To assess the quality of aquatic ecosystems, the consultancy firm Phyto-Quality uses the microalgae and cyanobacteria as biological indicators. These organisms, essentially photosynthetic and autotrophic, form the basis of food webs. Thus, the slightest change in their composition and abundance implies repercussions on the dynamics of the upper compartments (zooplankton, benthic fauna, fish, birds).

Why use microalgae and cyanobacteria as water quality indicators?

• Because of their short generation times these microscopic organisms are among the first to react to water quality changes.
• Some species show preferences for particular environmental conditions, and thus provide precise information about the ecosystem health.
• The occurrence of blooms (e.g. harmful cyanobacteria) or the dominance of low water quality taxa provide early warning signals of abnormal conditions of aquatic ecosystems.
• These informations will allow the water managers to authorize, limit or prohibit the use of aquatic environments (e.g. bathing, fishing, recreation) in order to limit the risks related to public health.