Transcript Ch.-11-CoralIce - Chaparral Star Academy

Marine Ecology
Coral Reefs
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.unepwcmc.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 lowlying islands
surrounding a lagoon
• 10km (or more) across
• Biological diversity
• Seabird colonies
• Charles Darwin
– Formation theory
http://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 sealevel
– 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
http://www.youtube.
com/watch?v=wsaZ
8-I7akg
• Recruitment
• Sexual and asexual
• Hermatypic
– Polyps; asexual budding
– Break off, settle, grow
• Sexual
– Long-distance dispersal
• Gonochoric- one
• Simultaneous- both
• Sequential Hermaphrodites- change
Coral Reproduction
• Brooding
http://www.youtube.c
om/watch?v=06BPlL
ATtgc
– 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
Coral Reproduction
• Fertilized eggs
– Settle in 1-3 days
http://www.youtube.
com/watch?v=_Mt0
h5v4xos
• Zooxanthellae aquired after
settlement and
metamorphosis
– Brooder larvae contain them
• Calcified base plate
• Grazing helps growth
• Influenced by environment
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
http://www.youtube.com
/watch?v=9pdmkckAN
H4
– Some coral can remove it
– Smothering, abrasion, shading,
recruitment inhibition
– Pulse Sediment
• Storms
• Not as harmful
– Suspended Sediment
• Human actions
• Reduced light for coral
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 eatenYUM!!
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
http://www.youtube.com/
watch?v=60jof35WuAo
• 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.c
om/watch?v=aEdoiz
geNJk
Coral Predators
http://www.youtube.com
/watch?v=2fE2gIARQW
A
• 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
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.y
outube.com/
watch?v=UB
7tqiL-Eqs
Reef Animals
• No one species can outcompete the other
• Reef structure is
http://www.youtube.com/w
complex
atch?v=xaJdXO_j2MY
• Symbiosis
– Coexist
– Cleaner fish
– Burrowers
http://www.youtube.com
/watch?v=UJbPej8uytw
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