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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)