2026-10-12T12:33:01Z https://api.figshare.com/v2/oai

oai:figshare.com:article/34003101 2026-09-26T14:14:21Z category_1 category_272 category_873 category_39 category_734 portal_63 item_type_3 month_year_09_2026

Response of the Carbonate System to Ocean Alkalinity Enhancement: A Mesocosm-Scale Experiment Selene Varliero (18564057) Piero Macchi (1422475) Daniela Basso (287016) Paraskevi Pitta (817537) Iordanis Magiopoulos (6505556) Chiara Santinelli (10067698) Giovanni Checcucci (3000996) Silvia Valsecchi (25114545) Laura Borromeo (25114548) Guido Raos (1714888) Biophysics Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Ecology Biological Sciences not elsewhere classified ocean liming via improving ocean liming eastern mediterranean sea dissolved inorganic carbon 20 μmol l 180 μmol l 120 μmol l 110 μmol l 1080 μmol l treated mesocosms show final net changes ocean alkalinity enhancement alkalinity dropped within low dosage mesocosms 2 </ sub total theoretical increment high dosage mesocosms scale experiment conducted control mesocosms total alkalinity theoretical limit scale experiment low dosages concurrent changes − 60 solid precipitates slight reduction secondary precipitation restricted air high ones external contaminants days due commonly adopted carbonate system calcium hydroxide 14 days We present the results of a mesocosm-scale experiment conducted in 2023 in the eastern Mediterranean Sea (Crete, Greece) to evaluate the effects of ocean liming via the addition of calcium hydroxide. We assessed two dosage regimes through repeated additionslow (20 μmol L^–1 alkalinity increase per addition, reaching a total theoretical alkalinity increment of 120 μmol L^–1) and high (180 μmol L^–1 per addition, reaching a total theoretical increment of 1080 μmol L^–1)comparing against control mesocosms over 14 days, monitoring the pH, total alkalinity, dissolved inorganic carbon, and solid precipitates. The results for the treated mesocosms show that the low dosage effectively increased the total alkalinity and maintained it over the duration of the experiment, unlike the high dosage mesocosms, where the alkalinity dropped within a few days due to the secondary precipitation of carbonates and degassing. In particular, the final net changes of alkalinity were +110 μmol L^–1 for low dosages (close to the theoretical limit) but amounted to about −330 μmol L^–1 for the high ones. The concurrent changes in pH were equal to +0.1 and +0.4, while those in dissolved inorganic carbon were equal to −60 and −620 μmol L^–1, respectively. The fact that, in the low dosage mesocosms, there was a slight reduction in the dissolved inorganic carbon (comparable to that occurring in control mesocosms) despite the total alkalinity increase suggests limited atmospheric CO₂ uptake. We attribute this to restricted air-sea gas exchange caused by the mesocosm lids, which are commonly adopted in these facilities to prevent the entrance of external contaminants. Our study highlights future directions for testing and enhancing the efficiency of CO₂ uptake by seawater, improving ocean liming as a viable climate mitigation strategy. 2026-09-26T00:00:00Z Dataset Dataset 10.1021/acsestwater.6c00342.s001 https://figshare.com/articles/dataset/Response_of_the_Carbonate_System_to_Ocean_Alkalinity_Enhancement_A_Mesocosm-Scale_Experiment/34003101 CC BY-NC 4.0