in themid-1980s. Improved phosphorus removal atwaste water treatment plants, management of fertilization in agriculture and removal of phosphates from detergents led to reduced riverine nutrient inputs and, consequently, reduced nutrient concentrations in theWadden Sea. The budgets suggest that the period of the initial net import of phosphorus and nitrogen switched to a net export in 1981 for nitrogen and in 1992 for phosphorus. Such different behaviour in nutrient budgets during the rise and fall of external nutriënt concentrations may be the result of different sediment-water exchange dynamics for P and N. It is hypothesized that during the period of increasing eutrophication (1976–1981) P, and to a lesser degree N, were stored in sediments as organic and inorganic nutrients. In the following period (1981–1992) external nutrient concentrations
(especially in the North Sea) decreased, but P concentrations in the Wadden Sea remained high due to prolonged sediment release, whilst denitrification removed substantial amounts of N. From1992 onwards, P andN budgetswere closed by net loss,most probably because P stores were then depleted and denitrification continued. Under the present conditions (lower rates of sediment import and depleted P stores), nutrient concentrations in this area are expected to be more strongly influenced by wind-driven exchange with the North Sea and precipitation-driven discharge from Lake IJssel. This implies that the consequences of climate change will be more important, than during the 1970s and 1980s.
- Wadden Sea
- Coastal North Sea
- Nutrient exchange
- Nutrient budgets
Jung, A. S. (Creator), Brinkman, A. G. (Creator), Folmer, E. O. (Creator), Herman, P. M. J. (Creator), van der Veer, H. W. (Creator) & Philippart, C. J. M. (Creator), NIOZ, 9 Feb 2017