Chapter 3
OPTICAL REMOTE SENSING TECHNIQUES TO ESTIMATE
PHYTOPLANKTON CHLOROPHYLL a CONCENTRATIONS IN
COASTAL WATERS WITH VARYING SUSPENDED MATTER AND CDOM
CONCENTRATIONS
JOHN F. SCHALLES
Biology Department, Creighton University, Omaha, NE 68178, USA,
jfsaqua@creighton.edu
1. Introduction
"Roughly 98% of the world’s oceans and coastal waters fall into the Case 1 category,
and almost all bio-optical research has been directed toward these phytoplanktondominated waters. However, near-shore and estuarine Case 2 waters are
disproportionately important to human interests such as recreation, fisheries, and
military operations. It is therefore likely that Case 2 waters will receive increasing
attention in coming years." – Curtis Mobley, 1994. Light and Water: Radiative
Transfer in Natural Waters
The estimation of chlorophyll concentrations is one of the most scientifically
relevant and commonly used applications of remote sensing to aquatic coastal systems.
This, however, is a far from trivial task because of the complex composition and
distribution of optically active constituents in many coastal waters. In the decade since
the publication of Mobley's "Light and Water", the hydrologic optics of turbid Case 2
waters (Morel and Prieur, 1977) have been vigorously examined. The advantages and
challenges of remote estimation of chlorophyll concentrations in Case 2 waters are now
relatively well defined, although operational monitoring schemes are not fully mature
and await further sensor and algorithm improvements (International Ocean-Color
Coordinating Group, 2000). This chapter will survey this important component of
coastal remote sensing. There is much to be gained from examining the commonalities
in the optical environments of inland and coastal water, and I will draw primarily from
empirical studies that span these diverse and optically complex environments. This
chapter also considers the transferability of the well developed, satellite remote sensing
approaches for chlorophyll assessments of open ocean, Case 1 waters (O'Reilly et al.,
1998) to Case 2 waters.
The terminology and rationale for Case 1 and Case 2 water classifications were
established by Morel and Prieur (1977) in their seminal work on the bio-optical basis
for ocean color variations. The optics and emergent color signals of Case 1 waters are
largely dominated by: 1) living phytoplankton cells; 2) organic tripton (detritus)
particles from death and decay of phytoplankton and the grazing products of
zooplankton; and 3) the dissolved organic matter produced by phytoplankton
metabolism, and decay of organic tripton (modified from Gordon and Morel, 1983).
Case 2 waters contain Case 1 constituents plus materials introduced from outside the
water column, which also effect optical properties. These include: 4) turbulent
resuspension of bottom particles in shallow areas; 5) inorganic and organic tripton from
river drainages, glaciers, and/or wind transport; 6) terrigenous and littoral zone colored
dissolved organic matter (CDOM); and 7) anthropogenic particulate and dissolved
27
and Management Applications, 27-79.
© 2006 Springer. Printed in the Netherlands.
L.L. Richardson and E.F. LeDrew (eds.), Remote Sensing of Aquatic Coastal Ecosystem Processes: Science
OPTICAL REMOTE SENSING TECHNIQUES TO ESTIMATE
PHYTOPLANKTON CHLOROPHYLL a CONCENTRATIONS IN
COASTAL WATERS WITH VARYING SUSPENDED MATTER AND CDOM
CONCENTRATIONS
JOHN F. SCHALLES
Biology Department, Creighton University, Omaha, NE 68178, USA,
jfsaqua@creighton.edu
1. Introduction
"Roughly 98% of the world’s oceans and coastal waters fall into the Case 1 category,
and almost all bio-optical research has been directed toward these phytoplanktondominated waters. However, near-shore and estuarine Case 2 waters are
disproportionately important to human interests such as recreation, fisheries, and
military operations. It is therefore likely that Case 2 waters will receive increasing
attention in coming years." – Curtis Mobley, 1994. Light and Water: Radiative
Transfer in Natural Waters
The estimation of chlorophyll concentrations is one of the most scientifically
relevant and commonly used applications of remote sensing to aquatic coastal systems.
This, however, is a far from trivial task because of the complex composition and
distribution of optically active constituents in many coastal waters. In the decade since
the publication of Mobley's "Light and Water", the hydrologic optics of turbid Case 2
waters (Morel and Prieur, 1977) have been vigorously examined. The advantages and
challenges of remote estimation of chlorophyll concentrations in Case 2 waters are now
relatively well defined, although operational monitoring schemes are not fully mature
and await further sensor and algorithm improvements (International Ocean-Color
Coordinating Group, 2000). This chapter will survey this important component of
coastal remote sensing. There is much to be gained from examining the commonalities
in the optical environments of inland and coastal water, and I will draw primarily from
empirical studies that span these diverse and optically complex environments. This
chapter also considers the transferability of the well developed, satellite remote sensing
approaches for chlorophyll assessments of open ocean, Case 1 waters (O'Reilly et al.,
1998) to Case 2 waters.
The terminology and rationale for Case 1 and Case 2 water classifications were
established by Morel and Prieur (1977) in their seminal work on the bio-optical basis
for ocean color variations. The optics and emergent color signals of Case 1 waters are
largely dominated by: 1) living phytoplankton cells; 2) organic tripton (detritus)
particles from death and decay of phytoplankton and the grazing products of
zooplankton; and 3) the dissolved organic matter produced by phytoplankton
metabolism, and decay of organic tripton (modified from Gordon and Morel, 1983).
Case 2 waters contain Case 1 constituents plus materials introduced from outside the
water column, which also effect optical properties. These include: 4) turbulent
resuspension of bottom particles in shallow areas; 5) inorganic and organic tripton from
river drainages, glaciers, and/or wind transport; 6) terrigenous and littoral zone colored
dissolved organic matter (CDOM); and 7) anthropogenic particulate and dissolved
27
and Management Applications, 27-79.
© 2006 Springer. Printed in the Netherlands.
L.L. Richardson and E.F. LeDrew (eds.), Remote Sensing of Aquatic Coastal Ecosystem Processes: Science