knowlton powerpoint pt2

7/28/2019 Knowlton Powerpoint Pt2

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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

knowlton powerpoint pt2

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