Rehana RajDFK 1307

I Ph.DCollege of Fisheries

Mangalore

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

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*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

Productivity of coral reef depends on:

a. illumination

b. temperature conditions

Shallow water coral ecosystem- most productive ecosystem of the world

Gross primary productivity-1-15gCm¯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

Main algal groups & their roles in coral reef ecosystem

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