring

Factors Regulating the Relationship Between Total and Size-Fractionated Chlorophyll-a in Coastal Waters of the Red Sea

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