The effect of ocean alkalinity enhancement on a coastal phytoplankton community was assessed via a microcosm experiment. The effect of alkalinity enhancement in two scenarios (i) when enclosed seawater was in equilibrium with atmospheric CO2 and (ii) when enclosed seawater was not in equilibrium with atmospheric CO2 were explored. Alkalinity was increased by ~497 umol/kg in these two treatments and plankton communities, carbonate chemistry, dissolved inorganic nutrients, particulate matter and chlorophyll a dynamics monitored over a 22 day period where a spring bloom occurred.

This dataset contains data measured using an autonomous, automated total alkalinity titrator installed at the University of New Hampshire's Coastal Marine Laboratory (CML). The CML is located at the outlet of the Great Bay estuary along the New Hampshire coast. Hourly data were measured from the lab's continuous seawater supply, located approximately one meter off the bottom. In addition to total alkalinity, salinity and water temperature data are included. Temporal data coverage runs from May 2016 to November 2019, although there are substantial data gaps, in particular from April 2018 until March 2019 due to a fire and subsequent repairs to the CML building. This effort was part of the NOAA Ocean Acidification Program (OAP) and Ocean Technology Transfer Project grant entitled "Tracking Ocean Alkalinity using New Carbon Measurement Technologies (TAACT)". Measurements of pCO2 at the CML site are available from the Northeastern Regional Association of Coastal Ocean Observing Systems: www.http://neracoos.org/datatools

This dataset includes discrete sample and profile data collected from PROFESSOR SIEDLECKI in the Adriatic Sea, Aegean Sea, Mediterranean Sea, Mediterranean Sea - Eastern Basin and Tyrrhenian Sea from 1988-11-17 to 1988-11-26. These data include DISSOLVED OXYGEN, NITRATE, Potential temperature (theta), SALINITY, TOTAL ALKALINITY (TA), WATER TEMPERATURE, pH and silicate. The instruments used to collect these data include Alkalinity titrator, CTD, bottle and pH sensors. These data were collected by AÃda F. RÃos of Institute of Marine Research Vigo (IIM) as part of the Biomass-IV and Biomass-IV Expedition ANA Cruise dataset. CDIAC associated the following cruise ID(s) with this dataset: 67SL19881117 and Biomass-IV Expedition ANA Cruise

AIMS, in collaboration with The Clean Ocean Foundation, has completed this proof-of-concept study to facilitate further sampling of microplastics in the Southern Ocean (a joint collaborative initiative involving the Australian Institute of Marine Science (AIMS), the Integrated Marine Observing System (IMOS) and solo yachtswoman Lisa Blair). In this project, AIMS trialled density flotation and chemical digestion separation methods to process subsurface seawater samples and retrieve environmental microplastics. This report presents findings from controlled spike recovery tests as well as opportunistic field sampling events of subsurface waters processed with both separation methods. Opportunistic samples were collected along the NSW coastline in December 2021. Given the location of the sampling transects, this report also provides the first spatial baseline information on microplastic contamination in NSW waters adjacent to estuary outflows and urban outfalls. After trialling both separation methods, microplastics retrieved from the NSW samples were physically and chemically characterized used stereomicroscopy and spectroscopy, respectively. No statistical analysis were performed due to the low number of replicates. Results showed repeated chemical digestion employing potassium hydroxide solutions was most effective at microplastic recovery. Microplastics were retrieved from each of the eight samples collected in NSW subsurface seawaters, with polyethylene and polyester fibres being the most prevalent polymer types detected. The highest numbers of microplastics were recorded adjcent to the estuary outflows and urban outfalls present within the sampling area. Overall, the sampling and processing protocols developed here are allowing for the extension of the spatial coverage of microplastic data in seawaters.

Ocean alkalinity enhancement (OAE) is an emerging carbon dioxide removal (CDR) strategy that leverages the natural processes of weathering and acid neutralisation to durably store atmospheric CO2 in seawater. OAE can be achieved with a variety of methods, all of which have different environmental implications. One widely considered method utilizes electrochemistry to remove strong acid from seawater, leaving sodium hydroxide (NaOH) behind. This study evaluates the impacts of OAE via NaOH (NaOH-OAE) on a coastal plankton bloom, with particular focus on how macronutrient regeneration in the aftermath of the bloom responds to the perturbation. To investigate this, we enclosed a natural coastal phytoplankton community, including coccolithophores, in nine microcosms. The microcosms were divided into three groups: control, unequilibrated (512.1 ± 2.5 µmol kg-1 alkalinity increase) and equilibrated (499.3 ±5.65 µmol kg-1 alkalinity increase). Light was provided for 11 days to stimulate a bloom (light phase) and lights were turned off thereafter to investigate alkalinity and nutrient changes for 21 days (dark phase). We found no detectable effect of equilibrated NaOH-OAE on phytoplankton community and bacteria abundances determined with flow cytometry but observed a small yet detectable restructuring of phytoplankton communities under unequilibrated conditions. NaOH-OAE had no significant effect on alkalinity, NOx- and phosphate regeneration, but increased silicate regeneration by 64% over 21 days under darkness in the unequilibrated treatments where seawater pH was highest (8.65 relative to 7.92 in the control). Additional dissolution experiments with two diatom species supported this outcome on silicate regeneration for one of the two species, thereby suggesting that the effect is species specific. Our results point towards the potential of NaOH-OAE to influence regeneration of silicate in the surface ocean and thus the growth of diatoms, at least under the very extreme NaOH-OAE conditions simulated here.

Ocean alkalinity enhancement (OAE) is an emerging carbon dioxide removal (CDR) strategy that leverages the natural processes of weathering and acid neutralisation to durably store atmospheric CO2 in seawater. OAE can be achieved with a variety of methods, all of which have different environmental implications. One widely considered method utilizes electrochemistry to remove strong acid from seawater, leaving sodium hydroxide (NaOH) behind. This study evaluates the impacts of OAE via NaOH (NaOH-OAE) on a coastal plankton bloom, with particular focus on how macronutrient regeneration in the aftermath of the bloom responds to the perturbation. To investigate this, we enclosed a natural coastal phytoplankton community, including coccolithophores, in nine microcosms. The microcosms were divided into three groups: control, unequilibrated (512.1 ± 2.5 µmol kg-1 alkalinity increase) and equilibrated (499.3 ±5.65 µmol kg-1 alkalinity increase). Light was provided for 11 days to stimulate a bloom (light phase) and lights were turned off thereafter to investigate alkalinity and nutrient changes for 21 days (dark phase). We found no detectable effect of equilibrated NaOH-OAE on phytoplankton community and bacteria abundances determined with flow cytometry but observed a small yet detectable restructuring of phytoplankton communities under unequilibrated conditions. NaOH-OAE had no significant effect on alkalinity, NOx- and phosphate regeneration, but increased silicate regeneration by 64% over 21 days under darkness in the unequilibrated treatments where seawater pH was highest (8.65 relative to 7.92 in the control). Additional dissolution experiments with two diatom species supported this outcome on silicate regeneration for one of the two species, thereby suggesting that the effect is species specific. Our results point towards the potential of NaOH-OAE to influence regeneration of silicate in the surface ocean and thus the growth of diatoms, at least under the very extreme NaOH-OAE conditions simulated here.

This dataset includes lab-based measurements of carbonate substrate bioerosion and calcification using living date mussels (Lithophaga) collected outside Kaneohe Bay, at Site OAH-OCC-005, Hawaiian islands, Pacific Ocean, from 2019-11-21 to 2020-01-08. Lithophaga are important macroboring organisms in the Pacific Ocean, presenting a threat to the persistence of reef frameworks throughout the tropics and subtropics. They bore into their substrate through a combination of mechanical and chemical means of eroding carbonate to provide a living space for themselves, thereby weakening the structure. Despite their ubiquity, it is difficult to accurately estimate their rates of erosion through traditional means. As such, we proposed a study whereby living Lithophaga were placed into artificially created bore holes in standardized calcium carbonate cores (dead Porites lobata) to assess the erosion of this substrate over time. These plugs were dry and buoyant, and weighed at the start and finish of the experiment to assess potential loss of mass over the course of the experiment due to Lithophaga erosion. Control cores had no Lithophaga present.

This dataset includes discrete sample and profile data collected from THALASSA in the North Atlantic Ocean from 2002-06-11 to 2002-07-11. These data include DISSOLVED OXYGEN, HYDROSTATIC PRESSURE, NITRATE, Potential temperature (theta), SALINITY, TOTAL ALKALINITY (TA), WATER TEMPERATURE, pH, phosphate and silicate. The instruments used to collect these data include Alkalinity titrator, CTD, bottle and spectrophotometer. These data were collected by Herlé Mercier of IFREMER Centre de Brest, Fiz F. Pérez of Institute of Marine Research Vigo (IIM), and Marta Álvarez of Spanish Institute of Oceanography (IEO) as part of the CARINA_35TH20020611_OVIDE 2002 dataset. CDIAC associated the following cruise ID(s) with this dataset: OVIDE 2002 The CARINA (CARbon dioxide IN the Atlantic Ocean) data synthesis project is an international collaborative effort of the EU IP CARBOOCEAN, and U.S. partners. It has produced a merged internally consistent dataset of open ocean subsurface measurements for biogeochemical investigations, in particular, studies involving the carbon system. The original focus area was the North Atlantic Ocean, but over time the geographic extent expanded and CARINA now includes data from the entire Atlantic, the Arctic Ocean, and the Southern Ocean.

Ocean alkalinity enhancement is a proposed method of marine carbon dioxide removal that enhances the ocean’s uptake of atmospheric carbon dioxide (CO2) and converts it to dissolved bicarbonate for long-term ocean storage. This method of marine carbon dioxide removal has been gaining attention for its potential to durably (10,000+ years) store large amounts of CO2 (Gt+ where 1 Gt = 1 x 10^9 tons), while potentially ameliorating acidification in the vicinity of the alkalinity release. This study focuses on a novel release of electrochemically derived aqueous alkalinity into Sequim Bay, WA, through a previously established wastewater treatment plant (WWTP). This research was made possible through the collaboration of industry, academic, and federal partners, which enabled the establishment of an Ebb Carbon electrochemical mCDR system at the Pacific Northwest National Laboratory in Sequim, WA, for ocean alkalinity enhancement field trials. During these field trials, pH was measured across the WWTP system from the initial alkalinity dosing, throughout the WWTP, and at the outfall. We use the NBS scale for pH throughout this study as it is the scale used in discharge permit limits specified for WWTP and NPDES regulation and compliance monitoring. The background pHNBS of Sequim Bay seawater was between 7.5 to 7.7 for the November and February field tests. The mixing tank's pHNBS was raised to the maximum value permitted for the WWTP (9.0) and maintained across the system (±0.2) during the outfall releases. At the outfall, the elevated pH and alkalinity was quickly diluted, such that the region with a measurable signal was limited to within ~2.5 m of the discharge pipe. We were able to successfully monitor an increase in pHNBS across all four pulses of alkalinity-enhanced seawater discharge during the February 2025 field trial, with peak pHNBS values of 8.3 or 8.1, as recorded by outfall-adjacent YSI Exo 2 sonde and SAMI-pH sensors, respectively. The alkalinity-enhanced seawater did not measurably alter the surrounding waters' temperature, salinity, turbidity, or oxygen. This study provides proof-of-concept for a conservative small-scale release of electrochemically generated alkalinity-enhanced seawater from a coastal outfall.