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Optical water quality variables (Secchi depth and Forel-Ule color indexes) observed during RV HEINCKE cruise HE626-2 from Bremerhaven, Germany to Bremerhaven, Germany

Water clarity and color were observed during the RV HEINCKE cruise HE626-2 (27.10.2023 - 01.11.2023, Wilhelmshaven, Germany - Wilhelmshaven, Germany) using a white Secchi disc with a diameter of 40 cm and a Forel-Ule color scale. The Secchi depth (SD) was recorded as a relative measure of water clarity at each in situ station during day time. At half SD the apparent color of the water above the submerged Secchi disc was determined using the Forel-Ule color scale. A Forel-Ule color scale is a classic tools used to differentiate the percieved color of water based on a scale from 1 (indigo blue) to 21 (cola brown). The measurements were conducted as recemmend in literature (Garaba and Zielinski, 2015; Wernand, 2011; Wernand and van der Woerd, 2010).

Optical water quality variables (Secchi depth and Forel-Ule color indexes) observed during RV HEINCKE cruise HE626 from Bremerhaven, Germany to Bremerhaven, Germany

Water clarity and color were observed during the RV HEINCKE cruise HE626 (20.07.2023 - 09.08.2023, Wilhelmshaven, Germany - Wilhelmshaven, Germany) using a white Secchi disc with a diameter of 40 cm and a Forel-Ule color scale. The Secchi depth (SD) was recorded as a relative measure of water clarity at each in situ station during day time. At half SD the apparent color of the water above the submerged Secchi disc was determined using the Forel-Ule color scale. A Forel-Ule color scale is a classic tools used to differentiate the percieved color of water based on a scale from 1 (indigo blue) to 21 (cola brown). The measurements were conducted as recemmend in literature (Garaba and Zielinski, 2015; Wernand, 2011; Wernand and van der Woerd, 2010).

Optical water quality variables (Secchi depth and Forel-Ule color indexes) observed during RV HEINCKE cruise HE614 from Bremerhaven, Germany to Bremerhaven, Germany

Water clarity and color were observed during the RV HEINCKE cruise HE614 (01.03.2023 to 21.03.2023), from Bremerhaven, Germany to Bremerhaven, Germany) using a white Secchi disc with a diameter of 40 cm and a Forel-Ule color scale. The Secchi depth (SD) was recorded as a relative measure of water clarity at each in situ station during day time. At half SD the apparent color of the water above the submerged Secchi disc was determined using the Forel-Ule color scale. A Forel-Ule color scale is a classic tools used to differentiate the percieved color of water based on a scale from 1 (indigo blue) to 21 (cola brown). The measurements were conducted as recemmend in literature (Garaba and Zielinski, 2015; Wernand, 2011; Wernand and van der Woerd, 2010).

Optical water quality variables (Secchi depth and Forel-Ule color indexes) observed during RV HEINCKE cruise HE609 from Bremerhaven, Germany to Bremerhaven, Germany

Water clarity and color were observed during the RV HEINCKE cruise HE609 (04.10.2022 to 26.10.2022), from Bremerhaven, Germany to Bremerhaven, Germany) using a white Secchi disc with a diameter of 40 cm and a Forel-Ule color scale. The Secchi depth (SD) was recorded as a relative measure of water clarity at each in situ station during day time. At half SD the apparent color of the water above the submerged Secchi disc was determined using the Forel-Ule color scale. A Forel-Ule color scale is a classic tools used to differentiate the percieved color of water based on a scale from 1 (indigo blue) to 21 (cola brown). The measurements were conducted as recemmend in literature (Garaba and Zielinski, 2015; Wernand, 2011; Wernand and van der Woerd, 2010).

Optical water quality variables (Secchi depth and Forel-Ule color indexes) observed during RV SENCKENBERG cruises SE202011-1, SE202103-1, SE202206-1, SE202208-1 and RV OTZUM cruise OT202103-1

Water clarity and color were observed during the RV SENCKENBERG cruises SE202011-1, SE202103-1, SE202206-1, SE202208-1 and RV OTZUM cruise OT202103-1 using a white Secchi disc with a diameter of 40 cm and a Forel-Ule color scale. The Secchi depth (SD) was recorded as a relative measure of water clarity at each in situ station during day time. At half SD the apparent color of the water above the submerged Secchi disc was determined using the Forel-Ule color scale. A Forel-Ule color scale is a classic tools used to differentiate the percieved color of water based on a scale from 1 (indigo blue) to 21 (cola brown). The measurements were conducted as recemmend in literature (Garaba and Zielinski, 2015; Wernand, 2011; Wernand and van der Woerd, 2010).

Reference measurements of surface waters and optical water quality variables (Secchi depth and Forel-Ule color indexes) collected during two RV Otzum cruises along the river Elbe in 2012 and 2013

Reference measurements of surface waters were collected during two RV Otzum cruises along the river Elbe in 2012 and 2013 (Ot2012_05: 21.-24.05., 30.-31.05.2012; Ot2013_05: 23.05., 27.-30.05.2013). Temperature [°C], salinity, turbidity [NTU], and chlorophyll from fluorescence [µg/L] were measured by a PocketFerrybox System (values given to the time of sampling). Water samples were taken from the outlet of the system. Suspended particular matter (SPM) and chlorophyll a (Chl a) were filtered onboard on glas fibre filters (GFF, 47mm, 0,7 µm) and frozen at -25°C and -80°C immediately after sampling. Values were determined in the lab after the cruise within 2 months, for SPM via gravimetric analysis (IOCC recommendations) and for Chl a according to EPA Method 445. Water clarity and color were observed using a white Secchi disc with a diameter of 30 cm and a Forel-Ule color scale. The Secchi depth (SD) was recorded as a relative measure of water clarity at each in situ station during day time. At half SD the apparent color of the water above the submerged Secchi disc was determined using the Forel-Ule color scale. A Forel-Ule color scale is a classic tool used to differentiate the percieved color of water based on a scale from 1 (indigo blue) to 21 (cola brown). The measurements were conducted as recommended in literature (Garaba and Zielinski, 2015; Wernand, 2011; Wernand and van der Woerd, 2010). Measurements were part of the project DOMsense (01.11.2011 - 31.05.2014, KF2866501DF1)