Article

Estuaries and Coasts

, Volume 33, Issue 2, pp 286-294

Open Access This content is freely available online to anyone, anywhere at any time.

Long-term Field Observations on Seasonality in Chlorophyll-a Concentrations in a Shallow Coastal Marine Ecosystem, the Wadden Sea

  • Catharina Johanna Maria PhilippartAffiliated withDepartment of Marine Ecology, Royal Netherlands Institute for Sea Research Email author 
  • , Jolanda Martine van IperenAffiliated withDepartment of Marine Ecology, Royal Netherlands Institute for Sea Research
  • , Gerhard Cornelis CadéeAffiliated withDepartment of Marine Ecology, Royal Netherlands Institute for Sea Research
  • , Alain François ZuurAffiliated withHighland Statistics LtdOceanlab, University of Aberdeen

Abstract

Analyses of long-term field observations (1974–2007) on chlorophyll-a concentrations in the western Wadden Sea showed no long-term trends in the timing of the wax and wane of phytoplankton spring blooms. There is weak evidence, however, that the height of the autumn bloom has decreased since the early 1990s. This fading of the autumn bloom may have had consequences for the carbon transfer to higher trophic levels, currently hampering primary consumer species that mostly rely on food supply during late summer. Current and other findings suggest a shortening of the growing season due to the fading of the autumn bloom in the Wadden Sea and a lengthening of the growing season due to an advancement of the spring bloom in the North Sea. These regionally different changes in seasonality may have contributed to the coinciding decrease in bivalve filtering capacity in the western Wadden Sea and the large-scale offshore shift of juvenile plaice from the Wadden Sea to the adjacent North Sea.

Keywords

Long-term dynamics Phytoplankton Chlorophyll-a Phenology Coastal marine ecosystems