DEFINING NUTRITIONAL BOTTLENECKS OF REEF CORAL GROWTH AND STRESS TOLERANCE

Among the most charismatic and diverse ecosystems on Earth, coral reefs sustain >25% of all marine biodiversity in only <1% of ocean surface area and the livelihoods of >0.5 billion people. Yet the habitat-building corals are acutely vulnerable to anthropogenic change. Best studied are the threats posed to coral reefs by ocean warming. Perturbations to the natural nutrient environment also represent an existential danger, but why is this the case? This question has old origins. More than 175 years after Charles Darwin's seminal observation, we still lack a convincing mechanistic explanation as to why reef corals thrive, sustaining exceptionally high rates of biological production, in nutrient-poor oceanic regions. The answer is certainly rooted in the symbiotic association between endocellular microalgae ("zooxanthellae") and the coral animal host but the physiological processes involved are far from understood. Recent field studies fundamentally contradict existing models for symbiosis functioning by suggesting that corals source most of their nutrients from the water column as dissolved inorganic nitrogen (DIN) and phosphorus (DIP) but there is no known mechanism for such a process in coral animals.

Our work (pilot study results herein) suggests that corals "graze" on their symbiont population, providing a novel mechanism for DIN and DIP transfer to the host. We propose to transform our understanding of nutrient cycling and symbiosis in corals worldwide by testing the grazing hypothesis in ten representative reef-building species.

We will: (i) Document DIN and DIP uptake and utilisation by symbiont-grazing through (15N) isotopic labelling and elemental analysis in controlled long-term experiments. ii) Quantify the efficiency of nutrient incorporation by symbiont-grazing versus zooplankton-feeding and compare the resulting effects on coral growth and stress tolerance. iii) Determine how present-day and projected future ocean temperature and pH influence the utilisation of dissolved inorganic nutrients and shape coral growth and symbiosis functioning.

We will also undertake a broad range of impact-promoting activities including a knowledge transfer workshop. For this event, we will bring stakeholders in coral reef management and policy development together with leading specialists in coral reef nutrient biology, spatial ecology and biogeochemical modelling to translate our findings into advice for policy makers and coral reef management.

The direct outcomes of the present project will be of prime interest for a large group of academic researchers and students both in the UK and globally.

Given the importance of coral reef ecosystems, the outcomes of the proposed research is of global significance for governmental policy makers and organisations involved in reef management and conservation.

Coral reefs have an iconic status among the general public, who are increasingly aware of their status among the biologically most diverse ecosystems and their importance for humanity. The concern about the potential loss of the reefs is correspondingly high.

We will engage with the relevant groups at different levels and through a range of customized activities to ensure an efficient knowledge transfer. We will achieve lasting impact through:

1) Publication of results in in top-rated scientific journals.

2) KnowledgeTransfer Workshop: We will organise a two day workshop with the aim to i) include the project findings in models at the reef ecosystem scale to analyse the influence of present day and future changes of the water chemistry, specifically the nutrient environment, and interacting heat stress on coral bleaching, mortality and recovery and to ii) translate the findings of the project and the workshop into advice for policy makers and coral reef managers.

We will achieve these aims through collaboration with influencial stakeholdes in the relevant areas who will be actively involved as project partners and supply large data sets, access to models and support the dissemination of the workshop outcomes in the form of at least one scientific publication and at least on policy report and reef manager's guide.

The underwriting project partners and attendants are:

-Dr. Mark Eakin (NOAA, USA)
-Dr. Assaf Zvulony (Israel Nature and Park Authority, Israel,)
-Prof. Jon Brodie (James Cook University, Australia)
-Prof. Bernhard Riegl (National Coral Reef Institute, NSU, USA)
-Prof. Elena Litchman (Michigan State University, USA)
-Dr. Gareth Williams (Bangor University, UK
-Dr. Karen Wild-Allen (CSIRO, Australia)

We plan to further maximise the reach and open the workshop to 10 additional attendants by acquiring funds for travel expenses and substistence of these delegates by applying for a Royal Society SciencePlus Meeting, a two-day meeting held at the Royal Society London.

3) Public outreach with a focus on schools and local UK organisations

4) Educational materials: We will produce an educational poster that gives a comprehensive overview of the nutrient cycling pathways within the coral - symbiont association, integrating our new concept of symbiovory in the existing model. We will also produce an educational short movie (5 min) for dissemination via YouTube that explains the mechanism of symbiovory and its implications for the functioning of coral reefs today and in the future.

5) A project specific webpage will be set up as a platform to explain the concept of symbiovory and disseminate the educational poster, policy brief, reef manager's guide and video.

6) Training: Opportunities for the PDRA for science communication training will be actively sought within the first 6 months of the project.

7) Communication with the general public: Our publications will be accompanied by press releases and associated outreach activities such as TV and radio interviews.

8) Public outreach articles will be published for instance in "Coral" , one of the most influential journals of marine aquarium / coral reef hobby, appearing in English, German, French, Italian, Polish and Russian language.

9) Continuous communications via our twitter account @theCoralReefLab.