The growth of motile algae: from plankton blooms to biofuel production

Microscopic algae are fascinating unicellular microorganisms ubiquitous on Earth. They play vital roles in global ecology and biotechnology. Like plants microalgae are photosynthetic, fixing atmospheric carbon from carbon dioxide into carbohydrates. Microalgae thus participate in the global carbon cycle and play a critical role in climate regulation. The photosynthetic ability of microalgae, together with the capacity of some species to produce oily compounds, also means they can be used as an alternative to plants as a feedstock for biofuels, which are urgently required to reduce carbon emissions and limit climate change.

In spite of recent advances, much about the growth of algal populations remains to be discovered, which limits our ability to control their growth. Indeed, microalgal populations in the environment can grow explosively into blooms, which colour their environment: from the vivid greens of ponds to the spectacular blue-greens or reds of plankton blooms in the ocean (some so extensive that they are visible from space!). Many of these blooms are benign, providing a bounty for organisms that feed on microalgae (from fish larvae to whales). However, some microalgal species form `harmful algal blooms' (HAB), noxious because of the toxins they produce, or because their growth starves or suffocates other species. Each year HABs kill significant numbers of fish, but also marine animals and people, with substantial economic impact. A better understanding of algal growth could help predict and prevent HABs. It could also help the production of microalgal biofuels. Oily plants are currently used for biofuel production, e.g. rapeseed is a common feedstock to make biodiesel. Competition with food crops, however, makes plants problematic biofuel candidates. Microalgae, on the other hand, grow almost anywhere, faster than plants, using only sunlight and recycled industrial/agricultural waste nutrients, gases and water. However, no biofuel is currently manufactured industrially from microalgae due to high production costs.

Many microalgal species have evolved the ability to swim and bias their swimming to better navigate in water and source food. Symbiosis with bacteria also provides nutritional benefits, such as essential vitamins. Recent advances in physics of biased swimming microalgae and the biology of symbiotic nutrition have not yet applied to the study of growth of swimming microalgal populations. We propose to carry out the first systematic study of the growing populations of swimming microalgae to consider both the physics of swimming and the role of symbiotic bacteria. In particular, using a combination of mathematical modelling and experiments we aim to quantify the growth of biased swimming microalgal populations. The results of our investigation will allow a more complete understanding of algal growth, which will in turn provide possible solutions to control HABs and to improve the economics of microalgal biofuel production.

Academic beneficiaries (direct)

The proposed work is strongly multidisciplinary and will benefit academics across different fields, particularly: applied mathematics, physics, algal biology, marine ecology, engineering, oceanography and climate science.

Algal nutrition and the collective dynamics of biased swimming microorganisms are topics of great current academic interest. Our study will provide the first quantitative analysis of the effects of biased swimming and the effect of vitamin acquisition from symbiotic bacteria on the growth of microalgal populations. Academic colleagues will benefit from the novel results we will discover and from the theoretical and experimental techniques we will develop. We will make our findings available by publication in peer-reviewed high-impact international journals, talks at conferences and meetings and scientific visits. Impact timescale: 1-2 years from start of research.

University-industry interface beneficiaries (direct)

Results from the proposed research will be of interest to engineers seeking to develop efficient bioreactors for biofuel production, including the Algal Bioenergy Consortium (ABC) at Cambridge. We will work closely with chemical engineering members of the ABC to see if some of our discoveries can be incorporated in innovative bioreactor designs. Dr Bees is also currently engaged in setting up a large international university-industry collaboration in Botswana to research the efficient culturing of algae in the field for beta-carotene and biofuels, and is also collaborating with engineers in South Africa. He will see if some of our findings can be applied by colleagues in Botswana. In addition, to communicate to the engineering community and accelerate the application of our results, we will publish some of our results in engineering journals in collaboration with our colleagues. Impact timescale: 3-4 years from start of research.

Commercial beneficiaries (indirect)

The proposed research will provide new results that will significantly contribute to current understanding of algal growth, improving in turn the understanding of plankton blooms, including harmful algal blooms (HABs), and biotechnological culture of microalgae for biofuels. The prediction of blooms and the development of microalgal biofuels are important practical challenges in urgent need of scientific solutions. It is important to find a way of controlling HABs, which every year cause millions of dollars of damage to the fishing industry worldwide and can cause the unnecessary death of marine mammals. Biofuels are needed with urgency given reserves of fossil fuels are dwindling and carbon emissions must be reduced to limit climate change. By taking an important step towards finding new ways of controlling blooms and developing microalgal biofuels, the proposed research could indirectly benefit the fishing and renewable energy industries. Impact timescale: 5-10 years from start of research.

Wider public beneficiaries (direct)

We will also be involved in outreach activities and events to communicate our research directly with the public. Prof Smith is very active in public engagement. Notably she has recently organised an exhibit `Meet the Algae: Diversity, Biology and Energy' as part of the Royal Society Summer Science Exhibition in 2010, and will be exhibiting again at the Big Bang! festival in London in 2011. During the follow-on grant Dr Croze will receive training in public communication of science and will help Prof Smith with her outreach activities. We will also endeavour to publish articles about our research in popular science magazines (New Scientist, Scientific American) and accessible accounts of our research on university outreach web pages. Impact timescale: 1-2 years from start of research.