Diagnostic phytoplankton pigments as indicators for measuring restoration success in coastal waters

The coastal zones are where more than half the world’s human population lives and this percentage continues to increase. Given the increasing pressure on coastal ecosystems, accelerated by human activity, restoration is needed where ecosystem services have declined, together with conservation of healthy sites.
As key primary producers, phytoplankton are the first link in the conversion of nutrients and sunlight into biomass, and they reflect immediate effects of changes in the input of nutrients in coastal ecosystems. They are therefore excellent indicators of water quality, marine ecosystem change and effectiveness of restoration efforts.
In this work, we use phytopigments that are diagnostic for phytoplankton functional groups to develop a new phytoplankton composition index (PPCI). PPCI is a multimetric index that integrates group-specific chemotaxonomic indicators (carotenoids) responding to pressures. The index was initially developed in the Mediterranean coastal waters where well known reference conditions deliver a baseline against which other phytoplankton variables can be anchored. Being very sensitive to human pressures, PPCI detects the effects of anthropogenic disturbances on both quantitative and qualitative phytoplankton communities structure over different spatial and temporal scales. PPCI is therefore a useful tool for assessing long-term effects of restoration measures and benefits of nutrient reduction strategies.
PPCI is transferable over a broad range of coastal zones (e.g. French Atlantic coastal waters). PPCI is easily implemented which enables it to be used by environment managers who are not experts in phytoplankton taxonomy.
An example of phytoplankton recovery after aquaculture closure is presented.