Impact of temperature on UV-susceptibility of two Ulva (Chlorophyta) species from Antarctic and Subantarctic regions
Ralf Rautenberger Institute for Polar Ecology Christian Albrechts University of Kiel (Germany)
Institute for Polar Ecology
Christian Albrechts University of Kiel
The „Antarctic ozone hole“
www.theozonehole.com
•
Establishment in austral spring every year•
In 2000 and 2003: 28 million km2•
Extended to South America: 45°S•
Results in an increase of UV-B- radiation on earths surface•
Increased UVB-radiation affects macroalgae as an important ecological componentImpact of temperature on UV-susceptibility
Water temperatures
• Controlling macroalgal growth, distribution and stress
• Potential changes of water temperatures in Antarctica affect marine life, e.g.
macroalgae
poet.jpl.nasa.gov
Material Objective Results Conclusions
Puerto Williams:
Ulva clathrata
cosmopolitan/cold-temperate species cold-temperate waters: 5-10 °C
Jubany Base:
Ulva bulbosa
Antarctic/cold-temperate species: -2-2 °C Tide pools: >> 2 °C
Ulva bulbosa Ulva clathrata
75°W
70° 65° 60°
55°W
65°S 60°
55°
50°S
Argentina
Chile
Falkland Islands
Puerto Williams
Dra ke
P ass
ag e
Jubany Base
Antarctic Peninsula
Algal material
© R. Rautenberger
© M.D. Guiry
Map: www.aquarius.geomar.de
Impact of temperature on UV-susceptibility Material
Objective
Results Conclusions
Temperature UV-radiation
Photosynthesis Oxidative stress
Objective of the study
Interactive effects of UV-radiation and temperature on the physiological and ecological level
PAR = 10 μmol photons m-2 s-1 UVA = 4.1 W m-2
UVB = 0.7 W m-2 2 = 10 °C
1 = 0 °C 4 days of cultivation
0 °C 10 °C
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0 1 2 3 4
PAR PAR+UVA PAR+UVA+UVB
Time of UV-exposure (days)
Fv/Fm (r.u.)
Photosynthesis of U. bulbosa
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0 1 2 3 4
UV-induced inhibition of photosynthesis compensation of UV-induced
photoinhibition by increased temperature
Impact of temperature on UV-susceptibility
Photosynthesis of U. clathrata
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0 1 2 3 4 0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0 1 2 3 4
0 °C 10 °C
PAR PAR+UVA PAR+UVA+UVB
Fv/Fm (r.u.)
UV-induced inhibition of photosynthesis
was much more pronounced compensation of UV-induced
photoinhibition by increased temperature Time of UV-exposure (days)
Material Objective
Results
Conclusions
Activities of superoxide dismutase in U. bulbosa
SOD activity (Units mg-1 protein) 0 50 100 150 200 250
0 2 4 0
50 100 150 200 250
0 2 4
0 °C 10 °C
PAR PAR+UVA PAR+UVA+UVB
Time of UV-exposure (days)
No significant differences between light and temperature treatments!
Impact of temperature on UV-susceptibility
0 °C 10 °C
0 50 100 150 200 250
0 2 4 0
50 100 150 200 250
0 2 4
PAR PAR+UVA PAR+UVA+UVB
Time of UV-exposure (days)
No significant differences between light treatments!
Activities of superoxide dismutase in U. clathrata
SOD activity (Units mg-1 protein)
Material Objective
Results
Conclusions
Content of malondialdehyde in U. bulbosa
0 °C 10 °C
MDA content (μmol mg-1 fw)
0 2 10-5 4 10-5 6 10-5 8 10-5 1 10-4 1.2 10-4 1.4 10-4
0 4
0 2 10-5 4 10-5 6 10-5 8 10-5 1 10-4 1.2 10-4 1.4 10-4
0 4
PAR PAR+UVA PAR+UVA+UVB
No significant differences between light treatments!
Time of UV-exposure (days)
Impact of temperature on UV-susceptibility
0 °C 10 °C
0 2 10-5 4 10-5 6 10-5 8 10-5 1 10-4 1.2 10-4 1.4 10-4
0 4
0 2 10-5 4 10-5 6 10-5 8 10-5 1 10-4 1.2 10-4 1.4 10-4
0 4
PAR PAR+UVA PAR+UVA+UVB
Time of UV-exposure (days) MDA content (μmol mg-1 fw)
Content of malondialdehyde in U. clathrata
No significant differences between light treatments!
Material Objective
Results
Conclusions
Physiological interpretation
• UV-radiation induced inhibition of photosynthesis at 0 °C but did not cause any oxidative stress
• Compensation of UV-induced photoinhibition by increased temperature, probably due to increased activities of key enzymes involved in photoprotection
• Higher SOD activities in U. bulbosa than in U. clathrata
suggest a more efficient management of oxidative stress
at permanent low temperatures
Impact of temperature on UV-susceptibility
Ecological Interpretation
© K. v. Juterzenka
•
U. bulbosa seems better adapted to cope with UV- radiation than U. clathrata at lower temperatures•
U. bulbosa in the eulittoral is affected by UV-radiation but photoinhibition is reversible•
In tide pools, increased temperatures may diminish UV- effects in U. bulbosa•
U. clathrata from South America does not experience similarly low temperatures•
There, higher water temperatures facilitate a higher activity of physiological protection mechanismsIntroduction Material Objective Results
Conclusions
Rautenberger R and Bischof K (2006) Impact of temperature on UV-susceptibility of two Ulva (Chlorophyta) species from Antarctic and Subantarctic regions. Polar Biology (Online First)
Institute for Polar Ecology
Christi
an Albrechts University of Kiel
