Productivity of coral reefs

Productivity of coral reefs

IntroductionProductivity- 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 wont 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 (gmy)

Coral reefs- worlds 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

Movement of molecules between coral tissue & zooxanthellae

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

Organisms - Proximate source of energy

Termed as primary producers

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*10 cells/cm 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

Productivity of coral reef depends on:

a. illumination

b. temperature conditions

Shallow water coral ecosystem- most productive ecosystem of the world

Gross primary productivity-1-15gCmday

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