Oelker, Julia; Bange, Hermann W; Booge, Dennis; Gaye, Birgit; Quack, Birgit; Schulz, Gesa; Wollschläger, Jochen (2025): Continuous optical chlorophyll-a and turbidity data along RV SONNE cruise SO305 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.982259
Always quote citation above when using data! You can download the citation in several formats below.
Published: 2025-05-14 • DOI registered: 2025-06-12
Abstract:
Underway optical chlorophyll-a and turbidity data were collected along the cruise track with Sea-Bird
Scientific ECO FLNTU sensors installed within two autonomous measurement systems, called self-
cleaning monitoring boxes (SMBs). The SMBs measure alternatingly. While one box is measuring, the
other one is being cleaned. The boxes switched generally every 12 hours which was reduced to 3
hours for about one week during the cruise. The water inlet for the SMBs is at about 4 m below sea
surface. Online monitoring of the NRT data stream revealed large offsets between the sensors and
negative chlorophyll-a values for one sensor. Consequently, the sensors in the measurement
containers were exchanged a few times by the scientific-technical service during the research cruise
for testing purposes, including a spare sensor. Analysis of the parallel operation time of the two
measurement boxes showed that all three sensors are highly correlated, but a significant offset was
observed for one sensor. The chlorophyll-a and turbidity data were therefore corrected to align the
sensors and obtain a consistent and non-negative time series. Chlorophyll-a and turbidity data were
both quality-controlled before and after sensor alignment. The data were then compared to
chlorophyll-a and suspended particulate matter (SPM) determined in the lab from discrete water
samples. A calibration was obtained based on comparison with the HPLC total chlorophyll-a by
splitting the time series into two different time periods based on different water masses. The time
period at the beginning of the cruise corresponds to the open Indian Ocean and the second time
period to the Bengal Shelf. Resulting calibrated chlorophyll-a matches well the HPLC chlorophyll-a.
Turbidity values were compared to discrete SPM samples. The correlation between these is low,
probably due to methodological sensitivity in these clear waters. A comparison with satellite data
using the GlobColour CHL1 and SPM-OC5 product is additionally provided for both parameters.
Details on all quality control steps, calibration and the comparison with satellite data can be found in
the data processing report. The resulting data set contains the original data and corresponding
quality flags achieved by the quality control algorithm as well as the calibrated data with
corresponding quality flag for chlorophyll-a and the corrected data through sensor alignment with
corresponding quality flag for turbidity. The data source is given through the name of the active SMB.
The data set contains data during transit time and station work. We recommend to use ship's speed
to filter for only transit data.
Related to:
Bange, Hermann W; Stoltenberg, Ina; Andersch, Tjark; Arévalo-Martínez, Damian L; Atlas, Elliot L; Babu Suja, Arun; Barbot, Antoine; Barthelmeß, Theresa; Becker, Kevin W; Booge, Dennis; Bristow, Laura Anne; Conventz, Anja; Czeschel, Rena; Dähnke, Kirstin; Deshmukh, Shravan; Duerkop, Felix; Eisnecker, Paula; Engel, Anja; Engelen, Bert; Feil, Hendrik; Fernández-Juárez, Victor; Firus, Albert; Frank, Martin; Gaye, Birgit; Gledhill, Martha; Golde, Sandra; Großelindemann, Hendrik; Hathorne, Edmund; Henning, Silvia; Hentschel, Isabell; Herrmann, Hartmut; Ingeniero, Riel Carlo O; Jacobsen, Mats; Kiko, Rainer; Lahajnar, Niko; Lange, K; Löscher, Carolin Regina; Marandino, Christa A; McKellar, Clara; Mickenbecker, Julia; Müller, Mario; Müller, Thomas; Nazzari, Leandro; Nielsen, Lubrina; Ploschke, Jule; Pohlker, Mira; Pontiller, Benjamin; Poulain, Laurent; Quack, Birgit; Rabe, René; Roa, Jon; Rolfes, Sönke; Sanders, Tina; Schlangen, Isabell; Schmidt, Leon; Schulz, Gesa; Sommer, Marcel; Thamdrup, Bo; Usinger, Jannis; van Bonn, Laurenz; van Pinxteren, Manuela; Zhong, Qingwen (2024): Biogeochemistry/atmosphere processes in the Bay of Bengal: A contribution to the 2nd International Indian Ocean Expedition, Cruise No. SO305
10 April - 22 May 2024, Colombo (Sri Lanka) - Singapore (Singapore). SONNE-Berichte, Begutachtungspanel Forschungsschiffe, SO305, 86 pp, https://doi.org/10.48433/cr_so305
References:
Arar, E J (1997): Method 447.0 - Determination of Chlorophylls a and b and Identification of Other Pigments of Interest in Marine and Freshwater Algae Using High Performance Liquid Chromatography with Visible Wavelength Detection. U.S. Environmental Protection Agency, Washington, DC, https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NERL&dirEntryId=309414 (M447_0.PDF)
Data processing report:
Oelker, Julia (2025): Continuous optical chlorophyll-a and turbidity data along R/V SONNE cruise SO305 - Data Processing Report. Institute for Chemistry and Biology of the Marine Environment (ICBM), School of Mathematics and Science, Carl von Ossietzky Universität Oldenburg, DAM_DataProcessingReport_SO305.pdf
Project(s):
DAM Underway Research Data (DAM_Underway)
Coverage:
Median Latitude: 8.602813 * Median Longitude: 88.549892 * South-bound Latitude: -1.492910 * West-bound Longitude: 79.658880 * North-bound Latitude: 16.000460 * East-bound Longitude: 103.818250
Date/Time Start: 2024-04-12T12:00:00 * Date/Time End: 2024-05-16T22:58:00
Minimum DEPTH, water: 4.0 m * Maximum DEPTH, water: 4.0 m
Event(s):
SO305_0_Underway-11 * Latitude Start: 6.942180 * Longitude Start: 79.846940 * Latitude End: 1.261850 * Longitude End: 103.818230 * Date/Time Start: 2024-04-12T12:00:00 * Date/Time End: 2024-05-16T22:58:00 * Campaign: SO305 (BIOCAT-IIEO2) * Basis: Sonne_2 * Method/Device: Fluorometer, Sea-Bird Scientific, ECO FLNTU * Comment: event was not logged in DSHIP
Parameter(s):
License:
Creative Commons Attribution 4.0 International (CC-BY-4.0)
Status:
Curation Level: Enhanced curation (CurationLevelC) * Processing Level: PANGAEA data processing level 2 (ProcLevel2)
Size:
436316 data points
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