Report on Harmonisation of freshwater biological methods

10. The sampling depth and volume sampled may contribute to large differences inthe measured phytoplankton biomass and taxonomic composition. The most frequentmethod involves the collection of surface samples or other discrete samples althoughsome countries take integrated samples (a few lakes by most countries in the NO,some in the AL, AT and ME GIGs) (Fig. 10).12010080Sampling depth%6040200AL AT BA CE EC ME NO1 surf. Sample 1 integrated sample +1 discrete sampleFigure 10. Phytoplankton sampling depth in the GIGs.11. Also, the metrics used in the assessment differ both within and among GIGs, butmost countries measure abundance and biomass and successively less countries recordbloom occurrence, size composition and primary productivity (Fig. 11).Phytoplankton metrics%1009080706050403020100AL AT BA CE EC ME NOsize compositionabundancebiomassbloom occurrenceprimary productivityFigure 11. Phytoplankton metrics in the GIGs.51