Abstract: Changes in water colour are linked to a number of processes of concern to society, including algal blooms. In order to motivate citizens to get engaged in environmental monitoring and to improve their environmental science capacity, bio-optical measurement tools for citizens are developed within the EU project "Citclops" (Citizens’ observatory for Coast and Ocean Optical Monitoring). Key parameter is an assessment of water colour by comparison to the Forel Ule (FU) colour scale. In one of the two Citclops test areas, the Ebro Delta, NW Mediterranean, measurements of water colour with the FU scale along weekly transects from May – June 2011 revealed colour changes over short distances and time frames, indicative of fast dynamics of phytoplankton in the area. The typical seasonal pattern of phytoplankton proliferations was reflected well by FU colours as retrieved from satellite data (Medium Resolution Imaging Spectrometer (MERIS) full resolution 300m data). The results show that a simplified classifications natural waters by its colour enhances our understanding of spatio-temporal dynamics in the Ebro Delta. Hence, such measurements can complement more accurate in-situ observations that allow the identification of harmful algal taxa and phycotoxins. Thereby, Citclops observations support phytoplankton surveillance for human health and food safety. Direct links to environmental issues strongly motivate the general public to engage in environmental surveillance and stewardship, and to support local monitoring efforts.
Abstract Why is it necessary to dedicate efforts in the development of a measurement system to determine fluorescence with smartphones? Because fluorescence is a proxy for algal biomass and dissolved material in water, and is therefore an indicator for different processes of societal concern. Fluorescence is conveniently used to measure such parameters within monitoring programs and scientific research. By utilizing smartphones citizens are enabled to actively participate in measurements of water quality to achieve a spacious data set of these parameters. In the EU-project Citclops (Citizens’ observatory for Coast and Ocean Optical Monitoring; 10) two new devices were developed to measure algal fluorescence with smartphones. We present a) a method and sensor geometry for the use of internal smartphone elements for retrieval of Chlorophyll a (Chl a) fluorescence, and b) a multi-parameter fluorometer which can be directly accessed by multiple mobile end-devices. Both approaches are easy to use, small and affordable for their respective field of use. Algorithms and applications to measure fluorescence of Chl a by means of smartphones were developed for citizen involvement for the two of them. The potential of the Citclops initiative is an almost synoptically and spacious data set of coastal seas based on participatory science.
Abstract: Framed within the European Project CITCLOPS (Citizens’ Observatory for Coast and Ocean Optical Monitoring), the aim of this study is to present a number of tools that can be employed by citizens to estimate the color of natural waters. Firstly, a scale that accurately matches the original Forel-Ule (FU) colors was developed using accessible and affordable materials. This Modern FU scale is presented as a ‘Do-It-Yourself’ kit that can be prepared using high-quality illumination filters and a frame made of a white Plexiglas (or other white material). Secondly, a smartphone application (APP) prototype that could be used by anyone willing to participate in environmental monitoring is presented.
Abstract: The colour comparator Forel-Ule scale has been used to estimate the colour of natural waters since the 19th century, resulting in one of the longest oceanographic data series. This colour index has been proven by previous research to be related to water quality indicators such as chlorophyll and coloured dissolved organic material. The aim of this study was to develop an affordable, ‘Do-it-Yourself’ colour scale that matched the colours of the original Forel-Ule scale, to be used in water quality monitoring programs by citizens. This scale can be manufactured with high-quality lighting filters and a white frame, an improvement with respect to the materials employed to manufacture the original scale from the 19th century, which required the mixing of noxious chemicals. The colours of the new scale were matched to the original colours using instrumental and visual measurements carried out under controlled lighting conditions, following the standard measurement protocols for colour. Moreover, the colours of the scale are expressed in Munsell notations, a standard colour system already successfully used in water quality monitoring. With the creation of this Modern Forel-Ule scale, as a ‘Do-it-yourself’ kit, the authors foresee a possible use of the Forel-Ule number as a water quality index that could be estimated by means of participatory science and used by environmental agencies in monitoring programs. [DOI: http://dx.doi.org/10.2971/jeos.2014.14025]
Abstract: One goal of the Citclops European project is to approach citizens and improve their understanding of aquatic environmental observations and monitoring for the enhancement of community decision-making and cooperative planning. As a potential solution to estimate water transparency related parameters, a low cost instrument is proposed, integrating quasi-digital optical sensors in the open-hardware Arduino platform.
Abstract: Multispectral information from satellite borne ocean colour sensors is at present used to characterize natural waters via the retrieval of concentration of the three dominant optical constituents; pigments of phytoplankton, non-algal particles and coloured dissolved organic matter. A limitation of this approach is that accurate retrieval of these constituents requires detailed local knowledge of the specific absorption and scattering properties. In addition, the retrieval algorithms generally use only a limited part of the collected spectral information. In this paper we present an additional new algorithm that has the merit to use the full spectral information in the visible domain to characterize natural waters in a simple and globally valid way. This Forel-Ule MERIS (FUME) algorithm converts the normalized multi-band reflectance information into a discrete set of numbers using uniform colourimetric functions. The Forel-Ule scale is a sea colour comparator scale that has been developed to cover all possible natural sea colours, ranging from indigo blue (the open ocean) to brownish-green (coastal water) and even brown (humic-acid dominated) waters. Data using this scale have been collected since the late nineteenth century, and therefore, this algorithm creates the possibility to compare historic ocean colour data with present-day satellite ocean colour observations. The FUME algorithm was tested by transforming a number of MERIS satellite images into Forel-Ule colour index images and comparing in situ observed FU numbers with FU numbers modelled from in situ radiometer measurements.
Abstract: The Citclops European Project aims to develop lowcost technologies to estimate parameters related to water optical properties. The wide variety of sensors involved makes it desirable to have a standardized description of the sensor itself and the data acquired by the sensor. This project presents a practical approach to modeling these descriptions and the graphical representation of this information.
Abstract: The Forel-Ule colour comparator scale has been applied globally and intensively by oceanographers and limnologists since the 19th century, providing one of the oldest oceanographic data sets. Present and future Forel-Ule classifications of global oceanic, coastal and continentalwaters can facilitate the interpretation of these long-term ocean colour data series and provide a connection between the present and the past that will be valuable for climate-related studies. Within the EC-funded project CITLOPS (Citizens’ Observatory for Coast and Ocean Optical Monitoring), with its main goal to empower end users, willing to employ community-based environmental monitoring, our aim is to digitalize the colours of the Forel-Ule scale to establish the colour of natural waters through smartphone imaging. The objective of this study was to reproduce the Forel-Ule scale following the original recipes, measure the transmission of the solutions and calculate the chromaticity coordinates of the scale as Wernand and Vander Woerd did in 2010, for the future development of a smartphone application. Some difficulties were encountered when producing the scale, so a protocol for its consistent reproduction was developed and is described in this study. Recalculated chromaticity coordinates are presented and compared to measurements conducted by former scientists. An error analysis of the spectral and colourimetric information shows negligible experimental errors.
Abstract: Marine primary productivity is an important agent in the global cycling of carbon dioxide, a major ‘greenhouse gas’, and variations in the concentration of the ocean's phytoplankton biomass can therefore explain trends in the global carbon budget. Since the launch of satellite-mounted sensors globe-wide monitoring of chlorophyll, a phytoplankton biomass proxy, became feasible. Just as satellites, the Forel-Ule (FU) scale record (a hardly explored database of ocean colour) has covered all seas and oceans – but already since 1889. We provide evidence that changes of ocean surface chlorophyll can be reconstructed with confidence from this record. The EcoLight radiative transfer numerical model indicates that the FU index is closely related to chlorophyll concentrations in open ocean regions. The most complete FU record is that of the North Atlantic in terms of coverage over space and in time; this dataset has been used to test the validity of colour changes that can be translated to chlorophyll. The FU and FU-derived chlorophyll data were analysed for monotonously increasing or decreasing trends with the non-parametric Mann-Kendall test, a method to establish the presence of a consistent trend. Our analysis has not revealed a globe-wide trend of increase or decrease in chlorophyll concentration during the past century; ocean regions have apparently responded differentially to changes in meteorological, hydrological and biological conditions at the surface, including potential long-term trends related to global warming. Since 1889, chlorophyll concentrations have decreased in the Indian Ocean and in the Pacific; increased in the Atlantic Ocean, the Mediterranean, the Chinese Sea, and in the seas west and north-west of Japan. This suggests that explanations of chlorophyll changes over long periods should focus on hydrographical and biological characteristics typical of single ocean regions, not on those of ‘the’ ocean.