Ocean Acidification (OA) on aquaculture: EIR release

Information requested

Under the Freedom of Information Act (2000) and the Environmental Information Regulations (2004), I am requesting information regarding Ocean Acidification. This request follows my review of a report concerning Marine Scotland’s findings of shell damage on marine snails and shellfish larvae off the coast of Stonehaven.

Please find my questions below:

Which species (current) are most at risk of dissolution and shell damage off the coast of Stonehaven?

Has Marine Scotland assessed the economic or social impact of Ocean Acidification on the Scottish shellfish aquaculture and fisheries industries? If so, what is the estimated monetary value of these effects?

Are Marine Scotland using any in-particular technologies to mitigate the negative implications of Ocean Acidification on species in Stonehaven and Scotland’s aquatic bodies?

How much is being invested, by the Scottish Government, in combatting Ocean Acidification?

Which bodies of water in Scotland are at the greatest risk to Ocean Acidification?

What are the estimated mortality rates for key marine species affected by ocean acidification in Scotland’s waters, particularly in areas like Stonehaven?

How is ocean acidification expected to affect marine food webs, particularly the availability of plankton and other base-level species crucial to Scotland’s marine ecosystems?

Are there any collaborative efforts between Marine Scotland and other environmental agencies to develop long-term solutions for mitigating ocean’s acidifications effects?

Response

As the information you have requested is ‘environmental information’ for the purposes of the Environmental Information (Scotland) Regulations 2004 (EIRs), we are required to deal with your request under those Regulations. We are applying the exemption at section 39(2) of the Freedom of Information (Scotland) Act 2002 (FOISA), so that we do not also have to deal with your request under FOISA.

This exemption is subject to the ‘public interest test’. Therefore, taking account of all the circumstances of this case, we have considered if the public interest in disclosing the information outweighs the public interest in applying the exemption. We have found that, on balance, the public interest lies in favour of upholding the exemption, because there is no public interest in dealing with the same request under two different regimes. This is essentially a technical point and has no material effect on the outcome of your request.

The answers to your questions are provided below.

1 - Which species (current) are most at risk of dissolution and shell damage off the coast of Stonehaven?

The available observations on ocean acidification parameters at Stonehaven have been recently published in the MCCIP evidence review on ‘Ocean Acidification around the UK and Ireland’ (Finlay et al., 2025). The latter reveals a decreasing tendency in pH at Stonehaven, in agreement with other observations and estimations in UK waters and OSPAR regions (McGovern et al., 2023). However, it is worth noting that the time series at Stonehaven is not long enough yet to distinguish if this trend is due to natural variability or to anthropogenic ocean acidification, so it is not possible to establish a direct cause-effect relationship between the shell dissolution observed and ocean acidification.

Further information can be found in the Scotland's Marine Assessment 2020 (https://marine.gov.scot/sma/), the paper by León et al. (2020; https://doi.org/10.1093/icesjms/fsz178), the OSPAR Quality Status report 2023: ocean acidification (McGovern et al., 2023; https://oap.ospar.org/en/ospar-assessments/quality-status-reports/qsr-2023/otherassessments/ocean-acidification), and the MCCIP Science Review 2025 on Ocean Acidification (Finlay et al., 2025; https://www.mccip.org.uk/ocean-acidification).

Additional information provided out with the EIRs

Under regulation 9 of the EIRs (our duty to provide advice and assistance) we would like to provide some further information that may help improve your understanding of ocean acidification and its effects on marine life.

Ocean acidification (OA) is a change in the chemical balance of the sea caused by the ocean uptake of part of the carbon dioxide released to the atmosphere by human activities. This process, which is decreasing the ocean pH and making it more acidic, might impact marine life in several ways. In particular, plants and animals with outer skeletons made of aragonite (a more soluble form of calcium carbonate) are thought to be particularly vulnerable to these changes since ocean acidification would create more corrosive conditions that may dissolve their calcareous shells and make harder for these organisms to build them. This group includes some marine snails routinely observed at Stonehaven such as pteropods (Limacina retroversa and Limacina helicina) and other gastropods as Caecum spp., Rissoa spp. and Janthina spp. (commonly known as bubble rafting snail). Larvae stages are also particularly sensitive to changes caused by ocean acidification due to the lack of specialised resilience mechanisms compared to adult stages. Larvae of shellfish observed at Stonehaven include (among others) species such as the blue mussel (Mytilus cf. edulis), the pullet carpet shell (Venerupis corrugata), the wrinkled rock borer (Hiatella arctica), and the horse mussel (Modiolus modiolus).

While our aim is to provide information whenever possible, the Scottish Government does not have some of the information you have requested in the following Questions 2 to 8. Therefore we are refusing your request under the exception at regulation 10(4)(a) of the EIRs. The reasons why that exception applies are provided under Annex A attached.

However, under regulation 9 of the EIRs (our duty to provide advice and assistance) we would like to provide additional information out with the EIR. Our responses to your questions are detailed as follows:

2 - Has Marine Scotland assessed the economic or social impact of Ocean Acidification on the Scottish shellfish aquaculture and fisheries industries? If so, what is the estimated monetary value of these effects?

A study on the economic impacts of ocean acidification on shellfish fisheries and aquaculture in the United Kingdom (Mangi et al., 2018) suggested a potential threat to the shellfish aquaculture industry in Scotland. There is currently no specific assessments of the potential economic or social impacts of ocean acidification on the Scottish coast, and the recent MCCIP evidence review on aquaculture indicates that the future implications of ocean acidification for the sector are still highly uncertain (Murray et al., 2025).

Although the shell damage on shellfish larvae observed at Stonehaven (see Léon et al., 2020) raises concern on the potential carry-over consequences for economic important bivalve species under ocean acidification projected future scenarios in the region, these observations need to be considered with precaution. On the one hand, the shell damage observed at Stonehaven was associated with natural seasonal decreases of calcium carbonate and not with the observed pH decreasing trend. On the other hand, the study only covered 3 years of data and longer time series of data will be required to elucidate these relationships further.

Further information can be found in the paper by Mangi et al. (2018; https://www.sciencedirect.com/science/article/abs/pii/S1462901117311528), paper by León et al. (2020; https://doi.org/10.1093/icesjms/fsz178), the MCCIP Science Review 2025 on Aquaculture
(Murray et al., 2025; https://www.mccip.org.uk/aquaculture).

3 - Are Marine Scotland using any in-particular technologies to mitigate the negative implications of Ocean Acidification on species in Stonehaven and Scotland’s aquatic bodies?

The Scottish Government’s Marine Directorate (SG-MD) is currently not mitigating the negative implication of ocean acidification on marine species. Our efforts are focused on monitoring carbonate chemistry parameters in Scottish waters at our monitoring sites at Stonehaven and Loch Ewe, with the aim of improving the knowledge on impacts of ocean acidification on marine ecosystems.

4 - How much is being invested, by the Scottish Government, in combatting Ocean Acidification?

Considering that OA directly correlates with atmospheric carbon dioxide concentration and warmer sea temperatures, any reduction in man-made emissions of this specific green-house gas can be considered as a mitigation measure against OA. The Scottish Government has set ambitious climate change legislation involving a target date for net zero emissions of all greenhouse gases by 2045. Our third National Adaptation Plan 2024 to 2029 describes what we and our partners are doing to respond to the impacts of climate change, which include reduction of carbon dioxide emissions.

5 - Which bodies of water in Scotland are at the greatest risk to Ocean Acidification?

Some marine regions are more rapidly affected by ocean acidification than others depending on their chemical composition, depth and temperature. However, to our knowledge, there is currently no specific assessment of the spatial variability of ocean acidification and its potential impacts along the Scottish waters. There is some information available for the wider region that can be found in the OSPAR Quality Status report 2023: ocean acidification
(https://oap.ospar.org/en/osparassessments/quality-status-reports/qsr-2023/other-assessments/ocean-acidification).

6 - What are the estimated mortality rates for key marine species affected by ocean acidification in Scotland’s waters, particularly in areas like Stonehaven?

The studies on the potential biological impacts of ocean acidification at Stonehaven (León et al., 2020; León et al., in preparation) do not allow to make any estimation on potential mortality rates on biological communities or specific groups. It is also worth noting that shell dissolution does not necessarily imply the death of the animal, since bivalve larvae can build their shells even in conditions of low calcium carbonate concentration (Waldbusser et al., 2014).

Further information can be found in the paper by Waldbusser et al. (2014; https://www.annualreviews.org/content/journals/10.1146/annurev-marine-121211-172238).

7 - How is ocean acidification expected to affect marine food webs, particularly the availability of plankton and other base-level species crucial to Scotland’s marine ecosystems?

The SG-MD is currently not undertaking any studies on the potential impact of ocean acidification on the food webs in Scottish marine ecosystems. Such studies may be in progress in the wider academic community or by international partners, but we are not aware of any of these currently focusing on Scotland’s marine ecosystems.

The Scottish Government recently commissioned the Centre of Expertise for Climate Change (ClimateXChange) to examine the impact of climate change and ocean acidification on target fish stocks to inform fisheries policy
(see climatexchange.org.uk/wp-content/uploads/2024/05/CXCInforming-Scotlands-fisheries-policies-to-be-adapted-and-resilient-May-2024.pdf)

8 - Are there any collaborative efforts between Marine Scotland and other environmental agencies to develop long-term solutions for mitigating ocean’s acidifications effects?

We do not currently have any information of potential mitigation plans carried out by the SG-MD or any other environmental agency including the Scottish sea areas. The SG-MD continues to monitor at our coastal monitoring sites to understand the impacts of ocean acidification. We also continue to work with collaborators across Scotland, the UK and internationally (for example through the Oslo-Paris Commission’s Working Group on Changing Ocean Climate and Ocean Acidification – see Climate change and ocean acidification | OSPAR Commission).

Marine Scotland was renamed to Marine Directorate - The Marine Directorate of the Scottish Government (SG-MD) – in summer 2023, in order to clarify the fact that the organisation is a core part of the Scottish Government, not a separate agency.

About FOI

The Scottish Government is committed to publishing all information released in response to Freedom of Information requests. View all FOI responses at https://www.gov.scot/foi-responses.

EIR 202500455960 - Information Released - Annex A

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