Vertical attenuation coefficient of photosynthetically active radiation as a function of chlorophyll concentration and depth in case 1 waters

Giles-Guzmán, Alma D.; Alvarez-Borrego, S.

doi:10.1364/ao.39.001351

Cited by 7 publications

(8 citation statements)

References 16 publications

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“…Detailed studies of the relationships between k and the chl a concentration for Case 1 waters have been done by Morel (1988) and Giles-Guzman & Alvarez-Borrego (2000) whose average results are very close to the result of Riley (1956) that we use below. The resulting k values averaged from the 3 relationships in the 1 to 10 mg m -3 of chl a interval (typical values for our region) exhibit a coefficient of variation of only 8% (4% in the 1 to 6 mg m -3 of chl a interval.…”

Section: Methodssupporting

confidence: 81%

Generalised model of primary production in the southern Benguela upwelling system

Demarcq¹,

Richardson²,

Field³

2008

Mar. Ecol. Prog. Ser.

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We provide a proof-of-concept demonstration using a novel method for estimating depth-integrated distributions of chlorophyll from archives of data from ships, buoys or gliders combined with remotely sensed data of sea surface temperature (SST) and surface chlorophyll a (chl a) from satellites. Our area of application has contrasting hydrographic regimes, which include the dynamic southern Benguela upwelling system and the stratified waters of the Agulhas Bank, South Africa. The method involves using self-organising maps (SOMs), a type of artificial neural network, to identify 'typical' chl a profiles regardless of their statistical form, provided several of a similar shape have been found in the training set. These are arranged in a linear array, ranging from uniform profiles low in chl a to profiles with high surface or subsurface peaks. We then use generalised modelling to relate these characteristic profiles to remotely sensed surface features, viz. surface chl a and SST, as well as area, season, and water depth (a proxy for distance offshore). The model accounts for 87% of the variability in chl a profile and is used to predict the type of profile likely for each pixel in monthly remote sensing composites of SST and surface chl a and then to estimate integrated chl a and primary production with the aid of a light model. Primary production peaks in mid-summer, reaching 5 mgC m -2 d -1 locally, with an average over the whole area and all seasons of 1.4 mg C m -2 d -1. Seasonal variation is greatest in the southern part of the west coast, and lowest in the stratified southeast. Annual primary production for the southern Benguela region including the Agulhas Bank is ca. 156 million tC yr -1 . This is the most robust estimate of primary production in the Benguela system to date because it combines the spatial and temporal coverage provided by remote sensing with realistic vertical chl a profiles.KEY WORDS: Remote sensing · SeaWiFS · Ocean colour · Primary production · Self-organising maps · SOM · Generalised additive model · SOM · Vertical chlorophyll a profile Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 354: [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74] 2008 related to their intrinsic complexity (Campbell et al. 2002), few of them directly incorporate information on the vertical distribution of phytoplankton.Sensitivity analyses of primary production models show that the error in estimates of photosynthesis can be considerable when the chlorophyll maximum is near the surface. This is generally the case in coastal upwelling areas, where profiles are variable due to the wide range of oceanic conditions from active upwelling cells and filaments inshore to stratified waters offshore.Several methods have been developed for describing non-uniform biomass profiles in the oceans. However, these methods tend to produce profile categories that are fixed for large spatial and temporal scales and may not be representative of the smaller...

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Section: Methodssupporting

confidence: 81%

Generalised model of primary production in the southern Benguela upwelling system

Demarcq¹,

Richardson²,

Field³

2008

Mar. Ecol. Prog. Ser.

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“…[] to partition the effects of different optical components on PAR attenuation in the open ocean. However, there has been little subsequent application of this approach [ Giles‐Guzman and Alvarez‐Borrego , ].…”

Section: Introductionmentioning

confidence: 99%

Abiotic control of underwater light in a drinking water reservoir: Photon budget analysis and implications for water quality monitoring

Watanabe

Laurion

Markager

et al. 2015

Water Resources Research

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In optically complex inland waters, the underwater attenuation of photosynthetically active radiation (PAR) is controlled by a variable combination of absorption and scattering components of the lake or river water. Here we applied a photon budget approach to identify the main optical components affecting PAR attenuation in Lake St. Charles, a drinking water reservoir for Quebec City, Canada. This analysis showed the dominant role of colored dissolved organic matter (CDOM) absorption (average of 44% of total absorption during the sampling period), but with large changes over depth in the absolute and relative contribution of the individual absorption components (water, nonalgal particulates, phytoplankton and CDOM) to PAR attenuation. This pronounced vertical variation occurred because of the large spectral changes in the light field with depth, and it strongly affected the average in situ diffuse absorption coefficients in the water column. For example, the diffuse absorption coefficient for pure-water in the ambient light field was 10-fold higher than the value previously measured in the blue open ocean and erroneously applied to lakes and coastal waters. Photon absorption budget calculations for a range of limnological conditions confirmed that phytoplankton had little direct influence on underwater light, even at chlorophyll a values above those observed during harmful algal blooms in the lake. These results imply that traditional measures of water quality such as Secchi depth and radiometric transparency do not provide a meaningful estimate of the biological state of the water column in CDOM-colored lakes and reservoirs.

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“…A modifi cation to this model proposed by Giles -Guzm á n and Á lvarez- Borrego (2000) was used for case I gulf waters: P T(z) = [P* m(z) φ max Chl (z) a* ph(z,Chl) PAR (z) ] × [(0.02315P* m(z) ) 2 + (PAR (z) a* ph(z,Chl) φ max ) 2 ] -0.5 .…”

Section: Estimates Of Phytoplankton Production From Satellite Imagerymentioning

confidence: 99%

“…The average specifi c absorption coeffi cient of phytoplankton is a* ph(z,Chl) (m 2 mg Chl -1 ) weighted by the in situ spectral distribution of PAR and calculated following Giles -Guzm á n and Á lvarez- Borrego (2000) . The factor 0.02315 converts mol C to mg C, seconds to hours, and mol photons to μ mol photons.…”

Section: Estimates Of Phytoplankton Production From Satellite Imagerymentioning

confidence: 99%

“…Hidalgo -Gonz á lez and Á lvarez- Borrego (2004) defi ned the chlorophyll vertical profi le for each season of the corresponding year, and for each region within the gulf, based on the average surface satellite values and following Hidalgo -Gonz á lez and Á lvarez- Borrego (2001) . The PAR profi le [PAR (z) ] for case I waters was defi ned following Giles -Guzm á n and Á lvarez- Borrego (2000) , and for case II waters the methodology proposed by Cervantes -Duarte et al (2000) was followed. The photosynthetic parameters [P* m(z) , α * PAR(z) , and φ max ) were taken from Valdez -Holgu í n et al (1999) .…”

Section: Estimates Of Phytoplankton Production From Satellite Imagerymentioning

confidence: 99%

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Phytoplankton biomass and production in the Gulf of California: a review

Alvarez-Borrego

2012

Botanica Marina

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The Gulf of California has three main natural fertilization mechanisms: upwelling, tidal mixing, and water exchange with the Pacifi c Ocean. Waters high in nutrients occur at very shallow depths in the gulf, and little energy is required for these nutrients to reach the euphotic zone. Upwelling off the eastern coast is strong, chlorophyll a concentration (Chl) can exceed 10 mg m -3 , and because of eddy circulation it increases the phytoplankton biomass across the gulf. Because of strong stratifi cation during summer, upwelling off the western coast causes Chl to increase only to ∼ 0.5 mg m -3 . The annual cycle is the dominant mode of Chl variability in most of the gulf. El Ni ñ o events cause the suppression of Chl mostly in areas on the eastern side of the central and southern gulf, with the effect decreasing from the mouth to the central gulf. 14 C data show that highest productivities occur during winter -spring, and in the Guaymas Basin (up to > 4 g C m -2 day -1 ). Averages of total integrated production (P Tint ) for " winter " and for whole regions within the gulf estimated from satellite imagery are in good agreement with averages of 14 C estimates ( ∼ 1.8 g C m -2 day -1 ). P Tint values for " summer " are ∼ 30 % of those for " winter. "Keywords: 14 C incubations; El Ni ñ o effect; Gulf of California; phytoplankton biomass and production; satellite color imagery. Brought to you by | University of Virginia Authenticated | 128.143.23.241 Download Date | 10/4/12 8:04 AM

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Vertical attenuation coefficient of photosynthetically active radiation as a function of chlorophyll concentration and depth in case 1 waters

Cited by 7 publications

References 16 publications

Generalised model of primary production in the southern Benguela upwelling system

Generalised model of primary production in the southern Benguela upwelling system

Abiotic control of underwater light in a drinking water reservoir: Photon budget analysis and implications for water quality monitoring

Phytoplankton biomass and production in the Gulf of California: a review

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