Effects of Olivine Sand on Marine Invertebrates Survival and Trace Metal Bioaccumulation

Abstract

Due to the anthropogenic increase of atmospheric CO2 emissions, humanity is facing the negative effects of rapid global climate change. Both active emission reduction and carbon dioxide removal (CDR) technologies are needed to meet the Paris Agreement and limit global warming to 1.5 °C by 2050. One promising CDR approach is coastal enhanced weathering (CEW), which involves the placement of sand made of (ultra)mafic minerals like olivine in coastal zones. Although the large-scale placement of olivine sand could beneficially impact the planet through the consumption of atmospheric CO2 and reduction in ocean acidification, it may also have physical and geochemical impacts on benthic communities. The dissolution of olivine can release dissolved constituents such as trace metals that may affect marine organisms. Here we tested acute and chronic responses of marine invertebrates to olivine sand exposure, as well as examined metal accumulation in invertebrate tissue resulting from olivine dissolution. Two different ecotoxicological experiments were performed on a range of benthic taxa (amphipod, polychaete, bivalve). The first experiment included acute survival and chronic growth tests (10 and 20 days, respectively) of olivine exposure while the second had longer (28 day) exposures to measure acute survival and bioaccumulation of trace metals (e.g. Ni, Cr, Co) derived from olivine sand dissolution. Across all fauna we observed no negative effects on acute survival or chronic growth resulting from olivine exposure. However, over 28 days of exposure, the bent-nosed clam Macoma nasuta (Conrad, 1837) accumulated 4.2 ± 0.7 µg g ww-1 of Ni and the polychaete Alitta virens (M. Sars, 1835) accumulated 3.5 ± 0.9 µg g ww-1 of Ni. No significant accumulation of any other metals was observed. Future work should include longer-term laboratory studies as well as CEW field studies to validate these findings under real-world scenarios.

Keywords: Carbon Dioxide Removal, ocean alkalinity enhancement, enhanced weathering, environmental impact, ecotoxicology, trace metals