Figure 3.

Frequency of the 1089 cm⁻¹ Raman spectrum peak from crustose coralline algae. Higher frequency is equivalent to higher Mg concentration in coralline algae from the north and south CO₂ venting sites at Castello Aragonese, Ischia island, Italy. Tiles containing algae were collected from ambient, low and extreme low pH zones at 3.5, 6.5 and 14 months after deployment. Mean ± s.d. with significant differences indicated by asterisk. Analyses not included where gypsum present.