Effects of temperature and UV radiation increases on the photosynthetic efficiency in four scleractinian coral species.
Experiments were performed on coral species containing clade A (Stylophora pistillata, Montipora aequituberculata) or clade C (Acropora sp., Pavona cactus) zooxanthellae. The photosynthetic efficiency (F(v)/F(m)) of the corals was first assessed during a short-term increase in temperature (from 27 degrees C to 29 degrees C, 32 degrees C, and 34 degrees C) and acute exposure to UV radiation (20.5 W m(-2) UVA and 1.2 W m(-2) UVB) alone or in combination. Increasing temperature to 34 degrees C significantly decreased the F(v)/F(m) in S. pistillata and M. aequituberculata. Increased UV radiation alone significantly decreased the F(v)/F(m) of all coral species, even at 27 degrees C. There was a combined effect of temperature and UV radiation, which reduced F(v)/F(m) in all corals by 25% to 40%. During a long-term exposure to UV radiation (17 days) the F(v)/F(m) was significantly reduced after 3 days' exposure in all species, which did not recover their initial values, even after 17 days. By this time, all corals had synthesized mycosporine-like amino acids (MAAs). The concentration and diversity of MAAs differed among species, being higher for corals containing clade A zooxanthellae. Prolonged exposure to UV radiation at the nonstressful temperature of 27 degrees C conferred protection against independent, thermally induced photoinhibition in all four species.
Centre Scientifique de Monaco, Avenue Saint Martin, MC-98000 Monaco. ferrier@centrescientifique.mc
Christine
C
Ferrier-Pagès
Cécile
C
Richard
Didier
D
Forcioli
Denis
D
Allemand
Michel
M
Pichon
J Malcolm
JM
Shick
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D037421:Anthozoa / Q000378:metabolism / Q000382:microbiology* / Q000528:radiation effects; D004141:Dinoflagellida / Q000235:genetics / Q000528:radiation effects*; D007259:Infrared Rays; D010788:Photosynthesis / Q000528:radiation effects*; D013559:Symbiosis / Q000528:radiation effects; D013696:Temperature; D013997:Time Factors; D014466:Ultraviolet Rays
D000596:Amino Acids