Transcript Coral Reef Ecosystems

Coral Reef Ecosystems
Ecology and Environmental
Management
Lecture content

Coral reef ecology
–
–
–
–
–
How they are formed
Physical Environment
Diversity patterns
Threats to coral reefs
Fisheries

Coral reef
management
– Assessing damage
– Management for
ecology and
economics
– Diversification
– Tourism
Introduction to coral reefs
What is a “coral reef”

Biological (“coral community”)
– Organic, Biogenic
– Coral and Algal communities
– Mostly “hermatypic” corals, algae, and other sessile
animals

Geological features (“reef”)
–
–
–
–
–
Carbonate
In situ buildup
Topographic relief
Wave resistant
Cemented, consolidated
Corals




Phylum
Anthazoa
Class Cnidaria
Hermatypic
(hard) corals
contain
symbiotic algae
Up to 500 spp.
at some sites
Rosen 1981
Building the reef
CaCo3 addition - CaCo3 loss = Accumulation
Biogenic
production
Biological
erosion
Sediment
Import
Mechanical
erosion
Cementation
Sediment
export,
dissolution
Reef
Growth
Kleypas et
al 2001
Types of reef

Fringing, Barrier, Atoll,
Drowned
Environmental requirements

Physical environment
– Temperature of 25-31oC (limited
Northwards by the 18oC minimum
isotherm)
– Salinity of 34-37 ppt
– Light level


Predominantly in top 30 m of water
Biological environment
– Oligotrophic, highly stratified water column

Coral reef distribution
Coral diversity patterns
Maps


For the lecture I used maps from a variety of locations, often more for clarity
than scientific detail. I would recommend the maps from the World
Conservation Monitoring Centre (www.wcmc.org.uk) which I would tend to
value as reliable.
The main point being that the high population densities in many coastal areas
which contain high coral reef species richness represent a serious threat.
Fish community







Mainly Perciform teleosts
2 faunas, Diurnal and Nocturnal
Often territorial/site attached
Intraspecific interactions (pair bonding and
harems) and interspecific mutualism (e.g.
cleaning stations)
Mostly planktonic larvae
Estimated 4500 spp, 25% of marine total
~10% of world fishery landings
Fishery species

Often large, high-value fish
Fish distribution patterns
World population distribution
And if that wasn’t bad
enough…..
Threats to coral reef systems
Overpopulation
 Unsustainable
fisheries
 Coastal
development
 Global climate
change

Coral reef fisheries
Essential to survival of many
 Managed sustainably for generations
 Diverse ecosystem

– Multispecies fisheries
– Interspecies interactions may invalidate
models
– Collection of sufficient data for all species may
not be practicable
– Reduction of fishing effort to sustain all fish
species wastes the productivity of most stocks
Non-selective and destructive
fishing methods
Subsistence fishing occurs regardless of
effort required
 Muro Ami, Dynamite (Blast), and
cyanide fishing
 Trawling
 Trapping and lines

– Ghost fishing

Total fishing mortality often not known
Malthusian overfishing
“...occurs when poor fishermen, faced
with declining catches and lacking any
alternative initiate wholesale resource
destruction in order to maintain their
incomes.
 This may involve in order of
seriousness, and generally in temporal
sequence...





1) Use of gears and mesh sizes not
sanctioned by government
2) Use of gears and mesh sizes not
sanctioned within the fisherfolk community…
3) Use of gears that destroy the resource
base
4) Use of gears such as dynamite or sodium
cyanide that do all of the above and even
endanger the fisherfolks themselves”
McManus 1997
Ecosystem effects of fisheries
Removal of predators
 Removal of algal grazers
 Change in dominance

– Californian Sea Otters
– Urchins
– Crown of Thorns starfish “COTS”
(Acanthaster planci)

Changes in size frequency of animals
Crown of Thorns Starfish
Crown of Thorns
Eats coral by everting gut
 Aggregations can remove 95% of coral
cover
 May result in collapse of remaining skeleton
 Pheromone controlled aggregated spawning
 Recovery takes at least 12 years
 Caused by loss of predators?
 Increased larval survival due to pollution?

Terrestrial impacts

Pollution
–
–
–
–


Sewage
Agriculture
Aquaculture
Rubbish
Sedimentation
Eutrophication



Construction on reef
flats
Coral mining
Mangrove
destruction
Climate change

Potential impacts on coral communities
– Changes in water temperature
– Increases in CO2 concentration
– Changes in solar irradiation (if cloud cover
changes)
– Sea level rises leading to drowning of reefs
– Changes in surface run-off (sedimentation)
– Changes in land-use patterns leading to
increased reef exploitation
Kleypas et al 2001
Coral bleaching
Loss of
symbiotic algae
 May cause
death of animal
 A symptom of
climate change?

Coral Bleaching
First described in 1984
 Multiple re-occurrences at same sites
 New sites impacted during 1990s
 Many known triggers

– Temperature (especially increases)
– Solar radiation (especially UV)
– Combination of UV and temperature
– Reduced salinity
– Infections
Effects of bleaching

Loss of symbiontic algae (Zooxanthellae) algae
by:
– Degradation In situ
– Loss of algae by exocytosis
– Expulsion of intact endodermal cells containing algae

Resulting impacts
– Vary between species, and even parts of the same
colony
– Loss of sensitive species (especially Acropora spp.)
– Recovery slow and highly variable between sites
The Problems
A large (and growing) number of
people are dependent on coral reefs
 Management of a multispecies fishery
is extremely complex, and often fails
 Terrestrial development may destroy
coastal reef systems
 Global climate change may exert new
pressures

Coral reef management
Management Issues


Biological
– What does the resource consist of?
– What state is it in?
– Is there overfishing?
– Is there habitat destruction?
Socio-ecomomic
– Levels of resource exploitation
– More sustainable ways of exploiting the
resource
– Alternatives to coral reef exploitation/damage
Monitoring coral reefs
What sites and parameters to monitor?
 Fish
 Macroinvertebrates
 Water quality
 Benthic habitat quality
 Coral health

Sources



Australian Institute for Marine Science (AIMS) website contains
all their standard techniques. From a comparability point of
view it is extremely helpful to use common techniques.
The AIMS site and their manual (English et al, 1997) even
explains how to store the data in a database and manage it.
Essential reading if you can get hold of it.
The use of volunteers for some types of coral reef survey work
is very common and slightly controversial. Common sense will
be necessary in determining what techniques a volunteer can
apply - in particular for qualitative judgements about reef
“quality” and levels of impact.
Large-scale studies

Rapid Ecological
Assessment
– “Manta tows”
– Estimates of % cover (live
and dead coral)
– Abundance of highly visible
species
– Human impacts

Mapping and aerial
photography
Monitoring fish

Visual census
– Transects
– Point counts
– Random searching
– Often allow biomass
estimates

Fisheries monitoring
Monitoring the benthos
Line intercept transects
 Visual transects
 Quadrats
 Photography and video

Line Intercept Transect
Marine protected areas

Fisheries reserves
– “No take zones” (NTZs)
– Controlled fishing

Effects on fish populations
– Coral reef fish often have small ranges
Effects on fishing revenue
 Local management and ownership

Sources



The marine protected areas case studies are based
on the work of Russ and Alcala.
I think these are classic studies because they show
both the conservation and economic benefits of
marine reserves AND how important co-operation
with the local community can be.
These are not new references, work from Roberts’s
paper for newer studies. See also Gell and Roberts
2003 – Trends in Ecology and Evolution, 18, 448 455
Biological effects of protection





Habitat protection
Biodiversity
Protection of
vulnerable species
Allow fish to grow to
maturity
Control (reference)
sites
Economic effects of protection





Increased size and
abundance of stock
species
Emmigration into fishing
grounds (Spillover)
Insurance against
management failure
Tourism “spin-offs”
Ease of enforcement
Marine reserves case study
Effects on fish diversity
Effects on fish abundance and
biomass
Factors to consider

Costs?
– Staff, setup,
monitoring
– Initial loss of fishing
revenue


– Any spin-off
benefits?
– Employment of local
staff?
– Compromise on size
of reserve?
Size/shape of
reserve?
– Life history and
behaviour of fish
– Fishing intensity
– 20-40% of fishing
ground
Can you sell it?

What management
outside reserve?
Impacts of tourism



Terrestrial development
Land reclamation and creation of beaches
– Mangrove removal
– Sand on reef flat
Boats
– Anchors
– Diver/snorkeller impacts and fish feeding
– Sewage
– Harbour dredging
Ras Mohammed project
Growth of reef tourism
Sources


This section is based on the works of David Medio
and Julie Hawkins. A couple of their references are
included at the end.
Much other material is directly from the Egyptian
Environmental Affarirs Agency (link at the end)
Divers reduce coral cover
….and scare away fish
Reducing diver impact


Mooring buoys
Most damage caused
my minority of divers
– Education
– Enforcement



Ban gloves
Monitoring
Zoning / Closure /
Rotation
Managing terrestrial impacts

Catchment management
– Agriculture
– Fertiliser
Seafront corridors
 Controls on sewage systems
 Limits on development
 Dry beaches and walkways

Who cares what happens to
coral reefs anyway?






Fisheries
Tourism
Coastal protection
Bioprospecting
Moral reasons
Many coral reef functions are Subsistence
– Do not show up as economic benefits
– REPLACEMENT value may be extremely
high
Summary

Coral reefs contain diverse fish and
invertebrate assemblages
– This makes them valuable, but difficult to
manage

Coral reefs are mainly found in the
poorest areas of the world
– This makes them prone to overexploitation
Summary
Reefs must be assessed and monitored
to allow management
 Marine protected areas may protect
biodiversity and maintain fish stocks
 Diversification of local economies may
be effective in reducing pressures
 Tourism brings new pressures which
must also be managed.

Reef diversity patterns
(Rosen 1981; Ormond and Roberts 1997)
Urchins, Climate change, bleaching
(Brown 1997; Lessios 1998; Kleypas et al. 2001)
Monitoring techniques
Australian Institute for Marine Science http://www.aims.gov.au/
(English et al. 1997)
Fisheries and reserves
(Roberts and Polunin 1993; Roberts 1995; Russ and Alcala 1996; McManus 1997; Russ and Alcala
1998; Jennings et al. 2001)
Tourism and zoning
Egyptian Environmental Affairs Agency www.eeaa.gov.eg/
(Medio et al. 1997; Hawkins et al. 1999)
Brown BE (1997) Coral Bleaching: causes and consequences. Coral Reefs 16:S129-138
English S, Wilkinson C, Baker V (1997) Survey Manual for Tropical Marine Resources. Australian
Institute for Marine Science, Townsville
Hawkins JP, Roberts CM, Van'T Hof T, De Meyer K, Tratalos J, Aldham C (1999) Effects of
recreational SCUBA diving on Caribbean coral and fish communities. Conservation Biology
13:888-897
Jennings S, Kaiser MJ, Reynolds JD (2001) Marine Fisheries Ecology. Blackwell Science Ltd., London
Kleypas JA, Buddemeier RW, Gattuso J-P (2001) The future of coral reefs in an age of global change.
International Journal of Earth Sciences 90:426-437
Lessios HA (1998) Mass mortality of Diadema antillarum in the Caribbean: what have we learned?
Annual Review of Ecological Systems 19:371-393
McManus JW (1997) Tropical marine fisheries and the future of coral reefs: a brief review with
emphasis on Southeast Asia. Coral Reefs 16:S121-S127
Medio D, Pearson M, Ormond RFG (1997) Effect of briefings on rates of damage to corals by divers.
Biol Cons 79:91-95
Ormond RFG, Roberts CM (1997) The biodiversity of coral reef fishes. In: Ormond RFG, Gage JD,
Angel MV (eds) Marine Biodiversity: Patterns and Processes. Cambridge University Press,
Cambridge, p 471
Roberts CM (1995) Effects of fishing on the ecosystem structure of coral reefs. Conservation Biology
9:988-995
Roberts CM, Polunin NVC (1993) Marine reserves: simple solution to managing complex fisheries?
Ambio 22:363-368
Rosen BR (1981) The tropical high diversity enigma - the corals'-eye view. In: Forey PL (ed) Chance,
change and challenge: the evolving biosphere. Cambridge University Press, London, p 103129
Russ GR, Alcala AC (1996) Do marine reserves export adult fish biomass? Evidence from Apo Island,
central Philippines. Mar Ecol Prog Ser 132:1-9
Russ GR, Alcala AC (1998) Natural fishing experiments in marine reserves 1983-1993: community
and trophic responses. Coral Reefs 17:383-397