Royal Netherlands Institute for Sea Research

The Rhythm of the Year

Since the early 1970s, developments in phytoplankton in the Marsdiep have been closely followed by NIOZ scientists, by taking weekly water samples from the NIOZ jetty. In addition to phytoplankton characteristics such as biomass, production and species composition, also growth conditions for phytoplankton (e.g. temperature, light, and nutrient concentrations) were measured, in order to study seasonality and long-term changes. 

Jolanda van Iperen en Katja Philippart taking water samples from the NIOZ jetty.

Using identical methods

Because the consistency of this series is of utmost importance, we took care that no change in methods occurred when the first generation responsible for this series (Gerhard Cadée and Jan Hegeman) was succeeded by the second (Katja Philippart and Jolanda van Iperen). During the past few years, more and more people take all kinds of measurements at the NIOZ-jetty simultaneously, and recently we joined forces in the JetSET group (Jetty Sampling, Experiments and Time series).

Yearly rhythm

This presentation of microscopic images in the Phytoplankton calendar illustrates the yearly rhythm of phytoplankton in the Marsdiep, the 'backyard' of the Royal NIOZ. Although for each month a characteristic species has been selected from photographs taken from January 2004 up to December 2006, the diversity of species is enormous and it is incorrect to assume that phytoplankton development and succession is similar each year. Even though re-apparent annual patterns occur, there is still much year-to-year variation in the wax and wane of involved species.