Data from: Abrupt alkalinization alters microbial diversity and promotes the proliferation of marine parasites in coastal microcosm experiments

Mitigation of anthropogenic climate interference will likely require the
removal of legacy atmospheric carbon dioxide (CO2). Ocean alkalinity
enhancement (OAE) is an abiotic marine carbon dioxide removal (mCDR)
approach that accelerates the natural Earth process of rock weathering,
but its effects on marine ecosystems remain uncertain. Here we used
outdoor microcosm experiments to investigate the effects of abrupt
limestone-inspired and NaOH alkalinity additions of ~750 umol kg-1,
reflecting model-predicted OAE scenarios that produce severe localized
impacts (e.g., large variations in pH and W). We assess the response of
seasonal marine microbial communities (phytoplankton, bacteria) and
viruses from the Santa Barbara Channel, analyzed by high-throughput
amplicon sequencing and flow cytometry. Alkalinization, particularly under
low-nutrient conditions, altered microbial diversity and promoted the
proliferation of parasites (Syndiniales), suggesting that abrupt
alkalinization could alter marine ecosystem composition, and potentially
its function, near coastal alkalinity deployment “hotspots”. We highlight
the need for rigorous environmental risk assessments prior to
implementation of OAE technologies.