Periodic water monitoring is very important to assess water quality.
Blooms of potentially toxic cyanobacteria are some of the most concerning threats affecting aquatic ecosystems. Therefore, it is important to develop sensitive monitoring programs that are directly applicable to the prediction and management of these events.
The monitoring of the different water bodies begins with planning, obtaining maps or sketches of the study area, choosing appropriate methods according to the purpose of the study and finally organizing adequate materials and equipment.
When carrying out sampling, the physical characteristics of the waterbody should be taken into account. According to the physical characteristics of water bodies it can be classified into lotic (rivers, streams, among others) and lentic (lakes, ponds, among others). They can also be classified according to their trophic state, that is, according to the increasing richness of its nutrients as: oligotrophic, mesotrophic and eutrophic. Lastelly, according to their use, water bodies can be classified as drinking water, irrigation water, recreational water, recycled water, etc.
The personnel responsible for monitoring generally use boots, latex gloves and life jackets as personal protective equipment, and for sampling materials and equipment they use GPS to register the sampling points, plastic and glass bottles, phytoplankton nets, hydrographic bottles, multiparameters, sechi disc, etc.
Water sampling Alqueva reservoir, Portugal. Source: TOXICROP project
The physical, chemical, and biological parameters of the water are always measured as these are essential to assess water quality. They provide a significant amount of data over time, allowing a record of useful variables to infer water quality.
Monitoring campaign in Alqueva reservoir, Portugal. Source: TOXICROP project
The World Health Organization (WHO) provides a series of recommendations when carrying out evaluations in water bodies to determine the presence of toxic blooms, which are based on observation such as foam formation, color, transparency, surrounding fauna and flora, and also provides a series of parameters to consider, such as concentrations of phosphorus and nitrogen. Additionally, it indicates that the water retention time, depth, pH, type of climate and tributaries must be taken into account.
In the event of suspected cyanobacterial bloom, and biovolumes above 0.3 mm3/L (drinking water), periodic sampling must be carried out, including microscopic analysis with identification and counting of colonies, determination of cyanotoxins using techniques such as High-Performance Liquid Chromatography (HPLC) or Enzyme-Linked Immunosorbent Assay (ELISA). If the presence of toxic blooms is confirmed, a set of measures must be deployed to restrict access to people and animals, as well as limit the use of this water. Cyanobacteria biovolumes above 0.3 mm3/L in water trigger the alert for the possible contamination of drinking water. In case this threshold value is observed, in-depth monitoring is needed as well as measures to avoid human exposure.
It is essential to promote research, development and innovation in techniques for detection, quantification and control of toxins and cyanobacteria. Besides, incorporate risk prediction systems and monitoring and control systems for harmful algae blooms (HABs).