Productivity of coral reefs
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Transcript of Productivity of coral reefs
Introduction Productivity- the rate at which new materials are
produced from their precursors by living things; new tissues, offspring, carbohydrates that leak from a cell
Productivity of an organism or population- rate at which it turns resources into more of itself
Productivity- represents the flux of nutrients from environment into living organism
Highly productive environment- organisms won’t have to travel far to get sufficient food
Less productive environment- have less food, support fewer numbers of individual
Productivity of an ecosystem- net primary productivity
The sum of all net production of all species of primary producers
Expressed as- dry wt of production in grams of carbon/m.sq/yr (gm¯²y¯¹)
Coral reefs- world’s most productive marine ecosystem
Tiny symbiotic algae (zooxanthellae)-convert sunlight & nutrients into fuel for coral growth & production
Provide structural habitats for many different vertebrate & invertebrates
Productivity in coral reefs - complex function of light capture, efficient nutrient recycling, hydrodynamic process
Unique mutualism between hermatypic corals & photosynthetic zooxanthellae-driving force for settlement, growth & productivity of coral reefs
Photosynthesis by zooxanthellae- fix large amounts of ‘carbon’; passes on to the host polyp
Mainly in the form of glycerol or glucose or alanine
Metabolic products are used by the polyp
Symbiotic relationship between corals & zooxanthellae- tight recycling of nutrients back & forth
Degree to which coral depends on zooxanthellae is species specific
Corals are more productive in shallow water bodies
Major energy is received from sunlight
Plants, algae & bacteria-capable of capturing the energy & produce organic matter
Zooxanthellae -primary producers in corals
Belong to the genus Symbiodinium
Important algae is Symbiodinium microadriaticum
Zooxanthellae occupies 1-10% of biomass of living corals
Density 1-5*10⁶ cells/cm² coral surface area
Varies with depth and season
Zooxanthellae translocate upto 90% of their fixed carbon (C) directly to coral hosts
Rate at which coral deposits new skeleton (the calcification rate) – measures production
Products of zooxanthellae are transferred directly to the coral tissues
Respired, stored or released into environments
Corals also feeds on tiny other organisms by the mucus produced by corals
Prey ranges from zooplankton to even small fishes
Shallow water coral ecosystem- most productive ecosystem of the world
Gross primary productivity-1-15gCm¯²day¯¹
High level of production- symbiotic algae in reef building corals & allied invertebrates
Symbiotic algae accounts-50-70% of the total primary production
Excess production from reef- 3% of total primary production
<1% of total production is available as harvestable form
Factors influencing rate of photosynthesis by zooxanthellaea
Chief determinants- light & temperature
Photosynthesis quantified by-flux of O₂ & converted into units of C
Availability of light for photosynthesis by zooxanthellae in corals varies & difficult to measure
O₂ consumption in the light provides a measure of net primary production
Gross primary production-net O₂ production under illumination & O₂ release by respiration in dark
Coral growing areas show high primary productivity-1500-3000gC/m²/yr
Contributed by zooxanthellae, free living algae, phytoplankters
Mucus secreted by coral- due to wave action & grazing of coral eating animals
Another source of Carbon available to plankters
Functional groups of coral reefs
-Primary producers-algae, other plankters
- Planktivores- fishes & invertebrates, including coralsPredators-piscivores, corallivores, invertebrate eaters-Detritivores-bioeroders – remove coral skeletons- scrapers – remove algae and sediments- grazers – remove macroalgae
Productivity & Diversity
High Productivity
Production (kg Carbon per m2 per year)Average Oceanic areas 0.1 kgRainforest 2 kgKelp forest 2 kgCoral Reef 1.5-5 kg• high productivity possible because of tight recycling of nutrients,photosynthetic fixation of carbon (by corals and algae) and nitrogen (by blue-green algae)
Coral reef fisheries
High species diversity compared to temperate & pelagic systems
Tropical reef support high standing crop of fishes
Highest richness of coral reef fisheries-Indo-West Pacific especially Philippines-2177 species
A yield of 9 million tonnes annually is possible world wide
Fish catch with traps on reef vary between 1.37-20 tonnes/km of coastline
Production of fish in reefs varies from 25-50 kg*10¯⁴ m¯² y¯¹
Number of Fish species in several coral reef areas
Geographical area Number of Fish Species
Philippine Islands 2177
New Guinea 1700
Great Barrier Reef 1500
Seychelles Islands 880
Marshall & Marina Islands 669
Bahama Islands 507
Hawaiian Islands 448
Chaetodontids (butterfly fishes)- dominant species of coral reef ecosystem
Great Barrier reef ranks first (50 species)
The Philippines ranks second
Indonesia ranks third
Other major inhabitants of coral ecosystem Sponges
Polychaete worms
Sea urchins
Star fish
Seabirds
Sea snakes
Green turtle
Gastropods
Giant clam
White tip reef shark
Banded coral shrimp
Spiny lobsters
Reef crabs
Carribean reef squid
More than 25,000 described species from 32 animal phyla live in reef habitats
4 times the number of animal phyla found in tropical rain forests
Play a crucial role as habitat & nursery grounds for 10-20% of the world fishery
Intimately connected to other marine communities such as mangrove forest, sea grass beds & open seas
Play significant role in the development of ecosystems-mangrove & wetlands
Protect coastline from wave action, erosion, property damage & loss of life
Provide livelihood for half a billion people from its production
