AUTHOR=Gardner Jessie , Peck Victoria L. , Bakker Dorothee C. E. , Tarling Geraint A. , Manno Clara 

TITLE=Contrasting life cycles of Southern Ocean pteropods alter their vulnerability to climate change

JOURNAL=Frontiers in Marine Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1118570

DOI=10.3389/fmars.2023.1118570

ISSN=2296-7745

ABSTRACT=<p>Pteropods are a key part of biogeochemical cycling and epipelagic food webs in the Southern Ocean. However, shelled pteropods are vulnerable to climate change, due to their aragonite shells being particularly sensitive to ocean acidification. Currently our understanding of pteropod responses to environmental change is hindered by uncertainties surrounding their life cycles and population dynamics. In this study, we describe polar shelled pteropod diversity in the north-eastern Scotia Sea, inferring life history and population structures of the dominant pteropod species, <italic>Limacina rangii</italic> (formerly <italic>Limacina helicina antarctica</italic>) and <italic>Limacina retroversa</italic>. An annual timeseries of <italic>Limacina</italic> shell morphometrics was derived from individuals collected in a moored sediment trap at 400 m depth. We found that <italic>L. rangii</italic> and <italic>L. retroversa</italic> have contrasting life history strategies. <italic>L. rangii</italic> has a continuous spawning and recruitment period from November to March and can overwinter as juveniles and adults. <italic>L. retroversa</italic> has discrete spawning events from November to May, producing non–overlapping cohorts of juveniles and adults. Their development to the adult stage takes between two and five months, upon which they overwinter as adults. Our findings suggest different vulnerabilities of <italic>L. rangii</italic> and <italic>L. retroversa</italic> to a changing ocean. For example, since all life stages of <italic>L. rangii</italic> co-exist, vulnerability of one cohort is not detrimental to the stability of the overall population whereas, if one <italic>L. retroversa</italic> cohort fails to recruit, the entire population is threatened. Changes in pteropod populations could have cascading ramifications to Antarctic ecosystems and carbon cycling.</p>