Environmental Engineering Reference
In-Depth Information
A polychromatic action spectrum of MAA synthesis in the dinoflagellate
Gyrodinium dorsum
MANFRED KLISCH, DONAT-P. HÄDER
Friedrich-Alexander-Universität, Institut für Botanik und Pharmazeutische Biologie,
Erlangen, Germany
Ultraviolet radiation, especially in the UV-B (280-315 nm) wavelength range
poses significant stress to aquatic life. One important tolerance strategy in
phytoplankton is the synthesis of mycosporine-like amino acids (MAA) 1 . So far an
action spectrum for the synthesis of MAA has only been available for a certain
cyanobacterium 2 . A polychromatic action spectrum has been determined in this study
because polychromatic radiation is a closer approximation to natural conditions than
monochromatic radiation 3 .
Gyrodinium dorsum was grown in F/2 medium 4 . A solar lamp (Dr. Hönle,
Martinsried, Germany) was used to provide PAR and UV radiation. The samples were
covered by filters (Schott & Gen., Germany) of different cut-off wavelengths from 665
nm to 225 nm, a UV-band pass filter (UG 11) or placed in darkness, respectively.
Samples were taken at 24 h-intervals for 72 h and extracted in 100 % methanol.
Spectrophotometric scans of the extracts from 250 nm to 750 nm were performed, and a
polychromatic action spectrum of MAA synthesis was determined.
The polychromatic action spectrum revealed maximal sensitivity of MAA
synthesis to radiation around 310 nm. Wavelengths >340 nm are only slightly effective
while short wavelength UV-B radiation inhibits MAA production. Thus increased UV-B
might even counteract this protective mechanism. On the other hand organisms located
at greater depths may produce MAAs in response to the radiation penetrating to their
level in the water column and thus become more resistant to surface level UV-B
radiation.
Acknowledgements The work outlined here was financially supported by the European
Union (DG XII, Environmental Programme, ENV4-CT97-0580).
References
1. Sinha RP, Klisch M, Gröniger A, Häder D-P (1998) Ultraviolet-absorbing/screening substances in
cyanobacteria, phytoplankton and macroalgae, J. Photochem. Photobiol. B: Biol. 83-94.
2. Portwich A, Garcia-Pichel F (2000) A novel prokaryotic UVB photoreceptor in the cyanobacterium
Chlorogeopsis PCC 6912, Photochem. Photobiol. 493-498.
3. Rundel RD (1983) Action spectra and estimation of biologically effective UV radiation, Physiol. Plant.
360-366.
4. Guillard RRL, Ryther JH (1962) Studies of marine planktonic diatoms I. Cyclotella nana Hustedt and
Detonula convervacea (Cleve) Gran., Can. J. Microbiol. 229-239.
Search WWH ::




Custom Search