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12. Habitats: Deep Water Corals What is a deep-water coral
Biogeography Feeding
Deep Water Coral Ecosystems
Growth & Archives
Threats to deep-water corals
Dr Rhian G. Waller 3rd May 2010 Reading: Roberts et. al., 2006
What is a Deep-Water Coral? No zooxanthellae Wide niche All oceans Temperatures from -1.5°C - ~12°C From 3m - >6000m
Known since early 18th century Taxonomy Ecological research started ~2000 “Oasis in the Deep” Over 1000 associated species Poster child for deep water research
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Taxonomy Lace Corals Stylasterids Stony Corals Scleractinians Black Corals Antipatharians
Zooanthids Soft Corals Alycyonacea
Sea Fans Gorgonians
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Solitary vs Colonial
Solitary Colonial Genetically distinct Polyps are clones Produced sexually Colonies produced sexually Only scleractinian solitary All types of coral have coral species colonial form Common deeper & colder Scleractinian – only to 2000m Other types - deeper
Shallow Water Corals
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Deep-Water Corals
Alex Sirotek, USGS
Deep Water Coral Distribution
Not limited but sunlight or by temperature
Found in all the worlds oceans
But there are patterns Reef building scleractinians – Continental Shelf Octocorals & Antipatharians – Bathyl Solitary scleractinians - Abyssal
Why?
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Deep Water Coral Distribution No definite reason as yet.. Calcification Carbonate saturation 2+ - ↔ Aragonite Ca + 2HCO3 CaCO3 + CO2 + H2O Scleractinians Calcite Octocorals
Patterns of ASH and CSH may control biogeography
Not getting energy from photosynthesis Feely et al., 2004
Deep Water Coral Feeding
No zooxanthellae – feed entirely on food fall Suspension feeders Zooplankton, phytoplankton, resuspended & detritus May be strategies Kiriakoulis et al., 2007 Two species side by side feeding on different matter Seamounts & Ridges Accelerated currents Internal waves Retention of food particles
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Cosmopolitan Species Lophelia pertusa Reef building scleractinian Most widespread (?)
Desmophyllum dianthus Solitary scleractinian Most diverse environmental tolerances (?) Oculina varicosa Reef building scleractinian Can be zooxanthellate OR azooxanthellate
Paragorgia arborea Bubblegum coral Octocoral
Limited Barriers
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Deep Water Coral Ecosystems
“Reefs of the Deep”
Røst Reef 400m depth NW coast of Norway Loften islands 40Km long, 3km wide 100km2 Largest known deep-water coral reef Lophelia pertusa Over 750 associate species
Deep Water Coral Ecosystems
Don’t have to be a reef builder to harbor other fauna
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Deep Water Coral Ecosystems
Deep Water Coral Ecosystems
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Growth What is growth? Per polyp? Linear? Reef?
“Rings” But what do they mean? Phytodetrital fall/oceanographic change influenced?
U/Th, 210Pb, C14 dating Ocotocorals >4000 years old (?) Grow ~4mm/year – L. pertusa
Roark et al., 2006
Corals as Archives Longevity over geologic time DWC evolved before SWC (?) 50,000 years of scleractinian growth
Paleoarchives
U/Th dating Population declines and increases Interglacial times ⌃
Stable Isotopes Reconstruct Temperature/ composition of water masses
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Anthropogenic Impacts
“Out of sight, out of mind”
Main causes of anthropogenic damage
Oil/Mineral Exploration
Coral Harvesting
Deep Water Bottom Trawling
Climate Change
Deep Water Coral Harvesting
Precious Corals (gold, pink, red - Octocorals) & Black corals Fetch high prices Black corals - ~10 grams = $50 Hawaiian Islands Only US state to allow fishery 20,000kg over 2 years Older estimates of age (~20 years)
Still in fisheries management plan CITES permit for Red corals – 2010 REJECTED!!!
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Deep Water Trawling
Upper pelagic fish stocks declining
Moving deeper to maintain catches Orange roughy, grouper, grenadier, oreo etc. Found close to the bottom Average trawler 10Km2 per day Most land gear on the bottom and drag More efficient
Anthropogenic Impacts Corner Rise Seamounts
Waller et al, 2007
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Anthropogenic Impacts
Anthropogenic Impacts
Waller et al, 2007
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Ocean Acidification
Cooler water = more CO2 absorbed = more acidic Deep water corals already living in acidic conditions Impacts greater than shallow water….
Feely et al., 2009
My pet peeve……
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Conclusions
Deep water corals are similar to their shallow water counterparts, but do not have zooxanthellae
They have a wider distribution, and have different limits of tolerance Aragonite saturation (?)
Cold-water corals are important Nursery and feeding habitat Archives of past climate Cold-water corals are being impacted too Deep water fishing Ocean acidification
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