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

2020 ◽  
Vol 12 (5) ◽  
pp. 826 ◽  
Author(s):  
Gemma Kulk ◽  
Trevor Platt ◽  
James Dingle ◽  
Thomas Jackson ◽  
Bror F. Jönsson ◽  
...  

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.

2017 ◽  
Author(s):  
Heather A. Bouman ◽  
Trevor Platt ◽  
Martina Doblin ◽  
Francisco G. Figueiras ◽  
Kristinn Gudmudsson ◽  
...  

Abstract. The photosynthetic performance of marine phytoplankton varies in response to a variety of factors, environmental and taxonomic. One of the aims of the MArine primary Production: model Parameters from Space (MAPPS) project of the European Space Agency is to assemble a global database of photosynthesis-irradiance (P-E) parameters from a range of oceanographic regimes as an aid to examining the basin-scale variability in the photophysiological response of marine phytoplankton and to use this information to improve the assignment of P-E parameters in the estimation of global marine primary production using satellite data. The MAPPS P-E Database, which consists of over 5000 P-E experiments, provides information on the spatio-temporal variability in the two P-E parameters (the assimilation number, PmB, and the initial slope, αB, where the superscripts B indicate normalisation to concentration of chlorophyll) that are fundamental inputs for models (satellite-based and otherwise) of marine primary production that use chlorophyll as the state variable. Quality-control measures consisted of removing samples with abnormally-high parameter values and flags were added to denote whether the spectral quality of the incubator lamp was used to calculate a broad-band value of αB. The MAPPS database provides a photophysiological dataset that is unprecedented in number of observations and in spatial coverage. The database would be useful to a variety of research communities, including marine ecologists, biogeochemical modellers, remote-sensing scientists and algal physiologists. The compiled data are available at https://doi.org/10.1594/PANGAEA.874087 (Bouman et al., 2017).


2013 ◽  
Vol 10 (1) ◽  
pp. 1551-1576
Author(s):  
Y. Huot ◽  
M. Babin ◽  
F. Bruyant

Abstract. To model phytoplankton primary production from remotely sensed data a method to estimate photosynthetic parameters describing the photosynthetic rates per unit biomass is required. Variability in these parameters must be related to environmental variables that are measurable remotely. In the Arctic, a limited number of measurements of photosynthetic parameter have been carried out with the concurrent environmental variables needed. Therefore, to improve the accuracy of remote estimates of phytoplankton primary production as well as our ability to predict changes in the future such measurements and relationship to environmental variables are required. During the MALINA cruise, a large dataset of these parameters were obtained. Together with previously published datasets, we use environmental and trophic variables to provide functional relationships for these parameters. In particular, we describe several specific aspects: the maximum rate of photosynthesis (Pmaxchl) normalized to chlorophyll decreases with depth and is higher for communities composed of large cells; the saturation parameter (Ek) decreases with depth but is independent of the community structure; and the initial slope of the photosynthesis versus irradiance curve (αchl) normalized to chlorophyll is independent of depth but is higher for communities composed of larger cells. The photosynthetic parameters were not influenced by temperature over the range encountered during the cruise (−2 to 8 °C).


2013 ◽  
Vol 10 (5) ◽  
pp. 3445-3454 ◽  
Author(s):  
Y. Huot ◽  
M. Babin ◽  
F. Bruyant

Abstract. To model phytoplankton primary production from remotely sensed data, a method to estimate photosynthetic parameters describing the photosynthetic rates per unit biomass is required. Variability in these parameters must be related to environmental variables that are measurable remotely. In the Arctic, a limited number of measurements of photosynthetic parameters have been carried out with the concurrent environmental variables needed. Such measurements and their relationship to environmental variables will be required to improve the accuracy of remotely sensed estimates of phytoplankton primary production and our ability to predict future changes. During the MALINA cruise, a large dataset of these parameters was obtained. Together with previously published datasets, we use environmental and trophic variables to provide functional relationships for these parameters. In particular, we describe several specific aspects: the maximum rate of photosynthesis (Pmaxchl) normalized to chlorophyll decreases with depth and is higher for communities composed of large cells; the saturation parameter (Ek) decreases with depth but is independent of the community structure; and the initial slope of the photosynthesis versus irradiance curve (αchl) normalized to chlorophyll is independent of depth but is higher for communities composed of larger cells. The photosynthetic parameters were not influenced by temperature over the range encountered during the cruise (−2 to 8 °C).


2020 ◽  
Vol 639 ◽  
pp. 53-71
Author(s):  
P Jacobs ◽  
JC Kromkamp ◽  
SM van Leeuwen ◽  
CJM Philippart

Pelagic primary production measurements provide fundamental information about the trophic status of a marine ecosystem. Measured carbon fixation rates generally have a limited temporal and spatial resolution, but can be combined with Earth Observation data to extrapolate the measurements. Here, P-E curves were fitted for 3 yr of 14C incubation data from the western Wadden Sea, using 4 different models; 2 with and 2 without photo-inhibition. The curve-fit model by Jassby & Platt (1976) best fit the data. Applying this model showed that the photosynthetic parameters, normalised for chlorophyll a concentration, of maximum production (PBmax) and initial slope of the P-E curve (αB) were correlated. Seasonality in photosynthetic parameters of this model and the relationship with environmental variables were explored, with a focus on variables that can be inferred from satellite algorithms. There were no significant correlations between αB and any of the environmental variables measured. While PBmax correlated with sea surface temperature (SST), the vertical light attenuation coefficient, silicate and nitrate + nitrite concentration, the multivariate model that best explained the variation in estimates of PBmax was a model that included SST and year. In the period from 2012-2014, daily and annual production ranged between 3.4 and 3800 mg C d-1 and between 131 and 239 g C m-2 yr-1, respectively. Comparison of these results with historical data (1990-2003) indicates that the decline in planktonic primary production that has been happening since the 1990s has halted. Although not tested, we believe that our approach is generally applicable to coastal waters.


2018 ◽  
Vol 10 (1) ◽  
pp. 251-266 ◽  
Author(s):  
Heather A. Bouman ◽  
Trevor Platt ◽  
Martina Doblin ◽  
Francisco G. Figueiras ◽  
Kristinn Gudmundsson ◽  
...  

Abstract. The photosynthetic performance of marine phytoplankton varies in response to a variety of factors, environmental and taxonomic. One of the aims of the MArine primary Production: model Parameters from Space (MAPPS) project of the European Space Agency is to assemble a global database of photosynthesis–irradiance (P-E) parameters from a range of oceanographic regimes as an aid to examining the basin-scale variability in the photophysiological response of marine phytoplankton and to use this information to improve the assignment of P-E parameters in the estimation of global marine primary production using satellite data. The MAPPS P-E database, which consists of over 5000 P-E experiments, provides information on the spatio-temporal variability in the two P-E parameters (the assimilation number, PmB, and the initial slope, αB, where the superscripts B indicate normalisation to concentration of chlorophyll) that are fundamental inputs for models (satellite-based and otherwise) of marine primary production that use chlorophyll as the state variable. Quality-control measures consisted of removing samples with abnormally high parameter values and flags were added to denote whether the spectral quality of the incubator lamp was used to calculate a broad-band value of αB. The MAPPS database provides a photophysiological data set that is unprecedented in number of observations and in spatial coverage. The database will be useful to a variety of research communities, including marine ecologists, biogeochemical modellers, remote-sensing scientists and algal physiologists. The compiled data are available at https://doi.org/10.1594/PANGAEA.874087 (Bouman et al., 2017).


1963 ◽  
Vol 14 (2) ◽  
pp. 139 ◽  
Author(s):  
HR Jitts

Simultaneous measurements with two types of incubators were made on replicate samples both in the incubators and in situ in the ocean. Both incubators used sunlight and blue glass filters to simulate light conditions at depths in the ocean. The first gave measurements of column production 1.58 times those in situ. This was due to the fact that at depths greater than 20 m the incubator gave much higher results with no significant relation to those measured in situ. In the second incubator the accuracy of reproduction of oceanic light conditions was improved by reducing reflected light and using a balance-by-depth twin photometer system for determining the depths of sampling. The measurements of column production in the second incubator were 1.03 times the in situ values.


2005 ◽  
Vol 17 (1) ◽  
pp. 33-45 ◽  
Author(s):  
DARYL MOORHEAD ◽  
JAMIE SCHMELING ◽  
IAN HAWES

A model was used to simulate primary production of benthic microbial mats in Lake Hoare, southern Victoria Land, Antarctica, and to compare potential benthic to planktonic production. Photosynthetic and respiratory characteristics of mats from five depths in the lake were extrapolated across depth, surface area and time, to estimate whole-lake, annual net primary production. Variation in under-ice light regimes resulting from changes in ice thickness and transparency, and light extinction in the water column was examined, and an uncertainty analysis of key model parameters performed. Daily mat production estimates were 0.98–37.83 mg C m−2 d−1, depending on depth and PAR, whereas in situ production of phytoplankton averaged 15% of this. Annual patterns of mat production achieved maximum rates of 15–16 g C m−2 y−1 at 10 m depth when ≥ 5% of ambient PAR was transmitted through the ice covering the lake; observed transmittance values were usually ≤ 5%. Increasing underwater PAR had little effect above 5–7% transmittance, as photosynthesis became saturated at this level. Uncertainties in estimates of maximum photosynthetic rate (Pmax), initial slope of photosynthetic-light response (α) and maximum respiration rate (Rmax) explained 72–99% of uncertainty in model behaviour; Pmax was increasingly important at high light levels whereas α was more important at low light levels, however Rmax exerted the greatest influence under most conditions.


2007 ◽  
Vol 4 (5) ◽  
pp. 853-868 ◽  
Author(s):  
Y. Huot ◽  
M. Babin ◽  
F. Bruyant ◽  
C. Grob ◽  
M. S. Twardowski ◽  
...  

Abstract. Probably because it is a readily available ocean color product, almost all models of primary productivity use chlorophyll as their index of phytoplankton biomass. As other variables become more readily available, both from remote sensing and in situ autonomous platforms, we should ask if other indices of biomass might be preferable. Herein, we compare the accuracy of different proxies of phytoplankton biomass for estimating the maximum photosynthetic rate (Pmax) and the initial slope of the production versus irradiance (P vs. E) curve (α). The proxies compared are: the total chlorophyll a concentration (Tchla, the sum of chlorophyll a and divinyl chlorophyll), the phytoplankton absorption coefficient, the phytoplankton photosynthetic absorption coefficient, the active fluorescence in situ, the particulate scattering coefficient at 650 nm (bp(650)), and the particulate backscattering coefficient at 650 nm (bbp(650)). All of the data (about 170 P vs. E curves) were collected in the South Pacific Ocean. We find that when only the phytoplanktonic biomass proxies are available, bp(650) and Tchla are respectively the best estimators of Pmax and α. When additional variables are available, such as the depth of sampling, the irradiance at depth, or the temperature, Tchla is the best estimator of both Pmax and α.


2013 ◽  
Vol 16 (2) ◽  
pp. 458-476 ◽  
Author(s):  
A. M. Y. Kamel ◽  
G. Y. El Serafy ◽  
B. Bhattacharya ◽  
T. van Kessel ◽  
D. P. Solomatine

Modelling fine sediment dynamics, including transport, deposition and re-suspension, is very complex. This led to studies that validate the modelled suspended particulate matter (SPM) based on in-situ measurements. While in-situ measurements are often sparse in time and space, satellite measurements provide us with higher spatial and temporal resolution. This information can be used to validate and enhance the model's capability of predicting the spatial and temporal distribution of SPM. In this paper, the SPM retrieved from the MEdium Resolution Imaging Spectrometer (MERIS) on board European Space Agency's ENVISAT spacecraft is used to carry out a thorough calibration and validation of the SPM description provided by the Delft3DWAQ model of the Southern North Sea for the year 2007. In an uncertainty analysis framework, the key model parameters affecting the SPM distributions were first identified in predefined physical regions. The sensitivity of the model to slight changes in those parameters is tested and the spatial and temporal errors compared to remote sensing images were identified and a new set of parameters has been suggested and further subjected to uncertainty to define prediction intervals of the SPM distribution at a number of locations. The so-called adapted model has been validated against independent data and has shown a decrease in errors, particularly along the Dutch coast.


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