Coral Reefs Marine Ecology. CORAL REEFS Most diverse and productive communities DIVERSITY! Protection from wave energy Foster ecological oases –Mangroves.

Coral ReefsCoral ReefsMarine EcologyMarine Ecology

CORAL REEFS• Most diverse and

productive communities

• DIVERSITY!

• Protection from wave energy

• Foster ecological oases– Mangroves– Seagrass beds

• Iconic ecosystem

• Sensitive

• Threatened by humans

Development and Distribution

• Biogenic • 30* N and S of equator • Cover <0.1% of global

ocean surface area• Host >25% of fish

species• Better than

rainforests!– Species per unit area

http://data.unep-wcmc.org/datasets

Development and Distribution

• Hermatypic– Reef-building– Tropics– Growth and

distribution influenced by physical environment

• Ahermatypic– Non reef-building– Mostly world-wide

Development and Distribution

• Temp: 18-36*C• Types of reef based

on;– Underlying

substratum• Existing carbonate reef• Igneous rock

– Sea level changes– Light levels– Wave action

Patch Reefs

• Bommies• Small reefs • Grow in shallow

lagoonal areas• Surrounded by sand• Deeper • Don’t go above

surface at low tide

Fringing Reefs

• Develop on shelving shores

• Rocky tropical islands

• Corals settle and grow on well-lighted and shallows areas

• Grow toward surface

Barrier Reefs

• Surround tropical islands• Separated from land by

lagoon• Usually 1-10km wide• Line of breaking surf• May develop from

fringing– After sea level rise

• Grow quickly– Exposure to wind/currents

Atolls

• A ring of reef with low-lying islands surrounding a lagoon

• 10km (or more) across

• Biological diversity• Seabird colonies• Charles Darwin

– Formation theoryhttp://www.youtube.com/watch?v=vrD1O5hex6Y

Reef Growth

• Not continuous– Periods of rapid growth– Periods of bioerosion

• Net reef growth– Fastest: 20m in 1000yrs– Usual: 3m in 1000yrs

• Growth affected by sea-level– Glaciers

Corals and Coral Communities

• CaCO3 skeletons• Polyps

– Protection and nutrients

• Zooxanthellae – Photosynthesizers – Dinoflagellate– Can live independently– No flagella/motility in

polyp

Corals and Coral Communities

• Zooxanthellae– Transmitted during

reproduction– Obtained from seawater– Produce energy– Autotrophic

• Waste from host- RECYCLE!

– High rate of photosyn more calcium carbonate

Coral Reproduction

• Recruitment • Sexual and asexual• Hermatypic

– Polyps; asexual budding– Break off, settle, grow

• Sexual– Long-distance dispersal

• Gonochoric- one• Simultaneous- both• Sequential Hermaphrodites- change

http://www.youtube.com/watch?v=wsaZ8-I7akg

Coral Reproduction

• Brooding– Fertilized internally – Planula develops inside

polyp

• Broadcasting– Certain period of the year

• Lunar cycle

– Synchronized• Common cues• Too many eggs for the evil

predators to eat

http://www.youtube.com/watch?v=06BPlLATtgc

Coral Reproduction

• Fertilized eggs– Settle in 1-3 days

• Zooxanthellae aquired after settlement and metamorphosis– Brooder larvae contain them

• Calcified base plate• Grazing helps growth• Influenced by environment

http://www.youtube.com/

watch?v=_Mt0h5v4xos

Coral Reproduction

• LIGHTlightlightlightlight

• Reef accretion – 0-10m– Hermatypic

• Rare below 30m

– Shallow, well-lit zone• More light• Less predators

• Sunburn!• Stenothermal

Coral Growth

• Evolved in stable temp– Less tolerant

• Evolved in variable temp– More tolerant

• Salinity 33-35ppt• Wave action currents

– Nutrient spreading– Can be harmful

• Hurricanes

Coral Growth

• Sediments – Some coral can remove it– Smothering, abrasion,

shading, recruitment inhibition

– Pulse Sediment• Storms• Not as harmful

– Suspended Sediment• Human actions• Reduced light for coral

http://www.youtube.com/

watch?v=9pdmkckANH4

Productivity

• Production recycled within the reef

• Carbon fixation– Less than half the

carbon they fix is available

– Few organisms feed on coral directly

• Reef algae – Very productive

• Grazed on and carbon

Productivity

• Phytoplankton!– Support zooplankton

• Support larger consumers

• Currents carry them across reef

– Currents carry them from outlying water, and over the reef…• Then they can be

eaten- YUM!!

Productivity

• 24-h cycle used to measure– Day- photosynthesis– Night- respiration– Excess Production- net

production which occurs (E)– Photosyn/Respiration ratio

• (P/R ratio)• E=0, P/R of 1

– E is relatively low• Competition• Nutrient recycling

Reef Fauna

• Could be home to over a million species

• Diiiiiiiiiverse!– Not uniform– Determined by reef history

and environment

• Reef building coral evolved over 200 mil yrs ago

• Large scale extinctions– Every 20-30 million years

Reef Fauna

• Diversity– Influenced by isolation

• Study– Began; 1950’s and

60’s– Focused on ecology– Realized instability– Research still young

THREATS!

• Humans (of course)– We suck!!

• Direct– Increased

sedimentation– Fishing– Ship stupidity– Pollution

• Indirection– Climate change– Over-fishin

Disease

• Yes, corals get sick too– Pathogens and parasites

• Can be aggravated by human influences

• Black band– 1st recorded– Affects brain coral– Caused by cyanobacteria– Create anoxia in the tissue– Physically damaged

• More susceptible

Bad Weather

• Storms– Branching corals– Reef fish

• Cyclones– (10-25* N/S)– Fast growing coral

that relocate

• Hurricanes– Fast growers – Acropora

Climate Change

• Climate change Rising sea level– Should be good for

shallow water coral– Increased ENSO due

to temp increase– HUMANS

• Nutrient input

– Deep corals will not do well

Coral Bleaching

• Stressed coral expel their zooxanthellae

• Skeleton becomes visible• Prolonged bleaching

leads to coral death• Bioerosion takes over• Algae move in

– Reduce reef accretion– Fish species will be lost

• High water temperature

http://www.youtube.com/

watch?v=aEdoizgeNJk

http://www.youtube.com/

watch?v=60jof35WuAo

Coral Predators

• Crown-of-thorns starfish– Feed on living coral– Free-spawners– 12-60mil eggs in a

spawning season– Evert their stomach on

coral, and secreting an enzyme which breaks down the coral

– Fishing may have reduced their predators

http://www.youtube.com/

watch?v=2fE2gIARQWA

Pollution, Sediments, Nutrients

• Deforestation, port development, and dredging– Run off

• Increased sediment load

• Nutrients from run-off– Increased algal growth– Phosphate; big no-no

• Oil pollution

http://www.youtube.com/watch?v=rkKs-5JGSoo

Fishing

• Expanding fisheries– Direct damage

• Habitat-destructive fishing– Reef drive netting– Trapping– Blast/chemical fishing

• Unselective • Illegal

Reef Growth

• Limestone produced– And broken down

• Coral rubble/sand

• Balance between accretion and bioerosion

• Erosion by organisms– Grazers

• Mollusc, echinoderm, fish

– Loss of hermatypic corals

Reef Animals

• Difficult to record densities

• Used as ‘laboratories’ – Behavior and ecology– Carrying capacity

• Recruitment limitation hypothesis– Population sizes limited

and determined by rates at which larval fish from plankton to adult

http://www.youtub

e.com/watch?

v=UB7tqiL-Eqs

Reef Animals

• No one species can out-compete the other

• Reef structure is complex

• Symbiosis – Coexist– Cleaner fish– Burrowers

http://www.youtube.com/

watch?v=UJbPej8uytw

http://www.youtube.com/watch?v=xaJdXO_j2MY

Reefs and Humans

• Provide food and income• Subsistence fishing

– Not recorded

• Tourism– Great Barrier Reef

• Over 10mil per year

– Towns can be supported by revenue

• Ecosystem services; help humans– Coastal defense – Coral mining, bleaching, sedimentation