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Early white paper draft version- October 2013 This preliminary draft is intended as a consultation document. Comments/edits welcome. Please do not use or cite.

Theme 7: Multiple stressors and ocean ecosystems Co-authors: Minhan Dai and Anja Engel

1. Brief statement defining the theme: Over the last century, the ocean ecosystems have been experiencing unprecedented changes driven by both natural and anthropogenic stressors such as temperature rising, eutrophication, deoxygenation/hypoxia, plastic litter and ocean acidification. Several of these stressors occur simultaneously and interact with each other, which presents an immense challenge to identify key stressors and combined effects on ocean biogeochemistry, air- sea interactions, as well as ecosystem functioning and services.

2. The scientific and societal basis justifying research on this issue. Why is it critical and why does it need to be done now? What is the end goal? Why is international coordination required? The ocean and its ecosystems provide a variety of valuable economic services to human society. Examples include supporting services of nutrient balance, hydrological balance, regulating services of pollutant attenuation and climate regulation and cultural services of science and education, recreational opportunities as well as food production. Theme 7 has thus a clear and direct relevance to the human society. Understanding how marine ecosystems respond to individual stressors and their combinations in the past, present and future is however scientifically challenging but essential in order to identify the associated ecological and economic implications of environmental changes, as well as to seek effective management strategies towards sustainability. Moreover, multiple changes in ecosystem structure, functioning and dynamics can be expected to differ from single stressor effects, and vary by region, and over time. International coordination is thus crucial in order to identify research priorities, evaluate and guide experimental and methodological approaches, and intercomparison of individual research results, and to translate scientific knowledge to support socioeconomic risk assessment and political decision making

The primary goal of theme 7 is to identify anthropogenic key stressors and to understand consequences of the simultaneous interaction of stressors resulting in multiple transitional ecosystem states and to significantly improve our predictive ability of the future marine ecosystem changes. In focus are the most vulnerable/hot, ecologically and economically important regions that currently experience unprecedented change (link to theme 8) such as human impacted coastal and marginal seas, large river delta systems, upwelling systems, and the pristine Polar Seas. The scientific challenge is to establish an ecosystem baseline, i.e. identify natural variability, to capture changes driven by anthropogenic stressors, and ultimately to provide a holistic view of multiple stressors interactions with respect to global and regional ecosystems. An FE related goal would be to estimate socioeconomic consequences of multiple stressors with respect to regional and global climate change, ocean productivity, ocean health and ecosystem services, and to transfer this knowledge to support policy and decision making.

3. Background – major scientific concepts, key prior work defining the issues: Human footprints have imbedded in and impacted on the ocean’s ecosystems on various ways and at different spatial-temporal scales (Fig. 1, Doney et al., 2010). Several key stressors can be identified: The progressive increase in atmospheric CO2 directly and indirectly affects the marine biosphere. Indirect effects are expected through global warming related rising of sea surface temperatures, which may cause increased surface ocean stratification and mixed layer insulation, thereby changing the dissolved oxygen content in seawater. Due to the rapid air-sea exchange of CO2, direct, and already determined, effects of increased atmospheric CO2 concentration are the rise of CO2 concentration in the surface ocean and a related shift in its chemical equilibrium (Chen and Millero 1979), including an unprecedented rapid decline in surface seawater pH, referred to as ocean acidification. Multiple effects of changes in pH, O2 and CO2 concentration are expected for plankton organisms, their physiological rates, species diversity, and population dynamics, in turn affecting the productivity and biogeochemical cycling of marine ecosystems (Gattuso and Hansson, 2011). Yet, mechanisms and

1 magnitude of biological and biogeochemical responses to environmental change in a “hot”, “sour” and “breathless” ocean are largely unknown. Another suites of stressors are primarily related to the nutrient influxes into the ocean through land-ocean (Cai et al., 2011) or air-sea interfaces (Kim et al., 2011). Accumulative and even excessive nutrients input into the ocean have clearly affected the coastal ecosystems, the similar signals of which have emerged in open waters. Since the middle of the last century, increasing global production of plastic material resulted in the accumulation of plastic litter in the ocean. Thereby, larger plastic litter mostly fragments over time to form a pool of microplastics (< 5 mm) together with primary plastic litter of micro-size. Microplastics can enter the food chain and affect the nutritional quality of marine products, particularly as they contain and adsorb toxins such as persistent organic polutants (POPs) (Hidalgo-Ruz et al. 2012).

We currently fail to understand how multiple stressors impact marine ecosystems and related biogeochemical processes, being themselves variable in time and space, primarily because we do not understand how marine ecosystems function. The number of studies addressing the ocean’s responses to environmental change has been vastly increasing over the past decades, yet the insight gained is relatively small. This is due to the complexity of the problem on the one hand, but also owing to a lack of coherent scientific approaches, resulting in the danger of global change research becoming ‘a Gordian Knot of disparate strands of data’ (Boyd, 2013) (Fig. 2). Moreover, there is a striking disparity between sound scientific knowledge and attempts/ needs to economically value the impact of multiple stressors on marine ecosystems.

(from Doney et al., 2010) Fig. 2 from Boyd, 2013, Nature Climate Change, 3, 530-533.

4. Approaches – what will it take to make substantive progress on the issue? What will be achieved in the 10 years of Future SOLAS? Theme 7 will expand the SOLAS theme of atmosphere-ocean interactions by emphasizing the effect of the human perturbation. SOLAS can improve and maximize the output of multiple stressor research by a series of actions. The primary aims would be to:  Gain coherence by i) stimulating the dialog between disciplines to identify the quality and quantity of observational data needed for regional and global physical-ecosystem coupled models and ii) set-up a frame for future sce- narios being tested (i.e. IPCC), iii) identify key regions  Improve quality by i) enforcing experimental and methodological standardization, ii) fostering intercomparison ex- ercises on disparate studies, iii) supporting capacity building  Enhance outreach of scientific results by i) promoting the assimilation of empirical and observational-based knowledge in Earth System Models, economic models, impact assessments, and policy frameworks, ii) foster in- formation exchange with FE, policy makers, stakeholders etc…

5. Community readiness – is there an existing community engaged on this issue? Are there institutional or other barriers to progress? Is infrastructure or human capacity building required in order to achieve the goals? 6. External connections – what partnerships are required in order to achieve the goals? What mechanisms will be used to accomplish the interactions? There is quite consensus in the scientific community that the ocean ecosystem is changing under multiple stressors. Such a consensus is at least partially attributable to the fast growing community in ocean acidification research. As a result, the Ocean Acidification Working Group jointly sponsored by SOLAS and IMBER has fostered a new initiative, the Ocean Acidification International Coordination Centre (OA-ICC) presently operated by the IAEA Environment Laboratories in Monaco. Given the magnitude of the problems and the complexity of the largely unknown future changes that the ocean ecosystem is facing requires international coordination more than the researches of ocean acidification. Partner coordination with OA-ICC would however be very beneficial in progressing the present multiple stressor theme.

3 7. Sustainability – articulate relationship (if any) between this project and the FE goals of Global Development and Transformation Towards Sustainability. The ocean ecosystem and multiple stressors is clearly a direct and complex issue of sustainability, which shall be an obvious goal of the FE.

References: Boyd, Philip W. "Framing biological responses to a changing ocean." Nature Climate Change 3.6 (2013): 530- 533. Cai, W.-J., X. Hu, W.-J. Huang, M.C. Murrell, J.C. Lehrter, S.E. Lohrenz, W.-C. Chou, W. Zhai, J.T. Hollibaugh, Y. Wang, P. Zhao, X. Guo, K. Gundersen, M. H. Dai, and G.-C. Gong (2011), Acidification of subsurface coastal waters enhanced by eutrophication, Nature Geoscience, 4 (11), 766-770. Chen, G.-T. and Millero, F.J. (1979). Gradual increase of oceanic CO2. Nature 277, 205-206. Doney, Scott C. "The growing human footprint on coastal and open-ocean biogeochemistry." Science 328.5985 (2010): 1512-1516. Gattuso J.-P. & Hansson L. (Eds.), 2011. Ocean acidification, 326 p. Oxford: Oxford University Press. Hidalgo-Ruz, Valeria, et al. "Microplastics in the marine environment: a review of the methods used for identification and quantification." Environmental science & technology 46.6 (2012): 3060-3075 Kim, Tae-Wook, et al. "Increasing N abundance in the northwestern Pacific Ocean due to atmospheric nitrogen deposition." Science 334.6055 (2011): 505-509.