Corals and coral reefs Dr. Rob van Woesik
Today Corals life cycle An amazing relationship symbiosis Coral growth Controlling factors
Coral polyp
A brief history Tynne (1859) reported coral gametogenesis,, but it was considered unusual; Brooding (viviparous) was the considered mode of reproduction (Marshall and Stephenson 1933; Yonge 1940; Kawaguti 1940); Photo. P. Harrison
Brooding (Wallace 1999)
Our understanding changed: (1) suggestions from Connell (1973) (2) discoveries of gamete release (Kojis and Quinn 1980; Szmant-Froelich et al. 1980), and
Mass synchronous spawning on the Great Barrier Reef (Harrison et al. 1984).
Broadcast spawning (Wallace 1999)
Acropora cerealis Acropora hyacinthus 50 60 45 40 50 Perpendicular size (cm) 35 30 25 20 15 10 5 3.333 26.667 50 73.333 96.667 above 0 0 5 10 15 20 25 30 35 40 45 50 Perpendicular size (cm) 40 30 20 10 0 0 10 20 30 40 50 60 0.033 0.267 0.5 0.733 0.967 above Maximum size (cm) Maximum size (cm)
Babcock et al. 1986. Marine Biology 90: 379-394
From Veron (2000)
The dogma 1. Rise in SSTs 2. Lunar phase 3. Night time Photo. P. Harrison
30 25 # SPECIES SPAWN 20 15 10 5 0 February March April May June July August September MONTH Penland et al 2004, Coral Reefs
Light
Japan spawning Solar insolation (kwh/m^2/day) DEC NOV OCT SEP AUG JUL JUN MAY APR MAR FEB JAN * * Amami-oshima * Okinawa Iriomote 22 24 26 28 30 32 34 36 38 Latitude * Shirigai 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 above
Three main variables 1. SSTs are poor predictors of coral spawning in the tropics. 2. Lunar phase - yes 3. Night time - yes solar insolation cycles coincide with coral spawning events.
Day 1 Day 3-4
6 March 2001
Gulf of Mexico Cyclone ACE Shelf Current LCE Cyclonic Gyre Mexico ACE U.S.A Cyclone LCE Loop Current 8 Yucatan Current Cayman Basin Nicaragua Rise Shelf Current Cyclone 9 7 CARE Cyclonic Gyre Florida Current Jamaica 5 4 CARE Columbian Basin Windward Passage 3 Atlantic Ocean Eddy Field Greater Antilles Mona Passage Caribbean Current Caribbean Sea 1 Venezuela Anegada Passage Netherlands Antilles Lesser Antilles YC: Yucatan Current LC: Loop Current LCE: Loop Current Eddy CARE: Caribbean Eddy ACE: (Smaller) Anticyclone
Black K. 1993. Coral Reefs 12: 43-53
Model Domains of the Triply Nested Modelling System Jinyu Sheng Outer Model (19 km) Inner Model (2 km) Middle Model (6 km)
dle (egg & sperm) Planulae Sea surface Sexual fertillisation Passive dispersal Most of planulae die Active selection oral spawning Settlement
Post-settlement settlement events Major drivers of coral community structure Van Woesik et al. 1999; Van Woesik 2000; Van Woesik 2002
Reef flat and deep slope Stressful habitat not many species. Why?
Reef flats are: Too hot in summer Too cold in winter Exposed to air
Deep slopes Low light; < 8% surface light becomes a problem.
Fragmentation = asexual budding
Remote sensing SeaWiFS 1000 m MOS 500 m Space Shuttle 30-50m Landsat 30 m Modis 4 m Lidar 0.10 m
Today Corals life cycle An amazing relationship symbiosis Coral growth Controlling factors
10 9 s 10 6 s 10 3 s 10 4 s 10 2 s 10 3 m 2 10-3 s 10 1 m 2 10-12 s hν PCP D2 QA D1 Fe QB 10-3 m 2 acppc Phe P680 Z PQH 2 PQ 10-6 m 2 10-5 m 2 Mn Mn hν fluorescence 2 H 2 O Mn Mn 4 H++4 e- +O 2 10-9 m 2 10-12 m 2
Zooxanthellae
Symbiosis
Acropora formosa Fagoonee et al. 1999. Science 283: 843-845
Symbiotic dysfunction
Multi-site approach -subjected to different degrees of human influence One site stations within sites A site (0.5-2 2 km scale), 2 stations (75 x 10 m) at each site, at least 7 sites within each region
Are reef productive? Yes and No. Yes; high gross production Most nutrients are recycled No; little net production
Birkeland C (1996) Life and death of coral reefs.
Hatcher B. 1990. Trends in Ecology and Evolution. 55: 149-155
Extraction Can only extract a little before reef is damaged
Today Corals life cycle An amazing relationship symbiosis Coral growth Controlling factors
Light Kawaguti 1944
Light intensity Porites sillimaniani Low-light High-light
120 100 80 60 40 20 0 Light attenuation 0 10 20 Depth (m) Light intensity (%). 30 cm 30 cm Sunlight
Sunlight Light resource Surface area 30 cm Large light resource 30 cm Same surface area
Solar insolation Amount of electromagnetic energy (solar radiation) incident on the surface of the earth (kw/m 2 /day -1 )
Massel and Done 1993 Corals of the World, Veron 2000
Wave energy stout Pocillopora damicornis colonies at a single location Corals of the World, Veron 2000
Ca 2+ + 2HCO - 3 = CaCO 3 + CO 2 + H 2 O Removal of CO 2 enhances precipitation Add CO 2, we increase dissolution
Carbonate Chemistry CO 2 photosynthesis respiration CO 2 aq (CO 2 + H 2 O) H 2 CO 3 Carbonic acid Alkalinity Mg 2+ Na + bicarbonate HCO 3 + H + Proportion of HCO 3 and CO 3 2 adjusts to balance alkalinity K + Ca 2+ carbonate CO 3 2 + H + [CO 3 2 ]= ALK TCO 2 CaCO 3 calcification
Changing Proportions of Carbonate Species 2x 1x
Massive corals: historical archives of shallow-water tropical ecosystems
1.7 1.6 density g.cm -3 1.5 1.4 1.3 1.2 1.1 0 2 4 6 8 10 12 14 16 18 20 22 24 distance cm Annual density banding provides: Chronology Linear extension rate Average skeletal density Calcification rate (extension x density)
What can coral records tell us Baseline data on coral growth characteristics recent and distant past How the quantity and quality of freshwater has changed in space & time Implications for coral growth and reef health of climatic & environmental change Identify past stresses to coral reefs Provide backdrop of natural climatic & environmental variability and change
Anthropogenic impacts Land use changes Exploitation Pollution Photos: Robert van Woesik
Disturbances Downstream areas are affected by upstream activities.
Deforestation & poor land use Increase sediment Increase freshwater runoff
Hughes T. 1994. Science 265: 1547-1551
Sustainability of reefs Manage the people
Management and enforcement Define protected areas Combine traditional and modern systems to ensure enforcement
What to protect Key spawning areas that supply other reefs
The future Recovery is rapid if the system is not influenced by humans Human disturbances induce slow recovery rates
Line 2 140 m 1998 2004
Line 1 160m 1998 2004
Line 2 160m 1998 2004
Line 1 180m 1998 2004
Line 2 180m 1998 2004