Environmental Engineering Reference
In-Depth Information
Table 17.1 Major attributes of corals and algae and the main rules utilized in the model
Corals
Algae
General information
Massive corals
Two groups according to reproductive mode:
1) Brooders, e.g.
Porites astreoides
2) Spawners, e.g.
Siderastrea siderea
Macroalgae and cropped algae
Age classes:
Cropped algae 0-6 months
Cropped algae 6-12 months
Macroalgae 0-6 months
Macroalgae 6-12 months
Reproduction/recruitment/dispersal
Larval production depending on maturity
state/size class for high coral cover:
juvenile (
Probabilistic overgrowth of cropped algae
(A) by macroalgae (M) within a von-
Neumann-Neighbourhood, depending
on proportions of macroalgae (M
4c
)
and corals (C)
if C
60 cm
2
)
no larvae
pubescent (60-250 cm
2
)
!
<
cm
2
!
~50 larvae
cm
2
Number of recruits that can settle per cell
depending on settling ground:
Bare substrate
250 cm
2
)
adult (
!
~210 larvae
>
0.5 PA
!
M
!
0.75
M
4c
if C
0.5 PA
!
M
!
M
4c
<
!
4 recruits
Cropped algae
!
2 recruits
Macroalgae
!
0 recruits
!
the density of spawning coral recruits is ten
times lower than that of brooding ones
Growth
Constant diametric growth rates:
8mm
If cropped algae are not grazed for 1 year
they turn into macroalgae
year
1
(brooders)
year
1
(spawners)
10 mm
Mortality
Periodic - annually
Smaller coral colonies are more susceptible to
partial and whole-colony mortality than
larger ones
Stochastic - hurricanes
Proportion of corals is subject to partial or
whole-colony mortality; based on mean
fraction of reef destruction across the
Caribbean
Periodic - annually
Proportion of algae which are eaten by
grazers
!
depending on grazer density
Stochastic - hurricanes
Proportion of macroalgae become cropped
algae if located on disturbed patch;
based on mean fraction of destruction
across the Caribbean
Interactions and processes
If corals reach maximum cell size (2,500 cm
2
):
!
Macroalgae can grow over cropped algae
Macroalgae can grow over corals
(depending on coral colony size) and
lead to partial or whole-colony
mortality
Larger colonies grow over smaller colonies
!
Corals grow over cropped algae
!
Corals can displace macroalgae
proportions of spatial cover had been reached with the rest being occupied by sand
and rubble.
Corals were divided into two functional groups according to their mode of
reproduction, comprising either brooders or spawners. Brooding corals produce
planula larvae which settle in the vicinity of their parent colony. Spawners (com-
monly referred to as broadcast spawners) release gametes and the planulae are
dispersed in the water column and may migrate many kilometres before settlement.
