86
I. De Vries et al.
considerable amounts of nutrients from domestic (resident and
tourist population), industrial and agricultural sources, directly due
to run-off and discharges and indirectly by atmospheric deposition.
The conditions in parts of the lagoon are characterized as hypertrophic, with massive Ulva spp. blooms and subsequent anoxic conditions with mass mortality of aerobic organisms as the most striking
features (Sfriso et al. 1989b).
3.2.2 Mass Balance Analysis
The three lagoons were compared by means of a descriptive mass
balance analysis, results of which showed annual carbon and nutrient
budgets which include the quantification of the role of the dominant
macrophytes.
Existing applications of an ecological model have been used for this
purpose (De Vries et al. 1988; Anonymous 1989; De Vries et al. 1990).
The model consists of two main parts with distinct functions. The
transport module deals with the transport of dissolved and suspended
substances between the computational elements (model segments) in
one, two or three directions (Postma 1988). Within each computational
element, the ecological module describes the most important processes
between substances and functional groups of organisms.
The schematization of Lake Grevelingen resulted in 11 model
segments in horizontal and vertical directions. Four water segments and
seven benthic segments were distinguished (Fig. 3.1). All mass transport
by water movement was formulated as dispersive transport because of
the wind driven circulation and a virtual absence of stratification.
The schematization of Lake Veere resulted in 18 segments in
horizontal and vertical directions, including nine water segments which
allowed a distinction to be made between shallow and deeper parts and
water layers above and below the halocline. Each water segment had an
adjacent bottom segment (Fig. 3.2). Information on the hydrodynamical environment was obtained from a detailed stratification model
(Bollebakker and van de Kamer 1989). The output consisted of a time
series of daily values for horizontal and vertical advective flows, entrainment, and vertical dispersion. For the Venice Lagoon, a two-dimensional
horizontal schematization was used with 18 water segments and 18
adjacent bottom segments (Fig. 3.3), allowing the representation of
differences due to local bathymetry as well as gradients imposed by
run-off from land and exchange with the Adriatic Sea.
I. De Vries et al.
considerable amounts of nutrients from domestic (resident and
tourist population), industrial and agricultural sources, directly due
to run-off and discharges and indirectly by atmospheric deposition.
The conditions in parts of the lagoon are characterized as hypertrophic, with massive Ulva spp. blooms and subsequent anoxic conditions with mass mortality of aerobic organisms as the most striking
features (Sfriso et al. 1989b).
3.2.2 Mass Balance Analysis
The three lagoons were compared by means of a descriptive mass
balance analysis, results of which showed annual carbon and nutrient
budgets which include the quantification of the role of the dominant
macrophytes.
Existing applications of an ecological model have been used for this
purpose (De Vries et al. 1988; Anonymous 1989; De Vries et al. 1990).
The model consists of two main parts with distinct functions. The
transport module deals with the transport of dissolved and suspended
substances between the computational elements (model segments) in
one, two or three directions (Postma 1988). Within each computational
element, the ecological module describes the most important processes
between substances and functional groups of organisms.
The schematization of Lake Grevelingen resulted in 11 model
segments in horizontal and vertical directions. Four water segments and
seven benthic segments were distinguished (Fig. 3.1). All mass transport
by water movement was formulated as dispersive transport because of
the wind driven circulation and a virtual absence of stratification.
The schematization of Lake Veere resulted in 18 segments in
horizontal and vertical directions, including nine water segments which
allowed a distinction to be made between shallow and deeper parts and
water layers above and below the halocline. Each water segment had an
adjacent bottom segment (Fig. 3.2). Information on the hydrodynamical environment was obtained from a detailed stratification model
(Bollebakker and van de Kamer 1989). The output consisted of a time
series of daily values for horizontal and vertical advective flows, entrainment, and vertical dispersion. For the Venice Lagoon, a two-dimensional
horizontal schematization was used with 18 water segments and 18
adjacent bottom segments (Fig. 3.3), allowing the representation of
differences due to local bathymetry as well as gradients imposed by
run-off from land and exchange with the Adriatic Sea.