Natural high pCO2 increases autotrophy in Anemonia viridis (Anthozoa) as revealed from stable isotope (C, N) analysis.
Contemporary cnidarian-algae symbioses are challenged by increasing CO2 concentrations (ocean warming and acidification) affecting organisms' biological performance. We examined the natural variability of carbon and nitrogen isotopes in the symbiotic sea anemone Anemonia viridis to investigate dietary shifts (autotrophy/heterotrophy) along a natural pCO2 gradient at the island of Vulcano, Italy. δ(13)C values for both algal symbionts (Symbiodinium) and host tissue of A. viridis became significantly lighter with increasing seawater pCO2. Together with a decrease in the difference between δ(13)C values of both fractions at the higher pCO2 sites, these results indicate there is a greater net autotrophic input to the A. viridis carbon budget under high pCO2 conditions. δ(15)N values and C/N ratios did not change in Symbiodinium and host tissue along the pCO2 gradient. Additional physiological parameters revealed anemone protein and Symbiodinium chlorophyll a remained unaltered among sites. Symbiodinium density was similar among sites yet their mitotic index increased in anemones under elevated pCO2. Overall, our findings show that A. viridis is characterized by a higher autotrophic/heterotrophic ratio as pCO2 increases. The unique trophic flexibility of this species may give it a competitive advantage and enable its potential acclimation and ecological success in the future under increased ocean acidification.
1] The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel [2] The Interuniversity Institute for Marine Sciences, P.O. Box 469, Eilat 8810300, Israel.
Rael
R
Horwitz
The Interuniversity Institute for Marine Sciences, P.O. Box 469, Eilat 8810300, Israel.
Esther M
EM
Borell
Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 7610001, Israel.
Ruth
R
Yam
Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 7610001, Israel.
Aldo
A
Shemesh
1] The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel [2] The Interuniversity Institute for Marine Sciences, P.O. Box 469, Eilat 8810300, Israel.
Maoz
M
Fine
D000818:Animals; D037421:Anthozoa / Q000502:physiology*; D052818:Autotrophic Processes; D002245:Carbon Dioxide; D002247:Carbon Isotopes / Q000032:analysis; D002734:Chlorophyll / Q000378:metabolism; D008940:Mitotic Index; D009587:Nitrogen Isotopes / Q000032:analysis; D012623:Seawater / Q000032:analysis / Q000737:chemistry; D013559:Symbiosis
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D002734:Chlorophyll; D002245:Carbon Dioxide