Cold-water corals and ocean acidification - Seb Hennige
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Cold-water corals and ocean acidification - Seb Hennige

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  • Abstract: Cold-water corals are amongst the most three-dimensionally complex deep-sea habitats known and are associated with high local biodiversity. Despite their importance, little is known about how these organisms will fare in the face of predicted future climate change. Currently, the long-term synergistic effects of projected increases in atmospheric p CO 2 and sea temperatures upon the cold-water coral Lophelia pertusa are unknown, and studies to date have only examined L. pertusa response to either increased temperature or increased p CO 2 on short time scales. Here, we present data on the effects of increased sea temperatures (by 3  C) and increased p CO 2 , (750 and 1000ppm) upon the metabolism and growth of cold-water coral Lophelia pertusa , collected from the Mingulay Reef Complex, Scotland, UK . Results from short-term exposure to increased temperature and p CO 2 on freshly collected corals will be contrasted with current data from an ongoing 18-month experiment. Comparison of short and long-term data will help define the impact of ocean acidification and increased temperatures upon the growth, physiology and structural integrity of the reef framework forming coral, Lophelia pertusa.
  • This work in on lophelia – branching species which is scleractinian (forms solid carbonate calcium skeleton which importantly exists after animal death) This means can form complex 3d habitats so very important environments. No symbiodimium like tropical corals – therefore relies on heterotrophy Since no photosynthesis not limited to photic zones – distributed from 40-3000m across latitudes Norway reefs Joubin paper called “cold water corals – a nuisance for deep sea trawlers” Not a lot of work to date as you need Rovs or submersibles
  • Combined with a potential increase in water temperature by 3°C over a relatively rapid time, these key habitats are under threat Acidity increawed by 30% since industrial revulition. Ocean acidification – not acid Neg impatc on calcifiers CO2 dissolves – carbonic acid, more H+ more acidiity 8.1 to about 7.8 or 7.9 Decreases availability of carbonate minerals Also reduce saturation state making harder to precipitate Dissultiion occurs below set value Depth at which this occurs is deep – real danger for deep speacies as as pH decreases, depth rises
  • These cold water corals are deep, change in ASH depth potentially disasterous
  • Data today on respiration, alk anom and BW
  • Also did side experiment of temperature shock vs acclimation - apparent from tropical literature that quite important so we wanted to quantify this before starting our long term experiments
  • Respiration normalised to tissue dry weight (as are all graphs from now on) Respiration decreases in acidified treatment – ties in with decreased feeding rates (other paper)
  • What is happening to energetic reserves? These being used to account for decreased respiration and feeding?
  • No sig difference between control and 1 stresors Only significnant with 2 stressors These are all data at Time + 3 months
  • Maier - 5 days - reduced calc rate Armin - 6 months, initial decrease then all same Maier 2009 - a few days again - used acid....

Cold-water corals and ocean acidification - Seb Hennige Cold-water corals and ocean acidification - Seb Hennige Presentation Transcript

  • Impacts of ocean acidification and warming on cold water corals: current and future work Sebastian Hennige, Wicks L.C., Kamenos N.A., Roberts J.M.1
  • Cold water corals Lophelia pertusa (the most common UK coral) • Scleractinia – framework forming •Complex habitats • No Symbiodinium (no photosynthesis) •Global distribution from 40 – 3000m •Reefs can be larger than some tropical (Norway reefs ~2000km2) •Historically known but relatively unstudied •Joubin 19152
  • Ocean Acidification and warming:....The other CO2 problem• Directly related to atmospheric CO2 • Current atm. pCO2 is 380ppm • By 2100: 750 – 1000ppm • pH ↓ from ca. 8.1 to ca. 7.8 •Negative impact on calcifiers: ↓ availability of carbonate ions Change in the ASH depth Harder to calcify Potential dissolutionCombined with a potential increase in water temperature by 3°C over arelatively rapid time, these key habitats are under threat3
  • Aragonite Saturation Horizon depth:1995 • By 2100, ASH predicted to be much2100 shallower than present day (Guinotte et al. 2006) • Deep water calcifiers particularly vulnerable4
  • Aims: • What are the long-term effects of increased CO2 and temperature upon cold water corals - Single and synergistic effects • Will acclimation occur? - To what extent?5
  • Methods – impacts of OA and warming Lophelia pertusa from Mingulay Reef Complex Ca. 180m • Metabolism • Feeding • Carbon production • Respiration •Calcification (growth) • Alkalinity anomaly • 45Ca or 14C uptake • Buoyant weight6
  • Methods – impacts of OA and warming • Short term experiments on RSS Discovery (21 days) • 380 and 750ppm CO2 (pre-mixed gas bubbling) • Long term at Heriot-Watt University (18 months) • Gas mixing system (380, 750 and 1000ppm CO2) • Two temperatures 9°C, 12°C7
  • Results & Discussion: Short term • Ocean Acidification – respiration - L. pertusa respiration decreased in acidified conditions (750ppm) over 21 days compared to present day conditions - Only different after 2 weeks8
  • Results & Discussion: Short term • Ocean Acidification – growth (alkalinity anomaly technique) - L. pertusa calcification rate (alkalinity anomaly) did not change in acidified conditions (750ppm) over 21 days - Growth rate maintained despite decreased respiration (Large variability) – energetic reserves?9
  • Results & Discussion: Long Term •At T + 3 months: •Control has highest respiration rate •Corals at elevated CO2 OR temperature had reduced respiration rates •Corals at elevated CO2 AND temperature had reduced respiration rates Control 1 stressor 2 stressors10
  • Results & Discussion: Long Term • No significant difference between 750ppm and control. Differs from short term experiment • Acclimation • No difference in respiration between 750 and 1000ppm treatments • No difference in respiration between a temperature increase, or increase in CO2 • Combined increase in CO2 and temperature • Significant reduction in respiration • Does this tie in with net growth (buoyant weight?11
  • Results & Discussion• Buoyant weight: •Percentage mass change •0-3 months: 750,12C significantly lower growth than control •3-6 months: non significant growth across treatments •Potentially higher growth in 12C? •Dead skeletons still to be cross compared
  • Conclusions: • Ocean Acidification - Significant effects in short term, but acclimation occurs by T + 3 months (in terms of respiration). - Net growth similar • Temperature - Impact on respiration not significant at T+ 3 months. Enhanced growth? • Combined effect (most likely scenario) - Significant reduction in respiration rate compared to controls at T+3 months - Net growth reduced during this time but is this just short term? - Acclimation at what cost, and what are the limits? - To be continued (6 months data to finish processing, 12 and 18 month data to be collected)13
  • Future work:• Using cold water corals to look at past climate history • Funded NERC proposal• Assessing internal pH regulation in tropical and coldwater corals in present and predicted future conditions • Submitted NERC fellowship
  • Future work: Where did all the CO2 go?Using cold water corals to reconstruct deglacialCO2 information (NERC)Why?CO2 responsible for warming the earth during interglacial periods is most likely stored in the deepsea during the intervening cold glacial periods. However, there is much uncertainty over: • How this happens • Where the CO2 is stored • How it rapidly reaches the surface and atmosphere during deglacialsHow? Quantifying the boron fractionation within: 1. Laboratory kept skeletons of cold water coral (calibration and validation) 2. Historic samples of cold water coral (application)Boron isotope fractionation in seawater strongly pH dependent, and by quantifying the amount incoral skeletons, we can calculate the ocean pH.Dr. Laura Wicks, Prof Murray Roberts, Dr. Sebastian Hennige and Dr. Gavin Foster (NOC)
  • Future work:Coral pH regulation and ocean acidification:‘winners and losers’• Reef building corals (tropical and cold) can regulate their internal pH tooffset external ocean acidification • Is this the same across all coral species ? • What is the extent of this regulation under different conditions? • What is the energetic cost of such regulation?Nearly impossible to determine in intact corals with conventional methods-therefore novel approaches needed • Tissue cultures • pH dyes with confocal microscopy • Microelectrodes • Boron isotopes
  • Thanks to:• NERC• DEFRA• DECC• HW technical staff• RRS Discovery participants and crew For more information see www.lophelia.org17