An investigation of the calcification response of the scleractinian coral Astrangia poculata to elevated pCO2 and the effects of nutrients, zooxanthellae and gender

[摘要] The effects of nutrients and pCO₂ on zooxanthellate and azooxanthellatecolonies of the temperate scleractinian coral Astrangia poculata (Ellis and Solander, 1786)were investigated at two different temperatures (16 °C and 24 °C).Corals exposed to elevated pCO₂ tended to have lower relativecalcification rates, as estimated from changes in buoyant weights.Experimental nutrient enrichments had no significant effect nor did thereappear to be any interaction between pCO₂ and nutrients. ElevatedpCO₂ appeared to have a similar effect on coral calcification whetherzooxanthellae were present or absent at 16 °C. However, at 24 °C,the interpretation of the results is complicated by a significantinteraction between gender and pCO₂ for spawning corals.

At 16 °C, gamete release was not observed, and no gender differences incalcification rates were observed – female and male corals showed similarreductions in calcification rates in response to elevated CO₂ (15%and 19% respectively). Corals grown at 24 °C spawned repeatedly andmale and female corals exhibited two different growth rate patterns – femalecorals grown at 24 °C and exposed to CO₂ had calcification rates39% lower than females grown at ambient CO₂, while males showed anon-significant decline of 5% under elevated CO₂. The increasedsensitivity of females to elevated pCO₂ may reflect a greaterinvestment of energy in reproduction (egg production) relative to males(sperm production). These results suggest that both gender and spawning areimportant factors in determining the sensitivity of corals to oceanacidification, and considering these factors in future research may becritical to predicting how the population structures of marine calcifierswill change in response to ocean acidification.

[学科分类] 地球化学与岩石