Impact of intentionally injected carbon dioxide hydrate on deep-sea benthic foraminiferal survival

Sequestration of carbon dioxide (CO(2)) in the ocean is being considered as a feasible mechanism to mitigate the alarming rate in its atmospheric rise. Little is known, however, about how the resulting hypercapnia and ocean acidification may affect marine fauna. In an effort to understand better the protistan reaction to such an environmental perturbation, the survivorship of benthic foraminifera, which is a prevalent group of protists, was studied in response to deep-sea CO(2) release. The survival response of calcareous, agglutinated, and thecate foraminifera was determined in two experiments at similar to 3.1 and 3.3 km water depth in Monterey Bay (California, USA). Approximately 5 weeks after initial seafloor CO(2) release, in situ incubations of the live-dead indicator CellTracker Green were executed within seafloor-emplaced pushcores. Experimental treatments included direct exposure to CO(2) hydrate, two levels of lesser exposure adjacent to CO(2) hydrate, and controls, which were far removed from the CO(2) hydrate release. Results indicate that survivorship rates of agglutinated and thecate foraminifera were not significantly impacted by direct exposure but the survivorship of calcareous foraminifera was significantly lower in direct exposure treatments compared with controls. Observations suggest that, if large scale CO(2) sequestration is enacted on the deep-sea floor, survival of two major groups of this prevalent protistan taxon will likely not be severely impacted, while calcareous foraminifera will face considerable challenges to maintain their benthic populations in areas directly exposed to CO(2) hydrate.