Altered epiphyte community and sea urchin diet in Posidonia oceanica meadows in the vicinity of volcanic CO2 vents

Ocean acidification (OA) predicted for 2100 is expected to shift seagrass epiphyte communities towards the dominance of more tolerant non-calcifying taxa. However, little is known about the indirect effects of such changes on food provision to key seagrass consumers. We found that epiphyte communities of the seagrass Posidonia oceanica in two naturally acidified sites (i.e. north and south sides of a volcanic CO2 vent) and in a control site away from the vent at the Ischia Island (NW Mediterranean Sea) significantly differed in composition and abundance. Such differences involved a higher abundance of non-calcareous crustose brown algae and a decline of calcifying polychaetes in both acidif…