Abstract

In many environments a large portion of particulate material is contained in aggregated particles; however, there is no validated framework to describe how aggregates in the ocean scatter light. Here we present the results of two experiments aiming to expose the role that aggregation plays in determining particle light scattering properties, especially in sediment-dominated coastal waters. First, in situ measurements of particle size distribution (PSD) and beam-attenuation were made with two laser particle sizing instruments (one equipped with a pump to subject the sample to aggregate-breaking shear), and measurements from the two treatments were compared. Second, clays were aggregated in the laboratory using salt, and observed over time by multiple instruments in order to examine the effects of aggregation and settling on spectral beam-attenuation and backscattering. Results indicate: (1) mass normalized attenuation and backscattering are only weakly sensitive to size changes due to aggregation in contrast to theory based on solid particles, (2) the spectral slope of beam-attenuation is indicative of changes in PSD but is complicated by instrument acceptance angle, and (3) the spectral shape of backscattering did not provide as clear a relationship with PSD as spectral beam attenuation, as is predicted by theory for solid spheres.

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2011 (1)

P. S. Hill, E. Boss, J. P. Newgard, B. A. Law, and T. G. Milligan, “Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer,” J. Geophys. Res. 116(C2), C02023 (2011), doi:.
[CrossRef]

2010 (1)

WET Labs, Inc., “ECO Triplet User’s Guide (triplet),” Revision P, 19 Jan. 2010. http://www.wetlabs.com/products/pub/eco/tripletp.pdf

2009 (5)

2008 (1)

Y. C. Agrawal, A. Whitmire, O. A. Mikkelsen, and H. C. Pottsmith, “Light scattering by random shaped particles and consequences on measuring suspended sediments by laser diffraction,” J. Geophys. Res. 113(C4), C04023 (2008), doi:.
[CrossRef]

2007 (3)

F. Maggi, “Variable fractal dimension: A major control for floc structure and flocculation kinematics of suspended cohesive sediment,” J. Geophys. Res. 112(C7), C07012 (2007), doi:.
[CrossRef]

W. R. Clavano, E. Boss, and L. Karp-Boss, “Inherent optical properties of non-spherical marine-like particles—from theory to observations,” Oceanogr. Mar. Biol. 45, 1–38 (2007).
[CrossRef]

M. S. Twardowski, H. Claustre, S. A. Freeman, D. Stramski, and Y. Huot, “Optical backscattering properties of the 'clearest' natural waters,” Biogeoscie. 4(6), 1041–1058 (2007).
[CrossRef]

2006 (4)

S. Ackleson, “Optical determinations of suspended sediment dynamics in western Long Island Sound and the Connecticut River plume,” J. Geophys. Res. 111(C7), C07009 (2006), doi:.
[CrossRef]

A. Khelifa and P. S. Hill, “Models for effective density and settling velocity of flocs,” J. Hydraul. Res. 44(3), 390–401 (2006).
[CrossRef]

O. A. Mikkelsen, P. S. Hill, and T. G. Milligan, “Single-grain, microfloc and macrofloc volume variations observed with a LISST-100 and a digital floc camera,” J. Sea Res. 55(2), 87–102 (2006).
[CrossRef]

W. H. Slade and E. S. Boss, “Calibrated near-forward volume scattering function obtained from the LISST particle sizer,” Opt. Express 14(8), 3602–3615 (2006).
[CrossRef] [PubMed]

2004 (2)

E. N. Flory, P. S. Hill, T. G. Milligan, and J. Grant, “The relationship between floc area and backscatter during a spring phytoplankton bloom,” Deep Sea Res. Part I Oceanogr. Res. Pap. 51(2), 213–223 (2004).
[CrossRef]

E. Boss, W. S. Pegau, M. Lee, M. S. Twardowski, E. Shybanov, G. Korotaev, and F. Baratange, “Particulate backscattering ratio at LEO 15 and its use to study particles composition and distribution,” J. Geophys. Res. 109(C1), C01014 (2004), doi:.
[CrossRef]

2003 (1)

Y. Xu and B. Gustafson, “Light scattering by an ensemble of small particles,” Recent Res. Dev. Opt. 3, 599–648 (2003).

2002 (1)

K. J. Curran, P. S. Hill, and T. G. Milligan, “The role of particle aggregation in size-dependent deposition of drill mud,” Cont. Shelf Res. 22(3), 405–416 (2002).
[CrossRef]

2001 (5)

E. Boss, M. S. Twardowski, and S. Herring, “Shape of the particulate beam attenuation spectrum and its inversion to obtain the shape of the particulate size distribution,” Appl. Opt. 40(27), 4885–4893 (2001).
[CrossRef]

C. Sorensen, “Light scattering by fractal aggregates: a review,” Aerosol Sci. Technol. 35, 648–687 (2001).

I. G. Droppo, “Rethinking what constitutes suspended sediment,” Hydrol. Process. 15(9), 1551–1564 (2001).
[CrossRef]

E. Boss, W. S. Pegau, W. D. Gardner, J. R. V. Zaneveld, A. H. Barnard, M. S. Twardowski, G. C. Chang, and T. D. Dickey, “Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf,” J. Geophys. Res. 106(C5), 9509–9516 (2001).
[CrossRef]

A. Hatcher, P. Hill, and J. Grant, “Optical backscatter of marine flocs,” J. Sea Res. 46(1), 1–12 (2001).
[CrossRef]

2000 (1)

Y. C. Agrawal and H. C. Pottsmith, “Instruments for particle size and settling velocity observations in sediment transport,” Mar. Geol. 168(1-4), 89–114 (2000).
[CrossRef]

1999 (1)

M. S. Twardowski, J. M. Sullivan, P. L. Donaghay, and J. R. V. Zaneveld, “Microscale quantification of the absorption by dissolved and particulate material in coastal waters with an ac-9,” J. Atmos. Ocean. Technol. 16(6), 691–707 (1999).
[CrossRef]

1995 (2)

P. S. Hill and A. R. M. Nowell, “Comparison of two models of aggregation in continental-shelf bottom boundary layers,” J. Geophys. Res. 100(C11), 22,749–22,763 (1995).
[CrossRef]

D. K. Costello, K. L. Carder, and W. Hou, “Aggregation of diatom bloom in a mesocosm: Bulk and individual particle optical measurements,” Deep Sea Res. Part II Top. Stud. Oceanogr. 42(1), 29–45 (1995).
[CrossRef]

1993 (1)

K. J. Voss and R. W. Austin, “Beam-attenuation measurements error due to small-angle scattering acceptance,” J. Atmos. Ocean. Technol. 10(1), 113–121 (1993).
[CrossRef]

1992 (1)

D. W. Townsend, M. D. Keller, M. E. Sieracki, and S. G. Ackleson, “Spring phytoplankton blooms in the absence of vertical water column stability,” Nature 360(6399), 59–62 (1992).
[CrossRef]

1986 (1)

D. Eisma, “Flocculation and de-flocculation of suspended matter in estuaries,” Neth. J. Sea Res. 20(2-3), 183–199 (1986).
[CrossRef]

1985 (1)

1983 (1)

I. McCave, “Particle size spectra, behavior, and origin of nepheloid layers over the Nova Scotian continental rise,” J. Geophys. Res. 88(C12), 7647–7666 (1983).
[CrossRef]

1982 (1)

1980 (1)

K. Kranck, “Experiments on the significance of flocculation in the settling of fine-grained sediment in still water,” Can. J. Earth Sci. 17, 1517–1526 (1980).
[CrossRef]

Ackleson, S.

S. Ackleson, “Optical determinations of suspended sediment dynamics in western Long Island Sound and the Connecticut River plume,” J. Geophys. Res. 111(C7), C07009 (2006), doi:.
[CrossRef]

Ackleson, S. G.

D. W. Townsend, M. D. Keller, M. E. Sieracki, and S. G. Ackleson, “Spring phytoplankton blooms in the absence of vertical water column stability,” Nature 360(6399), 59–62 (1992).
[CrossRef]

Agrawal, Y. C.

Y. C. Agrawal and O. A. Mikkelsen, “Empirical forward scattering phase functions from 0.08 to 16 deg. for randomly shaped terrigenous 1-21 microm sediment grains,” Opt. Express 17(11), 8805–8814 (2009).
[CrossRef] [PubMed]

Y. C. Agrawal, A. Whitmire, O. A. Mikkelsen, and H. C. Pottsmith, “Light scattering by random shaped particles and consequences on measuring suspended sediments by laser diffraction,” J. Geophys. Res. 113(C4), C04023 (2008), doi:.
[CrossRef]

Y. C. Agrawal and H. C. Pottsmith, “Instruments for particle size and settling velocity observations in sediment transport,” Mar. Geol. 168(1-4), 89–114 (2000).
[CrossRef]

Austin, R. W.

K. J. Voss and R. W. Austin, “Beam-attenuation measurements error due to small-angle scattering acceptance,” J. Atmos. Ocean. Technol. 10(1), 113–121 (1993).
[CrossRef]

Baratange, F.

E. Boss, W. S. Pegau, M. Lee, M. S. Twardowski, E. Shybanov, G. Korotaev, and F. Baratange, “Particulate backscattering ratio at LEO 15 and its use to study particles composition and distribution,” J. Geophys. Res. 109(C1), C01014 (2004), doi:.
[CrossRef]

Barnard, A. H.

E. Boss, W. S. Pegau, W. D. Gardner, J. R. V. Zaneveld, A. H. Barnard, M. S. Twardowski, G. C. Chang, and T. D. Dickey, “Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf,” J. Geophys. Res. 106(C5), 9509–9516 (2001).
[CrossRef]

Behrenfeld, M.

Behrenfeld, M. J.

G. Dall'Olmo, T. K. Westberry, M. J. Behrenfeld, E. Boss, and W. H. Slade, “Significant contribution of large particles to optical backscattering in the open ocean,” Biogeosci. 6(6), 947–967 (2009).
[CrossRef]

Boss, E.

P. S. Hill, E. Boss, J. P. Newgard, B. A. Law, and T. G. Milligan, “Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer,” J. Geophys. Res. 116(C2), C02023 (2011), doi:.
[CrossRef]

E. Boss, W. H. Slade, and P. Hill, “Effect of particulate aggregation in aquatic environments on the beam attenuation and its utility as a proxy for particulate mass,” Opt. Express 17(11), 9408–9420, 420 (2009).
[CrossRef] [PubMed]

G. Dall'Olmo, T. K. Westberry, M. J. Behrenfeld, E. Boss, and W. H. Slade, “Significant contribution of large particles to optical backscattering in the open ocean,” Biogeosci. 6(6), 947–967 (2009).
[CrossRef]

E. Boss, W. H. Slade, M. Behrenfeld, and G. Dall’Olmo, “Acceptance angle effects on the beam attenuation in the ocean,” Opt. Express 17(3), 1535–1550 (2009).
[CrossRef] [PubMed]

W. R. Clavano, E. Boss, and L. Karp-Boss, “Inherent optical properties of non-spherical marine-like particles—from theory to observations,” Oceanogr. Mar. Biol. 45, 1–38 (2007).
[CrossRef]

E. Boss, W. S. Pegau, M. Lee, M. S. Twardowski, E. Shybanov, G. Korotaev, and F. Baratange, “Particulate backscattering ratio at LEO 15 and its use to study particles composition and distribution,” J. Geophys. Res. 109(C1), C01014 (2004), doi:.
[CrossRef]

E. Boss, W. S. Pegau, W. D. Gardner, J. R. V. Zaneveld, A. H. Barnard, M. S. Twardowski, G. C. Chang, and T. D. Dickey, “Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf,” J. Geophys. Res. 106(C5), 9509–9516 (2001).
[CrossRef]

E. Boss, M. S. Twardowski, and S. Herring, “Shape of the particulate beam attenuation spectrum and its inversion to obtain the shape of the particulate size distribution,” Appl. Opt. 40(27), 4885–4893 (2001).
[CrossRef]

Boss, E. S.

W. H. Slade and E. S. Boss, “Calibrated near-forward volume scattering function obtained from the LISST particle sizer,” Opt. Express 14(8), 3602–3615 (2006).
[CrossRef] [PubMed]

C. R. Russo, E. S. Boss, W. H. Slade, and J. Newgard, “An investigation of the acoustic backscatter response to suspensions of clay aggregates and natural sediments,” Cont. Shelf Res. (submitted).

Burd, A. B.

A. B. Burd and G. A. Jackson, “Particle aggregation,” Ann. Rev. Mar. Scie. 1(1), 65–90 (2009).
[CrossRef]

Carder, K. L.

D. K. Costello, K. L. Carder, and W. Hou, “Aggregation of diatom bloom in a mesocosm: Bulk and individual particle optical measurements,” Deep Sea Res. Part II Top. Stud. Oceanogr. 42(1), 29–45 (1995).
[CrossRef]

Chang, G. C.

E. Boss, W. S. Pegau, W. D. Gardner, J. R. V. Zaneveld, A. H. Barnard, M. S. Twardowski, G. C. Chang, and T. D. Dickey, “Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf,” J. Geophys. Res. 106(C5), 9509–9516 (2001).
[CrossRef]

Claustre, H.

M. S. Twardowski, H. Claustre, S. A. Freeman, D. Stramski, and Y. Huot, “Optical backscattering properties of the 'clearest' natural waters,” Biogeoscie. 4(6), 1041–1058 (2007).
[CrossRef]

Clavano, W. R.

W. R. Clavano, E. Boss, and L. Karp-Boss, “Inherent optical properties of non-spherical marine-like particles—from theory to observations,” Oceanogr. Mar. Biol. 45, 1–38 (2007).
[CrossRef]

Costello, D. K.

D. K. Costello, K. L. Carder, and W. Hou, “Aggregation of diatom bloom in a mesocosm: Bulk and individual particle optical measurements,” Deep Sea Res. Part II Top. Stud. Oceanogr. 42(1), 29–45 (1995).
[CrossRef]

Curran, K. J.

K. J. Curran, P. S. Hill, and T. G. Milligan, “The role of particle aggregation in size-dependent deposition of drill mud,” Cont. Shelf Res. 22(3), 405–416 (2002).
[CrossRef]

Dall’Olmo, G.

Dall'Olmo, G.

G. Dall'Olmo, T. K. Westberry, M. J. Behrenfeld, E. Boss, and W. H. Slade, “Significant contribution of large particles to optical backscattering in the open ocean,” Biogeosci. 6(6), 947–967 (2009).
[CrossRef]

Dickey, T. D.

E. Boss, W. S. Pegau, W. D. Gardner, J. R. V. Zaneveld, A. H. Barnard, M. S. Twardowski, G. C. Chang, and T. D. Dickey, “Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf,” J. Geophys. Res. 106(C5), 9509–9516 (2001).
[CrossRef]

Donaghay, P. L.

M. S. Twardowski, J. M. Sullivan, P. L. Donaghay, and J. R. V. Zaneveld, “Microscale quantification of the absorption by dissolved and particulate material in coastal waters with an ac-9,” J. Atmos. Ocean. Technol. 16(6), 691–707 (1999).
[CrossRef]

Droppo, I. G.

I. G. Droppo, “Rethinking what constitutes suspended sediment,” Hydrol. Process. 15(9), 1551–1564 (2001).
[CrossRef]

Eisma, D.

D. Eisma, “Flocculation and de-flocculation of suspended matter in estuaries,” Neth. J. Sea Res. 20(2-3), 183–199 (1986).
[CrossRef]

Flory, E. N.

E. N. Flory, P. S. Hill, T. G. Milligan, and J. Grant, “The relationship between floc area and backscatter during a spring phytoplankton bloom,” Deep Sea Res. Part I Oceanogr. Res. Pap. 51(2), 213–223 (2004).
[CrossRef]

Freeman, S. A.

M. S. Twardowski, H. Claustre, S. A. Freeman, D. Stramski, and Y. Huot, “Optical backscattering properties of the 'clearest' natural waters,” Biogeoscie. 4(6), 1041–1058 (2007).
[CrossRef]

Gardner, W. D.

E. Boss, W. S. Pegau, W. D. Gardner, J. R. V. Zaneveld, A. H. Barnard, M. S. Twardowski, G. C. Chang, and T. D. Dickey, “Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf,” J. Geophys. Res. 106(C5), 9509–9516 (2001).
[CrossRef]

Grant, J.

E. N. Flory, P. S. Hill, T. G. Milligan, and J. Grant, “The relationship between floc area and backscatter during a spring phytoplankton bloom,” Deep Sea Res. Part I Oceanogr. Res. Pap. 51(2), 213–223 (2004).
[CrossRef]

A. Hatcher, P. Hill, and J. Grant, “Optical backscatter of marine flocs,” J. Sea Res. 46(1), 1–12 (2001).
[CrossRef]

Gustafson, B.

Y. Xu and B. Gustafson, “Light scattering by an ensemble of small particles,” Recent Res. Dev. Opt. 3, 599–648 (2003).

Hatcher, A.

A. Hatcher, P. Hill, and J. Grant, “Optical backscatter of marine flocs,” J. Sea Res. 46(1), 1–12 (2001).
[CrossRef]

Herring, S.

Hill, P.

Hill, P. S.

P. S. Hill, E. Boss, J. P. Newgard, B. A. Law, and T. G. Milligan, “Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer,” J. Geophys. Res. 116(C2), C02023 (2011), doi:.
[CrossRef]

A. Khelifa and P. S. Hill, “Models for effective density and settling velocity of flocs,” J. Hydraul. Res. 44(3), 390–401 (2006).
[CrossRef]

O. A. Mikkelsen, P. S. Hill, and T. G. Milligan, “Single-grain, microfloc and macrofloc volume variations observed with a LISST-100 and a digital floc camera,” J. Sea Res. 55(2), 87–102 (2006).
[CrossRef]

E. N. Flory, P. S. Hill, T. G. Milligan, and J. Grant, “The relationship between floc area and backscatter during a spring phytoplankton bloom,” Deep Sea Res. Part I Oceanogr. Res. Pap. 51(2), 213–223 (2004).
[CrossRef]

K. J. Curran, P. S. Hill, and T. G. Milligan, “The role of particle aggregation in size-dependent deposition of drill mud,” Cont. Shelf Res. 22(3), 405–416 (2002).
[CrossRef]

P. S. Hill and A. R. M. Nowell, “Comparison of two models of aggregation in continental-shelf bottom boundary layers,” J. Geophys. Res. 100(C11), 22,749–22,763 (1995).
[CrossRef]

Hou, W.

D. K. Costello, K. L. Carder, and W. Hou, “Aggregation of diatom bloom in a mesocosm: Bulk and individual particle optical measurements,” Deep Sea Res. Part II Top. Stud. Oceanogr. 42(1), 29–45 (1995).
[CrossRef]

Huot, Y.

M. S. Twardowski, H. Claustre, S. A. Freeman, D. Stramski, and Y. Huot, “Optical backscattering properties of the 'clearest' natural waters,” Biogeoscie. 4(6), 1041–1058 (2007).
[CrossRef]

Jackson, G. A.

A. B. Burd and G. A. Jackson, “Particle aggregation,” Ann. Rev. Mar. Scie. 1(1), 65–90 (2009).
[CrossRef]

Karp-Boss, L.

W. R. Clavano, E. Boss, and L. Karp-Boss, “Inherent optical properties of non-spherical marine-like particles—from theory to observations,” Oceanogr. Mar. Biol. 45, 1–38 (2007).
[CrossRef]

Keller, M. D.

D. W. Townsend, M. D. Keller, M. E. Sieracki, and S. G. Ackleson, “Spring phytoplankton blooms in the absence of vertical water column stability,” Nature 360(6399), 59–62 (1992).
[CrossRef]

Khelifa, A.

A. Khelifa and P. S. Hill, “Models for effective density and settling velocity of flocs,” J. Hydraul. Res. 44(3), 390–401 (2006).
[CrossRef]

Korotaev, G.

E. Boss, W. S. Pegau, M. Lee, M. S. Twardowski, E. Shybanov, G. Korotaev, and F. Baratange, “Particulate backscattering ratio at LEO 15 and its use to study particles composition and distribution,” J. Geophys. Res. 109(C1), C01014 (2004), doi:.
[CrossRef]

Kranck, K.

K. Kranck, “Experiments on the significance of flocculation in the settling of fine-grained sediment in still water,” Can. J. Earth Sci. 17, 1517–1526 (1980).
[CrossRef]

Latimer, P.

Law, B. A.

P. S. Hill, E. Boss, J. P. Newgard, B. A. Law, and T. G. Milligan, “Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer,” J. Geophys. Res. 116(C2), C02023 (2011), doi:.
[CrossRef]

Lee, M.

E. Boss, W. S. Pegau, M. Lee, M. S. Twardowski, E. Shybanov, G. Korotaev, and F. Baratange, “Particulate backscattering ratio at LEO 15 and its use to study particles composition and distribution,” J. Geophys. Res. 109(C1), C01014 (2004), doi:.
[CrossRef]

Maggi, F.

F. Maggi, “Variable fractal dimension: A major control for floc structure and flocculation kinematics of suspended cohesive sediment,” J. Geophys. Res. 112(C7), C07012 (2007), doi:.
[CrossRef]

McCave, I.

I. McCave, “Particle size spectra, behavior, and origin of nepheloid layers over the Nova Scotian continental rise,” J. Geophys. Res. 88(C12), 7647–7666 (1983).
[CrossRef]

Mikkelsen, O. A.

Y. C. Agrawal and O. A. Mikkelsen, “Empirical forward scattering phase functions from 0.08 to 16 deg. for randomly shaped terrigenous 1-21 microm sediment grains,” Opt. Express 17(11), 8805–8814 (2009).
[CrossRef] [PubMed]

Y. C. Agrawal, A. Whitmire, O. A. Mikkelsen, and H. C. Pottsmith, “Light scattering by random shaped particles and consequences on measuring suspended sediments by laser diffraction,” J. Geophys. Res. 113(C4), C04023 (2008), doi:.
[CrossRef]

O. A. Mikkelsen, P. S. Hill, and T. G. Milligan, “Single-grain, microfloc and macrofloc volume variations observed with a LISST-100 and a digital floc camera,” J. Sea Res. 55(2), 87–102 (2006).
[CrossRef]

Milligan, T. G.

P. S. Hill, E. Boss, J. P. Newgard, B. A. Law, and T. G. Milligan, “Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer,” J. Geophys. Res. 116(C2), C02023 (2011), doi:.
[CrossRef]

O. A. Mikkelsen, P. S. Hill, and T. G. Milligan, “Single-grain, microfloc and macrofloc volume variations observed with a LISST-100 and a digital floc camera,” J. Sea Res. 55(2), 87–102 (2006).
[CrossRef]

E. N. Flory, P. S. Hill, T. G. Milligan, and J. Grant, “The relationship between floc area and backscatter during a spring phytoplankton bloom,” Deep Sea Res. Part I Oceanogr. Res. Pap. 51(2), 213–223 (2004).
[CrossRef]

K. J. Curran, P. S. Hill, and T. G. Milligan, “The role of particle aggregation in size-dependent deposition of drill mud,” Cont. Shelf Res. 22(3), 405–416 (2002).
[CrossRef]

Newgard, J.

C. R. Russo, E. S. Boss, W. H. Slade, and J. Newgard, “An investigation of the acoustic backscatter response to suspensions of clay aggregates and natural sediments,” Cont. Shelf Res. (submitted).

Newgard, J. P.

P. S. Hill, E. Boss, J. P. Newgard, B. A. Law, and T. G. Milligan, “Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer,” J. Geophys. Res. 116(C2), C02023 (2011), doi:.
[CrossRef]

Nowell, A. R. M.

P. S. Hill and A. R. M. Nowell, “Comparison of two models of aggregation in continental-shelf bottom boundary layers,” J. Geophys. Res. 100(C11), 22,749–22,763 (1995).
[CrossRef]

Pegau, W. S.

E. Boss, W. S. Pegau, M. Lee, M. S. Twardowski, E. Shybanov, G. Korotaev, and F. Baratange, “Particulate backscattering ratio at LEO 15 and its use to study particles composition and distribution,” J. Geophys. Res. 109(C1), C01014 (2004), doi:.
[CrossRef]

E. Boss, W. S. Pegau, W. D. Gardner, J. R. V. Zaneveld, A. H. Barnard, M. S. Twardowski, G. C. Chang, and T. D. Dickey, “Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf,” J. Geophys. Res. 106(C5), 9509–9516 (2001).
[CrossRef]

Pottsmith, H. C.

Y. C. Agrawal, A. Whitmire, O. A. Mikkelsen, and H. C. Pottsmith, “Light scattering by random shaped particles and consequences on measuring suspended sediments by laser diffraction,” J. Geophys. Res. 113(C4), C04023 (2008), doi:.
[CrossRef]

Y. C. Agrawal and H. C. Pottsmith, “Instruments for particle size and settling velocity observations in sediment transport,” Mar. Geol. 168(1-4), 89–114 (2000).
[CrossRef]

Russo, C. R.

C. R. Russo, E. S. Boss, W. H. Slade, and J. Newgard, “An investigation of the acoustic backscatter response to suspensions of clay aggregates and natural sediments,” Cont. Shelf Res. (submitted).

Shybanov, E.

E. Boss, W. S. Pegau, M. Lee, M. S. Twardowski, E. Shybanov, G. Korotaev, and F. Baratange, “Particulate backscattering ratio at LEO 15 and its use to study particles composition and distribution,” J. Geophys. Res. 109(C1), C01014 (2004), doi:.
[CrossRef]

Sieracki, M. E.

D. W. Townsend, M. D. Keller, M. E. Sieracki, and S. G. Ackleson, “Spring phytoplankton blooms in the absence of vertical water column stability,” Nature 360(6399), 59–62 (1992).
[CrossRef]

Slade, W. H.

Sorensen, C.

C. Sorensen, “Light scattering by fractal aggregates: a review,” Aerosol Sci. Technol. 35, 648–687 (2001).

Stramski, D.

M. S. Twardowski, H. Claustre, S. A. Freeman, D. Stramski, and Y. Huot, “Optical backscattering properties of the 'clearest' natural waters,” Biogeoscie. 4(6), 1041–1058 (2007).
[CrossRef]

Sullivan, J. M.

M. S. Twardowski, J. M. Sullivan, P. L. Donaghay, and J. R. V. Zaneveld, “Microscale quantification of the absorption by dissolved and particulate material in coastal waters with an ac-9,” J. Atmos. Ocean. Technol. 16(6), 691–707 (1999).
[CrossRef]

Townsend, D. W.

D. W. Townsend, M. D. Keller, M. E. Sieracki, and S. G. Ackleson, “Spring phytoplankton blooms in the absence of vertical water column stability,” Nature 360(6399), 59–62 (1992).
[CrossRef]

Twardowski, M. S.

M. S. Twardowski, H. Claustre, S. A. Freeman, D. Stramski, and Y. Huot, “Optical backscattering properties of the 'clearest' natural waters,” Biogeoscie. 4(6), 1041–1058 (2007).
[CrossRef]

E. Boss, W. S. Pegau, M. Lee, M. S. Twardowski, E. Shybanov, G. Korotaev, and F. Baratange, “Particulate backscattering ratio at LEO 15 and its use to study particles composition and distribution,” J. Geophys. Res. 109(C1), C01014 (2004), doi:.
[CrossRef]

E. Boss, W. S. Pegau, W. D. Gardner, J. R. V. Zaneveld, A. H. Barnard, M. S. Twardowski, G. C. Chang, and T. D. Dickey, “Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf,” J. Geophys. Res. 106(C5), 9509–9516 (2001).
[CrossRef]

E. Boss, M. S. Twardowski, and S. Herring, “Shape of the particulate beam attenuation spectrum and its inversion to obtain the shape of the particulate size distribution,” Appl. Opt. 40(27), 4885–4893 (2001).
[CrossRef]

M. S. Twardowski, J. M. Sullivan, P. L. Donaghay, and J. R. V. Zaneveld, “Microscale quantification of the absorption by dissolved and particulate material in coastal waters with an ac-9,” J. Atmos. Ocean. Technol. 16(6), 691–707 (1999).
[CrossRef]

Voss, K. J.

K. J. Voss and R. W. Austin, “Beam-attenuation measurements error due to small-angle scattering acceptance,” J. Atmos. Ocean. Technol. 10(1), 113–121 (1993).
[CrossRef]

Wamble, F.

Westberry, T. K.

G. Dall'Olmo, T. K. Westberry, M. J. Behrenfeld, E. Boss, and W. H. Slade, “Significant contribution of large particles to optical backscattering in the open ocean,” Biogeosci. 6(6), 947–967 (2009).
[CrossRef]

Whitmire, A.

Y. C. Agrawal, A. Whitmire, O. A. Mikkelsen, and H. C. Pottsmith, “Light scattering by random shaped particles and consequences on measuring suspended sediments by laser diffraction,” J. Geophys. Res. 113(C4), C04023 (2008), doi:.
[CrossRef]

Xu, Y.

Y. Xu and B. Gustafson, “Light scattering by an ensemble of small particles,” Recent Res. Dev. Opt. 3, 599–648 (2003).

Zaneveld, J. R. V.

E. Boss, W. S. Pegau, W. D. Gardner, J. R. V. Zaneveld, A. H. Barnard, M. S. Twardowski, G. C. Chang, and T. D. Dickey, “Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf,” J. Geophys. Res. 106(C5), 9509–9516 (2001).
[CrossRef]

M. S. Twardowski, J. M. Sullivan, P. L. Donaghay, and J. R. V. Zaneveld, “Microscale quantification of the absorption by dissolved and particulate material in coastal waters with an ac-9,” J. Atmos. Ocean. Technol. 16(6), 691–707 (1999).
[CrossRef]

Aerosol Sci. Technol. (1)

C. Sorensen, “Light scattering by fractal aggregates: a review,” Aerosol Sci. Technol. 35, 648–687 (2001).

Ann. Rev. Mar. Scie. (1)

A. B. Burd and G. A. Jackson, “Particle aggregation,” Ann. Rev. Mar. Scie. 1(1), 65–90 (2009).
[CrossRef]

Appl. Opt. (3)

Biogeosci. (1)

G. Dall'Olmo, T. K. Westberry, M. J. Behrenfeld, E. Boss, and W. H. Slade, “Significant contribution of large particles to optical backscattering in the open ocean,” Biogeosci. 6(6), 947–967 (2009).
[CrossRef]

Biogeoscie. (1)

M. S. Twardowski, H. Claustre, S. A. Freeman, D. Stramski, and Y. Huot, “Optical backscattering properties of the 'clearest' natural waters,” Biogeoscie. 4(6), 1041–1058 (2007).
[CrossRef]

Can. J. Earth Sci. (1)

K. Kranck, “Experiments on the significance of flocculation in the settling of fine-grained sediment in still water,” Can. J. Earth Sci. 17, 1517–1526 (1980).
[CrossRef]

Cont. Shelf Res. (2)

K. J. Curran, P. S. Hill, and T. G. Milligan, “The role of particle aggregation in size-dependent deposition of drill mud,” Cont. Shelf Res. 22(3), 405–416 (2002).
[CrossRef]

C. R. Russo, E. S. Boss, W. H. Slade, and J. Newgard, “An investigation of the acoustic backscatter response to suspensions of clay aggregates and natural sediments,” Cont. Shelf Res. (submitted).

Deep Sea Res. Part I Oceanogr. Res. Pap. (1)

E. N. Flory, P. S. Hill, T. G. Milligan, and J. Grant, “The relationship between floc area and backscatter during a spring phytoplankton bloom,” Deep Sea Res. Part I Oceanogr. Res. Pap. 51(2), 213–223 (2004).
[CrossRef]

Deep Sea Res. Part II Top. Stud. Oceanogr. (1)

D. K. Costello, K. L. Carder, and W. Hou, “Aggregation of diatom bloom in a mesocosm: Bulk and individual particle optical measurements,” Deep Sea Res. Part II Top. Stud. Oceanogr. 42(1), 29–45 (1995).
[CrossRef]

Hydrol. Process. (1)

I. G. Droppo, “Rethinking what constitutes suspended sediment,” Hydrol. Process. 15(9), 1551–1564 (2001).
[CrossRef]

J. Atmos. Ocean. Technol. (2)

M. S. Twardowski, J. M. Sullivan, P. L. Donaghay, and J. R. V. Zaneveld, “Microscale quantification of the absorption by dissolved and particulate material in coastal waters with an ac-9,” J. Atmos. Ocean. Technol. 16(6), 691–707 (1999).
[CrossRef]

K. J. Voss and R. W. Austin, “Beam-attenuation measurements error due to small-angle scattering acceptance,” J. Atmos. Ocean. Technol. 10(1), 113–121 (1993).
[CrossRef]

J. Geophys. Res. (8)

Y. C. Agrawal, A. Whitmire, O. A. Mikkelsen, and H. C. Pottsmith, “Light scattering by random shaped particles and consequences on measuring suspended sediments by laser diffraction,” J. Geophys. Res. 113(C4), C04023 (2008), doi:.
[CrossRef]

E. Boss, W. S. Pegau, M. Lee, M. S. Twardowski, E. Shybanov, G. Korotaev, and F. Baratange, “Particulate backscattering ratio at LEO 15 and its use to study particles composition and distribution,” J. Geophys. Res. 109(C1), C01014 (2004), doi:.
[CrossRef]

F. Maggi, “Variable fractal dimension: A major control for floc structure and flocculation kinematics of suspended cohesive sediment,” J. Geophys. Res. 112(C7), C07012 (2007), doi:.
[CrossRef]

P. S. Hill, E. Boss, J. P. Newgard, B. A. Law, and T. G. Milligan, “Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer,” J. Geophys. Res. 116(C2), C02023 (2011), doi:.
[CrossRef]

E. Boss, W. S. Pegau, W. D. Gardner, J. R. V. Zaneveld, A. H. Barnard, M. S. Twardowski, G. C. Chang, and T. D. Dickey, “Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf,” J. Geophys. Res. 106(C5), 9509–9516 (2001).
[CrossRef]

S. Ackleson, “Optical determinations of suspended sediment dynamics in western Long Island Sound and the Connecticut River plume,” J. Geophys. Res. 111(C7), C07009 (2006), doi:.
[CrossRef]

I. McCave, “Particle size spectra, behavior, and origin of nepheloid layers over the Nova Scotian continental rise,” J. Geophys. Res. 88(C12), 7647–7666 (1983).
[CrossRef]

P. S. Hill and A. R. M. Nowell, “Comparison of two models of aggregation in continental-shelf bottom boundary layers,” J. Geophys. Res. 100(C11), 22,749–22,763 (1995).
[CrossRef]

J. Hydraul. Res. (1)

A. Khelifa and P. S. Hill, “Models for effective density and settling velocity of flocs,” J. Hydraul. Res. 44(3), 390–401 (2006).
[CrossRef]

J. Sea Res. (2)

O. A. Mikkelsen, P. S. Hill, and T. G. Milligan, “Single-grain, microfloc and macrofloc volume variations observed with a LISST-100 and a digital floc camera,” J. Sea Res. 55(2), 87–102 (2006).
[CrossRef]

A. Hatcher, P. Hill, and J. Grant, “Optical backscatter of marine flocs,” J. Sea Res. 46(1), 1–12 (2001).
[CrossRef]

Mar. Geol. (1)

Y. C. Agrawal and H. C. Pottsmith, “Instruments for particle size and settling velocity observations in sediment transport,” Mar. Geol. 168(1-4), 89–114 (2000).
[CrossRef]

Nature (1)

D. W. Townsend, M. D. Keller, M. E. Sieracki, and S. G. Ackleson, “Spring phytoplankton blooms in the absence of vertical water column stability,” Nature 360(6399), 59–62 (1992).
[CrossRef]

Neth. J. Sea Res. (1)

D. Eisma, “Flocculation and de-flocculation of suspended matter in estuaries,” Neth. J. Sea Res. 20(2-3), 183–199 (1986).
[CrossRef]

Oceanogr. Mar. Biol. (1)

W. R. Clavano, E. Boss, and L. Karp-Boss, “Inherent optical properties of non-spherical marine-like particles—from theory to observations,” Oceanogr. Mar. Biol. 45, 1–38 (2007).
[CrossRef]

Opt. Express (4)

Recent Res. Dev. Opt. (1)

Y. Xu and B. Gustafson, “Light scattering by an ensemble of small particles,” Recent Res. Dev. Opt. 3, 599–648 (2003).

Other (6)

K. L. Carder, and D. K. Costello, “Optical effects of large particles,” in Ocean Optics, R. Spinrad, K. Carder, and M. J. Perry, eds. (Oxford University Press, 1994).

W. Hou, K. L. Carder, and D. K. Costello, “Scattering phase function of very large particles in the ocean,” Proc. SPIE 2963 (Ocean Optics XIII), 579–584 (1997).

WET Labs, Inc., “ECO Triplet User’s Guide (triplet),” Revision P, 19 Jan. 2010. http://www.wetlabs.com/products/pub/eco/tripletp.pdf

N. Briggs, “Analysis of optical spikes reveals dynamics of aggregates in the twilight zone,” University of Maine M.S. Thesis (2010). http://www.library.umaine.edu/theses/pdf/BriggsN2010.pdf

K. S. Shifrin, Physical Optics of Ocean Water (American Institute of Physics, 1995).

K. Kranck, and T. G. Milligan, “Grain size in oceanography,” in Theory, Methods and Applications of Particle Size Analysis, J. P. M. Syvitski, ed. (Cambridge University Press, 1991).

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Figures (8)

Fig. 1
Fig. 1

– PSD for the two treatments: (A) during the experiment when LISST B was fitted with a sample chamber fed by a pump to subject aggregates to shear, and (B) during the control when both LISST sample volumes were open to the environment.

Fig. 2
Fig. 2

– Time series of optical and particle size properties during the in situ disaggregation experiment. The experimental package was deployed in a bottom-mounted configuration thus tidal variability is shown as pressure in each plot. Unfilled symbols indicate the control data where the pump and sample chamber were removed from LISST B and both instruments were open to the environment. (A) Beam-attenuation for the open treatment. (B) Average particle size for both treatments. (C) The ratio of beam-attenuation from the two treatments. (D) The ratio of beam-attenuation to volume concentration as measured by the LISST, indicative of aggregates (see text).

Fig. 3
Fig. 3

– (A) LISST PSD snapshots over time. The thick blue line represents the distribution shortly (~10 min) after the start of the experiment, with the suspension dominated by small particles. Blue long-dashed PSD show the evolution of aggregated particles during the predominantly aggregation phase of the experiment. The red short-dashed lines show the evolution of PSD as settling and particle scavenging become more important. As a function of time, the population changes from domination by small particles to bi-modal. The thin red line shows the final measurement made by the LISST approximately 3.4 h after starting. (B) Time series of suspended area concentration for three size ranges of particles corresponding to primary particles, small aggregates, and large aggregates, as well as average particle size. Error bars for Davg indicate 16th and 84th percentiles (the difference of which is twice the standard deviation in the case of a normal distribution) for binned data.

Fig. 4
Fig. 4

– Microphotographs of the particle suspension made during a previous experiment with identical setup but different instrumentation. Initially, particles are disaggregated (A), but after ~1.5 h (B) aggregates are visible. Scale bar is for both (A) and (B). Note that particle size in (A) appears exaggerated due to halos.

Fig. 5
Fig. 5

– (A) Time series of average particle size, Davg , calculated from area PSD measurements derived from the LISST during the laboratory aggregation-settling experiment, along with measurements of suspended particulate mass (SPM). For SPM, small black dots and the large blue dots represent the individual measurements and mean of triplicate measurements, respectively. Horizontal error bars show the duration of sampling. (B) Time series of beam-attenuation measured using the two transmissometers with different acceptance angles, as well as volume scattering function measured at 117° in the backwards direction. Each optical property shows decrease concurrent with decrease in suspended mass. (C) Mass-normalized optical properties are relatively constant despite changes in PSD during experiment. Uncertainty has been propagated according with standard methods, as Eq. (3). Note that symbols in (C) are offset slightly for clarity.

Fig. 6
Fig. 6

– (A) Time series of beam-attenuation spectral slope and ratio of beam-attenuation for instruments (ac-9 and LISST) with differing acceptance angle. (B) The ratio of beam-attenuation to volume concentration as measured by the LISST, indicative of aggregate density. (C) Spectral shape of volume scattering function at 117° for two wavelength pairs (circles, squares) as well as the power law fit to all three wavelengths (diamonds). Note that symbols in (A) and (C) are offset slightly for clarity.

Fig. 7
Fig. 7

– The ratio of beam-attenuations from instruments with different acceptance angle is strongly correlated with average particle size. As particle size increases, scattering is increased in the near-forward angles; resulting in a greater amount of light captured (transmitted rather than attenuated) by the wider acceptance angle of the ac-9.

Fig. 8
Fig. 8

– (A) Relationship between beam-attenuation magnitude and slope over the course of the laboratory experiment. (B) Relationship between spectral slope and average particle size. Diamonds signify data points corresponding to the experiment times identified in the figure.

Equations (4)

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D a v g = i = 1 32 A ( D i ) D i / i = 1 32 A ( D i ) ,
β p ( 117 ° , λ ) = β t o t ( 117 ° , λ ) β b l a n k ( 117 ° , λ ) .
γ b b ( λ 1 , λ 2 ) = log ( β p ( λ 2 ) β p ( λ 1 ) ) / log ( λ 1 λ 2 ) .
δ c p = c ¯ p ( ( δ M M ¯ ) 2 + ( δ c p c ¯ p ) 2 ) 1 / 2 ,

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