Waddenzee fresher than ever

September 11, 2002

The seawater in the Waddenzee is becoming fresher. More river water is reaching the Waddenzee via the outlet sluices of the IJsselmeer Dam. This is the conclusion of Dr. Hendrik van Aken from the Netherlands Institute for Sea Research. Along with the fresh water, more nitrate and phosphate are entering the Waddenzee.

During the past 140 years the average quantity of fresh water in the Waddenzee has doubled. This is due to a strong increase in the water supply from the IJsselmeer. The river IJssel in particular is transporting increasingly more water. Over the last 70 years the discharge from the IJssel has in fact doubled. This is due to human intervention in the course of the rivers Waal, Nederrijn and IJssel. One of the aims of this has been to improve the navigability of the IJssel.

Since the 1970s, the Netherlands Institute for Sea Research has not only measured the salinity, but also the water temperature, the quantity of plankton and the species composition of plankton. The measurements are carried out in the western part of the Waddenzee, in the Marsdiep. The KNMI [Netherlands Meteorological Institute] has carried out systematic measurements of the salinity there since 1861.

With the greater influx of river water the Waddenzee is also been supplied with more nutrients, in particular nitrate and phosphate. This is further increased by the fact that the rivers themselves contain more nutrients. Furthermore, the self-cleaning capacity of the IJsselmeer has decreased. In the 1950s about 70% of the nitrate compounds entering the lake were decomposed. Now this is scarcely 50%. The plankton in the IJsselmeer are no longer able to clean up the large quantities of nitrate. This is in part due to the fact that the volume of water in the IJsselmeer has decreased since the closing off of the Markermeer.

The measurements in the Marsdiep reveal that in particular the quantity of nitrate and to a lesser extent the quantity of phosphate have increased. The Netherlands Institute for Sea Research has also observed a shift in the species composition of the plankton. Species which thrive at high concentrations of nutrients are becoming more common. The algal bloom is also continuing to increase.

The lower salinity, however, scarcely affects the composition of the marine life in the Waddenzee. Species there are very tolerant for other salinities. This is hardly surprising because the salinity in the Waddenzee varies strongly per season.
Further information can be obtained from Dr. Hendrik van Aken, Netherlands Institute for Sea Research, tel 31-222-369-416, fax 31-222-319-674, e-mail aken@nioz.nl or from Dr. Wim van Raaphorst, tel 31-222-399-446, e-mail wimvr@nioz.nl. At the start of October a paper about this study will appear in a special edition of the journal ICES Marine Science Symposia, which is completely devoted to long-term changes in the sea.

The research was funded by the Netherlands Organisation for Scientific Research (NWO).

Netherlands Organization for Scientific Research

Related Plankton Articles from Brightsurf:

Plankton turn hunters to survive dinosaur-killing asteroid impact
New research by an international team of scientists shows how marine organisms were forced to 'reboot' to survive following the asteroid impact 66 million years ago which killed three quarters of life on earth.

Red Sea plankton communities ebb and flow with the seasons
Studies of plankton communities in Red Sea waters provide insights into seasonal variations and dominant control mechanisms.

Dramatic decrease in cold-water plankton during industrial era
There has been a dramatic decrease in cold-water plankton during the 20th century, in contrast to thousands of years of stability, according to a new UCL-led study.

Study shows six decades of change in plankton communities
New research published in Global Change Biology shows that some species have experienced a 75% population decrease in the past 60 years, while others are more than twice as abundant due to rises in sea surface temperatures.

Tiny, but effective
Barely visible to the naked eye, gelatinous zooplankton is an important part of the marine ecosystem.

There are variations in plankton biodiversity and activity from the equator to the poles
New results from the Tara Oceans expedition, led by a collaboration between the Tara Ocean Foundation and teams from the CNRS, EMBL, CEA, Sorbonne Université and Université Paris Science Lettres between 2009 and 2013 show that the diversity and functions of planktonic species in the global ocean change dramatically according to latitude.

UCI-led study: Plankton are more resilient to nutrient stress than previously thought
Surface ocean phosphate is a key mineral supporting the growth and diversification of phytoplankton, a marine organism the absorbs significant amounts of carbon dioxide from Earth's atmosphere.

Ancient plankton help researchers predict near-future climate
Temperature data inferred from plankton fossils from the Pliocene, an era with CO2 levels similar to today's, allowed a UA-led team to rectify discrepancies between climate models and other proxy temperature measurements.

Dinoflagellate plankton glow so that their predators won't eat them
Some dinoflagellate plankton species are bioluminescent, with a remarkable ability to produce light to make themselves and the water they swim in glow.

Plankton as a climate driver instead of the sun?
Fluctuations in the orbital parameters of the Earth are considered to be the trigger for long-term climatic fluctuations such as ice ages.

Read More: Plankton News and Plankton Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.