Future of the Sea: Ocean Acidification

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By Milthon Lujan

Executive Summary
Ocean acidification (OA) and climate change are both influenced by increasing carbon dioxide concentrations coming from the atmosphere. However, the distinction between OA and climate change, is that OA is an alteration of the chemistry of seawater, therefore not a direct climatic process. The ocean is the largest natural reservoir of dissolved carbon and holds an immense buffering capacity for changes in atmospheric CO2 concentrations. The rapid increase of atmospheric CO2 since the industrial revolution has caused oceans and seas to absorb increasingly greater amounts of CO2. This process disturbs the pre-existing chemical equilibrium of the sea, resulting in seas changing their chemical state and altering the ocean pH, becoming more acidic.


Ocean acidification has become one of the most studied topics in the last 10 years (Williamson et al. 2017; Browman 2016). The UK has made a significant contribution in understanding OA effects on biodiversity and biogeochemistry, and the socioecological impacts across species and ecosystems. The evidence suggests that OA will act differently across species with some impacts already occurring for sensitive marine species and with direct and indirect repercussions for ecosystems. The direct effects will include changes in species morphology, ecology and behaviour whilst indirect effects may be repercussions for processes or higher trophic groups (e.g. wider food web effects and interactions within and between species). This review summarises the available ‘state of the art’ information with regards to OA effects, current issues and further recommendations for consideration on what will be the likely future issues for OA. This information intends to support marine planning decisions and future policy adaptations. A detailed section is included on how these changes will affect UK interests (e.g. maritime industries, fishing, health and wellbeing). A summary of key highlights is outlined below.

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– Monitoring data conducted over the North Sea assessments have shown clear pH changes in shelf and coastal sites. Trends of pH variability are still uncertain, and further work to disentangle the observed variability does require additonal investigation.

– By 2100, under medium emissions scenarios, ocean pH is projected to decrease by 0.3 pH units from levels 100 years ago. Evidence suggests that similar trends in acidification during the Paleocene-Eocene Thermal Maximum (PETM) (around 56 million years ago), where the rate of release of CO2 was estimated to have been around one-tenth of current rate of anthropogenic
emissions, caused the extinction of many seafloor organisms.

– Though the future impacts of OA on commercial fisheries are still uncertain, recent research has indicated that annual economic losses in the UK resulting from the effects of OA could reach US $97.1 million (GBP £7.47 million) by


– The integrity of some UK species and habitats of conservation importance (included under the current Marine Protected Areas – MPAs – designation) could be affected by future changes in pH and temperature.

– Ocean acidification research has demonstrated that some species may be more susceptible to changes in pH. These results are particularly important for UK shellfisheries and shellfish aquaculture, as these industries could be negatively affected.

Reference (open):
Dr Silvana Birchenough, Dr Phillip Williamson and Dr Carol Turley . Future of the Sea: Ocean Acidification. Goverment Office for Science – Foresight. 19 p.

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