Monitoring Requirements

This pre-core indicator and its threshold values are yet to be commonly agreed in HELCOM. 
The indictor is included as a test indicator for the purposes of the 'State of the Baltic Sea' report, and the results are to be considered as intermediate.

Monitoring methodology

Monitoring of phytoplankton biovolume according to the HELCOM Monitoring Manual.


Current monitoring

The monitoring activities relevant to the indicator, that are currently carried out by HELCOM Contracting Parties are described in the HELCOM Monitoring Manual in the programme topic: Phytoplankton. The methods for sampling, sample analysis and calculation of carbon biomass are described in the COMBINE manual. The COMBINE manual guidelines are under review for inclusion in the HELCOM Monitoring Manual. For this indicator, only samples from the upper mixed layer from spring are necessary. For the alternative Dia/Dino index, also silicate data are required.

These data are already taken in the running COMBINE monitoring. Also additional data from research projects can be included if the methods prescribed in the HELCOM Monitoring Manual are used. Unfortunately, the open sea monitoring activities of many countries have been reduced during the last years.

The indicator is operational as:

  • A monitoring programme for getting the samples is established (HELCOM COMBINE)
  • Samples are taken and processed according to guidelines (COMBINE manual)
  • Data are delivered by experts belonging to the HELCOM Phytoplankton Expert Group (PEG) and are therefore of high quality
  • The data are regularly reported and stored in national and international data banks (ICES)

Description of optimal monitoring

In fact, the Dia/Dino index has simply to reflect whether the spring bloom is dominated by diatoms or by dinoflagellates. The sampling schedule has to ensure that the duration and magnitude of the spring bloom has been captured adequately. Weekly sampling would be optimal, resulting in 12 samples per station during spring. This number is reached as shown in Results table 2. However, sampling occasions are frequently clustered, leading to gaps despite a high number of samples. Therefore, samples have to be evenly distributed over the time and to be taken at different stations that are representative for the area. Also samples from ships-of-opportunity and from research projects can be included if quantitatively analyzed according to the HELCOM Monitoring Manual. The contribution of data from all contracting parties is necessary to reach a sufficient data coverage.