Short-term impact assessment of ocean liming: a copepod exposure test

Highlights

• Ocean liming (OL) may cause temporary pH peaks which can be dangerous for marine life.
• Short-term exposure tests (<24 h) are required to evaluate the impact of OL.
• At pH 9 for exposures lower than 6 h, copepods showed no adverse effects.
• At pH ≥ 10, adverse effects on copepods were seen for exposures shorter than 3 h.

Abstract

Ocean liming (OL) is a potential carbon dioxide removal (CDR) method that aims to increase the ocean’s capacity to absorb atmospheric CO₂ by adding hydrated lime to the surface ocean. Modeling studies indicate that OL may cause temporary pH spikes lasting several minutes, depending on the lime sparging rate. Little is known about the short-term effects of these spikes on marine organisms. Aim of the present study is to investigate these effects on the copepod Acartia tonsa. Copepods were exposed to different pH conditions (9, 10, 11, 12) by dosing different hydrated lime solutions. Copepod mortality, movements, and behavior were recorded. At pH 9 for short exposure times (<6 h), no negative effects were observed indicating a potential tolerable threshold for OL applications. At longer exposure times (>6 h) and pH higher than 9, negative effects (mortality and sublethal effects) were found significantly higher than in the control.

Camatti E., Valsecchi S., Caserini S., Barbaccia E., Santinelli C., Basso D. & Azzellino A., 2024. Short-term impact assessment of ocean liming: a copepod exposure test. Marine Pollution Bulletin 198: 115833. doi: 10.1016/j.marpolbul.2023.115833. Article.

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