Objective: to determine the ecological effects of elevated CO2 levels in coastal habitats. In an 8 month training period at CNRS Roscoff and the MBA Plymouth the student will monitor variations in carbonate chemistry and biota of rockpool habitats. The student will be trained by a supervisory team that is world-leading in ecosystem based ocean acidification research using natural analogues. The student will then apply these skills to monitor spatial and temporal variability in pH (Total Scale) and seawater carbonate chemistry (DIC and total alkalinity) on coastal habitats off Pantelleria and Vulcano (Sicily) where gas vents are shallow (<10 m depth) and have shorelines with mean pCO2 levels of 380, 1000 and 2000 ppm, similar to those recently described in Nature by the PI off Ischia. These gas vent sites have been chosen carefully and are suited to test the following hypotheses; 1) near-future levels of ocean acidification (year 2100 scenarios) may enhance the growth and reproduction of sea grasses and certain invasive macroalgae in natural settings, 2) chronic hypercapnia can lead to an overall reduction in benthic biodiversity, including the loss of numerous calcified species, with negative effects on ecosystem function in intertidal and subtidal habitats, 3) transplant experiments, coupled with sampling along pCO2 gradients, confirm that some species can adapt to long-term acidification by altering skeletal mineralogy, 4) active metazoans (e.g. shrimp and fish) can withstand high levels of CO2 as adults but do not complete their life-histories at naturally acidified sites. This approach is innovative as ecosystem effects are difficult to assess using methods adopted by the BIOACID and EPOCA programmes, whereby CO2 levels are manipulated in aquaria and mesocosms over timescales of weeks-months. This studentship is designed to meet the UK OA Science Plan which states that 'Powerful insights may also be gained from studies of areas with natural CO2 enrichment'. The studentship addresses Aims 3.1, 3.3 and will also obtain data to improve our understanding of OA impacts for commercially important species. The lead supervisor is a PI within the EPOCA program and co-author of their 'Guide to Best Practices in Ocean Acidification Research' which will be the methodological basis of this studentship. Comparisons will be made of benthic biodiversity and biomass on replicate plots from 380 to mean 1000 and 2000 ppm CO2 using hand-held cores in sediments (e.g. for foraminifera) and 0.5 m2 quadrats on rock. Settlement plates will be deployed to investigate recruitment processes at different levels of pCO2 and transplant experiments (of coralline algae, mussels and oysters) will be used to determine the effects of long-term exposures to high CO2 levels on calcification, fecundity and growth. Photosynthesis (using PAM), reproduction and growth will be measured on seagrass (Posidonia) and macroalgae (Sargassum, Asparagopsis). The student will examine whether calcified algae, foraminifera and corals can adapt their mineralogy depending on the amounts of CO2 in the surrounding seawater under supervision in Bijma's BIOACID group using Atomic force- and Raman-microscopy to study the impact on the fine- and ultra-structure of calcified organisms that grew at high CO2. During field excursions in 2012 repeated visual counts will be used to assess the diversity, behavior and abundance of shrimps and fish recording the distribution of gravid females and fish nests in relation to CO2 monitoring zones, as juvenile stages can be the most vulnerable to OA effects. The range of hypotheses to be tested are not too ambitions for doctoral research, given our supervisory track-record, preliminary surveys of Vulcano and Pantelleria and our experience at Ischia.

Quantitative prediction of future sea level is currently impossible because we lack an understanding of how the mass balance of the Earth's great ice sheets can be affected by climate change. Chief among the uncertainties are how changes in ocean circulation and/or temperature will influence the thickness and extent of the ice shelves and how the outflow from the ice sheet will change in response. Observations of the ocean under ice shelves are very sparse and difficult to obtain. Hence, numerical modelling has been used to provide insight into the structure and dynamics of the ocean flow in ice shelf cavities, as well as their influence on the larger scale. However, the complexities associated with this application means that models based upon hydrostatic dynamics, uniform mesh resolution and a layered structure in the vertical, may be improved upon. These complexities include the presence of a grounding line where the water column depth goes to zero under ice deep below mean sea level. The importance of this very limited region to the ice shelf above, and the associated grounded ice sheet, is massive but this is exactly the point where conventional models need to make the largest compromises in representing the real world. Also, the shape of the base of the ice shelf, and the steep change at the front between the ice and the open ocean, place important constraints on the ocean dynamics and hence they need to be represented well in a model in a similar manner to sea floor bathymetry. This, along with the representation of critical buoyancy driven processes that may be of small scale, points towards the use of non-uniform resolution in both the horizontal and vertical directions. In this project we will adapt our state-of-the-art numerical model to study the ocean circulation in the cavities beneath floating ice shelves. Unstructured and anisotropic dynamically-adaptive mesh methods in three dimensions will allow simulations with a resolution and geometric flexibility that is greater than has been possible before. Model developments will be benchmarked against earlier model results and validated on a hierarchy of test problems. Real world applications under the Filchner-Ronne and Pine Island Glacier ice shelves will be used to calibrate and validate the model against observational (including new Autosub) data. Highly timely new science will be preformed in these areas, and this project will also be an important step towards the inclusion of ice shelf cavities in global scale ocean models of the future. The final result will be an improved understanding of the physical processes occurring under ice shelves, and a powerful tool that will enable the explicit inclusion of ice shelves in global scale ocean and climate models of the future. This project fits well with NERC strategy. In particular the prediction of the future contribution of the ice sheets to sea level rise is seen as a high priority goal that cuts across the themes of Climate Systems, Earth System Science and Natural Hazards. Development of the next generation climate models is also a priority for the Climate Systems and Technologies themes.

Global warming is rapidly altering ocean temperature, pH, carbon saturation state, circulation, and oxidation state, and this will impact the community composition of phytoplankton; the primary producers in the world's oceans. Predicting which marine phytoplankton species will persist and dominate under these changing environmental conditions requires an understanding of the adaptive evolutionary potential of these species. With this project, we will improve understanding and predictive capability of the dynamics of polar marine phytoplankton communities, especially diatoms, and the limits of their adaptive capacities in response to environmental change driven by global warming. As single-celled microbes with large population sizes and high replication rates, phytoplankton species have considerable potential to adapt rapidly to changing environmental conditions. This can happen by (i) individual organisms adapting their phenotypes through epigenetic processes (i.e. phenotypic plasticity), (ii) by natural selection acting on individual genotypes, and by (iii) group selection (i.e. lineage and species-sorting). These three fundamental levels of selection result in changes in physiology, population genetic composition and community structure, respectively, which in turn can drive changes in both biogeochemical cycles and higher trophic levels. These adaptive changes already occur in the Arctic Ocean, yet existing climate models fail to capture these combined ecological and evolutionary adaptive responses. This proposal aims to address this fundamental gap in knowledge by studying adaptive evolution at the level of the genome, epigenome and transcriptome of a model species for polar diatoms, Fragilariopsis cylindrus, as well as 10 diatom species from the Arctic Ocean. We will thus address how environmental changes such as the loss of sea ice in the Arctic Ocean will impact the adaptive evolution and diversity of key primary producers with consequences for biogeochemical cycles in an ecosystem that is under extreme threat by global warming.

Following the polar amplification of global warming in recent decades, we have witnessed unprecedented changes in the coverage and seasonality of Arctic sea ice, enhanced freshwater storage within the Arctic seas, and greater nutrient demand from pelagic primary producers as the annual duration of open-ocean increases. These processes have the potential to change the phenology, species composition, productivity, and nutritional value of Arctic sea ice algal blooms, with far-reaching implications for trophic functioning and carbon cycling in the marine system. As the environmental conditions of the Arctic continue to change, the habitat for ice algae will become increasingly disrupted. Ice algal blooms, which are predominantly species of diatom, provide a concentrated food source for aquatic grazers while phytoplankton growth in the water column is limited, and can contribute up to half of annual Arctic marine primary production. Conventionally ice algae have been studied as a single community, without discriminating between individual species. However, the composition of species can vary widely between regions, and over the course of the spring, as a function of local environmental forcing. Consequently, current approaches for estimating Arctic-wide marine productivity and predicting the impact of climate warming on ice algal communities are likely inaccurate because they overlook the autecological (species-specific) responses of sea ice algae to changing ice habitat conditions. Diatom-ARCTIC will mark a new chapter in the study of sea ice algae and their production in the Arctic. Our project goes beyond others by integrating the results derived from field observations of community composition, and innovative laboratory experiments targeted at single-species of ice algae, directly into a predictive biogeochemical model. The use of a Remotely-Operated Vehicle during in situ field sampling gives us a unique opportunity to examine the spatio-temporal environmental controls on algal speciation in natural sea ice. Diatom-ARCTIC field observations will steer laboratory experiments to identify photophysiological responses of individual diatom species over a range of key growth conditions: light, salinity and nutrient availability. Additional experiments will characterise algal lipid composition as a function of growth conditions - quantifying food resource quality as a function of species composition. Furthermore, novel analytical tools, such as gas chromatography mass spectrometry and compound specific isotope analysis will be combined to better catalogue the types of lipid present in ice algae. Field and laboratory results will then be incorporated into the state-of-the-art BFM-SI biogeochemical model for ice algae, to enable accurate simulations of gross and net production in sea ice based on directly observed autecological responses. The model will be used to characterise algal productivity in different sea ice growth habitats present in the contemporary Arctic. By applying future climate scenarios to the model, we will also forecast ice algal productivity over the coming decades as sea ice habitats transform in an evolving Arctic. Our project targets a major research gap in Phase I of the CAO programme: the specific contribution of sea ice habitats to ecosystem structure and biogeochemical functioning within the Arctic Ocean. In doing so, Diatom-ARCTIC brings together and links the activities of ARCTIC-Prize and DIAPOD, while further building new collaborations between UK and German partners leading up to the 2019/20 MOSAiC campaign.

The study of past climate change, especially that which has occurred since the end of the last ice age about 11,000 years ago (the period known as The Holocene), provides important insights into how climate may change in the future and the influence of changes in ocean circulation and air masses. It also improves the ability of climate scientists to predict the scale and rapidity of future climate change and recognise the urgency to respond. Climate records collected at weather stations do not extend back long enough in time to capture the full extent of natural climate variability needed to be able to predict future climate change. However, it is possible to reconstruct past climate over thousands of years by studying the remains of plants and animals preserved in the mud that accumulates at the bottom of lakes. Diatoms, freshwater microscopic algae, and the larvae of non-biting midges (chironomids) respond in characteristic ways depending on summer temperatures or the relative acidity (pH) or amount of nutrients in the lake water. By finding out which temperatures, pH or nutrient concentrations are favoured by particular species of diatoms or chironomids today we can reconstruct quantitatively past environmental conditions from the semi-fossilised remains of these creatures, which are preserved in lake sediments. Thus analysis of a sediment core several metres long taken from a lake can be sliced at intervals of 1 cm or less and dated using radiocarbon to provide a highly detailed record of past climate change over thousands of years. In this project we propose to analyse midges and diatoms from three cores previously collected from Kamchatka in the far east of Russia. Kamchatka is a key region for understanding the extent of climate linkages between the North Atlantic and North Pacific regions, and hence some of the most important ways in which global climate change is driven. However, climate variability during the Holocene in this region is poorly understood as only a few studies have been completed. We will analyse midges from our three sediment cores over most of the Holocene at intervals of 40-80 years. We will use a 'midge thermometer' developed from modern distribution records of midges from throughout northern Russia, to reconstruct Holocene summer air temperatures. We will also use these midge records to reconstruct past changes in continentality or conversely oceanicity. A continental climate is governed by the relative influence of westerly winds blowing across northern Eurasia, which brings cold winters, short warm summers and less rainfall, whereas a more oceanic climate is influenced by Pacific winds which bring milder winters, cooler summers and more rain. Similarly, we will use diatoms from the same cores to quantify changes in the length of the summer and also any changes in pH or nutrients. An innovative aspect of this project will be to analyse the stable oxygen isotopes that are incorporated into the chitinous cuticle of the midge heads. Oxygen forms part of the chitin molecule and is derived from the water in which the midges are living. We expect that the ratio of stable oxygen isotopes incorporated into the midge heads will reflect the source of the water when the midge was alive. In non evaporative lakes this will tell us which air masses were driving the prevailing climate at that time (i.e. either from Eurasia or the North Pacific). By comparing our records with Holocene climate records available from other sites in the North Atlantic region, Eurasia, Alaska and the North Pacific we will be able to establish the extent of global climate links at times of different climatic regimes, for example the magnitude and timing of the Holocene Thermal Maximum and the Little Ice Age.