Coral reefs are the most productive marine ecosystem in the world due to the tight recycling of nutrients and symbiotic relationship between coral polyps and algae called zooxanthellae. The zooxanthellae live inside the coral tissues and produce nutrients through photosynthesis, up to 90% of which is transferred to the coral to support its growth and production. This high productivity supports a great diversity of species, making coral reefs important habitats and nurseries for many organisms, as well as providing food and livelihoods for coastal human populations.

2. 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

3.  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

4.  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)

6.  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

7.  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

8.  Photosynthesis by zooxanthellae- fix large amounts of
‘carbon’; passes on to the host polyp
 Mainly in the form of glycerol or glucose or alanine

9.  Metabolic products are used by the polyp
 Symbiotic relationship between corals &
zooxanthellae- tight recycling of nutrients back &
forth

10. Movement of molecules between
coral tissue & zooxanthellae

11.  Degree to which coral depends on zooxanthellae is
species specific
 Corals are more productive in shallow water bodies

12.  Major energy is received from sunlight
 Plants, algae & bacteria-capable of capturing the
energy & produce organic matter

13.  Organisms - Proximate source of energy
 Termed as primary producers

14.  Zooxanthellae -primary producers in corals
 Belong to the genus Symbiodinium
 Important algae is Symbiodinium microadriaticum

15.  Zooxanthellae occupies 1-10% of biomass of living
corals
 Density 1-5*10⁶ cells/cm² coral surface area
 Varies with depth and season

16.  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

17. Products of zooxanthellae are transferred directly to the
coral tissues
Respired, stored or released into environments

18.  Corals also feeds on tiny other organisms by the mucus
produced by corals
 Prey ranges from zooplankton to even small fishes

19.  Productivity of coral reef depends on:
a. illumination
b. temperature conditions

20.  Shallow water coral ecosystem- most productive
ecosystem of the world
 Gross primary productivity-1-15gCm¯²day¯¹

21.  High level of production- symbiotic algae in reef
building corals & allied invertebrates
 Symbiotic algae accounts-50-70% of the total primary
production

22.  Excess production from reef- 3% of total primary
production
 <1% of total production is available as harvestable
form

23. 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

24.  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

25.  Coral growing areas show high primary productivity-
1500-3000gC/m²/yr
 Contributed by zooxanthellae, free living algae,
phytoplankters

26.  Mucus secreted by coral- due to wave action & grazing
of coral eating animals
 Another source of Carbon available to plankters

27. Functional groups of coral reefs
-Primary producers
-algae, other plankters
- Planktivores
- fishes & invertebrates, including corals
Predators
-piscivores, corallivores, invertebrate eaters
-Detritivores
-bioeroders – remove coral skeletons
- scrapers – remove algae and sediments
- grazers – remove macroalgae

28. Main algal groups & their roles in
coral reef ecosystem

29. Productivity & Diversity
High Productivity
Production (kg Carbon per m2 per year)
Average Oceanic areas 0.1 kg
Rainforest 2 kg
Kelp forest 2 kg
Coral 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)

30. 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

31.  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

32. 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

33.  Chaetodontids (butterfly fishes)- dominant species of
coral reef ecosystem
 Great Barrier reef ranks first (50 species)
 The Philippines ranks second
 Indonesia ranks third

34. 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

35.  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

36.  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

37.  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