Statistical analysis of phytoplankton biomass in coastal waters: Case study of the Wadden Sea near Lauwersoog (The Netherlands) from 2000 to 2009

As the most important indicator of the coastal ecosystem, various studies on phytoplankton have frequently been proposed in coastal waters. In this study, the statistical analysis of phytoplankton biomass (in terms of chlorophyll a) is performed in the Wadden Sea near Lauwersoog (53.4167° N, 6.2000° E), The Netherlands, determined by the 10-year's historical dataset from 2000 through 2009. Boxplot analysis is introduced to give insight in the seasonal variations of phytoplankton biomass and physical-chemical conditions. Annually, a big difference is found in chlorophyll a, showing that the maximum values occur in the months of April and July, and the minimum values occur in winter (December, January, and February). The phytoplankton biomass is positively correlated with the physical conditions (salinity, light intensity, and water temperature), and is negatively correlated with the nutrients (nitrate, ammonium, and silicate). Factor analysis distinguishes the driving variables that represent most of the total variance using three extraction methods (principal component analysis, unweighted least squares, and maximum likelihood). Nitrate dominates the main activity in the first rotated component/factor, and ammonium contributes the most in the second rotated component/factor. The findings of this study are significant for understanding the roles of the environmental conditions upon the phytoplankton variability, and for reducing the overlapping information to characterize the driving variables.