Ocean acidification
Project Leader: Dr Jason Hall-Spencer
BackgroundThe global oceans currently absorb over 25 million tons of CO2 every day. This has caused surface waters to become 30% more acidic since wide-spread burning of fossil fuels began. As well as lowering pH, increased CO2 levels are altering surface water chemistry, causing a decline in carbonate ions, an increase in bicarbonate ions and lowering calcium carbonate saturation states. Falling calcite and aragonite levels are a concern since these are the building-blocks of shells for a range of marine organisms from tiny coccolithophores to giant coral reefs. Research into the marine environmental effects of increased oceanic CO2 levels is mainly being carried out using short-term-shock experiments whereby pH or CO2 levels are manipulated in aquaria and enclosures over short timescales.
To watch Jason discuss his work on Euronews click here.
In the Field
Jason has teamed up with scientists from labs in France, the UK, Israel and Italy to document the first ecosystem-wide responses to long-term changes in ocean pH. The effects are being studied on marine communities around underwater volcanic vents, where carbon dioxide bubbles-up like a Jacuzzi (Fig. 1). Gas analyses showed that such vents release millions of litres of CO2 per day (Fig. 2) causing seawater acidification but it is important to study areas where the gas is at ambient temperature and lacks the poisonous hydrogen sulphide which typifies most volcanic vents. Impacts on marine life include 30% reductions in biodiversity in areas where average pH has dropped by 0.4 units compared with areas at normal seawater pH (8.2).
To watch Jason discuss his work on Euronews click here.
In the Field
Jason has teamed up with scientists from labs in France, the UK, Israel and Italy to document the first ecosystem-wide responses to long-term changes in ocean pH. The effects are being studied on marine communities around underwater volcanic vents, where carbon dioxide bubbles-up like a Jacuzzi (Fig. 1). Gas analyses showed that such vents release millions of litres of CO2 per day (Fig. 2) causing seawater acidification but it is important to study areas where the gas is at ambient temperature and lacks the poisonous hydrogen sulphide which typifies most volcanic vents. Impacts on marine life include 30% reductions in biodiversity in areas where average pH has dropped by 0.4 units compared with areas at normal seawater pH (8.2).
 Figure 1 Carbon dioxide vents off Ischia Island, Bay of Naples |
 Figure 2 SCUBA diver collecting volcanic gases for analyses. |
 Figure 3 Dramatic dissolution of intertidal limpet living near CO2 vents |
Acidic futures?
Natural CO2 vents can provide insights into which species are tolerant of long-term high CO2 levels and can be used to test predictions based on modelling and laboratory work, such as what levels of CO2 exposure restrict the ability of marine organisms to build shells (Fig 2). Although lush stands of seagrasses thrived at increased CO2 levels (Fig 3), major groups such as corals, sea urchins and bivalves were removed from the ecosystem and replaced by algae such as Sargassum sp. and Caulerpa spp. In brief, the research has so far shown:
We are now undergoing the fastest rate of ocean acidification the Earth has seen for at least the past 20 million years so this study adds urgency to the international policy drive to reduce CO2 emissions.
Natural CO2 vents can provide insights into which species are tolerant of long-term high CO2 levels and can be used to test predictions based on modelling and laboratory work, such as what levels of CO2 exposure restrict the ability of marine organisms to build shells (Fig 2). Although lush stands of seagrasses thrived at increased CO2 levels (Fig 3), major groups such as corals, sea urchins and bivalves were removed from the ecosystem and replaced by algae such as Sargassum sp. and Caulerpa spp. In brief, the research has so far shown:
- major ecological tipping points along a gradient of increasing CO2 levels.
- acidification dissolved the shells of calcified species such as corals, sea urchins and snails, which were absent in areas with a pH less than 7.4
- high CO2 favoured the production of seagrass and removed its calcareous epiphytes.
- the amount of calcified algae, which bind coral reefs together in the tropics, fell from more than 60 per cent cover outside the vent areas to zero within these areas.
- invasive alien species, which cause damage to ecosystems worldwide, may thrive at high CO2 levels.
We are now undergoing the fastest rate of ocean acidification the Earth has seen for at least the past 20 million years so this study adds urgency to the international policy drive to reduce CO2 emissions.
Project Update: 2009
The broad aim of the next phase of this project is to act as a wake-up-call to raise public awareness of the problems associated with ocean acidification and to get people to think about the consequences of unabated CO2 emissions. The new results that this project will generate will be used as a platform for educating children and adults alike, it will be publicized using interactive public lectures, on websites and through the media.
The objectives of this project are to create as much publicity as possible for preliminary findings from CO2 vent areas showing the dramatic ecosystem tipping points that occur when the pH of seawater is lowered to the levels expected by the year 2100 if current emissions continue unabated. We will now obtain better video images of the sites, visit more CO2 vent sites and engage with the specialist scientific community at conferences to encourage the idea that a larger, fully resourced international programme designed to harness naturally acidified areas to refine our understanding of the conservation consequences of ocean acidification under the various emissions scenarios predicted by the Intergovernmental Panel on Climate Change is urgently needed. The main secondary aim of the project is to publish the findings from research into CO2 vent fields in the scientific literature.
The objectives of this project are to create as much publicity as possible for preliminary findings from CO2 vent areas showing the dramatic ecosystem tipping points that occur when the pH of seawater is lowered to the levels expected by the year 2100 if current emissions continue unabated. We will now obtain better video images of the sites, visit more CO2 vent sites and engage with the specialist scientific community at conferences to encourage the idea that a larger, fully resourced international programme designed to harness naturally acidified areas to refine our understanding of the conservation consequences of ocean acidification under the various emissions scenarios predicted by the Intergovernmental Panel on Climate Change is urgently needed. The main secondary aim of the project is to publish the findings from research into CO2 vent fields in the scientific literature.