Environmental Engineering Reference
In-Depth Information
Fig. 17.3 Effect of disturbed patch size on community composition while the total fraction of
disturbed reef area was kept constant. Mean percent cover at 500 years for the most abundant
species (Mc
Montastraea cavernosa
,Ma
Montastraea annularis
,Mm
Meandrina meandrites
,Ag
Agaricia
spp.) and bare substratum (BS). [From Langmead and Sheppard (2004)]
some interesting information can be deduced from this approach, the overall
applicability of the model in a broader context of coral reef dynamics and effects
of disturbance events is limited due to its small size and the lack of other key
components such as grazers and algae, which can play a crucial role in structuring
coral reef communities.
17.4 Macroalgal Growth Patterns Simulated with
an Individual-Based Model
Many macroalgae exhibit non-deterministic phenotypic growth, which enables
them to thrive under different environmental conditions. Yniguez et al. (2008)
designed an individual-based (or agent-based, see Chap. 12) model (SPREAD,
Spatially-Explicit Reef Algae Dynamics) to investigate the effects of key growth
factors (nutrients, light, temperature) as well as disturbance and mortality on the
growth rates and growth morphology of the calcifying algae
Dictyota
and
Halimeda
spp. at four different sites (two inshore and two offshore reefs) within the Florida
Keys Reef Tract. Model performance was empirically evaluated with local growth
rate and structure for
H. tuna
at these sites.
To determine the effects of different environmental conditions on the growth
patterns of the algae, Yniguez et al. (2008) used single modules (see Fig.
17.4
) as the
interacting components in their model rather than representing whole algal indivi-
duals. The emergent properties of superordinate hierarchies such as the whole
individual organism, the population or the algal community were thus derived
from interactions of single modules. The model environment was composed of a
three-dimensional cubical grid (edge length ~30 cm) and subdivided into 1 cm
3
cells. Each cell contained information about light and space availability, nutrients
and temperature. Temperature and nutrients were kept uniform for all cells at each
time step but changed with season. Light availability was determined for each cell
