Closing Plenary: Where is ocean acidification research going?

Chair: Jean-Pierre Gattuso

Ken Caldeira (1)

1 Dept. of Global Ecology, Carnegie Institution for Science, Stanford CA 94305 USA.

Background
Ocean acidification research has at least two related goals: To build mechanistic understanding of how the world works, and to provide useful information that can help people understand likely consequences of possible actions.

Findings
Ocean acidification research is now spreading out in spatial and temporal scales. One important line of research goes down in spatial scale from organism to molecule. Another line of research goes up in spatial scale, from organism to populations, communities, and ecosystems. Further, there is an important temporal dimension yielding investigations into issues related to acclimation, adaptation, and evolution.
These deeper kinds of research often require exponentially greater resources than do short-term examinations of small populations in laboratory aquaria. Unfortunately, funding for research is not expanding exponentially in parallel, and in some cases funding for ocean acidification research has diminished.

Conclusions
How can the research effort get exponentially more ambitious in its goals if the funding is not also increasing exponentially? Part of the answer involves in collaboration with people working in other disciplines. And part of the answer lies in recognizing that research is resource limited and not every experiment will be able to measure every desirable parameter or be able to control for every possible source of unexplained variation. Authors will need to be more forthright about study weaknesses. And if such studies are to be publishable, reviewers will need to focus a bit more on what is valuable and can be learned from a study, and be a bit more generous in understanding that not every study can be conducted as if we were living in an ideal world without resource constraints. And of course, part of the answer involves working to increase overall research budgets.
If ocean acidification research focuses on improving mechanistic understanding while seeking to provide policy makers and the public with actionable information, and the research community, through meetings such as this one, can work together towards common goals, ocean acidification research will play an increasing role in both research funding and policy decisions.

Plenary Session: Projections of the responses of living marine resources to carbon emissions

Chair: Alistair Hobday

Associate Professor William Cheung

Climate change and ocean acidification in a high CO2 world are challenging the conservation and sustainable management of living marine resources (LMR). Projecting the future marine ecosystems that are grounded by theories, observations and local knowledge has become an important decision support tool to inform mitigation and adaptation options for managing the ocean. This presentation aims to (1) review the existing projections of LMR and their implications for human societies under contrasting scenarios of carbon emissions in the 21st century, and (2) highlight major areas of development in scenario modelling that would improve their utilities in understanding the responses of natural and human systems to carbon emissions and in informing policies. These projections include global and regional changes in oceanographic drivers (temperature, oxygen, and pH), primary productivity, phenology, biogeography, life history traits, fisheries catches, revenues and rent. Particularly, these projections highlight areas, species and human communities that are most vulnerable to CO2 emission. Systematic exploration of uncertainty to examine confidence in LMR projections is being undertaken; current findings suggest that projected decreases in potential catches in tropical oceans and increases in the polar regions have relatively higher confidence than other regions, while the direction of changes in most mid-latitude (or temperate) and upwelling regions is more uncertain. Increasing focus is being put in quantifying the role of adaptation (natural and human), policy interventions and other human pressures (e.g., fishing, pollution) in moderating the risk of impacts on LMR from carbon emissions, as well as their cross-scale linkages and feedbacks. Given the Paris Agreement, projections of LMR and their linkages to other components of human and earth systems contribute to informing policy makers, stakeholders and the public about what the different pathways of the reaching agreed goal would mean for the oceans.

Plenary Session: Predicting evolution in marine microbes

Dr Sinead Collins

Institute of Evolutionary Biology, University of Edinburgh

How will marine microbes evolve in response environmental change? What information about extant populations and their environments can we use to predict how evolution could change primary production in the ocean (or lakes, or puddles, or even test tubes)? I will pull together microbial evolution experiments that deal with the roles of environmental predictability and variation, multiple drivers or environmental complexity, and phenotypic plasticity to map out where we are, and discuss where we need to go next to get to the point of predicting evolutionary change.

Plenary Session: Effects of multiple global and local drivers on marine species and ecosystems

Sam Dupont (1)

1 University of Gothenburg, Fiskebäckskil, 45178, Sweden

For decades, humans have caused local damage in many marine ecosystems by a variety of means including contamination by pollutants, over-fishing, physical destruction of the habitat etc. More recently, we realized that humans also had a global impact on the ocean. Global warming is leading to an increase of seawater temperature and the earth’s oceans are becoming more acidic as they draw rising levels of carbon dioxide (CO2) from the atmosphere, a phenomenon known as ocean acidification. In the future ocean, ocean acidification and global warming will operate in concert with other anthropogenic stressors and at present, very little is known about the potential interactions. This strongly limits our ability to make the needed large scale projections of the future human impacts on marine species, ecosystems and services.

New generation of experiments testing the impact of global changes on marine species and ecosystems tend to include more than one driver (e.g. ocean acidification and temperature). Some other key aspects such as the natural variability or the species niche only start to be considered. Current approaches throw up huge technical challenges and mainly involve constructing complex orthogonal multi-drivers experiments, which very quickly become impractical/ impossible with a moderate increase in the environmental complexity. Not only are the data produced often difficult to interpret or lead to apparent contradiction between studies (e.g. species specificity in response or different types of interactions for different combination of drivers) but there has been considerable criticism, particularly in the popular press, about the perceived use of suboptimal experimental design. Finally, it is also impossible to experimentally test all species and ecosystems including relevant environmental conditions (and their variability).

To be able to tackle the challenge of multiple drivers, it is then urgent to propose new scientific strategies. Combining literature review of existing data on mechanistic response to single and multiple stressors, established concepts in ecotoxicology with a theoretical approach (virtual species), I will explore and evaluate alternative experimental approaches.

Plenary Session: Predicting the future of coral reefs in a high-CO2 world

Katharina Fabricius

Australian Institute of Marine Science, Townsville, Qld 4810, Australia

Background
Tropical and subtropical coral reefs are the most biodiverse marine ecosystems on earth. Their future integrity, and that of the hundreds of thousands of species associated with coral reefs, depends on (1) the physiological capacity of these species to deal with ocean acidification (OA), and (2) the flow-on effects of the multitude of ecological changes likely to be caused by OA.

Methods
To date, most knowledge about ecological responses of reefs to OA has been derived from field studies around carbon dioxide seeps and from mesocosm experiments. I will (1) review some of the known and predicted principles about direct and indirect OA effects on coral reefs, (2) present new results from these studies, and (3) outline the most significant gaps in our knowledge.

Findings
Field and mesocosm studies have shown that ecological shifts from corals to seaweed, and increasing bioerosion, are only some of the many widespread consequences of OA. Data suggest that functional losses will progressively worsen with increasing levels of atmospheric CO2. Additionally, acclimatisation by corals to high CO2 is rarely observed today, and it has not occurred in the geological past. However, the OA effects on coral reefs are so complex that predicting the key functional bottlenecks in a high-CO2 world will remain a key challenge in the future.

Conclusions
More than 500 million people depend on healthy coral reefs for their livelihoods, as do many hundreds of thousands of marine species. OA will be irreversible on time scales of thousands of years, and is causing major upheaval for coral reefs. These facts alone make it a moral, ecological and economic imperative to restrict future increases in atmospheric CO2 beyond present day levels.

Plenary Session: Challenge of assessing and projecting ecological impacts

Kristy J. Kroeker

University of California Santa Cruz

CO2-driven changes in ocean chemistry and temperature will fundamentally affect organismal physiology, with potentially cascading effects on populations, communities and ecosystems. Interactions among the numerous abiotic and biotic factors that govern ecosystem dynamics, however, limits our ability to easily scale-up the results from studies on component parts of the system to make predictions about community dynamics and ecosystem functions in the future. For example, context is critical for forecasting the ecological effects of ocean change, and studies spanning a wide range of conditions are necessary to aid interpretation of global change experiments. Moreover, the effects of ocean change on individual species will be mediated by the interactions with other species in an ecosystem. Thus, studies are needed in diverse, functioning ecosystems that incorporate species interactions. Addressing the ecological effects of ocean change requires creative methods to study complex and dynamic multi-species assemblages in natural settings and incorporate critical interaction networks. Experimental and observational studies across natural gradients in environmental conditions, as well as mesocosm experiments, have provided important, initial forecasts of ecological changes associated with increased CO2 concentrations, although much is still unknown. Moving forward, the application of ecological theory in ocean change research is essential for guiding the necessary shift towards increasingly complex and nuanced ecological research.

Plenary Session: Challenge of deciphering information for the paleo record

Bärbel Hönisch

Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, 10964, USA

Global warming and ocean acidification are widely discussed to impact marine life, but evidence from laboratory experiments and observations of reduced calcification in modern and historic records is challenged by the short duration and limited complexity of experimental work, as well as potential preservation bias of original calcification signals. The geological record provides opportunities to study the long-term response of marine organisms to ocean acidification, warming and deoxygenation, in particular when supported by independent geochemical evidence. However, translating geochemical proxies to past environmental conditions requires sound knowledge of the elemental and isotopic composition of seawater, in addition to constraints on vital effects in proxy carrier organisms that may now be extinct. Furthermore, it is important to realize that for paleocean acidification to impact marine calcification, CO2 release must have been massive and rapid, but constraining the duration of such events in Earth distant history is fraught with uncertainty.

I will provide an overview of these challenges, using the Paleocene-Eocene Thermal Maximum as an example, but also raise questions about how well we understand fundamental proxy systematics, and the temptation to infer physiological processes from geochemical proxy relationships in foraminifers and corals.