Abstract
One of the options to mitigate atmospheric CO2 increase is CO2 Capture and Storage in sub-seabed geological formations. Since predicting long-term storage security is difficult, different CO2 leakage scenarios and impacts on marine ecosystems require evaluation. Submarine CO2 vents may serve as natural analogues and allow studying the effects of CO2 leakage in a holistic approach. At the study site east of Basiluzzo Islet off Panarea Island (Italy), gas emissions (90–99% CO2) occur at moderate flows (80–120 L m−2 h−1). We investigated the effects of acidified porewater conditions (pHT range: 5.5–7.7) on the diversity of benthic bacteria and invertebrates by sampling natural sediments in three subsequent years and by performing a transplantation experiment with a duration of one year, respectively. Both multiple years and one year of exposure to acidified porewater conditions reduced the number of benthic bacterial operational taxonomic units and invertebrate species diversity by 30–80%. Reduced biodiversity at the vent sites increased the temporal variability in bacterial and nematode community biomass, abundance and composition. While the release from CO2 exposure resulted in a full recovery of nematode species diversity within one year, bacterial diversity remained affected. Overall our findings showed that seawater acidification, induced by seafloor CO2 emissions, was responsible for loss of diversity across different size-classes of benthic organisms, which reduced community stability with potential relapses on ecosystem resilience.
Highlights
The combustion of fossil fuels and industrialization are the main causes of the current exceptionally high rates of increase in atmospheric CO2, which in turn contributes to climate change (Blanco et al, 2014)
We focus on the effect of CO2 leakage on the biodiversity of the vent system at Basiluzzo Islet and explore the relation between biodiversity and temporal stability in structural aspects of the benthos
While we focus on bacteria at the level of operational taxonomic units (OTUs), we addressed the most dominant meio- and macrofauna taxa at species level and tested the following hypotheses: 1) Both one year and at least 3 years of exposure to acidified porewater conditions reduces OTU or species diversity of benthic organisms belonging to different size classes
Summary
The combustion of fossil fuels and industrialization are the main causes of the current exceptionally high rates of increase in atmospheric CO2, which in turn contributes to climate change (Blanco et al, 2014). Dashfield et al, 2008; Ingels et al, 2018; Widdicombe et al, 2009; Schade et al, 2016; Thistle et al, 2006), injected liquefied CO2 into corrals deposited on the deep-sea floor (porewater pH: 5.4; Carman et al, 2004; Barry et al, 2005) or released CO2 gas via a borehole at 11 m below the seafloor (porewater pH: 7.5; Widdicombe et al, 2015) Those experiments are very relevant in determining the effects of more or less severe, acute Studies at such natural analogues may provide answers to whether species from originally undisturbed natural environments are able to persist and tolerate, and eventually adapt to the highly acidified conditions, or whether they are being replaced by colonizing tolerant species and what consequences this might have for the biodiversity and the role they fulfil within an ecosystem under high biochemical pressure (Molari et al, 2018; Zeppilli et al, 2015)
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