Presentation on theme: "Coral Reef Ecosystems Ecology and Environmental Management."— Presentation transcript:
Coral Reef Ecosystems Ecology and Environmental Management
Lecture content n Coral reef ecology –How they are formed –Physical Environment –Diversity patterns –Threats to coral reefs –Fisheries n Coral reef management –Assessing damage –Management for ecology and economics –Diversification –Tourism
Introduction to coral reefs
What is a coral reef n Biological (coral community) –Organic, Biogenic –Coral and Algal communities –Mostly hermatypic corals, algae, and other sessile animals n Geological features (reef) –Carbonate –In situ buildup –Topographic relief –Wave resistant –Cemented, consolidated
Corals n Phylum Anthazoa n Class Cnidaria n Hermatypic (hard) corals contain symbiotic algae n Up to 500 spp. at some sites Rosen 1981
Building the reef CaCo 3 addition - CaCo 3 loss = Accumulation Biogenic production Sediment Import Cementation Biological erosion Mechanical erosion Sediment export, dissolution Reef Growth Kleypas et al 2001
Types of reef n Fringing, Barrier, Atoll, Drowned
Environmental requirements n Physical environment –Temperature of o C (limited Northwards by the 18 o C minimum isotherm) –Salinity of ppt –Light level n Predominantly in top 30 m of water n Biological environment –Oligotrophic, highly stratified water column
n Coral reef distribution
Coral diversity patterns
Maps n 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. n 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 n Mainly Perciform teleosts n 2 faunas, Diurnal and Nocturnal n Often territorial/site attached n Intraspecific interactions (pair bonding and harems) and interspecific mutualism (e.g. cleaning stations) n Mostly planktonic larvae n Estimated 4500 spp, 25% of marine total n ~10% of world fishery landings
Fishery species n Often large, high-value fish
Fish distribution patterns
World population distribution
And if that wasnt bad enough…..
Threats to coral reef systems n Overpopulation n Unsustainable fisheries n Coastal development n Global climate change
Coral reef fisheries n Essential to survival of many n Managed sustainably for generations n 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 n Subsistence fishing occurs regardless of effort required n Muro Ami, Dynamite (Blast), and cyanide fishing n Trawling n Trapping and lines –Ghost fishing n Total fishing mortality often not known
Malthusian overfishing n...occurs when poor fishermen, faced with declining catches and lacking any alternative initiate wholesale resource destruction in order to maintain their incomes. n This may involve in order of seriousness, and generally in temporal sequence...
n 1) Use of gears and mesh sizes not sanctioned by government n 2) Use of gears and mesh sizes not sanctioned within the fisherfolk community… n 3) Use of gears that destroy the resource base n 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 n Removal of predators n Removal of algal grazers n Change in dominance –Californian Sea Otters –Urchins –Crown of Thorns starfish COTS (Acanthaster planci) n Changes in size frequency of animals
Crown of Thorns Starfish
Crown of Thorns n Eats coral by everting gut n Aggregations can remove 95% of coral cover n May result in collapse of remaining skeleton n Pheromone controlled aggregated spawning n Recovery takes at least 12 years n Caused by loss of predators? n Increased larval survival due to pollution?
Terrestrial impacts n Pollution –Sewage –Agriculture –Aquaculture –Rubbish n Sedimentation n Eutrophication n Construction on reef flats n Coral mining n Mangrove destruction
Climate change n Potential impacts on coral communities –Changes in water temperature –Increases in CO 2 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 n Loss of symbiotic algae n May cause death of animal n A symptom of climate change?
Coral Bleaching n First described in 1984 n Multiple re-occurrences at same sites n New sites impacted during 1990s n Many known triggers –Temperature (especially increases) –Solar radiation (especially UV) –Combination of UV and temperature –Reduced salinity –Infections
Effects of bleaching n Loss of symbiontic algae (Zooxanthellae) algae by: –Degradation In situ –Loss of algae by exocytosis –Expulsion of intact endodermal cells containing algae n 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 n A large (and growing) number of people are dependent on coral reefs n Management of a multispecies fishery is extremely complex, and often fails n Terrestrial development may destroy coastal reef systems n Global climate change may exert new pressures
Coral reef management
Management Issues n Biological –What does the resource consist of? –What state is it in? –Is there overfishing? –Is there habitat destruction? n Socio-ecomomic –Levels of resource exploitation –More sustainable ways of exploiting the resource –Alternatives to coral reef exploitation/damage
Monitoring coral reefs n What sites and parameters to monitor? n Fish n Macroinvertebrates n Water quality n Benthic habitat quality n Coral health
Sources n 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. n 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. n 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 n Rapid Ecological Assessment –Manta tows –Estimates of % cover (live and dead coral) –Abundance of highly visible species –Human impacts n Mapping and aerial photography
Monitoring fish n Visual census –Transects –Point counts –Random searching –Often allow biomass estimates n Fisheries monitoring
Monitoring the benthos n Line intercept transects n Visual transects n Quadrats n Photography and video
Line Intercept Transect
Marine protected areas n Fisheries reserves –No take zones (NTZs) –Controlled fishing n Effects on fish populations –Coral reef fish often have small ranges n Effects on fishing revenue n Local management and ownership
Sources n The marine protected areas case studies are based on the work of Russ and Alcala. n 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. n These are not new references, work from Robertss paper for newer studies. See also Gell and Roberts 2003 – Trends in Ecology and Evolution, 18,
Biological effects of protection n Habitat protection n Biodiversity n Protection of vulnerable species n Allow fish to grow to maturity n Control (reference) sites
Economic effects of protection n Increased size and abundance of stock species n Emmigration into fishing grounds (Spillover) n Insurance against management failure n Tourism spin-offs n Ease of enforcement
Marine reserves case study
Effects on fish diversity
Effects on fish abundance and biomass
Factors to consider n Costs? –Staff, setup, monitoring –Initial loss of fishing revenue n Size/shape of reserve? –Life history and behaviour of fish –Fishing intensity –20-40% of fishing ground n Can you sell it? –Any spin-off benefits? –Employment of local staff? –Compromise on size of reserve? n What management outside reserve?
Impacts of tourism n Terrestrial development n Land reclamation and creation of beaches –Mangrove removal –Sand on reef flat n Boats –Anchors –Diver/snorkeller impacts and fish feeding –Sewage –Harbour dredging
Ras Mohammed project
Growth of reef tourism
Sources n This section is based on the works of David Medio and Julie Hawkins. A couple of their references are included at the end. n 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 n Mooring buoys n Most damage caused my minority of divers –Education –Enforcement n Ban gloves n Monitoring n Zoning / Closure / Rotation
Managing terrestrial impacts n Catchment management –Agriculture –Fertiliser n Seafront corridors n Controls on sewage systems n Limits on development n Dry beaches and walkways
Who cares what happens to coral reefs anyway? n Fisheries n Tourism n Coastal protection n Bioprospecting n Moral reasons n Many coral reef functions are Subsistence –Do not show up as economic benefits –REPLACEMENT value may be extremely high
Summary n Coral reefs contain diverse fish and invertebrate assemblages –This makes them valuable, but difficult to manage n Coral reefs are mainly found in the poorest areas of the world –This makes them prone to over- exploitation
Summary n Reefs must be assessed and monitored to allow management n Marine protected areas may protect biodiversity and maintain fish stocks n Diversification of local economies may be effective in reducing pressures n Tourism brings new pressures which must also be managed.