The oceans support a large proportion of global biodiversity. Sustaining life at the base of marine food chains are photosynthetic microbes, known collectively as phytoplankton. These organisms are vital in regulating our climate, absorbing carbon dioxide from the atmosphere. They also generate almost half the oxygen we breathe. Phytoplankton are probably best known for their formation of massive 'algal blooms' in the ocean, due to rapid population growth triggered by a combination of physical and biological factors. Due to the release of harmful toxins, some phytoplankton blooms can have a negative impact on marine ecosystems, fisheries and human health. Effects of climate change and nutrient pollution have led to more severe and frequent blooms. However, many blooms are not caused by harmful species, and are vital for sustaining marine ecosystems including fish populations. To better understand factors that control bloom dynamics and toxicity, we need to learn more about the molecular processes that trigger their sudden proliferation, and subsequent demise. In many parts of the ocean, nutrients such as nitrogen and phosphorus are in scarce supply. This can limit phytoplankton growth, and cause competition between microbes for survival. In the marine environment a combination of physical factors can lead to sporadic increases in nutrients. This is one of the factors that can stimulate rapid proliferation of phytoplankton cells and lead to algal bloom formation. One of the most successful phytoplankton groups in modern oceans is the diatoms. Diatoms are particularly good at detecting favourable conditions and are often the first to dominate the early stages of bloom formation. Moreover, their success in regions of pulsed nutrient supply suggests that they possess sophisticated mechanisms for sensing and responding to fluctuations in nutrients. However, the sensory mechanisms that mediate the cellular responses of diatom cells to key environmental stimuli remain poorly understood. This represents a major knowledge gap, especially since it is the signalling mechanisms that coordinate acclimation to the environment that likely underpin the ecological success and global impact of the diatoms. I have generated a cutting-edge toolkit to study how diatoms are able to sense changes in their environment using the signalling molecule calcium, which functions as a messenger within the cell. This has led to the remarkable discovery that diatoms use calcium for detecting pulses of the nutrient phosphorus. This novel nutrient signalling mechanism is distinct from plants and animals and points to fundamental differences in nutrient perception between these organisms, which need to be elucidated. I will dissect specific components of this signalling pathway to identify how it helps diatoms respond rapidly to changing nutrient conditions and contribute towards bloom formation. Using my innovative tools, I will also examine other unknown aspects of the diatom sensory system. Alongside physical factors, biological interactions of diatoms with other microbes such as competitors, parasites and predators can critically regulate their growth and bloom development. In the second part of my proposal I will examine how diatoms are able to sense, and alter their behaviour to interact with, their microbial neighbours. Since both nutrient supply and bacteria can govern toxin production by harmful diatoms, a key objective will be to expand my molecular tool kit to the toxic bloom-forming diatom Pseudo-nitzschia multiseries. This research will identify mechanisms that govern dynamics of a globally important phytoplankton group that supports some of our major marine resources. The work will moreover provide insight of regulatory processes and 'master-regulators' that coordinate cellular responses to key environmental drivers that impact diatom growth and toxicity of harmful diatom species, allowing us to better predict bloom formation and toxicity.

Ecosystems are communities of organisms that interact with each other and their environment. They are often considered in terms of food webs or chains, which describe the interactions between different organisms and their relative hierarchies, known as trophic position. Ocean ecosystems provide key services, such as nutrition, control of climate, support of nutrient cycling and have cultural significance for certain communities. It is thus important that we understand how changes to the environment reshape ecosystems in order to manage climate change impacts. The Arctic Ocean is already being heavily impacted by climate change. It is warming faster than any other ocean region and as it absorbs fossil fuel emissions, it is gradually acidifying. Arctic sea ice is declining by 10% per decade. This affects the availability of sea ice habitats for organisms from plankton to mammals and modifies the ocean environment. Finally, the Arctic is affected by changes in the magnitude of water movement to and from the Pacific and Atlantic Oceans and composition of these waters. Thus Arctic ecosystems are being impacted by multiple concurrent stressors and must adapt. To understand how Arctic ecosystems will evolve in response to multiple stressors, it is crucial to evaluate the effects of on going change. Often these questions are tackled by studies that focus on a specific ecosystem in one location and document the various components of the food chain. However the Arctic is diverse, with a wide range of environments that are responding to unique stressors differently. We require a new approach that can provide information on Arctic ecosystems from a pan-Arctic perspective over decadal timescales. To effectively monitor changes to pan-Arctic ecosystems requires tracers that focus on key ecosystem components and provide quantitative information on ecosystem structure, providing information for management and conservation of ecosystem services. Our goal is to respond to this challenge. We will focus simultaneously on the base of the food chain, controlled by the activity of marine phytoplankton, and key Arctic predators, harp and ringed seals. Seals are excellent candidates to monitor the food web due to their pan-Arctic distribution and foraging behaviour, which means they are exposed to the changing environment. Nitrogen and carbon stable isotopes are often used to examine ecosystems as they are modified during trophic transfer up the food chain. Hence, they can quantify seal trophic position and food chain length, key determinants of ecosystem structure. Crucial in this context however is the isotope value of the base of the food web, known as the isoscape, which is itself affected by a range of environmental characteristics and fluctuates in space and time. Equally, by virtue of changing migration patterns, seals themselves may feed on similar prey in different isoscapes, which would affect the interpretation of ecosystem structure from stable isotopes. These are the major challenges in using stable isotopes. We will link stable isotopes to novel tracers of the food web, known as biomarkers. When these tracers are compared against observations of the shifting isoscape and data on seal foraging, they permit seals to be used to monitor the Arctic ecosystem by quantifying their trophic position and overall food chain length. Via a range of observational platforms, our new food web tracers will be mechanistically linked to the spatial and seasonal trends in the Arctic isoscape and seal behaviour. By then combining historical observations from around the Arctic basin with state of the art ocean and seal population modelling, we can quantify past and future changes in Arctic ecosystems. This will provide information on past changes to Arctic ecosystems, but also put in place an approach that can be used to monitor future changes and aid in the management and conservation of ecosystem services

Emiliania huxleyi is a fast growing 'coccolithophorid' phytoplankton species that forms calcium carbonate (CaCO3) plates on the outside of its cells. In the modern ocean, E. huxleyi is one of the most abundant 'bloom forming' phytoplankton species and consequently plays a major role in removal (export) of both carbon and alkalinity from surface waters. Substantial laboratory research has previously examined how environmental factors, such as light, temperature and nutrients, interact to affect the growth and calcification of E. huxleyi. However, the major factor that is critical to the balance between growth and calcification for E. huxleyi is the pH of seawater. With this in mind, global attention has focused upon how E. huxleyi will respond to the decrease in ocean pH (ocean acidification) that has been predicted as a result of elevated atmospheric CO2 concentrations. Recent research has demonstrated that an increase in atmospheric CO2 directly reduces calcification by E. huxleyi; in turn, the efficiency with which this organism can export material from the surface ocean will likely decrease. Despite such progress, the last report of the Intergovernmental Panel on Climate Change highlighted that 'the impact of ocean acidification on marine biota especially for organisms achieving bio-calcification remains a key uncertainty'. Of major concern is that the species of E. huxleyi is comprised of an 'untold number' of genetic variants and independent experiments (including CO2 perturbations) do not always examine environmentally-driven characteristics for the same variant. Results from our laboratory support this statement: two variants exhibited very different modes of acclimation to perturbations of light and CO2 conditions for growth. Changes in gene expression are the bases by which these organisms appear to respond to environmental change, a fact that has led to suggestions that genomics and transcriptomics should be applied to increase our knowledge of ocean biogeochemistry. However, a huge conceptual gap still exists between molecular genetics and biogeochemistry: geochemists need generalisations that can be applied to the entire ocean over long time periods; biologists focus on what makes an organism unique. Key to bridging the current gap between molecular biology and biogeochemistry is to examine the extent with which variability in gene expression is due to genetic differences amongst isolates versus general responses to environmental forcing. This study builds immediately upon previous NERC grants held by the investigators by addressing how gene expression responds to changes of ocean pH for genetic variants of E. huxleyi. We propose a programme of collaborative research involving the University of Essex and Marine Biological Association of the UK under the SOFI call 'Coccolithophore gene expression profiles in chemostat culture and microarray analysis' (WP 2.8, 2.9) within priority topic area marine biogeochemical cycles. 'pH-stat' technology developed in our laboratory will be used to grow four E. huxleyi genetic variants at two pH conditions (present day versus that predicted beyond the year 2100). Microarray-based molecular signals in response to the different pH conditions within and between variants will be compared but also analysed alongside physiological signals (photosynthesis and calcificiation). Work proposed here will establish a core link between two research centers with an excellent track record investigating E. huxleyi biology, the University of Essex and the UK's Marine Biological Association, which is an Ocean 2025 Centre.

See lead proposal

The ambition of AtlantECO is to develop and apply a novel, unifying framework for providing knowledge-based resources to design policies, support decisions making and engage with citizens to encourage responsible behaviour to manage the Atlantic system and protect its Ecosystem Services (ES) provision. The aim of AtlantECO is to determine the structure and function of Atlantic microbiome in the context of ocean circulation and presence of pollutants, e.g., plastics, to assess its role in driving the dynamics of Atlantic ecosystems at basin and regional scales; its potential of being used as a sensor of ecosystem state and the mechanisms by which it drives the provision of 5ES. This is key to improve our predictions on future provision of ES in the basin and to favour the establishment of a sustainable Blue Growth strategy for an All-Atlantic community. To realise this vision, AtlantECO has four objectives which are to 1) Assess dynamics of Atlantic marine ecosystems, their ES provision and the interplay of both with socio-economic activities; 2 increase knowledge and data on microbiomes, plastics, the plastisphere and carbon fluxes that support ecosystems at basin scale using best practices and integrative sampling strategies, novel genomics, imaging and biogeochemical methods, bioinformatics and modelling approaches; 3) Assess and predict the cumulative impacts of multiple stressors on ecosystem status and dynamics and ES provision, identifying their drivers and role on tipping points, assessing their changes in recovery of ecosystem structures, functions and services, and developing eco-socio-economic models to predict future trajectories and 4) Deploy a systemic strategy to build capacity and transfer knowledge for a seamless engagement between science, industry, policy, and society. To achieve these objectives AtlantECO brings together experts and pioneers from Europe, South America and South Africa with the relevant resources, knowledge and experience.