Variability and Trends of Phytoplankton in the Baltic Sea and Kattegat-Skagerrak
The aim of this report is to evaluate whether or not the existing Swedish coastal marine phytoplankton monitoring programs are suitable in order to fulfill the needs of the EU Water Framework Directive.
The three main objectives of the report were to
- investigate the statistical strength of time series of phytoplankton biomass
- investigate the variability of species composition between stations
- investigate the temporal variability regarding species composition.
Results indicate how long time series are needed to detect change at a certain level. Also the variability in biodiversity is shown with some examples.
To investigate differences in biodiversity, data from intense sampling campaigns made in the period 2010–2012 was used. The sampling was made at a much larger number of locations compared to the normal monitoring program.
Results of cluster analysis (Euclidian distance) on the species composition show that weekly sampling describes the natural variability in phytoplankton biodiversity well while sampling once a month does not resolve the natural variability in biodiversity.
When investigating the spatial variability, in other words the differences in species composition between stations, results indicate that samples from the same water mass, for example the southern Kattegat, are similar. The differences in closely located bays and fjords are large in regard to plankton biodiversity.