12. Habitats: Deep Water Corals

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1 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 3 rd 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 18 th century Taxonomy Ecological research started ~2000 Oasis in the Deep Over 1000 associated species Poster child for deep water research 1

2 4/29/10 Taxonomy Lace Corals Stylasterids Stony Corals Scleractinians Black Corals Antipatharians Zooanthids Soft Corals Alycyonacea Sea Fans Gorgonians 2

3 Solitary vs Colonial Solitary Genetically distinct Produced sexually Only scleractinian solitary coral species Common deeper & colder Colonial Polyps are clones Colonies produced sexually All types of coral have colonial form Scleractinian only to 2000m Other types - deeper Shallow Water Corals 3

4 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? 4

5 Deep Water Coral Distribution No definite reason as yet.. Carbonate saturation Aragonite Scleractinians Calcite Octocorals Patterns of ASH and CSH may control biogeography Calcification Ca HCO 3 - CaCO 3 + CO 2 + H 2 O 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 5

6 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 6

7 Deep Water Coral Ecosystems Reefs of the Deep Røst Reef 400m depth NW coast of Norway Loften islands 40Km long, 3km wide 100km 2 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 7

8 Deep Water Coral Ecosystems Deep Water Coral Ecosystems 8

9 Growth What is growth? Per polyp? Linear? Reef? Rings But what do they mean? Phytodetrital fall/oceanographic change influenced? U/Th, 210 Pb, C 14 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 9

10 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!!! 10

11 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 10Km 2 per day Most land gear on the bottom and drag More efficient Anthropogenic Impacts Corner Rise Seamounts Waller et al,

12 4/29/10 Anthropogenic Impacts Anthropogenic Impacts Waller et al,

13 Ocean Acidification Cooler water = more CO 2 absorbed = more acidic Deep water corals already living in acidic conditions Impacts greater than shallow water. Feely et al., 2009 My pet peeve 13

14 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 14