Structural and geochemical alterations in the Mg calcite bryozoan Myriapora truncata under elevated seawater pCO2 simulating ocean acidification

Chiara Lombardi, Riccardo Rodolfo-Metalpa, Silvia Cocito, Maria Cristina Gambi, Paul David Taylor

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Abstract

The possible effects of ocean acidification on the calcareous skeleton of the Mediterranean bryozoan Myriapora truncata (Pallas, 1766) were studied by transplanting live and dead colonies into an area of natural volcanic CO2 vents at Ischia (Gulf of Naples, Tyrrhenian Sea), Italy. Morphology and geochemistry were compared between colonies from normal (mean pH=8.07, min. pH 7.95), below-normal (mean pH 7.66, min. pH 7.32) and acidic (mean pH 7.43, min. pH 6.83) conditions after colonies had been exposed in situ for 45 and 128days. Both distal (juvenile) and proximal (adult) parts of the branches were investigated. Skeletons of live colonies in acidic pH site after 45days of exposure were less corroded than those of dead colonies, suggesting that the organic tissues enveloping the skeleton play a protective role. Colonies remained alive at the below-normal and acidic pH sites during the 45-day experiment but corrosion was very striking after 128days, with colonies from the acidic site showing significant loss of skeleton. Compared to the control, these colonies also had lower levels of Mg (mean 8 versus 9.5 wt% Mg) within their skeletons. Electron microprobe mapping showed Mg to be higher in the outer layers of the skeletal walls in colonies from the normal pH site. Corrosion of outer layers of the walls probably explains the lower Mg level found in colonies exposed to acidic conditions. As solubility of calcite increases with Mg content, the enrichment of Mg in outer layers of the skeleton should enhance the vulnerability of Myriapora truncata to dissolution. These findings raise concerns over the survival of bryozoans with Mg calcite skeletons in the face of predicted decreases in oceanic pH levels. © 2010 Blackwell Verlag GmbH.
Original languageEnglish
Pages (from-to)211 - 221
Number of pages11
JournalMarine Ecology
Volume32
Issue number2
DOIs
Publication statusPublished - Jun 2011
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Aquatic Science
  • Ecology, Evolution, Behavior and Systematics
  • Ecology

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