5 Spatial and Temporal Distribution Patterns and
Their Underlying Causes
5.1
Distribution of Nutrients, Algae and Zooplankton in the
Spiekeroog Backbarrier System
Verena Niesel & Carmen-Pia Gunther
Abstract: Temporal developments of dissolved nutrients, phytoplankton and zooplankton in the water column were investigated on different time scales from 1994
to 1996. Measurements of single tidal cycles allowed to assess the fate of some
species in the Wadden Sea. Dissolved nutrients showed some regularly recurring
patterns, which could be explained by the tidal mixing of water bodies with different nutrient concentrations. Seasonal cycles of the nutrients, phytoplankton and
zooplankton showed a large interannual variability. Timing and extension of algal
blooms influenced the occurrence of many meroplanktonic larvae. Most of the
algal species in the backbarrier system of Spiekeroog were part of the phytobenthos and the phytoplankton.
5.1.1
Introduction
The seasonal cycles of nutrients, phytoplankton and zooplankton in the Wadden
Sea are closely tied. The amount of dissolved nutrients (phosphate, silicate, ammonia, nitrite, nitrate) together with other factors influences the strength of algal
blooms and the composition and change of phytoplankton communities (Cadee &
Hegemann 1991). The spring bloom is normally built up by diatoms and usually
ends due to silicate depletion. If enough nitrogen and phosphate are available, a
flagellate bloom can follow, which is often dominated by Phaeocystis spp. Algae
are food for many of the zooplankton and macrozoobenthic organisms. As timing
and extension of the phytoplankton bloom influences the occurrence of the meroplanktonic larvae, some authors called the algal blooms a trigger for the spawning
of several macrofauna species (Starr et al. 1991; Himmelman 1975). Therefore, the
seasonal dynamic of the planktonic primary producers is of importance for the
qualitative and quantitative composition of the zooplankton.
The Wadden Sea is a highly dynamic and turbulent system, where exchange
processes between the water volume and the sediment are important (Postma
1984). The consequences of this coupling on the algae species in the benthos and
water column were of special interests. Microphytobenthic algae are temporarily
suspended into the water column by currents and waves (Baillie & Welsh 1980;
Drebes 1974; de Jonge & von Beusekom, 1995). The flexibility of diatoms in the
Wadden Sea to live either in the benthic or pelagic environment will be reported in
this study.
Their Underlying Causes
5.1
Distribution of Nutrients, Algae and Zooplankton in the
Spiekeroog Backbarrier System
Verena Niesel & Carmen-Pia Gunther
Abstract: Temporal developments of dissolved nutrients, phytoplankton and zooplankton in the water column were investigated on different time scales from 1994
to 1996. Measurements of single tidal cycles allowed to assess the fate of some
species in the Wadden Sea. Dissolved nutrients showed some regularly recurring
patterns, which could be explained by the tidal mixing of water bodies with different nutrient concentrations. Seasonal cycles of the nutrients, phytoplankton and
zooplankton showed a large interannual variability. Timing and extension of algal
blooms influenced the occurrence of many meroplanktonic larvae. Most of the
algal species in the backbarrier system of Spiekeroog were part of the phytobenthos and the phytoplankton.
5.1.1
Introduction
The seasonal cycles of nutrients, phytoplankton and zooplankton in the Wadden
Sea are closely tied. The amount of dissolved nutrients (phosphate, silicate, ammonia, nitrite, nitrate) together with other factors influences the strength of algal
blooms and the composition and change of phytoplankton communities (Cadee &
Hegemann 1991). The spring bloom is normally built up by diatoms and usually
ends due to silicate depletion. If enough nitrogen and phosphate are available, a
flagellate bloom can follow, which is often dominated by Phaeocystis spp. Algae
are food for many of the zooplankton and macrozoobenthic organisms. As timing
and extension of the phytoplankton bloom influences the occurrence of the meroplanktonic larvae, some authors called the algal blooms a trigger for the spawning
of several macrofauna species (Starr et al. 1991; Himmelman 1975). Therefore, the
seasonal dynamic of the planktonic primary producers is of importance for the
qualitative and quantitative composition of the zooplankton.
The Wadden Sea is a highly dynamic and turbulent system, where exchange
processes between the water volume and the sediment are important (Postma
1984). The consequences of this coupling on the algae species in the benthos and
water column were of special interests. Microphytobenthic algae are temporarily
suspended into the water column by currents and waves (Baillie & Welsh 1980;
Drebes 1974; de Jonge & von Beusekom, 1995). The flexibility of diatoms in the
Wadden Sea to live either in the benthic or pelagic environment will be reported in
this study.