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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 103, NO. C10,
PAGES 21,683–21,695,
1998
Bio-optical properties of the southwestern Ross Sea
Kevin R. Arrigo
Oceans and Ice Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland
Dale H. Robinson
Universities Space Research Associates, Oceans and Ice Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland
Denise L. Worthen
Science Systems and Applications, Inc., Lanham, Maryland
Brian Schieber
General Sciences Corporation, Laurel, Maryland
Michael P. Lizotte
Department of Biology and Microbiology, University of Wisconsin-Oshkosh
Abstract
The bio-optical properties of the southwestern Ross Sea were measured as part of the Antarctic research program Research on
Atmospheric Variability and Atmospheric Response in the Ross Sea (ROAVERRS). The study area contained three distinct phytoplankton
blooms, distinguishable by species composition. The largest in area was located to the north of the Ross Ice Shelf and was
dominated by the prymnesiophyte Phaeocystis antarctica; chlorophyll a (Chl a) ranged from 0.45 to 8.2 mg m−3. Beam attenuation and particle absorption at 435 nm were as high as 3.4 m−1 and 0.35 m−1, respectively. A bloom of diatoms was more spatially restricted, located to the north and west of the P. antarctica bloom, with Chl a generally below 4 mg m−3. Neither diatoms nor P. antarctica exhibited evidence of the level of pigment packaging measured in waters near the Antarctic Peninsula during the Research
on Antarctic Coastal Ecosystem Rates (RACER) program, possibly because of their smaller sizes. A much smaller cryptophyte
bloom, located south of the Drygalski Ice Tongue, displayed a lower pigment-specific absorption spectra than did P. antarctica or diatoms, a sign of greater pigment packaging. Pigment-specific diffuse attenuation coefficients were consistent with the
pigment-specific particle absorption coefficients
(
a
p
h
*
)
, both being ∼3 times greater than similar measurements made during RACER. Spectral absorption by solutes determined through
regression analysis of K d against Chl a for the ROAVERRS data set was nearly identical to that measured during RACER. Total diffuse attenuation spectra at a given
station could be reconstructed by summing the inherent optical properties of the major optical components (pure water, soluble
material, detritus, phytoplankton) measured there. Differences in the absorption ratio of
a
p
h
*
(
λ
)
at 490 nm to
a
p
h
*
(
λ
)
at 555 nm among the three dominant phytoplankton taxa in the southwestern Ross Sea were responsible for most of the variability
in the ratio of remote sensing reflectance (R rs) at these same wavelengths. At a given concentration of Chl a, the ratio log [R rs(490):R rs(555)] was greatest in cryptophyte-dominated waters, which also possessed the lowest
a
p
h
*
(
490
)
:
a
p
h
*
(
555
)
ratio, and lowest in P. antarctica–dominated waters. These bio-optical differences suggest that no simple empirical relationship between Chl a and log [R rs(490):R rs(555)] will apply to all three taxonomically distinct phytoplankton blooms in the southwestern Ross Sea.
Received 31
December
1997;
accepted 24
June
1998.
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Citation: Arrigo, K. R., D. H. Robinson, D. L. Worthen, B. Schieber, and M. P. Lizotte
(1998),
Bio-optical properties of the southwestern Ross Sea,
J. Geophys. Res.,
103(C10),
21,683–21,695.
Copyright 1998 by the American Geophysical Union.
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