Effects of ocean acidification and high temperatures on the bryozoan Myriapora truncata at natural CO 2 vents

• Published in: Marine Ecology
• Main Authors: Rodolfo‐Metalpa, R, Lombardi, C, Cocito, S, Hall‐Spencer, JM, Gambi, MC
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2010
• Subjects: Bryozoan; calcification; global warming; Mediterranean Sea; Myriapora truncata; ocean acidification; volcanic CO2 vents; Ocean acidification
• Online Access: http://hdl.handle.net/10026.1/1336; https://doi.org/10.1111/j.1439-0485.2009.00354.x

<jats:title>Abstract</jats:title><jats:p>There are serious concerns that ocean acidification will combine with the effects of global warming to cause major shifts in marine ecosystems, but there is a lack of field data on the combined ecological effects of these changes due to the difficulty of creating large‐scale, long‐term exposures to elevated CO<jats:sub>2</jats:sub> and temperature. Here we report the first coastal transplant experiment designed to investigate the effects of naturally acidified seawater on the rates of net calcification and dissolution of the branched calcitic bryozoan <jats:italic>Myriapora truncata</jats:italic> (Pallas, 1766). Colonies were transplanted to normal (pH 8.1), high (mean pH 7.66, minimum value 7.33) and extremely high CO<jats:sub>2</jats:sub> conditions (mean pH 7.43, minimum value 6.83) at gas vents off Ischia Island (Tyrrhenian Sea, Italy). The net calcification rates of live colonies and the dissolution rates of dead colonies were estimated by weighing after 45 days (May–June 2008) and after 128 days (July–October) to examine the hypothesis that high CO<jats:sub>2</jats:sub> levels affect bryozoan growth and survival differently during moderate and warm water conditions. In the first observation period, seawater temperatures ranged from 19 to 24 °C; dead <jats:italic>M. truncata</jats:italic> colonies dissolved at high CO<jats:sub>2</jats:sub> levels (pH 7.66), whereas live specimens maintained the same net calcification rate as those growing at normal pH. In extremely high CO<jats:sub>2</jats:sub> conditions (mean pH 7.43), the live bryozoans calcified significantly less than those at normal pH. Therefore, established colonies of <jats:italic>M. truncata</jats:italic> seem well able to withstand the levels of ocean acidification predicted in the next 200 years, possibly because the soft tissues protect the skeleton from an external decrease in pH. However, ...