Optimising island-scale biological buffering of ocean acidification

Chair: Jessica Ericson

Mathieu Mongin(1*), Mark E. Baird(1), Scott Hadley, (1), , Andrew Lenton(1),

1CSIRO Oceans and Atmosphere Flagship, Hobart, Australia

Abstract
The equilibration of rising CO2 between the atmosphere and the ocean is lowering pH in the tropical waters by about 0.01 every decade. Coral reefs and the ecosystems they support are regarded as one of the most vulnerable ecosystems to ocean acidification, threatening their long-term viability. In response to this threat, different strategies for buffering the impact of ocean acidification have been proposed. As the pH experienced by individual corals on a natural reef system depends on many processes over different time scales, the efficacy of these buffering strategies remains largely unknown. Here we assess the feasibility and potential efficacy of reef-scale biological buffering, through the addition of seaweed farms within the Great Barrier Reef (GBR) at the Heron Island. First, using diagnostic time-dependent age tracers in a hydrodynamic model, we determine the optimal location and size of the seaweed farms. Secondly, we analytically calculate the optimal density of the seaweed and harvesting strategy, finding, for the seaweed growth parameters used, a mean biomass of 42 g N m−2 with a harvesting rate of up 3.2 g N m−2 d−1 maximises the carbon sequestration and removal. Numerical experiments show that the optimally-sized (1.9 km2) and optimally-harvested (removing biomass above 42 g N m−2 every 7 days) seaweed farm increased aragonite saturation by 0.1 over 24 km2 of the Heron Island reef. The most effective seaweed farm can only delay the impacts of global ocean acidification at the reef scale by 7-21 years, depending on future global carbon emissions. Our results highlight that large seaweed farms will be required to locally mitigate ocean acidification in natural reef environments.

Using physiology to optimise water quality and the sustainability of intensive recirculating aquaculture systems (RAS)

Chair: Tommy Moore

R.P.Ellis (1), Mauricio A. Urbina (1,2), D. Phillips (3), R.W.Wilson (1)
1 Department of Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
2 Departamento de Zoología, Facultad de Ciencias Naturales y Oceanográficas, Universidad de Concepción, Casilla 160-C,
Concepción, Chile
3 Anglesey Aquaculture Ltd, Black Point, Beaumaris, LL58 8RR, United Kingdom

Background
Aquaculture is one of the fastest growing food production sectors globally. It now provides more fish for human consumption than wild-capture fisheries, offering the only foreseeable way to increase production in the face of human population growth. Understanding the threat climate change poses to this sector is therefore of vital socioeconomic importance. Traditionally aquaculture practices adopt an open, natural water flow-through system for fish production; with little environmental control these are particularly vulnerable to shifting climatic conditions. Recirculating aquaculture systems (RAS) are an alternative solution, minimising water use and environmental impacts, thus improving sustainability of intensive fish protein production. However, using RAS also produces unique water chemistry issues; specifically very high CO 2 levels and raised carbonate alkalinity. Understanding the challenges facing the organisms produced under these conditions is therefore a priority.

Methods
Working with 5 industry partners, covering a range of farming practices from open systems to RAS, we investigated the carbonate chemistry conditions experienced in situ over an annual cycle. We then investigated the impact of the unprecedented carbonate chemistry within RAS on the physiology, growth and health of a farmed species, the European sea bass.

Findings
Within each setting investigated, organisms are exposed to carbonate chemistry conditions that exceed traditional end of century high CO 2 projections. Furthermore, within RAS these conditions are unprecedented with respect to natural carbonate perturbations. Despite this the physiological tolerance of sea bass to such perturbation ensures RAS production remains viable commercially.

Conclusions
Understanding the carbonate conditions experienced within a range of UK aquaculture settings presently will help predict the impact of climate change for this sector. Furthermore, by working together it is clear aquaculture practitioners and researchers can improve the productivity and viability of RAS aquaculture, alongside improving understanding of the physiological tolerances of aquaculture species exposed to extreme high CO2 perturbations.

The Pacific Partnership on Ocean Acidification

Chair: Jessica Ericson

Dr. Tommy S. Moore (1)

1 Secretariat of the Pacific Regional Environment Programme, Apia, Samoa

Background
Ocean acidification will have significant detrimental impacts on the environment (ecosystem services provided by areas vulnerable to OA such as coral reefs and associated fisheries), and the economic sectors of fisheries (directly through impacts on fish behaviour and indirectly on loss of critical habitat), and tourism (degradation of coral reefs and coastal ecosystems), and importantly, community and infrastructure resilience to disasters (degradation of natural coastal barriers to climate hazards). The Pacific ocean region, and the small island developing states (SIDS) therein, are particularly vulnerable to these impacts due to their heavy reliance on fisheries for food security, their high economic dependence on the fisheries and tourism sectors, and vulnerability to climate related disasters. With the support of the New Zealand Ministry of Foreign Affairs and Trade (MFAT) the Pacific Islands Ocean Acidification Partnership is working to build ecosystem and social resilience to ocean acidification by reducing local stressors on the marine environment.

Methods
Implementation of practical adaptation actions at selected pilot sites.

Findings
None to date, the project has just begun.

Conclusions
Globally, ocean acidification can only be addressed by reducing CO 2 emissions. Locally, social and ecosystem resilience to ocean acidification can be achieved by reducing other local stressors such as pollution and overfishing.

Sensitivity of cultured larval mussels (Perna canaliculus) to seawater aragonite saturation state

Chair: Tommy Moore

Norman L. C. Ragg (1), Ellie Watts (1), Samantha Gale (1), Le Viet Dung (1,3), Zoë Hilton (1), Nikki Hawes (2), Jolene Taylor (1), Tim Young (3), Jess Ericson (4), Bridget Finnie (4), Gretchen Hofmann (5), Caitlin Fielder (1), Carol Peychers (1), Hannah Mae (1), Graeme Covell (1), Nick King (1)

1 Cawthron Institute, Nelson 7010, New Zealand
2 SPATNZ, Nelson 7047, New Zealand
3 Auckland University of Technology, Auckland 1010, New Zealand
4 Kono Seafoods, Nelson 7010, New Zealand
5 University of California, Santa Barbara CA 93106, USA

The Greenshell mussel, Perna canaliculus, represents a key component of the benthic ecosystem and supports New Zealand’s largest aquaculture industry. This study explores the effects of aragonite saturation (ΩA) manipulation upon embryogenesis and larval performance of P. canaliculus, providing an indication of the extent to which commercial hatchery water could be modified to enhance production and a preliminary indication of vulnerability to ocean acidification (OA).
Commercial ‘Incubation’ and ‘Larval Rearing’ phases were examined separately. The 48h ‘Incubation’ uses static seawater containing 4µM EDTA, allowing fertilized eggs to undergo embryogenesis and form the first prodissoconch shell. ‘Larval Rearing’ supports development of grazing veligers through to metamorphosis. In Incubation, sodium carbonate enrichment created ΩA environments of 2.7, 4.8 and ~7 (pHT8.0, 8.2 and >8.5), while elevated pCO2 simulated extreme OA conditions of ΩA0.7 and 0.5 (pHT7.4, 7.3). Performance during 48h Incubation was compared to controls (ΩA1.6, pHT7.8; n=3); all veligers produced were then raised under common conditions to establish carry-over effects. The Larval Rearing trial subjected naïve veligers to ΩA similar to those described above for 18d (n=6).
Incubation survival was unaffected by ΩA (~75%); however development was severely arrested in under-saturated ΩA treatments, with mussels failing to advance beyond trochophore stage at ΩA0.5 or forming misshapen, under-size veligers at ΩA0.7, ultimately resulting in 100% mortality. Enriching to ΩA4.8 increased baseline veliger, and ultimately metamorphosing pediveliger, yield by 13%.
Veligers exposed to under-saturated ΩA experienced ~25% reduction in shell growth, resulting in 4.7% net pediveliger yield, compared to 15.3% in control seawater. Elevating ΩA had no apparent effect on veligers and no consistent carry-over effects were observed in settled juveniles.
Embryo and trochophore stages are ultimately killed by extreme OA and, reciprocally, respond positively to enhanced ΩA, whereas larger veligers appear remarkably resilient, showing only minor growth responses.

Options for Adapting to ocean acidification: U.S. Perspective

Chair: Jessica Ericson

Jewett, Elizabeth B.
National Oceanic and Atmospheric Administration
Ocean Acidification Program

Given that carbon dioxide levels in the atmosphere will likely not start dropping for decades, it is imperative that state and federal coastal resource managers develop strategies for coping with increasingly corrosive waters as marine ecosystems are compromised. These options are currently limited but might be expanded with concerted effort as the science develops. The current options range from devising biological methods to extract excess carbon dioxide from waters (planting seaweeds, seagrasses or other primary producers) to reducing nutrient enrichment which fosters high levels of biological respiration, leading to low oxygen and additional carbon dioxide, to enhancing other aspects of water quality under local control in an effort to build overall system resilience. NOAA is considering how to support novel adaptation strategies in light of rapidly evolving scientific understanding of biological responses. Monitoring and, eventually, forecasting the changing chemistry and related biological impacts are also important components for developing an appropriate response. This session will describe the range of adaptation options being considered and tested in the U.S. and globally.

Relative potential impacts of local and global CO2 release: comparison of natural variability and trends to Carbon Capture and Storage (CCS) risk for Bass Strait, Australia

Chair: Zoë Hilton

Nick Hardman-Mountford(1), Jim Greenwood(1), Bronte Tilbrook(
2)

1 CSIRO Oceans & Atmosphere, Floreat, WA 6913, Australia
2 CSIRO Oceans & Atmosphere, Hobart, TAS 7001, Australia

Background
The rise in atmospheric CO2 levels since the preindustrial era has increased the concentration of carbon dioxide and pH of surface ocean waters beyond the envelope of documented changes over 10s of millions of years. Coastal regions are home to many calcifying organisms, including those with significant commercial importance. Their carbonate chemistry and resident populations experience wider ranges of variability than are typical for open ocean environments. Quantifying this range of variability is vital for assessing potential impacts of such ocean acidification on these populations.
Subsea geological storage of CO2 is a proposed mitigation strategy for industrial CO2 emissions. Geological containment structures are recognised as being highly secure gas stores. Nonetheless, assessments of possible leak scenarios are required to provide public and regulatory confidence in the approach.

Methods
Here we describe seasonal and interannual variability in the carbonate system of Bass Strait using a time series of carbonate-system variables collected by a ship-of-opportunity. This variability is contrasted with modelling results describing putative leak scenarios from stored CO2 reservoirs or pipelines into Bass Strait waters.

Findings
The range of seasonal variability in pH is of the order of changes in ocean pH over the past 200 years. Hence, organisms are now likely to be experiencing CO2 conditions that remain outside their pre-industrial seasonal range for most of the year. This could have severe implications for the highly biodiverse marine ecosystem of Bass Strait and particularly for the high-value shellfish industry in this region. In contrast, potential changes in pH from CCS-related CO2 leakage would be highly localised and, in most cases, unlikely to exceed the range of natural seasonal variability.

Conclusions
We conclude that subsea geological storage of CO2 may be an effective method of mitigating industrial CO2 emissions and the global impacts of ocean acidification on coastal ecosystems.

The efficacy and impacts of large-scale ocean alkalinity injection

Chair: Jessica Ericson

Andrew Lenton (1), David Keller (2), Viviane Scott (3), Naomi Vaughan (3)
1 CSIRO Oceans and Atmosphere, Hobart, Australia
2 GEOMAR, Helmholtz Centre for Ocean Research, Kiel, Germany
3 University of Edinburgh, School of Geosciences, Edinburgh, UK
4 University of East Anglia, Tyndall Centre for Climate Change Research, Norwich, UK

Background
Ocean alkalinity addition has been proposed as technique to both buffer ocean acidification and enhance oceanic carbon uptake. While limited modelling studies to date have suggested that ocean alkalinity injection may play a role in mitigating ocean acidification, it is recognised that any large-scale Climate Intervention will likely impact the ecosystem services (e.g. food production) provided by the ocean, there will certainly be positive and negative effects on human societies, and on their responses and strategies for adaptation to a changing climate. In this context there is an identified need for ongoing research to explore the short and longer-term impacts of ocean alkalinity injection.

Methods
Here we present simulations of the oceanic response to ocean alkalinity from the Carbon Dioxide Removal Model Intercomparison Project (CDRMIP). This involves injecting large amounts of alkalinity into the upper ocean, in conjunction with RCP 8.5, in the period 2020-2100. This allows the efficacy of ocean alkalinity injection to be quantified and the biogeochemical response to this injection to be explored. CDRMIP is made up of a suite of earth system and intermediate complexity models.

Findings
We discuss and quantify the degree to which CDR could help mitigate ocean acidification or reverse its effect, and discuss the potential effectiveness and risks/benefits of different ocean alkalinity injection proposals. We also explore the impact of cessation of alkalinity injection and quantify the time-scales associated with this.

Conclusions
This work provides key insights into the potential of this technique to offset ocean acidification, and identifies where future efforts should be directed. It also highlights that alkalinity injection will likely result in areas of potential negative impact on the marine ecosystem. This work does not consider important issues such as how alkalizing substances could be mined, processed, transported, and delivered to the ocean in a form that would easily dissolve and enhance alkalinity.

Increased Mortality, Organ Damage and Variable Expression of Alleles in Yellowfin Tuna Larvae under ocean acidification

Chair: Tommy Moore

Jane Wiliamson (1)*, Don Bromhead (2), Andrea Frommel (3), Michael Gillings (1), Jon Havenhand (3), Simon Hoyle (2), Tatiana Ilyina (4), Patrick Lehodey (5), Cleridy Lennert-Cody (6), Daniel Marguiles (6), Simon Nicol (2), Vernon Scholey (6), Maria Stein (6), Liette Vandine (1), Jeanne Wexler (6)

1 Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
2 Secretariat of the Pacific Community, BP D5 Noumea, New Caledonia
3 Department of Marine Science, Tjärnö, University of Gothenburg, 45296, Sweden
4 Max Planck Institute for Meteorology, Bundesstr. 53, D-20146 Hamburg, Germany
5 Collecte Localisation Satellites, Space Oceanography Division, 31520 Ramonville Saint-Agne, France
6 Inter-American Tropical Tuna Commission, 8901 La Jolla Shores Drive, La Jolla, CA 92037-1509 USA

Background
The majority of ocean acidification (OA) studies involving fish have focused on survival, growth and behavioural responses in coastal or reef species. OA can affect these fishes by disrupting physiological processes, and impairing neurological and behavioural responses. It is not known if OA will have similar impacts on pelagic predators inhabiting the open ocean. Yellowfin Tuna, Thunnus albacares, are widely dispersed top predators in pelagic ecosystems. In the Pacific Ocean, they form the basis of one of the largest and most valuable fisheries globally. This research assesses the impact of OA on survival, organ damage and differential gene expression on eggs and larvae of Yellowfin Tuna.

Methods
Experiments were done at the Inter-American Tropical Tuna Commission’s tuna breeding hatchery in Panama. Eggs and larvae were exposed to levels of OA projected to occur in their spawning habitat in near and far future IPCC scenarios. Survival of individuals, along with their morphometric data, was assessed throughout the experiment. Samples were also assessed for vial organ development and for genetic analysis.

Findings
We found lowered rates of survival and larval growth at greater levels of OA, which correlated closely with histological observations of progressive degradation of vital organs. Using genetic techniques we also showed variable expression of alleles in several of the 8 optimised loci that corresponded to increases in OA. These may indicate rapid selection of OA-tolerant individuals.

Conclusions
Substantial changes occurred in the early life history stages of yellowfin tuna in response to OA in our laboratory experiment. While it should be noted that this was an exploratory experiment looking at a small part of the life history of a longer-lived organism, our results show that OA does have the potential to impact on pelagic predators such as tuna.

Governing ocean acidification: Evaluating the international policy response

Chair: Zoë Hilton

Ellycia Harrould-Kolieb (1)

1
University of Melbourne, Melbourne, VIC, 3010, Australia

Background
Ocean acidification poses a substantial threat to the ocean, marine wildlife and the goods and services they provide and as a result presents a great regulatory challenge at the international, regional, national and sub-national levels. In the international space ocean acidification is of relevance to many treaties and yet, does not fall neatly within the mandate of any. As a result, ocean acidification is not currently addressed by any international instrument or stand-alone agreement, nor does there appear to be any coherent regulatory framework for responding to this issue. Despite this, there are a number of international institutions, including treaty bodies and specialised UN agencies that have expressed an interest in ocean acidification and have begun to initiate an array of relevant activities.

Methods
Via an analysis of over 600 primary documents this research offers a review of the ocean acidification activities undertaken by international institutions and evaluates whether, when combined, they provide an adequate policy framework able to respond to ocean acidification.

Findings
This research finds that over 30 international institutions have initiated activities around ocean acidification in the past decade. These activities can be grouped into four main categories: minimal engagement, political engagement, knowledge production and substantive activities. Within the current policy landscape very few institutions are actively engaged in activities that could be defined as substantive, such as rule-making and implementation mechanisms. In addition, those that are largely focus on activities, that while important, are secondary to the primary need to reduce carbon dioxide emissions.

Conclusions
This research concludes that there are substantial gaps in the international governance of ocean acidification and that despite a wide array of interest in the issue the current policy responses are unlikely to form an adequate policy framework for responding to ocean acidification.

From larval performance to socio-economy: an integrative ecophysiological study on ocean acidification and warming effects in gadoid fish

Chair: Tommy Moore

Felix C Mark (1)*, Christian Bock (1), Christopher Bridges (2), Catriona Clemmesen (3), Flemming Dahlke (1), Stephan Frickenhaus (1), Gwendolin Göttler (2), Stefan Gößling-Reisemann (4), Christoph Held (1), Rainer Knust (1), Stefan Koenigstein (4), Kristina Kunz (1), Elettra Leo (1), Silke Lischka (3), Magnus Lucassen (1), Barbara Niehoff (1), Hans-O. Pörtner (1), Martin Quaas (5), Franz-Josef Sartoris (1), Matthias Schmidt (1), Daniela Storch (1), Henrieke Tonkes (1), Rüdiger Voss (5), Heidrun Windisch (2)

1 Alfred Wegener Institute, Bremerhaven, D-27570, Germany
2 Heinrich-Heine-Universität, Düsseldorf, D-40225, Germany
3 GEOMAR, Kiel, D-24148, Germany
4 Universität Bremen, Bremen, D-28359, Germany
5 Christian-Albrechts-Universität, Kiel, D-24188, Germany

Background
As the oceans are warming, fish stocks are moving with the water masses of their preferred temperatures to stay within a physiologically optimal temperature range, provided further factors such as food availability and competition with other species allow for that. In response to this warming trend, the North Arctic stock of Atlantic cod (Gadus morhua) has also shifted spawning areas to the north and expanded its range into the Barents Sea. For the greatest part of the year, juvenile Atlantic cod are now frequently found in the coastal waters of Spitsbergen, with an as yet unclear outcome for the ecosystems species composition. Ocean acidification is an additional stressor developing in parallel to ongoing climate warming. Future impacts of ocean acidification on organisms and ecosystems are expected to be greatest in cold regions, while thermal tolerance windows are narrower and thus sensitivities to combined stressor effects are likely to be higher in cold-adapted polar compared to temperate species. The expected rise in carbon dioxide concentrations and temperature in the oceans may thus prove to be particularly threatening to Boreal and Arctic ecosystems.
Some of the commercially most important fish species in the North Atlantic belong to the family of Gadidae, namely Atlantic cod, haddock, pollock, whiting, and Polar cod. Any shift in the population structure, caused by ocean acidification and warming (OAW) could thus have far reaching effects not only on the ecosystem itself but also on fisheries, and further, on aquaculture. The socio–economic consequences of such scenarios have not yet been evaluated.

Methods
Within the German ocean acidification research programme BIOACID in its second phase from 2012-2015, we investigated how the combined effects of OAW affect different life stages and interactions between polar gadoid fish species and their prey.
Objectives included addressing the question whether OAW affects interacting species differently due to divergent physiological optima and ranges, expressed in thermal tolerance windows and associated performance capacities and phenologies of specific life stages.

Findings
I will report an overview of our collective efforts to identify fundamental mechanisms and unravel the connections between levels of biological organisation, from the genomic, molecular to cellular, individual and population level. Scopes for acclimation (physiology and behaviour) and adaptation (evolution) that together define species resilience were studied in various life stages (eggs, larvae, juveniles, adults) to identify the most sensitive one(s). We fed these data into socio-economic models to assess stock sensitivity and resilience to evaluate the possible consequences for fishery, aquaculture and last but not least, society.