222
water clarity on a global scale. The resulting Secchi disk depth is an established
observable of monitoring programs, derivable both from field measurements and
satellite observations of water color, bridging scales in time and space.
The recent increase of electro-optical sensors measuring inherent and apparent
optical properties means a reduction of field measurements with the Secchi disk
method. Lee et al. (2018) as well as the author of this chapter advocate for continue
monitoring of the Secchi disk depth in freshwater and marine environments to
bridge the past and the future. The combination of historic and modern Secchi disk
depth measurements along with products derived from satellite observations could
be used to generate a unique, century-long dataset of water clarity and its changes
in relation to natural and anthropogenic influences.
Acknowledgments This manuscript is dedicated to Marcel R. Wernand, who passed away in the
early concept phase of this work. Marcel (re)discovered historical approaches for investigating the
color and clarity of the sea, shedding light on the individuals behind it, and he transformed their
findings into modern methodologies and devices. Proof reading support of Claudia Thölen is gratefully acknowledged. Part of the work was carried out as part of the Coastal Ocean Darkening
project, funded by the Ministry for Science and Culture of Lower Saxony, Germany (VWZN3175).
References
Aarup, T. (2002). Transparency of the North Sea and Baltic Sea – A Secchi depth data mining
study. Oceanologia, 44, 323–337.
Aas, E., Høkedal, J., & Sørensen, K. (2014). Secchi depth in the Oslofjord-Skagerrak area: Theory,
experiments and relationships to other quantities. Ocean Science, 10, 177–199.
Aksnes, D. L., Dupont, N., Staby, A., Fiksen, Ø., Kaartvedt, S., & Aure, J. (2009). Coastal water
darkening and implications for mesopelagic regime shifts in Norwegian fjords. Marine Ecology
Progress Series, 387, 39–49.
Arnone, R. A., Tucker, S. P., & Hilder, F. A. (1985). Secchi depth atlas of the world coastlines.
Proceedings of SPIE, 489, 195–201.
Boyce, D. G., Lewis, M. R., & Worm, B. (2010). Global phytoplankton decline over the past century. Nature, 466, 591–596.
Burns, N. M., Rockwell, D. C., Bertram, P. E., Dolan, D. M., & Ciborowski, J. J. (2005). Trends
in temperature, Secchi depth, and dissolved oxygen depletion rates in the central basin of Lake
Erie, 1983–2002. Journal of Great Lakes Research, 31, 35–49.
Busch, J. A., Bardaji, R., Ceccaroni, L., Friedrichs, A., Piera, J., Simon, C., Thijsse, P., Wernand,
M., Woerd, H. J., & Zielinski, O. (2016). Citizen bio-optical observations from coast- and ocean
and their compatibility with ocean colour satellite measurements. Remote Sensing, 8, 879.
Capuzzo, E., Stephens, D., Silva, T., Barry, J., & Forster, R. M. (2015). Decrease in water clarity
of the southern and Central North Sea during the 20th century. Global Change Biology, 21(6),
2206–2214.
Chinnici, I. (2019). Decoding the stars. A biography of Angelo Secchi, Jesuit and scientist.
Leiden: Brill.
Cialdi, A., & Secchi, A. (1865). Sur la transparence de la mer. Comptes rendus de l’Académie des
Sciences, 61, 100–104.
Crooke, B., McKinna, L. I., & Cetinić, I. (2017). From toes to top-of-atmosphere: Fowler’s sneaker
depth index of water clarity for the Chesapeake Bay. Optics Express, 25(8), A361–A374.
O. Zielinski
water clarity on a global scale. The resulting Secchi disk depth is an established
observable of monitoring programs, derivable both from field measurements and
satellite observations of water color, bridging scales in time and space.
The recent increase of electro-optical sensors measuring inherent and apparent
optical properties means a reduction of field measurements with the Secchi disk
method. Lee et al. (2018) as well as the author of this chapter advocate for continue
monitoring of the Secchi disk depth in freshwater and marine environments to
bridge the past and the future. The combination of historic and modern Secchi disk
depth measurements along with products derived from satellite observations could
be used to generate a unique, century-long dataset of water clarity and its changes
in relation to natural and anthropogenic influences.
Acknowledgments This manuscript is dedicated to Marcel R. Wernand, who passed away in the
early concept phase of this work. Marcel (re)discovered historical approaches for investigating the
color and clarity of the sea, shedding light on the individuals behind it, and he transformed their
findings into modern methodologies and devices. Proof reading support of Claudia Thölen is gratefully acknowledged. Part of the work was carried out as part of the Coastal Ocean Darkening
project, funded by the Ministry for Science and Culture of Lower Saxony, Germany (VWZN3175).
References
Aarup, T. (2002). Transparency of the North Sea and Baltic Sea – A Secchi depth data mining
study. Oceanologia, 44, 323–337.
Aas, E., Høkedal, J., & Sørensen, K. (2014). Secchi depth in the Oslofjord-Skagerrak area: Theory,
experiments and relationships to other quantities. Ocean Science, 10, 177–199.
Aksnes, D. L., Dupont, N., Staby, A., Fiksen, Ø., Kaartvedt, S., & Aure, J. (2009). Coastal water
darkening and implications for mesopelagic regime shifts in Norwegian fjords. Marine Ecology
Progress Series, 387, 39–49.
Arnone, R. A., Tucker, S. P., & Hilder, F. A. (1985). Secchi depth atlas of the world coastlines.
Proceedings of SPIE, 489, 195–201.
Boyce, D. G., Lewis, M. R., & Worm, B. (2010). Global phytoplankton decline over the past century. Nature, 466, 591–596.
Burns, N. M., Rockwell, D. C., Bertram, P. E., Dolan, D. M., & Ciborowski, J. J. (2005). Trends
in temperature, Secchi depth, and dissolved oxygen depletion rates in the central basin of Lake
Erie, 1983–2002. Journal of Great Lakes Research, 31, 35–49.
Busch, J. A., Bardaji, R., Ceccaroni, L., Friedrichs, A., Piera, J., Simon, C., Thijsse, P., Wernand,
M., Woerd, H. J., & Zielinski, O. (2016). Citizen bio-optical observations from coast- and ocean
and their compatibility with ocean colour satellite measurements. Remote Sensing, 8, 879.
Capuzzo, E., Stephens, D., Silva, T., Barry, J., & Forster, R. M. (2015). Decrease in water clarity
of the southern and Central North Sea during the 20th century. Global Change Biology, 21(6),
2206–2214.
Chinnici, I. (2019). Decoding the stars. A biography of Angelo Secchi, Jesuit and scientist.
Leiden: Brill.
Cialdi, A., & Secchi, A. (1865). Sur la transparence de la mer. Comptes rendus de l’Académie des
Sciences, 61, 100–104.
Crooke, B., McKinna, L. I., & Cetinić, I. (2017). From toes to top-of-atmosphere: Fowler’s sneaker
depth index of water clarity for the Chesapeake Bay. Optics Express, 25(8), A361–A374.
O. Zielinski