Cryptophytes: An emerging algal group in the rapidly changing Antarctic Peninsula marine environments

Abstract

The western Antarctic Peninsula (WAP) is a climatically sensitive region where foundational changes at the basis of the food web have been recorded; cryptophytes are gradually outgrowing diatoms together with a decreased size spectrum of the phytoplankton community. Based on a 11‐year (2008–2018) in‐situ dataset, we demonstrate a strong coupling between biomass accumulation of cryptophytes, summer upper ocean stability, and the mixed layer depth. Our results shed light on the environmental conditions favoring the cryptophyte success in coastal regions of the WAP, especially during situations of shallower mixed layers associated with lower diatom biomass, which evidences a clear competition or niche segregation between diatoms and cryptophytes. We also unravel the cryptophyte photo‐physiological niche by exploring its capacity to thrive under high light stress normally found in confined stratified upper layers. Such conditions are becoming more frequent in the Antarctic coastal waters and will likely have significant future implications at various levels of the marine food web. The competitive advantage of cryptophytes in environments with significant light level fluctuations was supported by laboratory experiments that revealed a high flexibility of cryptophytes to grow in different light conditions driven by a fast photo‐regulating response. All tested physiological parameters support the hypothesis that cryptophytes are highly flexible regarding their growing light conditions and extremely efficient in rapidly photo‐regulating changes to environmental light levels. This plasticity would give them a competitive advantage in exploiting an ecological niche where light levels fluctuate quickly. These findings provide new insights on niche separation between diatoms and cryptophytes, which is vital for a thorough understanding of the WAP marine ecosystem.

Long days and long nights: an integrative study reveals survival strategies of an Antarctic diatom during the cold and dark polar winter

“…Diatom communities are negatively impacted by climate‐related change. For example, in the western Antarctic Peninsula, over time cryptophyte populations are replacing diatoms (Mendes et al ., 2023).…”

Long‐term studies on West Antarctic Peninsula phytoplankton blooms suggest range shifts between temperate and polar species

“…These cumulative changes have triggered modifications in biological communities (Antacli et al., 2021; Braeckman et al., 2021). Specifically, at the phytoplankton level, studies show an increase in cryptophytes relative to diatoms in response to decreased salinity (Mendes et al., 2013; Moline et al., 2004) or shallow mixed layers (Mendes et al., 2023). Conversely, a reverse pattern (diatom dominated, rather than cryptophyte dominated) has been linked to the development of a stratified water column (Höfer et al., 2019; Vernet et al., 2008).…”

“…These cumulative changes have triggered modifications in biological communities (Antacli et al, 2021;Braeckman et al, 2021). Specifically, at the phytoplankton level, studies show an increase in cryptophytes relative to diatoms in response to decreased salinity (Mendes et al, 2013;Moline et al, 2004) or shallow mixed layers (Mendes et al, 2023).…”

Drivers of Marine CO2‐Carbonate Chemistry in the Northern Antarctic Peninsula

“…Concomitantly, hydrographic and biogeochemical changes in ocean water masses are taking place around Antarctica, such as freshening trends of shelf and deep waters (Azaneu et al., 2013; De Lavergne et al., 2014; Dotto et al., 2016; Haumann et al., 2016; Hellmer et al., 2011), increased frequency of Circumpolar Deep Water (CDW) intrusions into coastal environments (Henley et al., 2019; Moffat & Meredith, 2018) and pH reduction over different time scales (McNeil & Matear, 2008; Midorikawa et al., 2012; Roden et al., 2013; Sabine et al., 2008). These changes are already impacting and changing the behavior of Southern Ocean ecosystems, which impact ocean health for the development of the sensitive Antarctic biota with different environmental roles, such as biogeochemical recycling and vertical energy fluxes (Figuerola et al., 2020, 2021; Henley et al., 2020; Mendes et al., 2023).…”

“…) and pH reduction over different time scales (McNeil & Matear, 2008;Midorikawa et al, 2012;Roden et al, 2013;Sabine et al, 2008). These changes are already impacting and changing the behavior of Southern Ocean ecosystems, which impact ocean health for the development of the sensitive Antarctic biota with different environmental roles, such as biogeochemical recycling and vertical energy fluxes (Figuerola et al, 2020(Figuerola et al, , 2021Henley et al, 2020;Mendes et al, 2023).…”