ECO-TS - Ecotechnologies & EcoServices

Optical Sensors and drone system for the spatial Survey of Cyanobacteria in freshwater ecosystems – OSS-CYANO

New tools for the monitoring of cyanobacteria in water bodies, the OSS-Cyano project

The OSS-Cyano project aimed to develop (i) an aerial optical sensor that could be coupled to a drone system to monitor cyanobacteria in aquatic ecosystems and (ii) a modeling tool to predict dynamics and distribution of cyanobacteria in water bodies.

Context and objectives of the project

Cyanobacteria are photosynthetic microorganisms able to proliferate in certain water bodies and rivers. These blooms pose a risk to animal and human health because of the ability of these bacteria to produce toxins. As a result, cyanobacteria are monitored in lakes and rivers that are used for recreational purposes or to produce drinking water.<br />This monitoring is most often based on water samples and laboratory analyzes to determine the number of cells and / or the amount of cyanotoxins in the water. It is time-consuming, which leads often results in a limited number of samples and analyzes carried out.<br />In addition, the delays in obtaining results are at least two days, which may present a health risk for human populations.<br />For all these reasons, water body managers need new monitoring tools that allow high frequency monitoring of cyanobacteria and deliver real-time information. The OSS-Cyano project is very directly involved in this issue with three major objectives:<br />- The development of a low cost air sensor<br />- The development of a drone system to carry the air sensor and other surveillance systems<br />- The development of a modeling tool and a user interface to predict the development of cyanobacteria on a scale of several days and to inform users of water bodies.

Regarding the air sensor, the technology chosen is based on proximal sensing measurments of reflected radiation by water bodies. When the surface layer of water bodies contains high concentrations of cyanobacteria, a significant variation in reflectance will be observed in the
wavelengths corresponding to the spectral signature of cyanobacteria. This spectral signature was determined by laboratory measurements of various strains of cyanobacteria and other microalgae frequent in water bodies. A sensor prototype using photodiodes was then tested in
the laboratory, then in experimental systems and finally in the field.
The drone system is a small helicopter allowing to carry a maximum of 4 kg of material.
Four types of devices needed to be attached to this helicopter:
o The reflectance based sensor developed in OSS-Cyano
o A small spectrophotometer performing absorbance measurements
o A multiparameter probe for making measurements in the water column
o A water sampling system
One of the most important technological challenges was to design interchangeable platforms each carrying one of these devices. All these systems have been tested under real conditions on water bodies.
Finally, the modeling module was based on the use of the Delft3D-Flow hydrodynamic model (Deltares, 2014). Calibration was performed on two lakes using continuous measurements from sub-aquatic sensors placed in these lakes. A graphical interface was then developed in order to provide to end-users a user-friendly interface for viewing the results.

Three major results were obtained during this project:
o The first one concerns the construction of a reflectance-based sensor allowing to follow the evolution of the quantity of cyanobacteria present in a water body. The advantage of this sensor is that its price is very low (<800 €) which is a very important parameter for its future use by water body managers.
o The second is the demonstration that it will be possible in the near future to use drones equipped with different platforms to monitor the water quality of an aquatic ecosystem.
o The third concerns the development of a user-friendly interface for the future users of a surveillance system based on the use of air and aquatic sensors feeding a predictive modeling module.

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The project was the subject of a first academic publication on the development of the air sensor, knowing that several other publications are in preparation. OSS-Cyano has also been the subject of various communications in national and international scientific meetings, but
also in several meetings with professionals, potential users of the sensor or of the drone. Finally, a special session and a satellite session were organized at the International Toxic Algae Conference held in Nantes in October 2018 (ICHA 2018) to present our final results to
the international scientific community as well as to the Follow-up Committee of the project which brought together professionals from various horizons (Water Agencies, Water Caterers ...) invited for this day.

Cyanobacteria blooms frequently disturb the functioning of freshwater ecosystems and their uses, due to the toxins dangerous to health that cyanobacteria are able to synthesize. Therefore, many countries have implemented monitoring programs aimed at reducing the risk of human exposure to these toxins. The main limitation is related to the heterogeneity of the spatial distribution of cyanobacteria. In the vertical dimension, these organisms can stay in different layers in the water column and in the horizontal scale, the cells may accumulate in some area of the water body, under the action of winds or currents. In an attempt to improve monitoring, many research projects have been undertaken in order to develop new tools, like buoys developed during the program PROLIPHYC (ANR PRECODD). This tool is highly relevant but it does not allow assessing the horizontal distribution of cyanobacteria and its cost remains expensive. In addition, if satellite remote sensing can be considered very useful for estimating biomass and horizontal distribution of cyanobacteria in a water body, the cost of this technology and the lack of satellite availability make it unaffordable for routine monitoring. In this context, our OSS-CYANO project aims to develop and validate a new, low-cost aerial sensor, to be used in a fixed single location, or deployed in network, to detect the presence of cyanobacteria in a water body. In addition, OSS-CYANO also aims to implement a drone capable of carrying the sensor to perform spatial measurements on large water bodies or river sections, and other instruments for water sampling or for performing underwater measurements. Our project is organized into five tasks. Task 1 is dedicated to (i) the coordination of the project, (ii) the scientific animation and dialogue with end-users through the formation of a monitoring committee and (iii) dissemination of results, including the organization at the end of the project of an international workshop dedicated to new monitoring tools. The second task will help to identify potential end-users and identify their expectations for the developed tools. Task 3, a key task of the project, will involve technical development of the sensor (wavelength selection, influence of natural processes on the measurements ...) and of the drone system (implementation of an adaptive platform for supporting the measuring equipments). These developments will largely benefit on the facilities offered by the support center PLANAQUA (French label "Investissement d’avenir ") which provides all the required facilities to carry out tests of the sensor on a range of aquatic systems, from microcosm to macrocosm. The fourth task will test in real conditions of application, and in the long term, the sensor and the drone on different lakes and river systems impacted by representative cyanobacteria. Finally, the last task will relate to (i) data processing methodologies and data integration, (ii) the implementation of a three-dimensional hydrodynamic model using data from the sensor and / or drone to forecast short-term changes of the spatial dispersion of cyanobacteria in a water body, and (iii) to define the characteristics of a future warning system. This project relies on the participation of six laboratories and a private company. All these teams have the required skills for all planned work and have already collaborated on previous research projects.

Project coordination

Jean françois Humbert (CNRS DR Paris B / Biogéochimie et Ecologie des Milieux Continentaux) – jean-francois.humbert@upmc.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

MNHN Cyanobactéries, cyanotoxines et environnement
ENPC/LEESU Laboratoire Eau, Environnement et Systèmes Urbains
Université Paris-Sud Ecology, Systematics and Evolution
IFSTTAR Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux
CNRS DR 2 / CEREEP CNRS DR Paris B / Centre de Recherche en Ecologie Expérimentale et Prédictive & Ecotron Ile-de-France
ARTELIA ARTELIA EAU & ENVIRONNEMENT
CNRS DR 2 / BIOEMCO-UMR 7618 CNRS DR Paris B / Biogéochimie et Ecologie des Milieux Continentaux

Help of the ANR 654,238 euros
Beginning and duration of the scientific project: December 2013 - 42 Months

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