The Baltic Sea is considered one of the most polluted seas in the world. In the water quality monitoring pilot, citizens are engaged to make observations about the water quality in the Baltic Sea and lakes of Finland. The citizen observations are then compared with satellite-based water quality products available for the Baltic Sea area, e.g. by the Finnish Environment Institute (Syke).

Algal bloom occurrence in water bodies varies largely both in time and space, even during short time periods, which makes reliable monitoring of the blooms difficult. Traditional manual monitoring with biweekly to monthly or longer sampling frequency easily leads to a situation where all bloom events cannot be detected. Remote sensing of algal mass occurrences by satellites can provide high temporal and spatial resolution bloom information, but it is expensive, and not applicable to smaller water bodies due to pixel resolution and cloudiness. One possibility to increase information on cyanobacteria surface bloom situation is to make visual observations of blooms by trained observers at fixed observation sites and periods, a method that has been used in Finland since 1998 to estimate average weekly surface bloom situation.

Although these results cannot at present be used as a bloom metric to assess ecological status due to lack of reference conditions and class boundary values, they can be used to support classification decision by expert judgement. Due to a large number of lakes in Finland (>188 000 with surface area of > 5 acres) visual observations by trained observers are restricted to a rather limited set of lakes. A possibility to increase both temporal and spatial coverage of surface bloom visual observations in a larger number of lakes and the coastal region of the Baltic Sea, is to include citizens as observers.

In the pilot, the citizen users are observing surface algal blooming, because algal mass occurrences, in particular cyanobacterial surface blooms, are one of the most distinguished effects of eutrophication in lakes and the coastal waters of the Baltic Sea. In addition, an auxiliary cheap device is in limited use for observing Secchi depth, which is a measure of water transparency that is one commonly used indicator of water quality. The pilot is developed in close collaboration with the Finnish Environment Institute. The overall conceptual view of the pilot is shown in figure below.

The conceptual architecture for citizen water quality monitoring