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Ecology and Environmental Management
Coral Reef Ecosystems Ecology and Environmental Management
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Lecture content Coral reef ecology Coral reef management
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
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Introduction to coral reefs
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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
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Corals Phylum Anthazoa Class Cnidaria
Hermatypic (hard) corals contain symbiotic algae Up to 500 spp. at some sites Rosen 1981
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CaCo3 addition - CaCo3 loss = Accumulation
Building the reef CaCo3 addition - CaCo3 loss = Accumulation Biological erosion Mechanical erosion Sediment export, dissolution Reef Growth Biogenic production Sediment Import Cementation Kleypas et al 2001
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Types of reef Fringing, Barrier, Atoll, Drowned
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Environmental requirements
Physical environment Temperature of 25-31oC (limited Northwards by the 18oC minimum isotherm) Salinity of ppt Light level Predominantly in top 30 m of water Biological environment Oligotrophic, highly stratified water column
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Coral reef distribution
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Coral diversity patterns
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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 ( 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.
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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
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Fishery species Often large, high-value fish
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Fish distribution patterns
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World population distribution
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And if that wasn’t bad enough…..
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Threats to coral reef systems
Overpopulation Unsustainable fisheries Coastal development Global climate change
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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
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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
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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...
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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
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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
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Crown of Thorns Starfish
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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?
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Terrestrial impacts Pollution Sedimentation Eutrophication
Sewage Agriculture Aquaculture Rubbish Sedimentation Eutrophication Construction on reef flats Coral mining Mangrove destruction
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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
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Coral bleaching Loss of symbiotic algae May cause death of animal
A symptom of climate change?
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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
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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
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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
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Coral reef management
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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
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Monitoring coral reefs
What sites and parameters to monitor? Fish Macroinvertebrates Water quality Benthic habitat quality Coral health
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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.
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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
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Monitoring fish Visual census Fisheries monitoring Transects
Point counts Random searching Often allow biomass estimates Fisheries monitoring
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Monitoring the benthos
Line intercept transects Visual transects Quadrats Photography and video
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Line Intercept Transect
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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
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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,
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Biological effects of protection
Habitat protection Biodiversity Protection of vulnerable species Allow fish to grow to maturity Control (reference) sites
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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
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Marine reserves case study
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Effects on fish diversity
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Effects on fish abundance and biomass
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Factors to consider Costs? Can you sell it? Size/shape of reserve?
Staff, setup, monitoring Initial loss of fishing revenue Size/shape of reserve? Life history and behaviour of fish Fishing intensity 20-40% of fishing ground Can you sell it? Any spin-off benefits? Employment of local staff? Compromise on size of reserve? What management outside reserve?
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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
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Ras Mohammed project
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Growth of reef tourism
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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)
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Divers reduce coral cover
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….and scare away fish
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Reducing diver impact Mooring buoys
Most damage caused my minority of divers Education Enforcement Ban gloves Monitoring Zoning / Closure / Rotation
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Managing terrestrial impacts
Catchment management Agriculture Fertiliser Seafront corridors Controls on sewage systems Limits on development Dry beaches and walkways
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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
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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 over-exploitation
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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.
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