CoastObs uses series of satellite imagery to analyse phytoplankton bloom appearance, intensity and lasting

Why is it important?

The study of the phytoplankton seasonal cycle (phenology) is relevant to understanding the functioning of the marine ecosystem. Phytoplankton bloom phenology addresses the question: when is how much of the phytoplankton where? Changes in phenology affect ecosystem functioning and productivity and have an impact on higher trophic levels and – via fisheries and aquaculture – on economic activities and food production. Phenology is also a sensitive indicator of climate change. Therefore, phytoplankton bloom phenology is of interest to environmental monitoring and management authorities as well as to aquaculture and fisheries regulators and producers. So far, phenological indicators have not been readily available, therefore uptake of this information has been limited.

What does CoastObs offer?

CoastObs offers yearly information on the following phenology metrics for the dominant phytoplankton bloom, subject to further discussion with the end-users:

  • Start timing (day of year)
  • End timing (day of year)
  • Length (days)
  • Peak timing (day of year)
  • Base concentration (mg m−3 )
  • Maximum concentration (mg m−3 )
  • Amplitude (mg m−3 )
  • Number of distinct blooms per year

For reporting regions or individual pixels, averages of the phenology metrics will be calculated and presented as graphs

How was the data validated?

Satellite-retrieved Chl-a concentrations were validated against ground data collected close in time to the satellite overpass. The Chl-a samples collected by UVIGO, CNR, USTIR and HZ were analysed at University of Stirling using High Performance Liquid Chromatography (HPLC).

Figure 1. Example of a Chl-a plot indicating some of the phenological parameters. Each bar could be a an average of a certain region. For simplicity, this plot shows monthly data, but time series can be made on a daily basis (depending on cloud cover) if preferred.

Additionally, for each of the phenology parameters, a trend analysis can be performed over the total period covered by the service on a pixel-by-pixel basis based on the existence and significance of a linear trend. The results of the trend analysis can be presented as a trend map per parameter

Figure 2. Start, end and peak of the phytoplankton bloom in different years. The different colours of the peak stand for different intensities of the peak.


  • Quality of retrieval depends on sensor characteristics, can be impacted by high suspended sediment or CDOM concentrations.
  • In shallow waters, bottom visibility can interfere with the signal.
  • Availability depends on cloud cover

Area Covered

We can cover any coastal area you may need.