Responses to questions posed by attendees at the third MERCES webinar on “Ecosystem Restoration in Deep Waters”

MERCES third webinar "Ecosystem Restoration in Deep Water" on 27 June, 2019



Marie-Lise Schläppy

Can really say that there was "nothing" before the structures and that it will return to nothing?

 Anne-Mette Jorgensen​This was answered in the webinar. No, of course we cannot say that there was ‘nothing’ before the installation was placed, but very often (in the North Sea area), there was no hard substrate in that location at the time the structures were introduced and hence, the local pre-construction ecosystem was very different from the ecosystem that has developed during the presence of the structure. After 30 years, it may not be realistic to expect that the pre-construction ecosystem will arise in the same way it was. Moreover, the pre-construction ecosystem may not at all be natural as such, but have been created e.g. by intensive bottom trawling or other seabed disturbing activities. 200 years ago, for example, large parts of the Southern North Sea was covered by flat oyster banks - now, this is all sand. In such cases, the installation may in fact resemble an older, more natural version of the ecosystem more than the pre-construction system did. In any case, it has added biodiversity. Importantly, this is not an argument that should be used for the placement of O&G installations: during the production phase, they may cause serious pollution and disturbance, next to developing as a reef. If we really want to restore reefs in such places, we can better build an artificial reef.


Marie-Lise Schläppy

The structures offer now a habitat but will they when they have collapsed and are not looked after by the oil & gas industry, i.e. when they rust?

 Anne-Mette Jorgensen​:That’s a question we cannot yet answer, but presumably it will at least take some 200 years, before the structures decay by rusting. Also for artificial reefs, steel and concrete is being used, so essentially that is not different. Possibly, reef-building species might also be able to use the structure as a starting point and then build a natural reef from there.


Leandro Freitas

Is there a discussion on how post decommissioning environmental monitoring should be organised ideally? How can your scenario be applied to floating structures (such as typical for new oil rigs in Brazil)?

Anne-Mette Jorgensen​No, not to my knowledge, but see Jones et al. (2019) “Autonomous marine environmental monitoring: Application in decommissioned oil fields”. Science of the Total Environment 668, 835-853) that discusses the methods that might be used in post-decommissioning monitoring: 


Brian Balcom

Can you please elaborate upon your recommendation to assess decommissioning impacts on the basis of ecosystem attributes? Would this be on the basis of ecosystem services, or a potentially more complex analysis of ecosystem characteristics/function (e.g., via Ecopath)?

Anne-Mette Jorgensen​:I am not an expert in this type of models, but I’d imagine a process is needed in which marine protection/restoration goals form the basis of assessing ecosystem attributes - e.g. the Good Environmental Status criteria of the EU - and then determining what kind of ecosystem services are key to achieve these goals in different areas and to what extent these are being supported by offshore installations. If for example there is a goal aiming to restore reef habitats in a certain area or resolve issues of eutrophication, it would certainly be relevant to look at the role played by offshore installations in supporting these goals.


Elisabetta Manea

Do you think we should really talk about ecosystem services delivered by platforms and other infrastructures that are present in the sea? Or maybe we should talk about the support that such infrastructures can give for ES delivery? Platforms are not environmental components or natural ecosystems…

 Anne-Mette Jorgensen​:this question was answered in the webinar. I have nothing further to add.


Anonymous Attendee

Are you aware of any cases where these exploratory deep-sea mining activities interact with existing commercial fisheries? If so, what management measures are needed to address this: RFMOs+ISA+mining company? Who would get priority?

Daphne Cuvelier: I am not aware of specific areas where these activities would overlap, though there are not yet any actual mining activities going on nowadays. It would also depend on the type of fishery (demersal/benthic or mid-water). In case of mining taking place, this will involve longer time spans (possibly years) of activities in the areas to be mined, I doubt it would be commercially interesting for fisheries to operate in these areas.

DSMB: Applications for exploration are assessed in the light of other potential users of the same area.  This is not restricted to fisheries but includes navigation (busy shipping lanes), marine protected areas etc.  If there are any significant conflicts of use then a dialogue between the would occur. For instance the ISA already has in place several Memoranda of Understanding with other UN bodies.  It would probably need several lawyers to sort out who has priority if a resolution could not be found and would depend on the legal standing of the various organisations.


Elisabetta Manea

When mineral resources are removed from deep-sea habitats such as hydrothermal vents or cold seeps, how will similar representative no-take areas be determined? There are APEI areas in the CCZ for instance, but in the case of chemosynthetic habitats can be appropriate no-take areas be identified?

Daphne CuvelierIt is indeed more complicated for the chemosynthetic ecosystems, since we only have a patchy knowledge of their location and there is an enormous amount of spatial and biogeographical variability within and among hydrothermal vent fields along one single Mid-Ocean Ridge. A possible way to go about this is to leave a certain %, or all, of the hydrothermal edifices/chimneys in a hydrothermal vent field intact and unmined. However, it will be hard to keep such a selected area free from any of the mining impacts or disturbances, since they will be located in close proximity to the mined sites (i.e. within a couple 100 metres). 

DSMB: The creation of APEIs (Areas of Particular Environmental Interest) is part of a larger Regional Environment Management Plan (REMP) for the Clarion Clipperton Zone (CCZ) which is currently under review by the International Seabed Authority (ISA).  The ISA is also formulating other REMPs for other regions in which mining activity may take place, such as the Mid Atlantic Ridge and Central Indian Ocean Ridge. The REMPs will need to address representativity of set aside areas not only for chemosynthetic communities but also for fauna found on inactive vents and the rocky slopes and sedimented areas surrounding a mine site.  Dunn et al. (2018) (Science Advances 4(7) e-aar4313. have made some suggestions about how representative communities might be protected on a large scale on the Mid Atlantic Ridge. 


Dario Fiorentino

HI! To what extent do you think the restoration action has also its own impact on the surrounding area?

Daphne Cuvelier: This is hard to predict since we do not even know how successful a restoration action for the ecosystem it aims to help recover will be. I think it will largely depend on the type of ecosystem and which part of the ecosystem will be targeted by the restoration action. An example form natural disturbance and recovery occurring at hydrothermal vents does point out that caution is needed, since following an eruption at the EPR, a nearby community that had not been disturbed by the eruption was invaded by the pioneers, possibly after they became established in the disturbed vents (Mullineaux et al. 2012). 


Tomás Bredariol

Any successful case of restoration of these kinds of habitats?

Daphne Cuvelier:No there aren’t any examples of (successful) restoration in the deep sea. This was answered during the webinar.


Anonymous Attendee 

How willing are companies to be part of these new [ecosystem restoration] approaches, and to experiment with the best solutions?

Daphne Cuvelier: This was answered during the webinar. David Billett gave the example of one company that implemented a possible restoration experiment, though their operations closed down before collecting the experiments and results. I think it is important to show there are experiments possible in the early exploration phases - even though we are uncertain of their outcome or success - which would enhance our knowledge and could help preserving an ecosystem. I also think it would be in a companies’ interests to participate in such measures for their public image and show to a wider public that they are actively trying to contribute to preserving the deep-sea ecosystems for future generations (Common Heritage of Mankind, UNCLOS).


Dario Fiorentino

What do you mean by a flexible approach in managing the impact of man-made structures?

Anne-Mette Jorgensenthis question was also answered in the webinar. It’s not about having a more flexible approach to managing the impact of man-made structures as such, but specifically to decommissioning. A more flexible approach is one that allows for different decommissioning options - partial removal and reefing, full removal to shore, etc. - on the basis of an assessment of what is best for the environment (or society in general) for that particular structure or group of structures in that particular location.


Dario Fiorentino

Is it a matter of having, for example, a diffuse distribution of such structures?

Anne-Mette JorgensenThe distance between structures is certainly a criterion that should be taken into account as this determines the interconnectivity of structures for various species. Some species (larvae) are able to move over longer distances than other. Especially, the distance to natural reefs, such as Lophelia reefs, that may be supported by larval flow from man-made structures is key.


Anonymous Attendee

Are you aware of any oil & gas drilling in the areas beyond national jurisdiction? If there are, would the ISA have the mandate for overseeing and providing standards for decommissioning these activities (even though they only explicitly talk about deep-sea mining as of now)? 

Anne-Mette Jorgensen:I don’t know whether and if so where there are drilling activities going on outside the national or OSPAR jurisdiction. The ISA might supervise this.

DSMB:Yes, the ISA has the legal competence to regulate oil and gas and methane extraction in Areas Beyond National Jurisdiction were any to be found and developed .


Marie-Lise Schläppy

Lots of fish around structures would appear to be a benefit, but could these places not be a trap where the fish is then more exploitable because the fishers know where to find them?

Anne-Mette JorgensenYes, this certainly is a potential problem. Therefore, it is key to make sure to keep a substantial no-fishing zone around the structure also after decommissioning - perhaps even larger than the current 500m safety zone - when parts of a structure are left in place. Also for safety reasons this is crucial.


Marcel Rozemeijer

Could I have the DOI of the article?

ERL: Cuvelier et al. (2018) Frontiers in Marine Science(467), 10 December 2018. |  

DSMB: Deep-sea restoration actions are also a major part of a MERCES project output:

Billett, D.S.M., Jones, D.O.B and Weaver, P.P.W. (2019) Improving Environmental Management Practices in Deep-Sea Mining. In: Sharma R. (Ed) Environmental Issues of Deep-Sea Mining. Impacts, Consequences and Policy Perspectives.Springer Nature Switzerland. pp 403-446.