waters, are dominated by in-water features as opposed to scattering. This is particularly
true of phytoplankton at the concentrations found in the coastal zone, which are
typically orders of magnitude higher than those of Case 1 waters. An important
ramification of this fact is that the widely used chlorophyll algorithms for ocean
chlorophyll break down under high concentrations of phytoplankton and/or suspended
sediment such as are typically found along the coast. Depending on the concentrations,
types, and proportions of phytoplankton and suspended sediments, Case 1 chlorophyll
algorithms can lead to either under- or over-estimation of chlorophyll concentration.
This is the basis for the ongoing and costly reanalysis of Coastal Zone Color Scanner
(CZCS) data, which were originally analyzed using algorithms designed for blue
offshore waters. The spectral bands on the CZCS, in fact, were selected based on Case
1 chlorophyll algorithms.
The optical properties of Case 2 waters are very different from those of Case 1
waters. Spectral analysis of Case 2 waters can provide relatively much more
information about the type(s) of both phytoplankton and sediment present in the water
column, information which is useful to scientists and managers alike. This is possible
due to the strong effects that these water constituents have on the water-leaving optical
signals of coastal waters when they are present at high concentrations such as found
near the coast. This subject is addressed in detail in Chapter 3 by John Schalles. In this
chapter experimental manipulations of phytoplankton (type and concentration),
sediments of different types, and combinations of phytoplankton and sediment were
analyzed in terms of spectral reflectance and existing chlorophyll algorithms. This
concept is further developed and illustrated in Chapter 4 by Peter Gege and Andreas
Albert. These authors have also provided an interactive software program in which
users can manipulate sediment and pigment constituents in a water column and observe
the effects on spectra. Chapter 4 includes the optical theory and algorithms that support
the interactive program.
In addition to phytoplankton and sediment signatures, many benthic communities
exhibit distinctive spectral signatures detectable using remote sensing. One of the most
successful coastal applications taking advantage of this is that of remote sensing of
coral reefs, which is addressed in several chapters in this book (e.g. Chapter 11 by
Newman et al.). Thus although the coastal zone is optically complex, this complexity
in itself can be the basis for extending the potential of remote sensing beyond what is
possible for Case 1 waters.
4. Science based connections between ecosystem processes and remote sensing
Many features of aquatic coastal ecosystems have strong optical signals. These
include the various photoreactive, photoprotective, and light harvesting pigments of
phytoplankton, submerged and emergent macroalgae, and coastal (terrestrial) plants.
Many of these organisms also have unique pigment combinations as well as indicator
fluorescence signals. Thus such populations can be monitored, measured, and
identified using optical properties.
Use of optical features in coastal biology is widespread and implemented by both
scientists and managers alike. The most common is optical (spectrophotometric)
detection of chlorophyll to estimate phytoplankton concentration and thus monitor
potential eutrophication as a proxy for the “health” of the aquatic ecosystem. This
approach is now being expanded to detect pigment signatures specific to toxin
3
Remote Sensing and Aquatic Coastal Ecosystems
true of phytoplankton at the concentrations found in the coastal zone, which are
typically orders of magnitude higher than those of Case 1 waters. An important
ramification of this fact is that the widely used chlorophyll algorithms for ocean
chlorophyll break down under high concentrations of phytoplankton and/or suspended
sediment such as are typically found along the coast. Depending on the concentrations,
types, and proportions of phytoplankton and suspended sediments, Case 1 chlorophyll
algorithms can lead to either under- or over-estimation of chlorophyll concentration.
This is the basis for the ongoing and costly reanalysis of Coastal Zone Color Scanner
(CZCS) data, which were originally analyzed using algorithms designed for blue
offshore waters. The spectral bands on the CZCS, in fact, were selected based on Case
1 chlorophyll algorithms.
The optical properties of Case 2 waters are very different from those of Case 1
waters. Spectral analysis of Case 2 waters can provide relatively much more
information about the type(s) of both phytoplankton and sediment present in the water
column, information which is useful to scientists and managers alike. This is possible
due to the strong effects that these water constituents have on the water-leaving optical
signals of coastal waters when they are present at high concentrations such as found
near the coast. This subject is addressed in detail in Chapter 3 by John Schalles. In this
chapter experimental manipulations of phytoplankton (type and concentration),
sediments of different types, and combinations of phytoplankton and sediment were
analyzed in terms of spectral reflectance and existing chlorophyll algorithms. This
concept is further developed and illustrated in Chapter 4 by Peter Gege and Andreas
Albert. These authors have also provided an interactive software program in which
users can manipulate sediment and pigment constituents in a water column and observe
the effects on spectra. Chapter 4 includes the optical theory and algorithms that support
the interactive program.
In addition to phytoplankton and sediment signatures, many benthic communities
exhibit distinctive spectral signatures detectable using remote sensing. One of the most
successful coastal applications taking advantage of this is that of remote sensing of
coral reefs, which is addressed in several chapters in this book (e.g. Chapter 11 by
Newman et al.). Thus although the coastal zone is optically complex, this complexity
in itself can be the basis for extending the potential of remote sensing beyond what is
possible for Case 1 waters.
4. Science based connections between ecosystem processes and remote sensing
Many features of aquatic coastal ecosystems have strong optical signals. These
include the various photoreactive, photoprotective, and light harvesting pigments of
phytoplankton, submerged and emergent macroalgae, and coastal (terrestrial) plants.
Many of these organisms also have unique pigment combinations as well as indicator
fluorescence signals. Thus such populations can be monitored, measured, and
identified using optical properties.
Use of optical features in coastal biology is widespread and implemented by both
scientists and managers alike. The most common is optical (spectrophotometric)
detection of chlorophyll to estimate phytoplankton concentration and thus monitor
potential eutrophication as a proxy for the “health” of the aquatic ecosystem. This
approach is now being expanded to detect pigment signatures specific to toxin
3
Remote Sensing and Aquatic Coastal Ecosystems