Quantification of blue carbon pathways contributing to negative feedback on climate change following glacier retreat in West Antarctic fjords

Abstract

Global warming is causing significant losses of marine ice around the polar regions. In Antarctica, the retreat of tidewater glaciers is opening up novel, low-energy habitats (fjords) that have the potential to provide a negative feedback loop to climate change.These fjords are being colonized by organisms on and within the sediment and act as a sink for particulate matter. So far, blue carbon potential in Antarctic habitats has mainly been estimated using epifaunal megazoobenthos (although some studies have also considered macrozoobenthos). We investigated two further pathways of carbon storage and potential sequestration by measuring the concentration of carbon of infaunal macrozoobenthos and total organic carbon (TOC) deposited in the sediment. We took samples along a temporal gradient since time of last glacier ice cover (1-1000 years) at three fjords along the West Antarctic Peninsula. We tested the hypothesis that seabed carbon standing stock would be mainly driven by time since last glacier covered. However, results showed this to be much more complex. Infauna were highly variable over this temporal gradient and showed similar total mass of carbon standing stock per m 2 as literature estimates of Antarctic epifauna. TOC mass in the sediment, however, was an order of magnitude greater than stocks of infaunal and epifaunal carbon and increased with time since last ice cover. Thus, blue carbon stocks and recent gains around Antarctica are likely much higher than previously estimated as is their negative feedback on climate change.

Blue carbon pathways in West Antarctic fjords

“…The blue carbon stocks from infauna averaged 2.58 gC m −2 , which is similar to that found for epifauna in the same study region (2.54 gC m −2 ; Barnes et al, 2020). This represents one of the most interesting findings of Zwerschke et al (2021), showing (1) the major importance of infauna in terms of benthic carbon stocks, and; (2) that current calculated blue carbon stocks (based on epifauna only) for SO shelves might be greatly underestimated. Thus, the role played by infauna in terms of ecosystem services and the negative feedback to climate change provided by Antarctic invertebrate benthos could be much greater than previously thought.…”

“…Invertebrate assemblages in fjords have an estimated epibenthic blue carbon production of 4536 t zC/year. The study of Zwerschke et al (2021) showed infauna to greatly vary between fjords too, with assemblages dominated by suspension feeders, deposit feeders, or a mix of both. The blue carbon stocks from infauna averaged 2.58 gC m −2 , which is similar to that found for epifauna in the same study region (2.54 gC m −2 ; Barnes et al, 2020).…”

“…The paper of Zwerschke et al (2021) on carbon gains driven by glacier retreat comes at a point where blue carbon is increasingly attracting not only scientists, but also management organizations, governments, and international bodies committed to the conservation of marine environments (Bax et al, 2020). Indeed, blue carbon and its mitigation potential have been international recognized, including being addressed by the Intergovernmental Panel on Climate Change (IPCC).…”

Can carbon storage in West Antarctic fjords have an impact on climate change, following glacier retreat?

“…Can carbon storage in West Antarctic fjords have an impact on climate change, following glacier retreat? Zwerschke et al (2021) offer an insight into the potential for carbon sequestration and storage within the new benthic habitats exposed through glacial retreat in Antarctica. The paper provides a description of spatial trends in the carbon stocks of the benthic macrofauna and sediments.…”

Response to concerns regarding the role of Antarctic blue carbon habitats in a global context

“…Response to concerns regarding the role of Antarctic blue carbon habitats in a global context Hunter (2021) has raised several concerns regarding our recent contribution to Global Change Biology (Zwerschke et al, 2022).…”