NIOZ Wadden Sea Phytoplankton

Since 1974, bucket water samples have been collected at the NIOZ-Texel sampling jetty, located at the northern side of the Marsdiep tidal inlet between the North Sea and the Wadden Sea (53°00′06″N, 4°47′21″E). Sampling resolution has occurred at an average of approximately 40 times per annum. The first parameters measured were phytoplankton species densities, Secchi disc depth, suspended particulate matter, dissolved nutrients, chlorophyll a, and primary production. The NIOZ Jetty was chosen as sampling location for logistical reasons including ease of access (no boat necessary) and close vicinity to the NIOZ buildings. Sampling was, and continues to be, performed at high water (±10min) as predicted for Den Helder to keep variation in parameter values as the result of tidal currents as limited as possible. Hence it is Dutch coastal water, which enters the Wadden Sea that is sampled, the phytoplankton in which forms an important subsidy to the food available for suspension feeders. Data of phytoplankton series (e.g. SST, salinity, TSM, chlorophyll-a) are also used to calibrate and validate automated measurements as performed by physical oceanographers at NIOZ.