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Corals and Coral Reefs
Nancy Knowlton
National Museumof Natural History
Part 2: Biodiversity
and why it matters
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Problem of understanding biodiversity not
limited to reef organisms!!
New species being discovered even
in commonly eaten organisms
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But reefs are especially challenging
Coral animals are hard to classifyCoral colonies are complex communitiesCoral reefs contain a multitude of species
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Coral animals are hard to classify
Problems at all taxonomic levelsfrom families to species
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Radial symmetry
One gut opening
All have nematocystsstinging cells fordefense and
capture of prey
All corals belong to the Phylum CnidariaCoralpolyp -basic building block
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Several different cnidarians are called corals
True corals(Scleractinia)
Blue corals
Organ pipecorals
Fire corals
octaco
rals
Four groups have stony skeletons
Plus black corals, seafans, soft corals
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Colonies grow in complex shapes
But these are not useful forrecognizing families of corals
Photo:OveHoegh-Guldberg
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Faviidae
Mussidae Pectiniidae
Meandrinidae*
Merulinidae
Astrocoeniidae*
Siderastreidae*
Agariciidae
Poritidae
Euphylliidae*
Molecules show traditional taxonomy is wrong
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intermediate
deep
shallowM. faveolata
M. annularis
M. franksi
Even species can be hard to tell apart Montastraea annularis complex
Lab rat of Caribbean coralsThought to be one species
Actually three speciesTook ten years to find out
Entire mitochondrial genome(16,134 bp) has only 25
variable sites (n=6)
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Coral colonies are complex communities
ThecoralholobiontDiverseassemblagesofalgae,bacteria,
Archaea,Fungiandvirusesincoral?ssues
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Symbiodinium microadriaticum
Zooxanthellae MUCH more diverse thanpreviously realizedBaker 2003
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All C Mostly B
coral testubeColony and depth zonation
Type C prefers low light (colony sides, deeper water)
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Zooxanthellae diversity and coral bleaching
Breakdown in symbiosis betweencoral and symbiotic algae
Caused by stress(including high light and temperature)
Could variation be due to
diversity of zooxanthellae???
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Shallow Water:Bleached in low lightmicro-environments
Deep Water: Bleached in high lightmicro-environments
Bleaching in Panama, 1995
B A B A B A B A B A B A B A B A
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Breakdown of RFLP Genotypes (222 Samples in Total)
Type B
2%
Type A
33%
Type C
12%
Type C2
28%
Type D
18%
Mixed Types
7%
Montastraea franksiBocas del Toro, Panama
Heat-resistant
Type A33%
Type C228%
Type D18%
Type B2%
Mixtures7%
One coral species - many resistant zooxanthellae
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Bleaching threshold
? ?
Resistant zooxanthellae could forestallannual mass coral bleaching
due to global warming
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CoralDisease:WhoarethePathogens
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What is the normal bacterial flora?
Specialized associations:
26/31 multiple occurrences on 1 coral sp
3 species of corals - 2 locations - 14 samples
~ 100 clones per sample - 16SrDNA240 unique sequences observed
~6000 species of bacteria - function??
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Two Competing Hypotheses:Specific Pathogens
Bacterial Releasecoral dies a
coral livesno algae
Sugars from algae stimulate bacteria livingin coral, which then kill the coral
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But most microbial sequences cannot be identified
Next-generation sequencing
Enormous diversity injust one species of coral
Wegley et al. 2007
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Rainforests of the seaEstimates so far are really guestimates
Coral reefs contain a multitude of species
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1 - 9 million reef species in total (?)1/4 of all marine species (?)
In any sample, most are rare and small
Coral are not the most diverse group(fewer than 1000 species)
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Standardization Allows results of different studies to be compared
Automation Identify species using molecular barcoding
Scalability World-wide sampling strategy is feasible
Census of Marine Life Global census ofbiodiversity of
coral reefs
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Pan-tropical comparison of coral reef diversity
Sites analyzed to date
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Analysis by DNA Barcoding
Hundreds of samples from
one dead coral head
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0
20
40
60
80
100
120
140
160
180
1 101 201 301 401 501 601 701 801 901 1001 1101 1201 1301
Nu
mberofspec
ies
Number of individuals sampled
LizardIsland
HeronIsland
Ningaloo
Moorea
LineIslands
FFS
Panama
8 heads
14 heads
6 ARMS
6 heads
Species numbers keep climbing
15 heads14 heads, 9 ARMS
21 heads
4182 Sequences
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6.3 m2 of reef rubble had ~80% of thecrab diversity of all Europe!
170 species
212 species
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What is the true diversity of reef brachyuran crabs?(5200 described species)
S = AzAsampled = 6.3 m2
Acoral reefs = 60,000 km2
Answer depends on z-value(which we dont know)
For z=0.1, ~0.5(5200) speciesFor z=0.4, ~800(5200) species
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Bulk sample
DNA amplified fromentire community
Next-Gen Sequences
The (Not too Distant) Future Surface with animals
Automatedbiodiversity monitoring
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Photo: Enric Sala
Diverse Coral Reefs -> Healthy ecosystemsand healthy people
Predators block crownof thorns
outbreaks
Toxins fromcone snailsprovide painkillers
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Monetary Value of Diversity
Tourism Non-extractive values
usually ~10x extractive values
Reefs worth ~30 billion
globally per year
Many reefs indeveloping countries
Donner and Potere 2007
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Many thanks to: Supporters: NSF, Alfred P. Sloan Foundation," Scripps Institution of Oceanography, Smithsonian
Colleagues: Nancy Budd, Don Levitan, Wes Toller, Rob Rowan,Forest Rohwer, Hiro Fukami, Laetitia Plaisance,Ryuji Machida, CoML scientists and photographers