Some Limitations of the In Vivo Fluorescence Technique

Loftus, M. E.; Seliger, H. H.

doi:10.2307/1350685

Cited by 107 publications

(38 citation statements)

References 40 publications

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“…Changes in environmental conditions (e.g. light intensity, nutrient availability) can induce modifications in taxonomic assemblages or in physiological states of phytoplankton, with an impact on the fluorescence to Chl a C ratio (Cullen, 1982;Althuis et al, 1994;Claustre et al, 1999;Cleveland and Perry, 1987;Loftus and Seliger, 1975). As mentioned above, fluorescence is not directly proportional to Chl a C but to a * · Chl a C .…”

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Towards a merged satellite and in situ fluorescence ocean chlorophyll product

et al. 2012

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Abstract. Understanding the ocean carbon cycle requires a precise assessment of phytoplankton biomass in the oceans. In terms of numbers of observations, satellite data represent the largest available data set. However, as they are limited to surface waters, they have to be merged with in situ observations. Amongst the in situ data, fluorescence profiles constitute the greatest data set available, because fluorometers have operated routinely on oceanographic cruises since the 1970s. Nevertheless, fluorescence is only a proxy of the total chlorophyll a concentration and a data calibration is required. Calibration issues are, however, sources of uncertainty, and they have prevented a systematic and wide range exploitation of the fluorescence data set. In particular, very few attempts to standardize the fluorescence databases have been made. Consequently, merged estimations with other data sources (e.g. satellite) are lacking.We propose a merging method to fill this gap. It consists firstly in adjusting the fluorescence profile to impose a zero chlorophyll a concentration at depth. Secondly, each point of the fluorescence profile is then multiplied by a correction coefficient, which forces the chlorophyll a integrated content measured on the fluorescence profile to be consistent with the concomitant ocean colour observation. The method is close to the approach proposed by Boss et al. (2008) to correct fluorescence data of a profiling float, although important differences do exist. To develop and test our approach, in situ data from three open ocean stations (BATS, HOT and DYFAMED) were used. Comparison of the socalled "satellite-corrected" fluorescence profiles with concomitant bottle-derived estimations of chlorophyll a concentration was performed to evaluate the final error (estimated at 31 %). Comparison with the Boss et al. (2008) method, using a subset of the DYFAMED data set, demonstrated that the methods have similar accuracy. The method was applied to two different data sets to demonstrate its utility. Using fluorescence profiles at BATS, we show that the integration of "satellite-corrected" fluorescence profiles in chlorophyll a climatologies could improve both the statistical relevance of chlorophyll a averages and the vertical structure of the chlorophyll a field. We also show that our method could be efficiently used to process, within near-real time, profiles obtained by a fluorometer deployed on autonomous platforms, in our case a bio-optical profiling float. The application of the proposed method should provide a first step towards the generation of a merged satellite/fluorescence chlorophyll a product, as the "satellite-corrected" profiles should then be consistent with satellite observations. Improved climatologies with more consistent satellite and in situ data are likely to enhance the performance of present biogeochemical models.

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Towards a merged satellite and in situ fluorescence ocean chlorophyll product

et al. 2012

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“…While the remote measurement of in vivo fluorescence emitted by phytoplankton is, in principle, straightforward (but see Letelier and Abbott 1996), obtaining an estimate of the quantum yield of fluorescence (the ratio of fluoresced to absorbed photons by phytoplankton) requires a complex algorithm (Abbott and Letelier 1999). Yet, this physiological measurement could foster a major leap in our understanding of the ocean by providing global coverage of a parameter linked to algal physiology (Kiefer and Reynolds 1992) and species composition (Loftus and Seliger 1975;Heaney 1978). In this study, we review the sources of variability of sun-induced fluorescence as they affect the MODIS data products and examine how they relate to the retrieval of the quantum yield of fluorescence and chlorophyll concentration.…”

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New algorithms for MODIS sun-induced chlorophyll fluorescence and a comparison with present data products

Huot

Brown

Cullen

2005

Limnol. Oceanogr. Methods

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The launch of the MODIS instrument (Esaias et al. 1998), with a waveband dedicated to the measurement of sun-induced chlorophyll fluorescence, has taken remote sensing of marine phytoplankton in a new direction. In theory, it is now possible to obtain a global quasi-synoptic assessment of near-surface fluorescence emission and its quantum yield. While the remote measurement of in vivo fluorescence emitted by phytoplankton is, in principle, straightforward (but see Letelier and Abbott 1996), obtaining an estimate of the quantum yield of fluorescence (the ratio of fluoresced to absorbed photons by phytoplankton) requires a complex algorithm (Abbott and Letelier 1999). Yet, this physiological measurement could foster a major leap in our understanding of the ocean by providing global coverage of a parameter linked to algal physiology (Kiefer and Reynolds 1992) and species composition (Loftus and Seliger 1975;Heaney 1978). In this study, we review the sources of variability of sun-induced fluorescence as they affect the MODIS data products and examine how they relate to the retrieval of the quantum yield of fluorescence and chlorophyll concentration. We propose new algorithms based on semi-empirical relationships from the bio-optical literature and compare our results to MODIS data products.Nature of the MODIS fluorescence measurement-Quantum yield of chlorophyll fluorescence. In this study, we define the quantum yield of chlorophyll a fluorescence in vivo (ϕ, dimensionless; see Table 1 for symbols and definitions) as the ratio of photons fluoresced by chlorophyll a over the whole fluorescence band to the photons absorbed by all cellular pigments. Others have referred to this as the apparent quantum yield of chlorophyll a fluorescence, limiting the term quantum yield of chlorophyll a fluorescence to the ratio of photons fluoresced by chlorophyll a (or by chlorophyll a associated with photosystem II [PSII]) to those absorbed only by photosynthetic pigments associated with PSII (e.g., Gilmore and Govindjee 1999). This distinction is important for the physiological interpretation of remote sensing data and for the comparison with laboratory measurements (see Web Appendix 2). New algorithms for MODIS sun-induced chlorophyll fluorescence and a comparison with present data products AbstractWe discuss important sources of variability in sun-induced chlorophyll fluorescence and examine difficulties in deriving fluorescence data products from satellite imagery, with a focus on the MODerate-resolution Imaging Spectroradiometer (MODIS) sensor. Our results indicate that there are limitations in the present MODIS algorithms that could lead to biases in the interpretation of the fluorescence products across gradients of chlorophyll concentration. To avoid some of these limitations, we suggest replacing the calculation of absorbed radiation by phytoplankton (ARP) over a finite depth with integration over the entire water column, and including a term accounting for cellular reabsorption of fluoresced light. These suggestions are in...

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“…The ratio of fluorescence to chlorophyll-a can vary depending on the species composition of the phytoplankton, the health of the cells, and the ambient light conditions (e.g., Loftus and Seliger 1975;Dandonneau and Neveaux 1997). In the present data, decreases in fluorescence can be seen almost daily during the middle of the day.…”

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Larval ecology and synchronous reproduction of two crustacean species : Semibalanus balanoides in New England, USA and Gecarcinus quadratus in Veraguas, Panama

Gyory¹

2011

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The environmental cues for synchronous reproduction were investigated for two highly abundant, ecologically important crustacean species: the temperate acorn barnacle, Semibalanus balanoides, and the tropical terrestrial crab, Gecarcinus quadratus. Larval ecology of these two species was also studied to determine potential sources of larval mortality and recruitment success. High-frequency observations revealed that early-stage larval abundance of S. balanoides was related to storms, and possibly turbidity. Field observations and experiments studied the effect of turbidity and phytoplankton on larval release response. Release coincided with increased turbidity at three sites along the northeast coast of the United States. A three-year time series of phytoplankton and zooplankton data showed that larval release was not consistently related to phytoplankton abundance (total or single species). When gravid barnacles were exposed to phytoplankton or synthetic beads, they released in response to both, suggesting that presence of particles is more important than identity of particles. Feeding experiments showed that adult cannibalism on newly released larvae is lower in highly turbid conditions. It is suggested here that S. balanoides synchronizes its reproduction with the onset of phytoplankton blooms, but turbidity may fine-tune the timing if it provides predation refuge for larvae. Adult G. quadratus females undertake synchronized breeding migrations to the ocean after the first rains of the rainy season, presumably when the risk of desiccation is lowest. They wait for darkness and an ebbing tide before releasing their eggs into the water. First-stage zoeas have dark pigmentation, long dorsal and rostral spines, and a pair of lateral spines. Hatching in darkness may help zoeas avoid predation from planktivorous diurnal fish, and the zoeal spines may deter predation from planktivorous nocturnal fish. In the laboratory, a G. quadratus zoea reached the megalopa stage in 21 days. A mass migration of megalopae and juveniles out of the water was observed 30 days after adult females released their eggs. Plankton pump samples taken near the island suggest that zoea abundance and distribution may be related to the phase of the internal tide. Synchronous reproduction in these two species appears to be the result of predator avoidance behaviors.

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Some Limitations of the In Vivo Fluorescence Technique

Cited by 107 publications

References 40 publications

Towards a merged satellite and in situ fluorescence ocean chlorophyll product

Towards a merged satellite and in situ fluorescence ocean chlorophyll product

New algorithms for MODIS sun-induced chlorophyll fluorescence and a comparison with present data products

Larval ecology and synchronous reproduction of two crustacean species : Semibalanus balanoides in New England, USA and Gecarcinus quadratus in Veraguas, Panama

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