Centre for Geobiology

Sub‐seabed CO2 Storage: Impact on Marine Ecosystems


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Acronym: ECO2
Project name:
Sub‐seabed CO2 Storage: Impact on Marine Ecosystems
Project coordinator:
Project partners
  28 international research institute and industrial partners
Researchers involved (CGB):
  ): Laila J. Reigstad, Andrew K. Sweetman (Associate Professor II at CGB and NIVA researcher), PhD student Karin Landschulze and first-semester CGB masters student, Camilla Bøe
Project period:

Project's main objectives:

The ECO2 project sets out to assess the risks associated with storage of CO2 below the seabed. There are five key objectives:

  • To investigate the likelihood of leakage from sub‐seabed storage sites
  • To study the potential effects of leakage on benthic organisms and marine ecosystems
  • To assess the risks of sub‐seabed carbon storage
  • To develop a comprehensive monitoring strategy using novel monitoring techniques
  • To define guidelines for the best environmental practices in implementation and management of sub‐seabed storage sites

Carbon Capture and Storage (CCS) is regarded as a key technology for the reduction of CO2 emissions.  However, little is known about the short‐term and long‐term impacts of CO2 storage on marine ecosystems. CO2 has already been stored sub‐seabed in the North Sea (Sleipner) for over 13 years and for one year in the Barents Sea (Snøhvit).

The ECO2 project will assess the likelihood of leakage as well as the potential impact of leakage on marine ecosystems. Novel monitoring techniques will be applied to detect and quantify the fluxes of formation fluids, natural gas, and CO2 from storage sites. A best practice guide will be developed for the management of sub‐seabed CO2 storage sites considering the precautionary principal and costs of monitoring and remediation.

ECO2 will study a sub‐seabed storage site in operation since 1996 (Sleipner), a recently opened site (Snøhvit, 2008), and a potential storage site located in the Polish sector of the Baltic Sea (B3 field site). With this selection of study sites, each at a different operative stage, ECO2 will be able to cover the major kinds of geological settings to be used for the storage of CO2. These include depleted oil and gas reservoirs (B3 field site, 80 m water depth), saline aquifers located at the continental shelf (Sleipner, 90 m water depth), and the upper continental slope (Snøhvit, 330 m water depth).

Field work at storage sites will be supported by numerical modelling and laboratory experiments and complemented by comprehensive process and monitoring studies at natural CO2 seeps that serve as analogues for potential CO2 leaks at storage sites.


CGB researchers are involved with Work Package 2 (WP2) and Work Package 4 (WP4)

WP2 Fluxes across the seabed

During ascent to the seafloor, fluids and gases leaking from sub‐seabed CO2 storage sites will interact with the overlying marine sediments. This will affect the flux of CO2 as well as other chemical constituents to the overlying water column. As yet we have little idea about the effects of interactions between fluids and gases that potentially leak from the reservoir with the sedimentary overburden. It is therefore difficult to predict either the chemical composition or fluxes of fluid and gas transported across the sediment‐seawater interface into the overlying water column resulting from potential leakages. Fluxes of methane and formation waters across the seabed have been quantified at a large number of natural seep sites by the research partners involved in WP2 as well as other research groups.

We need to know more about the how the, fluids and gases leaking from sub‐seabed CO2 storage sites will interact with the overlying marine sediments , not least because these fluids may contain high levels of potentially toxic metals. Furthermore, recent studies focusing on the effects of ocean acidification have demonstrated that dissolution of CO2 in seawater causes fundamental shifts in seawater chemistry, lowering pH and changing the availability of key biological substrates such as carbonate and bicarbonate, with far‐reaching effects on marine ecosystems.

In WP2 some of Europe’s leading institutions in marine geochemistry and sub‐seafloor fluid flow have combined with modellers and experimentalists to tackle this issue. Together, these researchers will undertake a unique combination of field, laboratory, and modelling studies. The results should contribute significantly to the development of monitoring strategies designed to detect both diffuse and focused leakage, and will provide key information on the potential impacts of leakage on marine ecosystems.


WP4 Impact of Leakage on Benthic Organisms and Marine Ecosystems

The ultimate aims of WP4 will be to quantify the biological impacts of CO2 leakage, to assess the biological risks associated with CO2 storage and to identify appropriate methods to monitor the marine environment above a storage site. 

Recent concern over the increasing oceanic uptake of atmospheric CO2 (known as ocean acidification) has stimulated a number of researchers to study the impacts of elevated CO2 on marine organisms and processes. Successful implementation of any sub‐seabed Carbon Capture and Storage (CCS) project will require that both regulators and the general public be satisfied that the biological impacts associated with any potential leak of CO2 into the marine environment have been fully considered. 

Of particular concern would be the potential for enhanced mobilization of sediment bound contaminants such as heavy metals leading to increased bioavailability and toxicity. There is also the potential for a chronic low level stress to the marine environment.

Natural CO2 seep systems can be studied as analogues for CO2 leakage events from sub‐seabed storage. In particular, natural CO2 seeps can be considered as appropriate mimics of localised, long‐term CO2 leakage, around which studies of organism behaviour (e.g. migration or avoidance) and health can be conducted, including shallow and deep water life. The seafloor surrounding the seeps often contains a variety of habitats each with abundant and diverse communities. These habitats and communities can be studied to determine the potential impact of elevated CO2 at an ecosystem level, including the relationship between diversity and function. These analogue sites can also be used to test and develop potential bioindicators for monitor CO2 leakage. 

Models have an important role in testing our understanding, quantifying impacts and providing predictive capabilities, being able to address a wider range of leak scenarios and environmental baselines than is possible to cover experimentally. To develop effective models we need to identify the physiological and behavioural mechanisms affected by leakage and how to express these in different community and sediment configurations.

Project web site.