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Coral Reefs, Diversity and Disturbance

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1962-1977 outbreaks in Great Barrier Reef. Killed over 80% of live corals. ... Large Reef Predators. Length-frequency distribution of catch of Epinephelus striatus ... – PowerPoint PPT presentation

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Title: Coral Reefs, Diversity and Disturbance


1
Coral Reefs, Diversity and Disturbance
  • Community Ecology Theory
  • Non-equilibrium and equilibrium processes
  • Biological and physical influences
  • Disturbances
  • Low salinity
  • Temperature
  • Dinoflagellates
  • Hurricanes
  • Acanthaster planci
  • Diadema antillarum
  • Fishing
  • Climate change

2
Coral Reefs Why the Diversity?Two perspectives
and Disturbance
  • Non-equilibrium
  • a. Intermediate disturbance
  • b. Lottery for space
  • c. Gradual change
  • Equilibrium
  • a. Niche diversification (structural
    complexity)
  • b. Compensatory mortality
  • c. Stability
  • Determinates
  • Biological
  • Predation
  • Competition
  • Disease
  • Environmental
  • Habitat age
  • Vicariance
  • Stability


The separation or division of a group of
organisms by a geographic barrier, resulting in
differentiation of the original group into new
varieties or species
3
Disturbances occur at different scales
Jackson, J.B.C. 1991 BioScience 41 475-482
4
Coral Reef Disturbances
  • Freshwater
  • Kaneohe Bay, Oahu 1965. 43 cm (17) of rain in
    a day coincided with low tides, killed coral to
    1.5 m.
  • Heat
  • 1982-83 El Nino killed corals in eastern Pacific
    (Costa Rica and Panama)
  • Cold
  • Cold winter of 1976-77 killed 96 of corals to 2
    m in the Dry Tortugas, Florida

Kaneohe Bay
Dry Tortugas
5
Coral Reefs Disturbances
Dinoflagellate bloom
  • Dinoflagellates
  • Mass mortality in Panama and Costa Rica to 3 m
    from dinoflagellates (toxin, smothering and low
    DO).
  • Hurricanes and Storms
  • Hurricane Allen hit Jamaica in 1980, smashed
    coral as deep as 10-20 m.
  • General Pattern damage most severe in shallow
    water and to faster growing corals.
    Re-colonization budding vs. larval transport

6
Coral Reef Bleaching
When stressed, corals become whitened
(bleached) from the loss of the zooxanthellae.
This can result from UV radiation or prolonged
high temperatures. Regions where the sea surface
temperature is 1 C greater than the maximum
expected summer time temperature are highlighted
on the map. The color scale indicates anomalies
greater than 1.0 C in yellow in red, with
anomalies between 0.25 to 1.0 C in purple to
blue. The yellow to red colors usually indicate
potential coral bleaching.
http//www.osdpd.noaa.gov/PSB/EPS/SST/climohot_200
4.html
7
Coral Reef Bleaching
8
Coral Bleaching and Temperature
Monthly anomalies of sea surface temperature
Papua New Guinea Davies et al. 1997
Extensive coral bleaching
9
Coral Reef Disturbances
  • Acanthaster planci
  • Crown of Thorns
  • Up to 40 cm across 12-19 arms
  • Consume coral polyps
  • Eggs and larvae toxic
  • Larval dispersal mobile adults
  • One starfish can feed on up to 20 sq km of coral
    per year (Perrins 1985)

10
crown of thorns
11
Acanthaster planci
12
Distribution of Acanthaster planci
13
Triton Snail (Charonia tritonis)
14
Acanthaster planci
  • Population explosions!
  • 158 stars in 10 m diameter
  • 1962-1977 outbreaks in Great Barrier Reef.
    Killed over 80 of live corals. 1979-85 another
    outbreak
  • Adults eaten but not preferred by Tritons
  • Outbreaks related triton removal?
  • Storms?
  • Human population?

15
Coral Reef Disturbances
  • Diadema antillarum
  • Omnivorous sea urchin (long-spined black urchin)
  • Western and Eastern Atlantic Oceans
  • Mildly toxic, mucous-covered spines
  • Migrate from coral (day) to seagrass areas at
    night (Kaplan 1988)
  • Prefer to feeds on algae (Carpenter 1981).
  • Produce planktonic larva throughout the year.

16
Diadema antillarum
  • Massive die-off reported in Panama in 1983
    spread to Bermuda and the Caribbean Sea by 1984,
    causing 95-99 mortality.
  • Result increase in algae, decrease in coral.
    Synergistic effects of hurricanes and fishing?
  • Side note massive die-offs of North Atlantic
    urchins (Strongylocentrotus) have occurred
    recently, caused by an amoeba, interacting with
    temperature and hurricanes (MEPS 152 155-165).

17
Long-term dynamics of echinoid Diadema antillarum
on Jamaican reefs
18
Degradation of Jamaican coral reefs
Changes in coral cover
Macroalgal cover at four depths
1975 1985 1995
1975 1985 1995
Year
19
Algal cover, Negril, Jamaica
20
Algal cover, Negril, Jamaica
21
Coral Community Ecology
1990s
0 20 40 60 80 100
Algal cover
1970s
0 20 40 60 80
100
Coral cover
Large-scale community phase shifts on Jamaican
reefs, from coral- to algal-dominated systems.
22
Large-scale changes in community structure before
and after sea urchin die-off
Sites gt300 km of the Jamaican coastline 1970s
23
Loss of coral reef cover A widespread and
long-term phenomenon
Results from the Caribbean Sea
Absolute coral cover
0 40 80 120
Number of studies
0 20 40 60
1977 1982 1987 1992
1997 2002
Gardner et al. 2003. Science 301 958-960
24
But
  • Was the shift from coral to algal dominated
    ecosystems caused by urchin mortality and
    (exploitation of herbivorous fishes?)
  • or
  • Were there other processes that caused loss of
    coral, and the algal expansion was the result but
    not the cause?

25
Hurricanes affect coral reefs
Gardner et al. 2005 Ecology
26
Percent coral cover at hurricane-impacted and
non-impacted sites across the Caribbean from 1980
to 2001
non-impacted sites
Can you see any effect?
impacted sites
Absolute percent cover of coral
1980 1985 1990 1995
2000
adapted from Gardner et al. 2005
27
Hurricanes accelerate the loss of coral cover
1980s
1990s
Black bars measured one year post-impact relative
to pre- impact. White bars are non-impacted
sites. Plt0.001 Gardner et al. 2005
28
An on-going controversy
  • Aronson and Precht (2006 Coral Reefs) argued that
    global climate change, hurricanes, and disease
    (e.g, white band disease) are causing loss of
    coral cover in the Caribbean, and algae are
    merely taking advantage of the opportunity.
  • Thus the association between Diadema mortality
    and coral loss in Jamaica may have been a
    coincidence.
  • Apparently a bacterial disease/syndrome that
    affects Acropora palmata (elkhorn) and A.
    cervicornis (staghorn) corals.
  • Disease is increasingly recognized as a major
    factor in coral ecology (e.g., Hydrobiologia
    special issue 460(1) in 2001).

29
Coral Reef Disturbance
  • Fishing
  • Species-selective consequences for the
    community
  • Size-selective Consequences for recruitment
  • Preserves How big should they be? How large an
    area will benefit? Socio-economic factors?
    Fishing vs. diving?

30
(No Transcript)
31
Large Reef Predators
32
Length-frequency distribution of catch of
Epinephelus striatus
0 10 20 30 40
Heavily fished reefs
Unexploited oceanic banks
Numbers
30 40 50
60 70 80 90
Total length (cm)
J. Fish Biol. 12115-146
33
Apo Island species diversity and predator
abundance in reserve and non-reserve reef areas
(Russ, in Sale (Ed.) 1991).
0 2 4
Mean number of predators/750m2
Mean number of species/750 m2
0 2 4 6
1983 1985 1988
1983 1985 1988
Non-reserve
Reserve
34
The effect of increases in length on fecundity of
some Caribbean reef fishes
Roberts and Polunin 1991. Rev. Fish Biol.
Fisheries 165-91
35
Population growth of Jamaica
36
  • The Fisherman
  • Row, Fisherman, row.
  • Keep on rowing your boat.
  • Lots of hungry belly pickney deh a shore.
  • (Millions of them)
  • Sitting in a bamboo hut, in a little old seaport
    town.
  • Three kids on the floor and another one to come
    in fall.
  • Living everyday by day.
  • I man stepping along the seashore.
  • The Congos

37
Species diversity and disturbance frequency
Number of species
10 20 30 40 50 60
70 80 90 100
Percent live coral
Connell 1978 Science 1991302-10
38
Relationship of fecundity to fork length
Peamouth chub
0 5 10 15 20 25 30
Fecundity (000)
150 200 250
300
Fork length
Fish 312 1996. Gonad 13.16 body weight
39
Relationship of fecundity and fork length
Yellow Perch
Fecundity (000)
0 1 2 3 4 5 6 7
8
150 200 250
300 350
Fork length
40
Hurricanes and Coral Reefs Hypothetical
interactions with other factors
Downward trajectory in coral cover
Recovery
Coral cover
Stasis
Hurricane Impact
Resumption
Synergy
Time
adapted from Gardner et al. 2005. Ecology
86(1) 174-184
41
Change in large predatory fish in Apo Island reef
reserve (Russ and Alcala 1996 MEPS 1321-9)
4 8 12 16
Density ratio (reserve/non-reserve)
2 4 6 8 10
Mean Density (no/1000m2)
2 4 6 8 10 12
2 4 6 8 10 12
Years of Reserve Protection
Years of Reserve Protection
Non-reserve
Reserve
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