218
The academic relevance of the Secchi disk can be assessed by searching scientific publication databases. Through a Google Scholar search (July 2019) applying
the search terms “Secchi disk” or “Secchi disc” or “Secchi depth,” a total of 31,500
entries were identified between 1865 and the present. Looking at the temporal distribution, one can see that 11% of these publications were published before 1980,
35% between 1980 and 1999, and 54% from 2000 until the present, indicating an
actual increase in relevance in recent years.
13.2 Secchi’s Achievements in Measuring
Water Transparency
It can be assumed that variability of the clarity of natural waters was recognized by
humankind from earliest times as an indicator of varying water quality in navigated
areas of the sea. Ships’ logs of ocean explorations regularly refer to the transparency
and color of seawater. In his work on historical subsea optics observational methods, Wernand records:
One of the oldest records describing the transparency of the ocean water was the one made
around Nova Zembla by the Captain J. Wood and dates back to 1676. He could see mussel
banks (possibly Mya-truncata, a marine bivalve mollusc) on a dark bottom, at a depth of
146 meters (Wernand et al. 2013).
Throughout the seventeenth, eighteenth, and nineteenth centuries, European
researchers documented the clarity of water using different approaches, including
glass vases (Luigi Ferdinando Marsigli, 1658–1730), red cloths (Otto von Kotzebue,
1787–1846), or white earthen plates (Adelbert von Chamisso, 1781–1838) (Wernand
2010). The first records of regular, tabulated measurements of the clarity or transparency of natural waters are those performed by the German naturalist Adelbert
von Chamisso during the Russian “Rurik” Expedition, in 1815–1818, under the
command of Otto von Kotzebue (1787–1846) (see Krümmel 1886). The Austrian
scientist Josef Roman Lorenz von Liburnau (1825–1911) experimented with submersible objects like white disks in the Gulf of Quarnero (Croatia) in the 1850s (see
Lorenz 1863). Two years later, an article on the same topic appeared in a weekly
publication of the French Academy of Science.
Alessandro Cialdi and Angelo Secchi performed transparency measurements in
the Tyrrhenian Sea offshore of Civitavecchia near Rome (Fig. 13.2; Chinnici 2019:
205–207). In an article merely three pages long, they described observations
onboard the papal corvette “Immacolata Concezione” and methods to establish the
water transparency (Cialdi and Secchi 1865) with a brief description of the size,
material, and color of the disks employed for that purpose.
According to Tyler (1968), the idea to investigate transparency of marine waters
systematically with a submersed disk originated in 1865 with the head of the Papal
Navy, Commander Alessandro Cialdi. Inspired by François Arago’s (1786–1853)
mention of Captain Béard’s observations of a dish in a net being visible at 40 m
O. Zielinski
The academic relevance of the Secchi disk can be assessed by searching scientific publication databases. Through a Google Scholar search (July 2019) applying
the search terms “Secchi disk” or “Secchi disc” or “Secchi depth,” a total of 31,500
entries were identified between 1865 and the present. Looking at the temporal distribution, one can see that 11% of these publications were published before 1980,
35% between 1980 and 1999, and 54% from 2000 until the present, indicating an
actual increase in relevance in recent years.
13.2 Secchi’s Achievements in Measuring
Water Transparency
It can be assumed that variability of the clarity of natural waters was recognized by
humankind from earliest times as an indicator of varying water quality in navigated
areas of the sea. Ships’ logs of ocean explorations regularly refer to the transparency
and color of seawater. In his work on historical subsea optics observational methods, Wernand records:
One of the oldest records describing the transparency of the ocean water was the one made
around Nova Zembla by the Captain J. Wood and dates back to 1676. He could see mussel
banks (possibly Mya-truncata, a marine bivalve mollusc) on a dark bottom, at a depth of
146 meters (Wernand et al. 2013).
Throughout the seventeenth, eighteenth, and nineteenth centuries, European
researchers documented the clarity of water using different approaches, including
glass vases (Luigi Ferdinando Marsigli, 1658–1730), red cloths (Otto von Kotzebue,
1787–1846), or white earthen plates (Adelbert von Chamisso, 1781–1838) (Wernand
2010). The first records of regular, tabulated measurements of the clarity or transparency of natural waters are those performed by the German naturalist Adelbert
von Chamisso during the Russian “Rurik” Expedition, in 1815–1818, under the
command of Otto von Kotzebue (1787–1846) (see Krümmel 1886). The Austrian
scientist Josef Roman Lorenz von Liburnau (1825–1911) experimented with submersible objects like white disks in the Gulf of Quarnero (Croatia) in the 1850s (see
Lorenz 1863). Two years later, an article on the same topic appeared in a weekly
publication of the French Academy of Science.
Alessandro Cialdi and Angelo Secchi performed transparency measurements in
the Tyrrhenian Sea offshore of Civitavecchia near Rome (Fig. 13.2; Chinnici 2019:
205–207). In an article merely three pages long, they described observations
onboard the papal corvette “Immacolata Concezione” and methods to establish the
water transparency (Cialdi and Secchi 1865) with a brief description of the size,
material, and color of the disks employed for that purpose.
According to Tyler (1968), the idea to investigate transparency of marine waters
systematically with a submersed disk originated in 1865 with the head of the Papal
Navy, Commander Alessandro Cialdi. Inspired by François Arago’s (1786–1853)
mention of Captain Béard’s observations of a dish in a net being visible at 40 m
O. Zielinski