Contributions of phytoplankton and bacteria to the optical backscattering coefficient over the Mid-Atlantic Ridge

Martinez‐Vicente, Victor; Tilstone, Gavin H.; Sathyendranath, Shubha; Miller, Peter I.; Groom, Steve

doi:10.3354/meps09388

Cited by 18 publications

(10 citation statements)

References 48 publications

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“…The observed uniformity in POC versus b bp slopes could be explained based on Mie theory, namely that planktonic organisms larger than >2 mm have an insignificant effect on bulk b bp [Stramski and Kiefer, 1991]. However, this hypothesis is contradictory to recent in situ and laboratory measurements [Dall'Olmo et al, 2009;Martinez-Vicente et al, 2012;Vaillancourt et al, 2004;Whitmire et al, 2010]. We did observe a significant decrease in the POC versus b bp slope below the pycnocline (Figure 7b).…”

Section: Natural Variability In Poc Versus B Bpcontrasting

confidence: 72%

“…Section 4 reviews NAB08 results in the context of previous findings, and uses the results of this study to infer the potential sources of variability among previously published POC proxies. While changes in plankton are unlikely to be the only cause of the POC optical proxy variability [ Chung et al , 1998; Grob et al , 2007; Martinez‐Vicente et al , 2012; Oubelkheir et al , 2005], we conclude that plankton community composition serves as a diagnostic for the overall particle assemblage accompanying these different plankton communities. In the appendix, we report a small data set for turbidity (broad‐angle sidescattering) and the corresponding POC versus turbidity slope.…”

Section: Introductionmentioning

confidence: 83%

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Particulate organic carbon and inherent optical properties during 2008 North Atlantic Bloom Experiment

et al. 2012

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[1] The co-variability of particulate backscattering (b bp ) and attenuation (c p ) coefficients and particulate organic carbon (POC) provides a basis for estimating POC on spatial and temporal scales that are impossible to obtain with traditional sampling and chemical analysis methods. However, the use of optical proxies for POC in the open ocean is complicated by variable relationships reported in the literature between POC and c p or b bp . During the 2008 North Atlantic Bloom experiment, we accrued a large data set consisting of >300 POC samples and simultaneously measured c p and b bp . Attention to sampling detail, use of multiple types of POC blanks, cross-calibration of optical instruments, and parallel measurements of other biogeochemical parameters facilitated distinction between natural and methodological-based variability. The POC versus c p slope varied with plankton community composition but not depth; slopes were 11% lower for the diatom versus the recycling community. Analysis of literature POC versus c p slopes indicates that plankton composition is responsible for a large component of that variability. The POC versus b bp slope decreased below the pycnocline by 20%, likely due to changing particle composition associated with remineralization and fewer organic rich particles. The higher b bp /c p ratios below the mixed layer are also indicative of particles of lower organic density. We also observed a peculiar platform effect that resulted in $27% higher values for downcast versus upcast b bp measurements. Reduction in uncertainties and improvement of accuracies of POC retrieved from optical measurements is important for autonomous sampling, and requires community consensus for standard protocols for optics and POC.Citation: Cetinić, I., M. J.

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Section: Natural Variability In Poc Versus B Bpcontrasting

confidence: 72%

Section: Introductionmentioning

confidence: 83%

Particulate organic carbon and inherent optical properties during 2008 North Atlantic Bloom Experiment

et al. 2012

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“…The main reason for this discrepancy rests on the nature of the particles contributing to both Chla and b bp signal. While phytoplankton cells contribute nearly all of the Chla signal (colored dissolved organic matter may also contribute slightly to the Chla signal; Xing et al, ), bacteria, protists, detritus, and mineral material also contribute to the b bp signal (Martinez‐Vicente et al, ; Stramski et al, , ; Stramski & Kiefer, ). Therefore, in the surface layer, an increase in phytoplankton production does not lead to a similar relative increase in the Chla and b bp signals.…”

Section: Discussionmentioning

confidence: 99%

The Intraseasonal Dynamics of the Mixed Layer Pump in the Subpolar North Atlantic Ocean: A Biogeochemical‐Argo Float Approach

Lacour

Briggs

Claustre

et al. 2019

Global Biogeochemical Cycles

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The detrainment of organic matter from the mixed layer, a process known as the mixed layer pump (ML pump), has long been overlooked in carbon export budgets. Recently, the ML pump has been investigated at seasonal scale and appeared to contribute significantly to particulate organic carbon export to the mesopelagic zone, especially at high latitudes where seasonal variations of the mixed layer depth are large. However, the dynamics of the ML pump at intraseasonal scales remains poorly known, mainly because the lack of observational tools suited to studying such dynamics. In the present study, using a dense network of autonomous profiling floats equipped with bio‐optical sensors, we captured widespread episodic ML pump‐driven export events, during the winter and early spring period, in a large part of the subpolar North Atlantic Ocean. The intraseasonal dynamics of the ML pump exports fresh organic material to depth (basin‐scale average up to 55 mg C·m−2·day−1), providing a significant source of energy to the mesopelagic food web before the spring bloom period. This mechanism may sustain the seasonal development of overwintering organisms such as copepods with potential impact on the characteristics of the forthcoming spring phytoplankton bloom through predator‐prey interactions.

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“…Empirical relationships based on in situ measurements have been proposed between [Chla] and the beam attenuation (scattering plus absorption) coefficient [e.g., Voss, 1992;Loisel and Morel, 1998;Behrenfeld and Boss, 2006], scattering coefficient [e.g., Gordon and Morel, 1983;Loisel and Morel, 1998;Huot et al, 2008], and backscattering coefficient [e.g., Reynolds et al, 2001;Stramska et al, 2006;Huot et al, 2008]. Changes in chlorophyll-specific particulate scattering coefficient, b* p (l) (i.e., particulate scattering coefficient per unit of [Chla]), observed in the field have been related to phytoplankton physiological status [Behrenfeld and Boss, 2003], but the role of cell size in scattering properties of natural phytoplankton communities has been addressed only in few recent studies [Gernez et al, 2011;Brewin et al, 2012;Martinez-Vicente et al, 2012]. The potentially high correlation between scattering and backscattering coefficients may support the use of satellite-derived [Chla] and particulate backscattering for investigation of phytoplankton biomass and physiology [Westberry et al, 2010] as well as size structure [Loisel et al, 2006].…”

Section: Introductionmentioning

confidence: 99%

Variability in light absorption and scattering of phytoplankton in Patagonian waters: Role of community size structure and pigment composition

et al. 2013

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[1] Intense phytoplankton blooms were observed along the Patagonian shelf-break with satellite ocean color data, but few in situ optical observations were made in that region. We examine the variability of phytoplankton absorption and particulate scattering coefficients during such blooms on the basis of field data. The chlorophyll-a concentration, [Chla], ranged from 0.1 to 22.3 mg m À3 in surface waters. The size fractionation of [Chla] showed that 80% of samples were dominated by nanophytoplankton (N-group) and 20% by microphytoplankton (M-group). Chlorophyll-specific phytoplankton absorption coefficients at 440 and 676 nm, a* ph (440) and a* ph (676), and particulate scattering coefficient at 660 nm, b* p (660), ranged from 0.018 to 0.173, 0.009 to 0.046, and 0.031 to 2.37 m 2 (mg Chla) À1 , respectively. Both a* ph (440) and a* ph (676) were statistically higher for the N-group than M-group and also considerably higher than expected from global trends as a function of [Chla]. This result suggests that size of phytoplankton cells in Patagonian waters tends to be smaller than in other regions at similar [Chla]. The phytoplankton cell size parameter, S f , derived from phytoplankton absorption spectra, proved to be useful for interpreting the variability in the data around the general inverse dependence of a* ph (440), a* ph (676), and b* p (660) on [Chla]. S f also showed a pattern along the increasing trend of a* ph (440) and a* ph (676) as a function of the ratios of some accessory pigments to [Chla]. Our results suggest that the variability in phytoplankton absorption and scattering coefficients in Patagonian waters is caused primarily by changes in the dominant phytoplankton cell size accompanied by covariation in the concentrations of accessory pigments.

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Contributions of phytoplankton and bacteria to the optical backscattering coefficient over the Mid-Atlantic Ridge

Cited by 18 publications

References 48 publications

Particulate organic carbon and inherent optical properties during 2008 North Atlantic Bloom Experiment

Particulate organic carbon and inherent optical properties during 2008 North Atlantic Bloom Experiment

The Intraseasonal Dynamics of the Mixed Layer Pump in the Subpolar North Atlantic Ocean: A Biogeochemical‐Argo Float Approach

Variability in light absorption and scattering of phytoplankton in Patagonian waters: Role of community size structure and pigment composition

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