The potential environmental response to increasing ocean alkalinity for negative emissions

Abstract

The negative emissions technology, artificial ocean alkalinization (AOA), aims to store atmospheric carbon dioxide (CO 2 ) in the ocean by increasing total alkalinity (TA). Calcium carbonate saturation state (ΩCaCO 3 ) and pH would also increase meaning that AOA could alleviate sensitive regions and ecosystems from ocean acidification. However, AOA could raise pH and ΩCaCO 3 well above modern-day levels, and very little is known about the environmental and biological impact of this. After treating a red calcifying algae (Corallina spp.) to elevated TA seawater, carbonate production increased by 60% over a control. This has implication for carbon cycling in the past, but also constrains the environmental impact and efficiency of AOA. Carbonate production could reduce the efficiency of CO 2 removal. Increasing TA, however, did not significantly influence Corallina spp. primary productivity, respiration, or photophysiology. These results show that AOA may not be intrinsically detrimental for Corallina spp. and that AOA has the potential to lessen the impacts of ocean acidification. However, the experiment tested a single species within a controlled environment to constrain a specific unknown, the rate change of calcification, and additional work is required to understand the impact of AOA on other organisms, whole ecosystems, and the global carbon cycle.

The Sensitivity of the Marine Carbonate System to Regional Ocean Alkalinity Enhancement

“…While HAMOCC6 resolves biological processes which influence TA (Ilyina et al, 2013a), there are no mechanisms by which the addition of the implemented conceptual TA tracer can directly affect the biological compartments. OAE influences environmental conditions such as increased calcite saturation states and pH (Feng et al, 2017;Renforth and Henderson, 2017;Gore et al, 2019) and indirectly impacts others, such as trace metal concentrations (Hartmann et al, 2013;Köhler et al, 2013) including iron. In some regions, elevated concentrations of iron in the surface ocean may have a fertilising effect on oceanic phytoplankton, which could subsequently enhance the biological carbon pump (Köhler et al, 2013;Bach et al, 2019).…”

“…In some regions, elevated concentrations of iron in the surface ocean may have a fertilising effect on oceanic phytoplankton, which could subsequently enhance the biological carbon pump (Köhler et al, 2013;Bach et al, 2019). However, unlike anthropogenic ocean acidification, where the effects on biota, ecosystems and human communities are undergoing continual research (Doney et al, 2020), the consequences of alkalinity enhancement (Bach et al, 2019;Gore et al, 2019) are less frequently investigated. Therefore, due to sparse information, bulk phytoplankton, cyanobacteria and zooplankton are implemented within HAMOCC6 with constant mortality rates and cannot respond to extremes of biogeochemical variables (Ilyina et al, 2013a) such as those which occur in the subpolar regional OAE simulations.…”

CO2 Removal With Enhanced Weathering and Ocean Alkalinity Enhancement: Potential Risks and Co-benefits for Marine Pelagic Ecosystems

“…While this is beginning for terrestrial environments (Beerling, 2017;Beerling et al, 2018), very little is known about impacts on marine systems. Here, several side effects have been conceived (Hartmann et al, 2013;Renforth and Henderson, 2017) but only in four cases were these specifically further investigated in silico (Köhler et al, 2013;Hauck et al, 2016) or in vitro (Cripps et al, 2013;Gore et al, 2018).…”

Public perceptions of carbon dioxide removal in the United States and the United Kingdom

“…Participants also voiced serious concerns over ocean impacts: The enhanced weathering o e, he said ost defi itel ot e ause it ould affe t the ildlife i the o ea "a a tha, Champaign-Urbana). This may be problematic for ERW in the near-term, pote tiall e e o stituti g a ed li e fo pu li s, e ause people already feel a strong emotional connection towards the ocean42 , and scientific understanding of ocean impacts is currently incomplete43 . Viewing the ocean as a particularly fragile, interconnected ecosystem, participants were generally unconvinced that an inert material would stay dissolved in ocean water without However, while we expected to find health concerns over dust from rock spreading, this was not mentioned frequently or vociferously.…”