title: Seagrass ecosystem response to long-term high CO2 in a Mediterranean volcanic vent.
abstract: We examined the long-term effect of naturally acidified water on a Cymodocea nodosa meadow growing at a shallow volcanic CO2 vent in Vulcano Island (Italy). Seagrass and adjacent unvegetated habitats growing at a low pH station (pH = 7.65 ± 0.02) were compared with corresponding habitats at a control station (pH = 8.01 ± 0.01). Density and biomass showed a clear decreasing trend at the low pH station and the below- to above-ground biomass ratio was more than 10 times lower compared to the control. C content and δ(13)C of leaves and epiphytes were significantly lower at the low pH station. Photosynthetic activity of C. nodosa was stimulated by low pH as seen by the significant increase in Chla content of leaves, maximum electron transport rate and compensation irradiance. Seagrass community metabolism was intense at the low pH station, with significantly higher net community production, respiration and gross primary production than the control community, whereas metabolism of the unvegetated community did not differ between stations. Productivity was promoted by the low pH, but this was not translated into biomass, probably due to nutrient limitation, grazing or poor environmental conditions. The results indicate that seagrass response in naturally acidified conditions is dependable upon species and geochemical characteristics of the site and highlight the need for a better understanding of complex interactions in these environments.
authors.affiliation: Institute of Oceanography, Hellenic Centre for Marine Research, PO Box 2214, 71003 Heraklion, Crete, Greece. Electronic address: eapost@hcmr.gr.
authors.forename: Eugenia T
authors.initials: ET
authors.lastname: Apostolaki
authors.affiliation: Department of Earth and Marine Sciences, University of Palermo, Via Archirafi 18, 90123 Palermo, Italy.
authors.forename: Salvatrice
authors.initials: S
authors.lastname: Vizzini
authors.affiliation: Global Change Department, Mediterranean Institute for Advanced Studies (CSIC-UIB), c/ Miquel Marquès 21, 07190 Esporles, Balearic Islands, Spain.
authors.forename: Iris E
authors.initials: IE
authors.lastname: Hendriks
authors.affiliation: Global Change Department, Mediterranean Institute for Advanced Studies (CSIC-UIB), c/ Miquel Marquès 21, 07190 Esporles, Balearic Islands, Spain; The UWA Oceans Institute and School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
authors.forename: Ylva S
authors.initials: YS
authors.lastname: Olsen
mesh_terms: D000704:Analysis of Variance; D018533:Biomass; D002244:Carbon / Q000032:analysis; D002245:Carbon Dioxide / Q000009:adverse effects / Q000032:analysis*; D017753:Ecosystem; D004579:Electron Transport / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D060086:Hydrothermal Vents / Q000737:chemistry*; D019684:Magnoliopsida / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D008522:Mediterranean Sea; D010788:Photosynthesis / Q000187:drug effects / Q000502:physiology
chemical_list: D002245:Carbon Dioxide; D002244:Carbon
keywords: Carbon cycling; Carbon sequestration; Metabolism; Ocean acidification; Photosynthesis; pH