Don't forget plankton in climate change models, says study

A new study from the University of Exeter, published in the journal Ecology Letters, found that phytoplankton – microscopic water-borne plants – can rapidly evolve tolerance to elevated water temperatures. Globally, phytoplankton absorb as much carbon dioxide as tropical rainforests and so understanding the way they respond to a warming climate is crucial.

Phytoplankton subjected to warmed water initially failed to thrive but it took only 45 days, or 100 generations, for them to evolve tolerance to temperatures expected by the end of the century. With their newfound tolerance came an increase in the efficiency in which they were able to convert carbon dioxide into new biomass.

The results show that evolutionary responses in phytoplankton to warming can be rapid and might offset some of the predicted declines in the ability of aquatic ecosystems to absorb carbon dioxide as the planet warms.

Dan Padfield a PhD student at the Environment and Sustainability Institute at the University of Exeter's Penryn Campus in Cornwall said: “Our findings suggest that evolution could play a key role in shaping how aquatic ecosystems respond to climate change. The phytoplankton in our study adapted to warmer water in the lab and evolved the ability to capture more atmospheric carbon dioxide.

“Our results demonstrate that evolutionary responses of phytoplankton to warming should be taken into account when developing models of how climate change will affect aquatic ecosystems. This experimental work provides the empirical basis for incorporating evolution into the models used to forecast future ocean productivity.”

The researchers exposed Chlorella vulgaris, a model species of phytoplankton, to temperatures of 20 – 33 degrees. Initially rates of growth peaked at 30 degrees, while 33 degrees was stressful and limited growth. After 100 generations (45 days) growth increased to levels expected from the exponential effects of temperature on physiological rates, showing that the algae had evolved the ability to thrive at the increased temperatures.

The underlying mechanism for the ability to tolerate warmer temperatures was an increase in the efficiency in which the alga was able to convert carbon dioxide into new biomass by reducing rates of respiration (production of carbon dioxide). It is this shift in the relative rates of respiration and photosynthesis that enabled the phytoplankton to cope with warmer temperatures.

While these experiments focused on a single species and strain of phytoplankton, the researchers believe that the rapid evolution of carbon-use efficiency will apply to other species of phytoplankton and substantially improve models describing ecological and biogeochemical effects of climate change.

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Image credit: Gabriel Yvon-Durocher

About the University of Exeter

The University of Exeter is a Russell Group university that combines world-class research with very high levels of student satisfaction. Exeter has over 19,000 students and is one of the global top 100 universities according to the Times Higher Education World University Rankings 2015-16, positioned 93rd. Exeter is also ranked 7th in The Times and The Sunday Times Good University Guide 2016, 9th in the Guardian University Guide 2016 and 10th in The Complete University Guide 2016. In the 2014 Research Excellence Framework (REF), the University ranked 16th nationally, with 98% of its research rated as being of international quality. Exeter was named The Times and The Sunday Times Sports University of the Year 2015-16, in recognition of excellence in performance, education and research. Exeter was The Sunday Times University of the Year 2012-13.

The University has four campuses. The Streatham and St Luke's campuses are in Exeter and there are two campuses in Cornwall, Penryn and Truro. In a pioneering arrangement in the UK, the Penryn Campus is jointly owned and managed with Falmouth University. At the campus, University of Exeter students can study programmes in the following areas: Animal Behaviour, Conservation Biology and Ecology, English, Environmental Science, Evolutionary Biology, Geography, Geology, History, Human Sciences, Marine Biology, Mining and Minerals Engineering, Politics and International Relations, Renewable Energy and Zoology.

The University has invested strategically to deliver more than £350 million worth of new facilities across its campuses in the last few years; including landmark new student services centres – the Forum in Exeter and The Exchange on the Penryn Campus in Cornwall, together with world-class new facilities for Biosciences, the Business School and the Environment and Sustainability Institute. There are plans for further investment between now and 2016. http://www.exeter.ac.uk/cornwall

About the University of Exeter's Environment and Sustainability Institute (ESI)

The Environment and Sustainability Institute is a £30M interdisciplinary centre, based on the Penryn Campus, undertaking cutting-edge research into solutions to problems of environmental change; in so doing it is enhancing people's lives by improving their relationships with the environment. The ESI has three research themes: clean technologies, natural environment, and social science and sustainability. It is engaging with hundreds of businesses in Cornwall, the Isles of Scilly and beyond to translate its research and expertise across these themes into innovative business practice, products and services.

The ESI building has been designed to achieve a BREEAM 'Outstanding' status, the highest classification available under the BRE Environmental Assessment Method which is the leading and most widely used environmental assessment method for buildings

The ESI was formally opened in April 2013 and has been funded by the European Regional Development Fund Convergence Programme (£22.9M) and the South West Regional Development Agency (£6.6M), with significant support from the Higher Education Funding Council for England.

The University of Exeter and Falmouth University are founding partners in the Combined Universities in Cornwall (CUC), a unique collaboration between six universities and colleges to promote regional economic regeneration through Higher Education, funded mainly by the European Union (Objective One and Convergence), the South West Regional Development Agency and the Higher Education Funding Council for England, with support from Cornwall Council. http://www.exeter.ac.uk/esi