title: Seaweed fails to prevent ocean acidification impact on foraminifera along a shallow-water CO2 gradient.
abstract: Ocean acidification causes biodiversity loss, alters ecosystems, and may impact food security, as shells of small organisms dissolve easily in corrosive waters. There is a suggestion that photosynthetic organisms could mitigate ocean acidification on a local scale, through seagrass protection or seaweed cultivation, as net ecosystem organic production raises the saturation state of calcium carbonate making seawater less corrosive. Here, we used a natural gradient in calcium carbonate saturation, caused by shallow-water CO2 seeps in the Mediterranean Sea, to assess whether seaweed that is resistant to acidification (Padina pavonica) could prevent adverse effects of acidification on epiphytic foraminifera. We found a reduction in the number of species of foraminifera as calcium carbonate saturation state fell and that the assemblage shifted from one dominated by calcareous species at reference sites (pH ∼8.19) to one dominated by agglutinated foraminifera at elevated levels of CO2 (pH ∼7.71). It is expected that ocean acidification will result in changes in foraminiferal assemblage composition and agglutinated forms may become more prevalent. Although Padina did not prevent adverse effects of ocean acidification, high biomass stands of seagrass or seaweed farms might be more successful in protecting epiphytic foraminifera.
authors.affiliation: Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, Plymouth University, Drake Circus Plymouth, PL4 8AA, U.K.
authors.forename: Laura R
authors.initials: LR
authors.lastname: Pettit
authors.affiliation: School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus Plymouth, PL4 8AA, U.K.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Smart
authors.affiliation: School of Geography, Earth and Environmental Sciences, Plymouth University, Drake Circus Plymouth, PL4 8AA, U.K.
authors.forename: Malcolm B
authors.initials: MB
authors.lastname: Hart
authors.affiliation: DiSTeM University of Palermo, CoNISMa via Archirafi 28, 90123, Palermo, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Milazzo
authors.affiliation: Marine Biology and Ecology Research Centre, School of Marine Science and Engineering, Plymouth University, Drake Circus Plymouth, PL4 8AA, U.K.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Hall-Spencer
keywords: Benthic foraminifera; blue carbon; coastal communities; ocean acidification; shallow-water CO2 seeps