16. The impact of angel’s wing on pteropod population in the Gulf of Naples (Western Mediterranean)

Sergio d’Albero (1,2,3)*, Paola Rumolo (2), Angelo Bonanno (2), Enrico Dinelli (3), Clara Manno (1)

1 BAS (British Antarctic Survey), Cambridge, Cambridgeshire, CB30ET, UK
2 IAMC-CNR, Napoli, Campania, Calata Porta di Massa, 80133, Italy
3 University of Bologna, Dep. Of Marine Biology, Emilia Romagna, 48123, Italy

Background
Thecosomate Pteropods are particularly vulnerable to Ocean Acidification since their shells are made by of aragonite, a highly soluble form of biogenic carbonate in sea water. Marine areas with naturally high levels of carbon dioxide in the water provide a natural laboratory to study the adaptation strategy of calcifying organisms exposed to chronic low pH level. The Naples of Bay (Western Mediterranean) is a notable case where the presence of CO2 vents was already documented by local fishermans in the 70’s when they described the phenomenon of bubbles coming out from the sea surface as “the Wing of the Angel”. Despite several studies investigated the impact of the CO2 vents on calcifying benthic compartment, the effect on pelagic calcifying community, such as pteropods, is still poor understood.

Methods
Thecosomate Pteropods were collected during a cruise in two regions characterised by similar hydrological and biological regime but different carbonate chemistry regime (with and without the presence of CO2 vents). To understand the impact of high pCO2 -low pH levels on the pteropod population, the variability in biodiversity, abundance and shell quality of pteropods between the two regions were investigated. Shell morphology, dissolution and repair were examined using scanning electron microscopy.

Findings
Pteropod abundance and biodiversity were higher in the control than the CO2 vents stations. In all the stations the dominant pteropod was C. conica. We observed a difference in shell degradation of C. conica where in CO2 vent stations this pteropod presented higher shell dissolution and lower shell weight than those collected in the control stations. Moreover C. conica found at CO2 vent stations were smaller than those found in control conditions.

Conclusions
We suggest that C. conica could develop physiological and morphological change to counteract the higher energy demand due to the presence of chronic low pH exposition.