Monitoring the Harmful algal blooms of Karaoun Reservoir and Mantua Lakes using remote sensing. Calibration and validation of Chlorophyll-a and phycocyanin algorithms.

Joint research project

Project leaders: Mariano Bresciani, Ali Fadel
Agreement: LIBANO - CNRS-L- not in force - National Council for Scientific Research of Lebanon
Call: CNR-CNRS-L 2016-2017
Department: Earth system science and environmental technologies
Thematic area: Earth system science and environmental technologies
Status of the project: New

Research proposal

Over 45,000 large dams had been constructed in more than 140 countries by the end of the 20th century (WCD 2000). An ongoing increase in the construction of reservoirs is expected in the future. These artificial water bodies meet human needs for drinking water supply, agricultural irrigation, power generation, industrial use, commercial fishing and recreational activities. But fertilizers and untreated sewage in their catchments often increase nutrient concentrations in these ecosystems and cause their eutrophication (Smith & Schindler 2009).
Eutrophication threatens freshwater bodies as it promotes the development and the persistence of harmful algal blooms, mostly cyanobacteria. These harmful photosynthetic species reduce ecosystem biodiversity and can produce toxins. Some of these toxins cause skin irritation upon contact, illness, intoxication and death to livestock, pets, and wildlife that ingest water contaminated with toxic cyanobacterial cells or toxins released from decaying of cyanobacterial cells (Nyakairu et al. 2010). In addition to this, cyanobacteria can aggregate and form surface layers on the water, reducing the penetration of light available for other organisms living inside the water column, which will damage the natural ecosystem functioning (Bresciani et al. 2014).
In the European Union, the phytoplankton community is used as a biological indicator of the ecological status of water bodies monitored in accordance with the Water Framework Directive. In addition, the World Health Organization (WHO) has established guideline values for drinking-water supplies and recreational waters which may contain harmful algal blooms (Chorus 2005).
Lakes and reservoirs' water quality can be monitored by traditional in situ sampling coupled with measurements and laboratory analyses, but it is usually very expensive and time consuming when several sampling sites should be monitored frequently during the season. Remote sensing is a key tool for assessing and monitoring the quality of lakes as it allows frequent surveys over large areas in a cost-effective way. Chlorophyll-a and phycocyanin are pigments used to asses total phytoplankton and cyanobacteria, and can be estimated from satellite images using retrieval algorithms. Cyanobacteria blooms are known to be extremely variable, both in space and time. It has been demonstrated that in eutrophic lakes cyanobacteria pigments concentration can vary up to one order of magnitude in one single day (Bresciani et al. 2013). The use of traditional sampling techniques can fail in the detection of single bloom events. This can be a problem when water is systematically exploited for human needs such as irrigation or drinking supply. The possibility of having temporally distributed images from remote sensors can help in the monitoring of temporal phytoplankton and cyanobacteria dynamics. Also, remote sensing techniques allow the analysis of events occurred in the past, increasing the detection temporal range, which can be useful for a better understanding of the phenomena evolution.
The variety of optical satellite and airborne sensors operating nowadays is an extraordinary source of information that can fit different study sites' characteristics. New generation sensors (e.g. Landsat-OLI and Sentinel2-MSI) provide high quality optical images suitable to water study applications.
Karaoun Reservoir is the largest freshwater body in Lebanon. It is used for power generation, irrigation, fishing and touristic activities. Harmful algal blooms of toxic cyanobacteria species, Microcystis aeruginosa and Aphanizomenon ovalisporum occur annually (Fadel et al. 2014a). A system for monitoring of these algal blooms of Karaoun Reservoir is urgent for Lebanon. Providing information about the spatial and temporal variation of cyanobacteria blooms to the Lebanese water quality authorities will help in management decisions. In addition, data about the evolution of the water quality of Karaoun Reservoir before the year 2005 is missing. Previous scenes of Satellite images will allow us to trace the evolution of algal blooms in this reservoir.
The Mantua Lakes are a chain of three shallow eutrophic lakes near the town of Mantua in northern Italy. They are fluvial lakes formed from a meander of the Mincio River that was dammed in the 12th century. The lakes are nutrient enriched, highly productivity and generally turbid. The phytoplankton community is typical of eutrophic and/or hypertrophic systems, cyanobacteria dominate in summer and autumn. This lakes are included in national monitoring program and are studied in EU-INFORM project.
Mantua Lakes share with Karaoun Reservoir the eutrophic status, the occurrence of periodic cyanobacteria bloom events, similar anthropic pressures on the water basin and human control on the hydrology of the lake. Furthermore, the two lakes are both influenced by the Mediterranean Sea and similar climatic conditions can take place. Comparison between Italian and Lebanon water bodies could help in the identification of different strains acting on comparable aquatic environments and their consequences.
This project will be conducted by the research Institute for Electromagnetic Sensing of the Environment (IREA-CNR, Italy), which has proved experience on the development of remote sensing methodologies and technologies aimed at environmental monitoring (Bresciani et al. 2014), and both by National Center of Remote sensing (CNRS, Lebanon) and the Laboratory of Microorganisms and Food Irradiation in the Lebanese Atomic Energy Commission (CNRS), which has been involved in monitoring of the dynamics harmful algal blooms in Karaoun Reservoir in response to environmental conditions (Fadel et al. 2014b). Joint research activities will be valuable for all the research institutions involved in the project; exchange of knowledge, experience and information will increase research potentialities and extend specific abilities.

Research goals

The main objective of this project is to implement and use remote sensing techniques to monitor the harmful algal blooms in Karaoun Reservoir (Lebanon) and Mantua Lakes (Italy). This includes several sub-objectives: 1) write a literature review of the available methods used to monitor harmful algal blooms, 2) design and apply a spatial ground monitoring of Chlorophyll-a and phycocyanin pigments in Karaoun Reservoir and Mantua Lakes, 4) test the previously developed algorithms used to determine phycocyanin pigment from satellite images, 5) develop the best phycocyanin retrieval algorithm for Karaoun Reservoir applicable to satellite images and 6) use this validated algorithm to determine the historical evolution of Karaoun reservoir in the last 20 years 7) find possible correlations between environmental drivers and phytoplankton dynamics.
Reciprocal exchanges and cooperation between Lebanese and Italian partners will contribute in the accomplishment of another goal of the project: the creation of new fruitful collaborations and the straightening of each single institution potentialities. The concurrent study of Lebanese and Italian water bodies will finally help in the understanding of different stressors triggering phytoplankton responses in similar environments.
The results of this project will help local authorities in monitoring these freshwater bodies and will be of great interest to the international scientific community.

Last update: 20/04/2024