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12. Habitats: Deep Water  What is a deep-water

 Biogeography  Feeding

 Deep Water Coral

 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   Ecological research started ~2000  “Oasis in the Deep”  Over 1000 associated  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  & Ridges  Accelerated currents  Internal waves  Retention of food particles

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Cosmopolitan Species  pertusa  Reef building scleractinian  Most widespread (?)

 Desmophyllum dianthus  Solitary scleractinian  Most diverse environmental tolerances (?)  Oculina varicosa  Reef building scleractinian  Can be zooxanthellate OR azooxanthellate

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  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 ?  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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