1. The effects of temperature and light on phytoplankton production Jan Bissinger S chool of B iological S ciences S chool of B iological S ciences

2. Some background Phytoplankton- microscopic unicellular autotrophic organisms At the base of the aquatic food chain Sustain the growth of heterotrophs at higher levels in the food chain

3. Global biogeochemical cycles CO 2 is fixed using energy from the sun, releasing oxygen Sink for anthropogenic carbon Phytoplankton produce 50% of the oxygen that we breath

4. Production is controlled by temperature and light Production can be calculated from the product of specific growth and biomass. Growth rates increase with temperature reaching a maximum at the optimum temperature, whereas cell volume decreases linearly Growth rates increase with light intensity to a maximum at the optimum light level, after which photoinhibition leads to reduced growth High light levels also lead to an increase in cell size

5. Experiments on Cryptomonas sp. 12 water baths at temperatures ranging from 7.5ºC to 27ºC 4 light levels Samples removed daily and counted under the microscope Specific growth rate calculated from the change in cell numbers with time Cell volumes estimated using a digital imaging system connected to the microscope

6. Analysing the data A number of possible mechanistic models relating ectotherm growth to temperature Non-linear regression Similar approach using multiple regression to examine the interactive effects of temperature and light on phytoplankton growth

7. Meta-analysis Synthesis of data from the literature of phytoplankton growth rates and cell volumes at different temperatures and irradiances Multiple regression analysis Examine the importance of taxon, habitat and cell size

8. Thanks: Dr David Atkinson Dr David Montagnes