Abstract

The optical signal leaving the surface of fluorescing corals is a combination of elastic and inelastic scatter. A new experimental method was developed to separate the fluorescence and the reflectance components that involves measurements with and without a long-pass cutoff filter that eliminates the fluorescence contribution to the signal. The required measurements were performed underwater to demonstrate the applicability of the method for in situ applications. Computations with prototype rather than individually measured fluorescence emission spectra do not significantly compromise the accuracy of the results. A model was developed for calculating the interaction of the reflectance and the fluorescence components with new incident illumination conditions. The model calculations were supported by field experiment. We show that the contribution of fluorescence to some coral’s spectra in various illumination conditions justifies consideration in optical models. The results are applicable to modeling the spectra of fluorescing corals under any irradiance spectrum and interpreting remote-sensing data in the relevant wavelength range. Further research is necessary to examine the significance of fluorescence near coral reefs at various scales.

© 2001 Optical Society of America

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References

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  1. S. Kawaguti, “On the physiology of reef corals VI, study of the pigments,” Palao Trop. Biol. Stand. Stud. 2, 617–674 (1944).
  2. C. Limbaugh, W. J. North, “Fluorescent, benthic, Pacific Coast coelenterates,” Nature (London) 178, 497–498 (1956).
    [CrossRef]
  3. L. Marden, “Camera under the sea,” Natl. Geogr. 109, 162–200 (1956).
  4. C. H. Mazel, “Spectral measurements of fluorescence emission in Caribbean cnidarians,” Mar. Ecol. Prog. Ser. 120, 185–191 (1995).
    [CrossRef]
  5. A. Logan, K. Halcrow, T. Tomascik, “Notes—UV excitation–fluorescence in polyp tissues of certain scleractinian corals from Barbados and Bermuda,” Bull. Mar. Sci. 46, 807–813 (1990).
  6. M. R. Myers, J. T. Hardy, C. H. Mazel, P. Dustan, “Report: optical spectra and pigmentation of Caribbean reef corals and macroalgae,” Coral Reefs 18, 179–186 (1999).
    [CrossRef]
  7. M. K. Wicksten, “Camouflage in marine invertebrates,” Ocean. Mar. Bio. Ann. Rev. 21, 177–193 (1983).
  8. C. H. Mazel, “Coral fluorescence characteristics: excitation-emission spectra, fluorescence efficiencies, and contribution to apparent reflectance,” in Ocean Optics XIII, S. G. Ackleson, R. Frouin, eds., Proc. SPIE2963, 240–245 (1997).
    [CrossRef]
  9. E. Fuchs, “Fluorescence in reef corals,” Ph.D. dissertation (Massachusetts Institute of Technology, Cambridge, Mass., 1999).
  10. F. Grum, “Colorimetry of fluorescent materials,” in Optical Radiation Measurements, Vol. 2. (Academic, New York, 1980), Chap. 6.
  11. J. Leland, N. Johnson, A. Arechchi, “Principles of bispectral fluorescence colorimetry,” in Photometric Engineering of Sources and Systems, A. V. Arecchi, ed., Proc. SPIE3140, 76–87 (1997).
    [CrossRef]
  12. E. Allen, “Separation of the spectral radiance factor curve of fluorescent substances into reflected and fluoresced components,” Appl. Opt. 12, 289–293 (1973).
    [CrossRef] [PubMed]
  13. The Photonics Design and Applications Handbook 4 (Laurin Publishing, Pittsfield, Mass., 1994).
  14. I. D. Campbell, R. A. Dwek, Biological Spectroscopy (Benjamin/Cummings Science, Menlo Park, Calif., 1984).
  15. A. Savitzky, M. J. E. Golay, “Smoothing and differentiation of data by simplified least squares procedure,” Anal. Chem. 36, 1627–1639 (1964).
    [CrossRef]
  16. C. H. Mazel, “Diver-operated instrument for in situ measurement of spectral fluorescence and reflectance of benthic marine organisms and substrates,” Opt. Eng. 36, 2612–2617 (1997).
    [CrossRef]
  17. E. Fux, C. Mazel, “Unmixing of coral fluorescence emission spectra and prediction of new spectra under different excitation conditions,” Appl. Opt. 38, 486–495 (1999).
    [CrossRef]

1999 (2)

M. R. Myers, J. T. Hardy, C. H. Mazel, P. Dustan, “Report: optical spectra and pigmentation of Caribbean reef corals and macroalgae,” Coral Reefs 18, 179–186 (1999).
[CrossRef]

E. Fux, C. Mazel, “Unmixing of coral fluorescence emission spectra and prediction of new spectra under different excitation conditions,” Appl. Opt. 38, 486–495 (1999).
[CrossRef]

1997 (1)

C. H. Mazel, “Diver-operated instrument for in situ measurement of spectral fluorescence and reflectance of benthic marine organisms and substrates,” Opt. Eng. 36, 2612–2617 (1997).
[CrossRef]

1995 (1)

C. H. Mazel, “Spectral measurements of fluorescence emission in Caribbean cnidarians,” Mar. Ecol. Prog. Ser. 120, 185–191 (1995).
[CrossRef]

1990 (1)

A. Logan, K. Halcrow, T. Tomascik, “Notes—UV excitation–fluorescence in polyp tissues of certain scleractinian corals from Barbados and Bermuda,” Bull. Mar. Sci. 46, 807–813 (1990).

1983 (1)

M. K. Wicksten, “Camouflage in marine invertebrates,” Ocean. Mar. Bio. Ann. Rev. 21, 177–193 (1983).

1973 (1)

1964 (1)

A. Savitzky, M. J. E. Golay, “Smoothing and differentiation of data by simplified least squares procedure,” Anal. Chem. 36, 1627–1639 (1964).
[CrossRef]

1956 (2)

C. Limbaugh, W. J. North, “Fluorescent, benthic, Pacific Coast coelenterates,” Nature (London) 178, 497–498 (1956).
[CrossRef]

L. Marden, “Camera under the sea,” Natl. Geogr. 109, 162–200 (1956).

1944 (1)

S. Kawaguti, “On the physiology of reef corals VI, study of the pigments,” Palao Trop. Biol. Stand. Stud. 2, 617–674 (1944).

Allen, E.

Arechchi, A.

J. Leland, N. Johnson, A. Arechchi, “Principles of bispectral fluorescence colorimetry,” in Photometric Engineering of Sources and Systems, A. V. Arecchi, ed., Proc. SPIE3140, 76–87 (1997).
[CrossRef]

Campbell, I. D.

I. D. Campbell, R. A. Dwek, Biological Spectroscopy (Benjamin/Cummings Science, Menlo Park, Calif., 1984).

Dustan, P.

M. R. Myers, J. T. Hardy, C. H. Mazel, P. Dustan, “Report: optical spectra and pigmentation of Caribbean reef corals and macroalgae,” Coral Reefs 18, 179–186 (1999).
[CrossRef]

Dwek, R. A.

I. D. Campbell, R. A. Dwek, Biological Spectroscopy (Benjamin/Cummings Science, Menlo Park, Calif., 1984).

Fuchs, E.

E. Fuchs, “Fluorescence in reef corals,” Ph.D. dissertation (Massachusetts Institute of Technology, Cambridge, Mass., 1999).

Fux, E.

Golay, M. J. E.

A. Savitzky, M. J. E. Golay, “Smoothing and differentiation of data by simplified least squares procedure,” Anal. Chem. 36, 1627–1639 (1964).
[CrossRef]

Grum, F.

F. Grum, “Colorimetry of fluorescent materials,” in Optical Radiation Measurements, Vol. 2. (Academic, New York, 1980), Chap. 6.

Halcrow, K.

A. Logan, K. Halcrow, T. Tomascik, “Notes—UV excitation–fluorescence in polyp tissues of certain scleractinian corals from Barbados and Bermuda,” Bull. Mar. Sci. 46, 807–813 (1990).

Hardy, J. T.

M. R. Myers, J. T. Hardy, C. H. Mazel, P. Dustan, “Report: optical spectra and pigmentation of Caribbean reef corals and macroalgae,” Coral Reefs 18, 179–186 (1999).
[CrossRef]

Johnson, N.

J. Leland, N. Johnson, A. Arechchi, “Principles of bispectral fluorescence colorimetry,” in Photometric Engineering of Sources and Systems, A. V. Arecchi, ed., Proc. SPIE3140, 76–87 (1997).
[CrossRef]

Kawaguti, S.

S. Kawaguti, “On the physiology of reef corals VI, study of the pigments,” Palao Trop. Biol. Stand. Stud. 2, 617–674 (1944).

Leland, J.

J. Leland, N. Johnson, A. Arechchi, “Principles of bispectral fluorescence colorimetry,” in Photometric Engineering of Sources and Systems, A. V. Arecchi, ed., Proc. SPIE3140, 76–87 (1997).
[CrossRef]

Limbaugh, C.

C. Limbaugh, W. J. North, “Fluorescent, benthic, Pacific Coast coelenterates,” Nature (London) 178, 497–498 (1956).
[CrossRef]

Logan, A.

A. Logan, K. Halcrow, T. Tomascik, “Notes—UV excitation–fluorescence in polyp tissues of certain scleractinian corals from Barbados and Bermuda,” Bull. Mar. Sci. 46, 807–813 (1990).

Marden, L.

L. Marden, “Camera under the sea,” Natl. Geogr. 109, 162–200 (1956).

Mazel, C.

Mazel, C. H.

M. R. Myers, J. T. Hardy, C. H. Mazel, P. Dustan, “Report: optical spectra and pigmentation of Caribbean reef corals and macroalgae,” Coral Reefs 18, 179–186 (1999).
[CrossRef]

C. H. Mazel, “Diver-operated instrument for in situ measurement of spectral fluorescence and reflectance of benthic marine organisms and substrates,” Opt. Eng. 36, 2612–2617 (1997).
[CrossRef]

C. H. Mazel, “Spectral measurements of fluorescence emission in Caribbean cnidarians,” Mar. Ecol. Prog. Ser. 120, 185–191 (1995).
[CrossRef]

C. H. Mazel, “Coral fluorescence characteristics: excitation-emission spectra, fluorescence efficiencies, and contribution to apparent reflectance,” in Ocean Optics XIII, S. G. Ackleson, R. Frouin, eds., Proc. SPIE2963, 240–245 (1997).
[CrossRef]

Myers, M. R.

M. R. Myers, J. T. Hardy, C. H. Mazel, P. Dustan, “Report: optical spectra and pigmentation of Caribbean reef corals and macroalgae,” Coral Reefs 18, 179–186 (1999).
[CrossRef]

North, W. J.

C. Limbaugh, W. J. North, “Fluorescent, benthic, Pacific Coast coelenterates,” Nature (London) 178, 497–498 (1956).
[CrossRef]

Savitzky, A.

A. Savitzky, M. J. E. Golay, “Smoothing and differentiation of data by simplified least squares procedure,” Anal. Chem. 36, 1627–1639 (1964).
[CrossRef]

Tomascik, T.

A. Logan, K. Halcrow, T. Tomascik, “Notes—UV excitation–fluorescence in polyp tissues of certain scleractinian corals from Barbados and Bermuda,” Bull. Mar. Sci. 46, 807–813 (1990).

Wicksten, M. K.

M. K. Wicksten, “Camouflage in marine invertebrates,” Ocean. Mar. Bio. Ann. Rev. 21, 177–193 (1983).

Anal. Chem. (1)

A. Savitzky, M. J. E. Golay, “Smoothing and differentiation of data by simplified least squares procedure,” Anal. Chem. 36, 1627–1639 (1964).
[CrossRef]

Appl. Opt. (2)

Bull. Mar. Sci. (1)

A. Logan, K. Halcrow, T. Tomascik, “Notes—UV excitation–fluorescence in polyp tissues of certain scleractinian corals from Barbados and Bermuda,” Bull. Mar. Sci. 46, 807–813 (1990).

Coral Reefs (1)

M. R. Myers, J. T. Hardy, C. H. Mazel, P. Dustan, “Report: optical spectra and pigmentation of Caribbean reef corals and macroalgae,” Coral Reefs 18, 179–186 (1999).
[CrossRef]

Mar. Ecol. Prog. Ser. (1)

C. H. Mazel, “Spectral measurements of fluorescence emission in Caribbean cnidarians,” Mar. Ecol. Prog. Ser. 120, 185–191 (1995).
[CrossRef]

Natl. Geogr. (1)

L. Marden, “Camera under the sea,” Natl. Geogr. 109, 162–200 (1956).

Nature (London) (1)

C. Limbaugh, W. J. North, “Fluorescent, benthic, Pacific Coast coelenterates,” Nature (London) 178, 497–498 (1956).
[CrossRef]

Ocean. Mar. Bio. Ann. Rev. (1)

M. K. Wicksten, “Camouflage in marine invertebrates,” Ocean. Mar. Bio. Ann. Rev. 21, 177–193 (1983).

Opt. Eng. (1)

C. H. Mazel, “Diver-operated instrument for in situ measurement of spectral fluorescence and reflectance of benthic marine organisms and substrates,” Opt. Eng. 36, 2612–2617 (1997).
[CrossRef]

Palao Trop. Biol. Stand. Stud. (1)

S. Kawaguti, “On the physiology of reef corals VI, study of the pigments,” Palao Trop. Biol. Stand. Stud. 2, 617–674 (1944).

Other (6)

C. H. Mazel, “Coral fluorescence characteristics: excitation-emission spectra, fluorescence efficiencies, and contribution to apparent reflectance,” in Ocean Optics XIII, S. G. Ackleson, R. Frouin, eds., Proc. SPIE2963, 240–245 (1997).
[CrossRef]

E. Fuchs, “Fluorescence in reef corals,” Ph.D. dissertation (Massachusetts Institute of Technology, Cambridge, Mass., 1999).

F. Grum, “Colorimetry of fluorescent materials,” in Optical Radiation Measurements, Vol. 2. (Academic, New York, 1980), Chap. 6.

J. Leland, N. Johnson, A. Arechchi, “Principles of bispectral fluorescence colorimetry,” in Photometric Engineering of Sources and Systems, A. V. Arecchi, ed., Proc. SPIE3140, 76–87 (1997).
[CrossRef]

The Photonics Design and Applications Handbook 4 (Laurin Publishing, Pittsfield, Mass., 1994).

I. D. Campbell, R. A. Dwek, Biological Spectroscopy (Benjamin/Cummings Science, Menlo Park, Calif., 1984).

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Figures (9)

Fig. 1
Fig. 1

(a) Schematic of fluorescence emission and absorption effects on the spectral radiance factor; (b) dashed thin curve, weakening-filter cutoff location; solid thin curve, killing fluorescence filter relative to excitation and emission spectra.

Fig. 2
Fig. 2

Fluorescence emission spectra (normalized to one) of the major pigments found in Caribbean corals to date.

Fig. 3
Fig. 3

Elastic reflectance spectrum of Colpophyllia natans calculated by the new method, TR. The dominating fluorescence pigment is 515. S1, sample illuminated by white light; RE, fluorescence eliminating filter; Excitation, excitation spectrum.

Fig. 4
Fig. 4

Elastic reflectance spectrum of Diploria labyrinthiformis (the dominant fluorescing pigment is 486), calculated with the modified fluorescence method. Lines notation is as in Fig. 3.

Fig. 5
Fig. 5

Example of finding parameter γ for a Colpophyllia natans. The mean value in the flat region (515–550 nm) is used to calculate elastic reflectance.

Fig. 6
Fig. 6

Elastic reflectance curves of Mycetophyllia sp. calculated with the modified, fluorescence-based method. The solid curve was calculated with fluorescence measured from the sample, compared with the dashed curve, where fluorescence was taken from a library of premeasured prototypes.

Fig. 7
Fig. 7

(a) Separated reflectance and fluorescence components of Colpophyllia natans. FLR, dotted curve, is the normalized fluorescence, FLR = γ × F N (λ)/E 0(λ). (b) Relative contribution of each component to the exitance signal.

Fig. 8
Fig. 8

Normalized downwelling irradiance at depths of solid curve, 8 m and, dashed curve, 17 m of coastal waters measured near Lee Stocking Island.

Fig. 9
Fig. 9

Comparison of predicted exitance spectra for incident irradiance at depths of (a) 8 m and (b) 17 m with measured spectra for Scolymia sp. Sample: thick solid curve, in situ measured data; thin dashed curve, calculated without separation; thin solid curve, calculated after separating the reflectance and fluorescence components.

Equations (9)

Equations on this page are rendered with MathJax. Learn more.

Eλ=Eiλ×RELλ+Fλ,
Eλ=EiλRELλ+γFNλ
SRFλ=RELλ+γ FNλEiλ,
γ=SRFλ-RELλEiλFNλ.
RELλ=SRFλ-γ FNλEiλ.
NAmax= EiλExλdλ,
NF= γFNλdλ.
ΦP=NF/NAmax,
NF,new=ΦP  Ei,newλExλdλ.

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