The Risk of Ocean Acidification to Ocean Ecosystems

Ocean acidification is a process that refers to major changes to the ocean’s carbonate chemistry, mainly caused by ocean uptake of anthropogenic emissions of carbon dioxide. This process involves a decrease in ocean pH (important for regulation of the internal acid balance and physiological health of many organisms) carbonate ions and calcium carbonate minerals such as aragonite and calcite (important for shell and skeleton builders) and an increase in bicarbonate ions (important for algal photosynthesis). To understand what marine ecosystems may look like in the future if carbon emissions continue unabated, it is necessary to know the severity of the perturbation that different ecosystems will be exposed to and their ability to adapt within the time-scales of change. The severity and speed of ocean acidification, the exposure and vulnerability of the component organisms of an ecosystem to ocean acidification and their role in an ecosystem contribute to the risk of impacts to ecosystem structure and function. Although there are great uncertainties moving from impacts on individual organisms to impacts on complex marine ecosystems, these basic changes to marine chemistry pose a substantial risk to marine ecosystem structure and function through the impacts on the growth, physiology, behaviour, predator-prey interactions, competitiveness and population dynamics of individual species and how these may cascade through the rest of the ecosystem. Some organisms are able to adapt to ocean acidification, especially if food resources are high, by trading-off energy from one physiological function to another, although this may impact their long-term survival and ecosystem function. Foodwebs where vulnerable organisms provide key trophic links, especially those exposed to undersaturated waters in polar, sub-polar and upwelling regions where severity will be greatest, will be at high risk of impact from ocean acidification. However, ecosystems formed by the aragonitic skeletons of deep-sea or tropical corals are also at high risk of impact from ocean acidification, either due to high severity, exposure or vulnerability or a combination of all three. Risk increases further when ocean acidification acts in concert with other global and/or local ocean stressors. Predicting impacts of changing biodiversity or community dynamics on ecosystem structure and function also requires expanding the scope of current experimental research to examine multi-stress impacts in multi-level foodwebs and complex ecosystems. Key Messages • Basic changes to marine chemistry pose a substantial risk to marine ecosystem structure and function through the impacts on the growth, physiology, behaviour, predator-prey interactions, competitiveness and population dynamics of individual species and how these cascade through the rest of the ecosystem; • Though some organisms may be able to adapt to ocean acidification by trading-off energy from one physiological function to another, this may impact their long-term survival and ecosystem function; • Risk of impacts will depend on the severity (of which strength and speed are components) of ocean acidification, and the exposure and vulnerability of organisms to ocean acidification especially those playing key roles in ecosystems. The higher the severity, exposure and vulnerability the greater the risk of impact to numbers of organisms and therefore to foodwebs and ecosystems; and • Foodwebs where vulnerable organisms provide key trophic links, especially those exposed to undersaturated waters in polar, sub-polar, deep sea and upwelling regions where severity will be greatest, will be at high risk of impact from ocean acidification. However, as ocean acidification progresses with increasing anthropogenic CO2 emissions, ecosystems across the whole ocean will be at risk

How can we minimise negative effects on ocean health? Policy card E1-E2

Rising temperatures and sea levels, acidification, and deoxygenation are carbon dioxide (CO2)-driven stressors that are already affecting the ocean, as well as the life it supports and the benefits it provides. These effects are in addition to pollution, over-fishing and lost habitats and their combination is likely to be worse than the sum of the parts: threatening ecosystems, human well being and the ability of the ocean to absorb CO2. Whilst damage is inevitable, actions can be taken to reduce its severit

Ocean acidification

KEY HEADLINES • Global-scale patterns and processes of ocean acidification are superimposed on other factors influencing seawater chemistry over local to regional space scales, and hourly to seasonal time scales. • Future ocean conditions will depend on future CO2 emissions; there is now international agreement that these should be reduced to net zero, thereby reducing the consequences of both climate change and ocean acidification. • Assessments of ocean acidification by the Intergovernmental Panel on Climate Change (IPCC) gave high or very high confidence to chemical aspects, but a much wider range of confidence levels to projected biological and biogeochemical impacts. Biotic impacts will depend on species-specific responses, interactions with other stressors and food-web effects. • Previous MCCIP statements are considered to still be valid, with increased confidence for some aspects. • Observed pH decreases in the North Sea (over 30 years) and at coastal UK sites (over 6 years) seem more rapid than in the North Atlantic as a whole. However, shelf sea and coastal data sets show high variability over a range of timescales, and factors affecting that variability need to be much better understood. • UK research on ocean acidification has been productive and influential. There is no shortage of important and interesting topic areas that would improve scientific knowledge and deliver societally-important outcomes

What has the UK Ocean Acidification research programme told us? An infographic for Defra.

This is an infographic requested by Defra on the findings of the UK Ocean Acidification research programme

Future of the Sea: Ocean Acidification

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. 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. 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. Ocean Acidification 5 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 2100. 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

Hot, Sour and Breathless – Ocean under Stress.

ISBN 978-0-9519618-6-

Open Ocean: Status and Trends, Summary for Policy Makers

The Open Ocean Assessment provides a baseline review of issues linking human well-being with the status of the open ocean through the themes of governance, climate change, ocean ecosystems, fisheries, pollution, and integrated assessment of the human-ocean nexus. It uses indices and indicators where data exist, in many cases with future projections due to global climate change, complemented by expert scientific assessment of numerous low certainty but potentially high impact issues where global ocean monitoring is inadequate

The Royal Society Climate Updates: What have we learnt since the IPCC 5th Assessment Report?

Climate has a huge influence on the way we live. For example, it affects the crops we can grow and the diseases we might encounter in particular locations. It also determines the physical infrastructure we need to build to survive comfortably in the face of extremes of heat, cold, drought and flood. Human emissions of carbon dioxide and other greenhouse gases have changed the composition of the atmosphere over the last two centuries. This is expected to take Earth’s climate out of the relatively stable range that has characterised the last few thousand years, during which human society has emerged. Measurements of ice cores and sea-floor sediments show that the current concentration of carbon dioxide, at just over 400 parts per million, has not been experienced for at least three million years. This causes more of the heat from the Sun to be retained on Earth, warming the atmosphere and ocean. The global average of atmospheric temperature has so far risen by about 1˚C compared to the late 19th century, with further increases expected dependent on the trajectory of carbon dioxide emissions in the next few decades. In 2013 and 2014 the Intergovernmental Panel on Climate Change (IPCC) published its fifth assessment report (AR5) assessing the evidence about climate change and its impacts. This assessment considered data from observations and records of the past. It then assessed future changes and impacts based on various scenarios for emissions of greenhouse gases and other anthropogenic factors. In 2015, almost every nation in the world agreed (in the so-called Paris Agreement) to the challenging goal of keeping global average warming to well below 2°C above pre-industrial temperatures while pursuing efforts to limit it to 1.5°C. With the next assessment report (AR6) not due until 2022, it is timely to consider how evidence presented since the publication of AR5 affects the assessments made then. The Earth’s climate is a complex system. To understand it, and the impact that climate change will have, requires many different kinds of study. Climate science consists of theory, observation and modelling. Theory begins with well-established scientific principles, seeks to understand processes occurring over a range of spatial and temporal scales and provides the basis for models. Observation includes long time series of careful measurements, recent data from satellites, and studies of past climate using archives such as tree rings, ice cores and marine sediments. It also encompasses laboratory and field experiments designed to test and enhance understanding of processes. Computer models of the Earth climate system use theory, calibrated and validated by the observations, to calculate the result of future changes. There are nevertheless uncertainties in estimating future climate. Firstly the course of climate change is dependent on what socioeconomic, political and energy paths society takes. Secondly there remain inevitable uncertainties induced for example by variability in the interactions between different parts of the Earth system and by processes, such as cloud formation, that occur at too small a scale to incorporate precisely in global models. Assessments such as those of the IPCC describe the state of knowledge at a particular time, and also highlight areas where more research is needed. We are still exploring and improving our understanding of many of the processes within the climate system, but, on the whole, new research confirms the main ideas underpinning climate research, while refining knowledge, so as to reduce the uncertainty in the magnitude and extent of crucial impacts