41
© The Author(s) 2018
S. Jungblut et al. (eds.), YOUMARES 8 – Oceans Across Boundaries: Learning from each other,
https://doi.org/10.1007/978-3-319-93284-2_4
Marine Optics and Ocean Color Remote
Sensing
Veloisa Mascarenhas and Therese Keck
Abstract
Light plays an important role in aquatic ecosystems, both
marine and freshwater. Penetration of light underwater
influences various biogeochemical processes and also
influences activities and behavioral patterns of marine
organisms. In addition, dissolved and particulate water
constituents present in the water column absorb and scatter light, giving water its characteristic color. The concentration or abundance of these constituents, referred to as
optically active constituents (OACs) also determine light
availability underwater. Thus color being an indicator of
water column content, serves as a water quality parameter. Monitoring of the ocean color variables, such as the
OAC concentrations and their optical properties, therefore, allows assessment of the health of an ecosystem.
Advances in optical methodologies have improved the
understanding of our ecosystems through multispectral
and hyperspectral in situ measurements and observations.
However, the ocean environment is vast and dynamic and
so limitations of spatial and temporal coverage have been
overcome with satellite remote sensing that provides
oceanographers with repeated synoptic coverage. Being
recognized as an essential climate variable (ECV) ocean
color is monitored as part of the climate change initiative
(CCI) of the European Space Agency (ESA). This chapter
aims to provide the reader with an overview of the science
of ocean color, introducing involved common terminologies and concepts and its global coverage using satellite
remote sensing.
Introduction to Ocean Color, Fundamental
Concepts, and Optical Tools
Veloisa Mascarenhas
Role of Light in Water
Sunlight plays a key role in the ecology of aquatic ecosystems. Its interaction with water, dissolved and particulate
suspended materials is an important physical phenomenon
and influences several biogeochemical processes in the
global ocean. Penetration of sunlight below water surface
facilitates associated biological processes like primary production or plankton distribution in the water column (Kirk
1994). In addition to facilitating photosynthetic processes
which form the base of ecological food chain, sunlight also
influences the behavioral patterns and activities of marine
organisms which are affected by the ambient light field that
undergoes vertical changes within the water column (Frank
et al. 2012). Mesopelagic fish and zooplankton abundances
in different coastal locations are known to correlate with
light availability (Aksnes et al. 2004) and changes in light
availability conditions are in turn known to have implications for mesopelagic regime shifts (Aksnes et al. 2009).
Fate of Light in Water: Optically Active
Constituents and Optical Properties
Fresh and marine waters are a witch’s brew of dissolved and
particulate matter, both organic and inorganic (Mobley 1994).
The dissolved and particulate materials in addition to water
molecules interact with light and are therefore known as optically active constituents (OACs). Phytoplankton, colored dissolved organic matter (CDOM), and suspended particulate
matter (SPM) being variable in time and space are the three
OACs extensively studied across fresh and marine water ecoV. Mascarenhas (*)
Institut für Chemie und Biologie des Meeres, Universität
Oldenburg, Wilhelmshaven, Germany
e-mail: veloisa.john.mascarenhas@uni-oldenburg.de
T. Keck
Institute for Space Sciences, Freie Universität Berlin,
Berlin, Germany
e-mail: therese.keck@wew.fu-berlin.de
© The Author(s) 2018
S. Jungblut et al. (eds.), YOUMARES 8 – Oceans Across Boundaries: Learning from each other,
https://doi.org/10.1007/978-3-319-93284-2_4
Marine Optics and Ocean Color Remote
Sensing
Veloisa Mascarenhas and Therese Keck
Abstract
Light plays an important role in aquatic ecosystems, both
marine and freshwater. Penetration of light underwater
influences various biogeochemical processes and also
influences activities and behavioral patterns of marine
organisms. In addition, dissolved and particulate water
constituents present in the water column absorb and scatter light, giving water its characteristic color. The concentration or abundance of these constituents, referred to as
optically active constituents (OACs) also determine light
availability underwater. Thus color being an indicator of
water column content, serves as a water quality parameter. Monitoring of the ocean color variables, such as the
OAC concentrations and their optical properties, therefore, allows assessment of the health of an ecosystem.
Advances in optical methodologies have improved the
understanding of our ecosystems through multispectral
and hyperspectral in situ measurements and observations.
However, the ocean environment is vast and dynamic and
so limitations of spatial and temporal coverage have been
overcome with satellite remote sensing that provides
oceanographers with repeated synoptic coverage. Being
recognized as an essential climate variable (ECV) ocean
color is monitored as part of the climate change initiative
(CCI) of the European Space Agency (ESA). This chapter
aims to provide the reader with an overview of the science
of ocean color, introducing involved common terminologies and concepts and its global coverage using satellite
remote sensing.
Introduction to Ocean Color, Fundamental
Concepts, and Optical Tools
Veloisa Mascarenhas
Role of Light in Water
Sunlight plays a key role in the ecology of aquatic ecosystems. Its interaction with water, dissolved and particulate
suspended materials is an important physical phenomenon
and influences several biogeochemical processes in the
global ocean. Penetration of sunlight below water surface
facilitates associated biological processes like primary production or plankton distribution in the water column (Kirk
1994). In addition to facilitating photosynthetic processes
which form the base of ecological food chain, sunlight also
influences the behavioral patterns and activities of marine
organisms which are affected by the ambient light field that
undergoes vertical changes within the water column (Frank
et al. 2012). Mesopelagic fish and zooplankton abundances
in different coastal locations are known to correlate with
light availability (Aksnes et al. 2004) and changes in light
availability conditions are in turn known to have implications for mesopelagic regime shifts (Aksnes et al. 2009).
Fate of Light in Water: Optically Active
Constituents and Optical Properties
Fresh and marine waters are a witch’s brew of dissolved and
particulate matter, both organic and inorganic (Mobley 1994).
The dissolved and particulate materials in addition to water
molecules interact with light and are therefore known as optically active constituents (OACs). Phytoplankton, colored dissolved organic matter (CDOM), and suspended particulate
matter (SPM) being variable in time and space are the three
OACs extensively studied across fresh and marine water ecoV. Mascarenhas (*)
Institut für Chemie und Biologie des Meeres, Universität
Oldenburg, Wilhelmshaven, Germany
e-mail: veloisa.john.mascarenhas@uni-oldenburg.de
T. Keck
Institute for Space Sciences, Freie Universität Berlin,
Berlin, Germany
e-mail: therese.keck@wew.fu-berlin.de