title: Towards Cost-Effective Operational Monitoring Systems for Complex Waters: Analyzing Small-Scale Coastal Processes with Optical Transmissometry.
abstract: The detection and prediction of changes in coastal ecosystems require a better understanding of the complex physical, chemical and biological interactions, which involves that observations should be performed continuously. For this reason, there is an increasing demand for small, simple and cost-effective in situ sensors to analyze complex coastal waters at a broad range of scales. In this context, this study seeks to explore the potential of beam attenuation spectra, c(λ), measured in situ with an advanced-technology optical transmissometer, for assessing temporal and spatial patterns in the complex estuarine waters of Alfacs Bay (NW Mediterranean) as a test site. In particular, the information contained in the spectral beam attenuation coefficient was assessed and linked with different biogeochemical variables. The attenuation at λ = 710 nm was used as a proxy for particle concentration, TSM, whereas a novel parameter was adopted as an optical indicator for chlorophyll a (Chl-a) concentration, based on the local maximum of c(λ) observed at the long-wavelength side of the red band Chl-a absorption peak. In addition, since coloured dissolved organic matter (CDOM) has an important influence on the beam attenuation spectral shape and complementary measurements of particle size distribution were available, the beam attenuation spectral slope was used to analyze the CDOM content. Results were successfully compared with optical and biogeochemical variables from laboratory analysis of collocated water samples, and statistically significant correlations were found between the attenuation proxies and the biogeochemical variables TSM, Chl-a and CDOM. This outcome depicted the potential of high-frequency beam attenuation measurements as a simple, continuous and cost-effective approach for rapid detection of changes and patterns in biogeochemical properties in complex coastal environments.
authors.affiliation: Department of Physical and Technological Oceanography, Institute of Marine Sciences (ICM-CSIC), Barcelona, Spain.
authors.forename: Marta
authors.identifier: http://orcid.org/9153-2615-8198-4310
authors.initials: M
authors.lastname: Ramírez-Pérez
authors.affiliation: Phytooptics Group, Physical Oceanography of Polar Seas, Climate Sciences Division, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Rafael
authors.initials: R
authors.lastname: Gonçalves-Araujo
authors.affiliation: Phytooptics Group, Physical Oceanography of Polar Seas, Climate Sciences Division, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Wiegmann
authors.affiliation: Department of Physical and Technological Oceanography, Institute of Marine Sciences (ICM-CSIC), Barcelona, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Torrecilla
authors.affiliation: Department of Physical and Technological Oceanography, Institute of Marine Sciences (ICM-CSIC), Barcelona, Spain.
authors.forename: Raul
authors.initials: R
authors.lastname: Bardaji
authors.affiliation: Remote Sensing Department, Institute for Coastal Research, Centre for Materials and Coastal Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany.
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Röttgers
authors.affiliation: Phytooptics Group, Physical Oceanography of Polar Seas, Climate Sciences Division, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.|Institute of Environmental Physics, University of Bremen, Bremen, Germany.
authors.forename: Astrid
authors.initials: A
authors.lastname: Bracher
authors.affiliation: Department of Physical and Technological Oceanography, Institute of Marine Sciences (ICM-CSIC), Barcelona, Spain.
authors.forename: Jaume
authors.initials: J
authors.lastname: Piera
mesh_terms: D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D003362:Cost-Benefit Analysis; D017753:Ecosystem; D004784:Environmental Monitoring / Q000191:economics / Q000379:methods*; D008522:Mediterranean Sea; D055620:Optical Phenomena; D012623:Seawater / Q000737:chemistry
chemical_list: D002734:Chlorophyll; D000077194:Chlorophyll A