Determining the marine ecosystem response to global change: Lessons from the past using a new Earth system model

The marine ecosystem can significantly impact on our planet, sustaining the ocean food chain and strongly regulating the climate through the activity of the phytoplankton. Phytoplankton are microscopic plants that live at the surface of the ocean, use sunlight as source of energy to grow via photosynthesis. Thanks to this reaction, phytoplankton consume today as much CO2 from the atmosphere as all the trees on the planet.

Phytoplankton in the ocean are in fact many thousands of different organisms, some bigger, some smaller, others protected with shells. Each of these organisms have a specific function in the marine ecosystem and hence the climate. For instance, coccolithophores produce calcium carbonate in form of beautiful shells that fall easily at the bottom of the ocean once they die. Their shells are at the origin of the famous White Cliffs of Dover, in the South-East of England. Other important marine phytoplankton are the diatoms, bigger in size forming a silica shell, or the cyanobacteria which are smaller in size and populate most tropical and subtropical ocean waters.

Today our climate is getting warmer due to large release of carbon to the atmosphere, causing our marine ecosystem to change. We however do not know exactly how the ecosystem will response to the change in climate, mainly because the ocean is a complex system where organisms keep interacting with each other and their environment. One way to understand better these interactions is to look at significant climate events in the past. The plan of this project is to look at both the Last Glacial Maximum (LGM) of 20 thousand years ago, which was a time when great ice sheets were covering our continent, and the Paleocene-Eocene thermal maximum (PETM) of 55 million years ago, which is a good analogue to today's climatic perturbations. The project will 1) compare the distribution and the diversity of the phytoplankton living in the ocean today with the ones of the LGM which had a much colder, more stratified and less acidic ocean, and 2) investigate the changes in the marine ecosystem due to the fast PETM warming event analogous to today. The outcome will help us to understand more how the marine ecosystem functions and reacts to changes in the climate.

The challenge for this project is that we do not have enough observations to reproduce the phytoplankton distribution and diversity of the global ocean in the past. Computer models can help solve this filling in the missing information. These models need to represent all the important factors that determine where different phytoplankton species prefer to live, such as a diverse population of organisms. In this project, we are taking an exciting approach and use a particularly sophisticated model called a self-assembling ecosystem model.

What is a self-assembling ecosystem model? Usually models represent only a couple of different sorts of phytoplankton, based on modern species which have been grown in the laboratory. Unfortunately there have not been enough experiments to realistically reproduce the wide diversity of phytoplankton of the real ocean. Our model therefore generates randomly a hundred phytoplankton 'characters', each with different abilities and properties to live. A diverse ecosystem then forms in the model while the diverse phytoplankton compete for nutrients and light. This model has already been very successful in representing most of the marine ecosystem of today, but has not been used to represent coccolithophores nor it has been applied to past climates. This project will be the first time either of these things will be done.

The core of the research will be done at the University of Bristol which has a strong group of research experts in climate observations and modelling. In addition close collaborations will be carried out with different experts: with the university of MIT in the US and with coccolithophore and diatom experts in London, Cardiff and Southampton.

Who will benefit and how will they benefit from this research?

General public: Topics related to global climate change and the ocean attract a lot of attention from the general public. Marine ecosystems are subjects which capture imagination and hence provide an ideal opportunity to transfer knowledge on issues related to the impact of climate on the environment and human lives. The proposed project will directly address how climatic changes impact the marine phytoplankton ecosystem and its diversity. The results will generate meaningful, visual outputs in a 3-dimensional form that communicate the conclusions clearly.

Environmental agencies: Assessment of the environmental impact and susceptibility of the marine plankton ecosystem to change, and the consequences for the base of the food change fisheries and marine protected areas, is important for environmental agencies in the UK (e.g. defra, Cefas, DECC, Natural England, MCCIP) and abroad (e.g. WWF, EU). The proposed project offers to improve the understanding of marine phytoplankton diversity, in particular to identify and highlight important responses in the marine ecosystem as a result of climatic and biogeochemical changes in the past. This research will relate directly to the initiative "Understanding marine ecosystem connections", which focuses on understanding the way marine ecosystems function and respond to change, from the agencies defra and Cefas who have called for additional scientific collaborations.

Women in science: Women are still a minority in the scientific community particularly in the area of geosciences. During my career as a female geoscientist I have been aided greatly by the support of other women of the field and I am keen to be able to extend that support to others, expanding the network of women working in the geosciences. Having a more balanced men/women representation in science will benefit the scientific community providing a neutral and supportive environment to work.

Scientific community: The scientific community will benefit from this research (as detailed in the Academic Beneficiaries). In addition to these areas, the proposed project will generate international collaborations between worldwide experts on marine ecosystem and climate (see Partnership Details), essential to provide original and outstanding research to the scientific community. Being interdisciplinary, this project will also bridge the gap between expertises in modelling, and data measurement and analysis, as well as between marine biology, atmospheric and ocean physics and chemistry. This project will provide the opportunity for scientists on both sides to learn new techniques and understand how to work better together.