215
© Springer Nature Switzerland AG 2021
I. Chinnici, G. Consolmagno (eds.), Angelo Secchi and Nineteenth Century Science,
Historical & Cultural Astronomy, https://doi.org/10.1007/978-3-030-58384-2_13
Chapter 13
The History and Future of the Secchi Disk
Oliver Zielinski
13.1 Secchi Disk Depth: A Parameter of Global Relevance
Climate change and anthropogenic activities affect freshwater and oceanic ecosystems worldwide. However, to identify and quantify trends and variabilities, the
availability of standardized long-term observations is of key relevance. Considering
timescales of decades to centuries, only a few aquatic observables are available in
sufficient number and spatial spread; these include observations of water temperature, color, and clarity (also denoted as transparency).
For many reasons – safety, fish finding, navigation around icebergs, and even the
recovery of goods lost at sea – sailors and scientists are interested in the determination of water transparency. One can define the intuitive idea of transparency as a
measure of the depth of light penetration into the water. Water transparency depends
on the abundance of particles and dissolved substances in the water (Watson and
Zielinski 2013). Particles can be inorganic (e.g., sediment from erosion) or organic
(such as algae, phytoplankton); these are called optically active components. During
its propagation in the water, the light is attenuated by absorption and dispersion of
these particles, combined with absorption from dissolved substances, until it completely disappears.
Water transparency is a key factor in ocean ecology, as the sun is the primary
source of energy for all biological phenomena (Dickey et al. 2011). When light
attenuates, it alters or limits the capacity of life of some marine biological communities and it reduces the possibility of photosynthesis (a process that produces the
O. Zielinski (*)
Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg,
Oldenburg, Germany
Marine Perception Research Group, German Research Center for Artificial Intelligence
(DFKI), Oldenburg, Germany
e-mail: oliver.zielinski@uol.de; oliver.zielinski@dfki.de
© Springer Nature Switzerland AG 2021
I. Chinnici, G. Consolmagno (eds.), Angelo Secchi and Nineteenth Century Science,
Historical & Cultural Astronomy, https://doi.org/10.1007/978-3-030-58384-2_13
Chapter 13
The History and Future of the Secchi Disk
Oliver Zielinski
13.1 Secchi Disk Depth: A Parameter of Global Relevance
Climate change and anthropogenic activities affect freshwater and oceanic ecosystems worldwide. However, to identify and quantify trends and variabilities, the
availability of standardized long-term observations is of key relevance. Considering
timescales of decades to centuries, only a few aquatic observables are available in
sufficient number and spatial spread; these include observations of water temperature, color, and clarity (also denoted as transparency).
For many reasons – safety, fish finding, navigation around icebergs, and even the
recovery of goods lost at sea – sailors and scientists are interested in the determination of water transparency. One can define the intuitive idea of transparency as a
measure of the depth of light penetration into the water. Water transparency depends
on the abundance of particles and dissolved substances in the water (Watson and
Zielinski 2013). Particles can be inorganic (e.g., sediment from erosion) or organic
(such as algae, phytoplankton); these are called optically active components. During
its propagation in the water, the light is attenuated by absorption and dispersion of
these particles, combined with absorption from dissolved substances, until it completely disappears.
Water transparency is a key factor in ocean ecology, as the sun is the primary
source of energy for all biological phenomena (Dickey et al. 2011). When light
attenuates, it alters or limits the capacity of life of some marine biological communities and it reduces the possibility of photosynthesis (a process that produces the
O. Zielinski (*)
Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg,
Oldenburg, Germany
Marine Perception Research Group, German Research Center for Artificial Intelligence
(DFKI), Oldenburg, Germany
e-mail: oliver.zielinski@uol.de; oliver.zielinski@dfki.de