Coastal Eutrophication and Marine Benthic Vegetation
81
and filamentous over foliose macro algae. The success of foliaceous
macroalgae over phytoplankton would therefore seem unfavourable
under most environmental conditions, but may enable these algae to
dominate a community undergoing increasing eutrophication. The key
question addressed in this chapter is: What makes the foliated macroalgae Ulva spp. outcompete phytoplankton under eutrophic, but still
nutrient controlled conditions?
To evaluate this question, we will pinpoint the controlling factors for
the competition between benthic marine macro algae and phytoplankton
at different levels of eutrophication. For this purpose, three marine
systems of different trophic status are investigated with respect to the
dynamics of macro algae and their competition with phytoplankton by
means of model analysis. The analysis will not attempt a deterministic
and prognostic simulation of population dynamics and seasonal evolution of the biomass of macro algae and/or seagrass as, for example, was
recently done for Ulva spp. along the French west coast (Menesguen
1992) and for Zostera marina in Danish waters (Bach et al. 1992; Bach
1993). Instead, a descriptive and comparative mass balance analysis is
performed, resulting in annual carbon and nutrient budgets of the three
lagoons. Several mechanisms explaining the enhanced competitive capabilities of macro algae over phytoplankton are discussed with reference to
the specific characteristic of the three lagoons.
3.2 Materials and Methods
3.2.1 Areas of Study
Three semi-enclosed polyhaline lagoons are considered in this
comparative study. The hydrographical and hydrochemical characteristics of the three water systems are summarized in Table 3.1. The
three lagoons cover the whole range of oligotrophic to hypertrophic
conditions in terms of nutrient input and eutrophication symptoms.
Lake Grevelingen
Lake Grevelingen, a former estuary in the Delta region of the
Netherlands (Fig. 3.1), was disconnected from the rivers Rhine and
Meuse in 1964 and from the North Sea in 1971 by enclosure dams. The
connection with the North Sea was partly re-established in 1978 by
means of a small exchange sluice, which is opened during winter to
81
and filamentous over foliose macro algae. The success of foliaceous
macroalgae over phytoplankton would therefore seem unfavourable
under most environmental conditions, but may enable these algae to
dominate a community undergoing increasing eutrophication. The key
question addressed in this chapter is: What makes the foliated macroalgae Ulva spp. outcompete phytoplankton under eutrophic, but still
nutrient controlled conditions?
To evaluate this question, we will pinpoint the controlling factors for
the competition between benthic marine macro algae and phytoplankton
at different levels of eutrophication. For this purpose, three marine
systems of different trophic status are investigated with respect to the
dynamics of macro algae and their competition with phytoplankton by
means of model analysis. The analysis will not attempt a deterministic
and prognostic simulation of population dynamics and seasonal evolution of the biomass of macro algae and/or seagrass as, for example, was
recently done for Ulva spp. along the French west coast (Menesguen
1992) and for Zostera marina in Danish waters (Bach et al. 1992; Bach
1993). Instead, a descriptive and comparative mass balance analysis is
performed, resulting in annual carbon and nutrient budgets of the three
lagoons. Several mechanisms explaining the enhanced competitive capabilities of macro algae over phytoplankton are discussed with reference to
the specific characteristic of the three lagoons.
3.2 Materials and Methods
3.2.1 Areas of Study
Three semi-enclosed polyhaline lagoons are considered in this
comparative study. The hydrographical and hydrochemical characteristics of the three water systems are summarized in Table 3.1. The
three lagoons cover the whole range of oligotrophic to hypertrophic
conditions in terms of nutrient input and eutrophication symptoms.
Lake Grevelingen
Lake Grevelingen, a former estuary in the Delta region of the
Netherlands (Fig. 3.1), was disconnected from the rivers Rhine and
Meuse in 1964 and from the North Sea in 1971 by enclosure dams. The
connection with the North Sea was partly re-established in 1978 by
means of a small exchange sluice, which is opened during winter to