234
(j StabIlIlY Propertic;, In the Wadden Sea
9.4
The Abiotic Ingredients of the Wadden Sea
The meteorological, hydrographical, morphological, sedimentological and biogeochemical conditions determine the abiotic framework for life and abiotic processes
within the Wadden Sea.
9.4.1
Meteorological Boundary Conditions and Disturbance Regime
Variable of interest
The most important meteorological variables of interest are wind speed and direction, temperature and, indirectly, water temperature. With respect to disturbance
regimes, the most important variable of interest is the mean frequency of disturbance events.
Significance of the ingredients for the Wadden Sea
Temperature is an important autecological parameter. In the Wadden Sea, the
winter temperature is decisive. Is the winter mild, i.e. without any frost? Or is the
winter severe, featuring longer periods of temperatures below 0 °C and hence the
formation of ice (an ice winter),) Ice winters have physiological and physical consequences. Some species exhibit reduced reproduction (e.g., Carcinus maenas,
Chap. 5.6); others may be hit by extremely high mortality (Lanice conchilega,
Chap. 5.3). On the other hand, species which are adapted to the cold may show
blooms after ice winters (e.g., Coscinodiscus coneinnus, Chaps. 5.1 and 7). For
some species, ice winters are advantageous. Their lowered metabolic rates mean
they do not have to use their gametes as energy reserves during periods of starvation. Consequently, they can produce unusually high numbers of larvae after ice
winters (Chap. 7).
The physical effects of ice winters are mainly linked to the occurrence of ice.
Blue mussels (Mvtilus edulis), for example, may be frozen to ice-floes and thus
transported to other regions during periods of drift ice. Besides organisms, sediment is also transported on the ice-tloes (Chap. 3.4), leading to changes in morphology and sediment properties. Thus, ice winters are events which intluence the
Wadden Sea on many different levels. Extremely hot summers are not known to
have similarly strong effects on the Wadden Sea.
Another major type of disturbance event linked to meteorological conditions are
storms and storm tides. The amount of sediments and nutrients transported during
these events may exceed that transported at all other times with no storm events by
several orders of magnitude (Reise et al. 1998). In addition, storms may strongly
affect the distribution of macrobenthic species, for example Mytilus edulis (Nehls
& Thiel 1993). However, during the four years ELA W AT lasted, no major storm
or storm tide event occurred.
(j StabIlIlY Propertic;, In the Wadden Sea
9.4
The Abiotic Ingredients of the Wadden Sea
The meteorological, hydrographical, morphological, sedimentological and biogeochemical conditions determine the abiotic framework for life and abiotic processes
within the Wadden Sea.
9.4.1
Meteorological Boundary Conditions and Disturbance Regime
Variable of interest
The most important meteorological variables of interest are wind speed and direction, temperature and, indirectly, water temperature. With respect to disturbance
regimes, the most important variable of interest is the mean frequency of disturbance events.
Significance of the ingredients for the Wadden Sea
Temperature is an important autecological parameter. In the Wadden Sea, the
winter temperature is decisive. Is the winter mild, i.e. without any frost? Or is the
winter severe, featuring longer periods of temperatures below 0 °C and hence the
formation of ice (an ice winter),) Ice winters have physiological and physical consequences. Some species exhibit reduced reproduction (e.g., Carcinus maenas,
Chap. 5.6); others may be hit by extremely high mortality (Lanice conchilega,
Chap. 5.3). On the other hand, species which are adapted to the cold may show
blooms after ice winters (e.g., Coscinodiscus coneinnus, Chaps. 5.1 and 7). For
some species, ice winters are advantageous. Their lowered metabolic rates mean
they do not have to use their gametes as energy reserves during periods of starvation. Consequently, they can produce unusually high numbers of larvae after ice
winters (Chap. 7).
The physical effects of ice winters are mainly linked to the occurrence of ice.
Blue mussels (Mvtilus edulis), for example, may be frozen to ice-floes and thus
transported to other regions during periods of drift ice. Besides organisms, sediment is also transported on the ice-tloes (Chap. 3.4), leading to changes in morphology and sediment properties. Thus, ice winters are events which intluence the
Wadden Sea on many different levels. Extremely hot summers are not known to
have similarly strong effects on the Wadden Sea.
Another major type of disturbance event linked to meteorological conditions are
storms and storm tides. The amount of sediments and nutrients transported during
these events may exceed that transported at all other times with no storm events by
several orders of magnitude (Reise et al. 1998). In addition, storms may strongly
affect the distribution of macrobenthic species, for example Mytilus edulis (Nehls
& Thiel 1993). However, during the four years ELA W AT lasted, no major storm
or storm tide event occurred.