Due to the elevated carbon-dioxide (CO2) level in the atmosphere, safe and effective carbon capture and storage methods are gaining more interest. The risks associated with storage and potential leakages for the marine environment are, however, largely unknown. CO2 release from sub-seabed reservoirs will have the greatest impact on the marine organisms living in or near the sea bottom. Areas where CO2 of volcanic origin is leaking from the seabed since centuries provide natural laboratories to study the long-term effects of high CO2 concentrations and subsequent seawater acidification. This study focused on the effects these environmental conditions have on meiofauna, and more particular on the community composition and diversity of the most two abundant taxa, i.e. nematodes and copepods. Samples were collected at natural CO2 seeps in Posidonia oceanica seagrass meadows near Panarea Island. In conjunction, a colonisation experiment with seagrass mimics was also carried out to look into the short-term effects of CO2 leakage. Our observations indicated no significant differences in meiofauna densities between CO2 impacted and non-impacted sites either on natural seagrass leaves, shoots or seagrass mimics. The only difference in meiofauna diversity was observed on natural seagrass shoots. On natural leaves, a shift in dominant harpacticoid species was found, however, community structure did not significantly differ. On the natural seagrass shoots, on the other hand, nematode communities showed a significant change in community structure and species dominance. The short-term colonisation experiment on seagrass mimics showed changes in the harpacticoid community structure at the seepage site; while the nematode community structure, showed no difference, only a change in species dominance was observed. In general, a rather remarkable lack of strong meiofaunal response to the reduced pH may be depended on indirect consequences of CO2 leakage, such as increased seagrass productivity, seasonal organic matter input and reduced macrofaunal predation, in addition to the species specific reactions to environmental disturbance. Since similar research has not been carried out in the shallow-water environment before, further studies are suggested to gain better knowledge of the adaption of meiofauna to the low pH/high CO2 world. |
