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

• Published in: Global Change Biology
• Main Authors: Mendes, Carlos Rafael Borges, Costa, Raul Rodrigo, Ferreira, Afonso, Jesus, Bruno, Tavano, Virginia Maria, Dotto, Tiago Segabinazzi, Leal, Miguel Costa, Kerr, Rodrigo, Islabão, Carolina Antuarte, Franco, Andréa de Oliveira da Rocha, Mata, Mauricio M., Garcia, Carlos Alberto Eiras, Secchi, Eduardo Resende
• Other Authors: Conselho Nacional de Desenvolvimento Científico e Tecnológico, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Fundação para a Ciência e a Tecnologia
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: Antarctic; Antarctic Peninsula; The Antarctic; Antarc*
• Online Access: http://dx.doi.org/10.1111/gcb.16602; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.16602; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/gcb.16602

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.