February 1st to 5th 2016
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Altered epiphyte community and sea urchin diet in Posidonia oceanica meadows in the vicinity of a volcanic CO2 vent

Scientific Exhibition
Future Oceans
Wednesday, February 3, 2016 -
18:30 to 20:00

Nogueira, P. 1 Gambi, M. C. 2 Vizzini, S. 3 Califano, G. 4 Tavares, A.M. 5 Santos, R. 6 Martínez-Crego, B. 7

1Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
2Stazione Zoologica Anton Dohrn (SZN)
3University of Palermo
4Friedrich-Schiller-Universität (FSU), Jena
5CCMARCentre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
6Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
7Centre of Marine Sciences (CCMAR), University of Algarve, Campus de Gambelas, 8005-139 Faro, Portugal

Uptake of anthropogenic CO2 from the atmosphere by the oceans is causing a progressive decrease in seawater pH, in a process commonly known as ocean acidification (OA). Changes in pH and carbonate chemistry predicted by the end of the century are expected to highly impact the growth and survival of most calcifying organisms. Sea urchins are key species in marine ecosystems and their feeding behaviour in seagrass meadows has been reported as closely linked to the presence and abundance of seagrass epiphytes. Shifts in the seagrass epiphyte community towards the dominance of more tolerant taxa (e.g. non-calcifying species) are expected under future OA, which may have relevant consequences in sea urchin diet. However, to our knowledge, this indirect effect of OA has not been investigated so far. To this aim, we compared the composition and abundance of the epiphyte community of the seagrass Posidonia oceanica, as well as the diet of the commercially important sea urchin Paracentrotus lividus, in a control site (usual pH) and in two sites close to volcanic CO2 vents (predicted pH by 2100) at the Ischia Island (NW Mediterranean Sea). We found significant differences between control and low-pH sites in the composition and abundance of epiphytes, with such differences related to a reduction in calcifying taxa in only one of the low-pH sites. Contrasting shifts in the epiphyte community at both low-pH sites translated to a lower abundance of seagrass and epiphytes and increased green algae in sea urchin diet. Overall, our study suggests that complex responses in CO2 vent systems may indirectly propagate through the food web, while it also indicates that factors other than direct OA effects may influence local differences within the whole CO2 vent system.
keywords: 
ocean acidification, pH, sea urchins, epiphytes, Posidonia oceanica

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