The effects of temperature and light on phytoplankton production

Jan Bissinger

SSchool chool of of

BBiological iological SSciencesciencesSSchool chool of of

BBiological iological SSciencesciences

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

Global biogeochemical cycles

• CO2 is fixed using energy from the sun, releasing oxygen

• Sink for anthropogenic carbon

• Phytoplankton produce 50% of the oxygen that we breath

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

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

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

Temperature°C

5 10 15 20 25 30

Sp

ecif

ic g

row

th r

ate

(µ)

d-1

-0.2

0.0

0.2

0.4

0.6

0.8

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

Thanks:

Dr David AtkinsonDr David Montagnes

Redrawn from Conover (1982)