A highly prevalent filamentous algal endophyte in natural populations of the sugar kelp Saccharina latissima is not detected during cultivation in Northern Brittany

Abstract

The sugar kelp Saccharina latissima is cultivated in Europe for food, feed and ultimately the production of chemical commodities and bioenergy. Being cultivated in the open sea, S. latissima is exposed to potentially harmful organisms, such as Laminarionema elsbetiae, a filamentous brown algal endophyte with a very high prevalence in wild populations of European S. latissima. As it was shown previously that S. latissima sporophytes get infected by L. elsbetiae very early in their life, seeding the spores on collectors and keeping them under controlled conditions during the critical time of a possible infection with filamentous endophytes could be advantageous over direct seeding techniques, where the ropes are deployed within days after seeding. We used a qPCR-assay to assess the prevalence of the endophyte L. elsbetiae in S. latissima cultivated during winter in Northern Brittany, comparing individuals from direct-seeded ropes and collector-seeded lines that were kept in laboratory conditions for different time spans. No DNA of the endophyte was detected in the samples, suggesting that either the kelps were not infected or the amount of endophytic filaments were below the detection rate of the qPCR assay. Furthermore, L. elsbetiae could not be detected in the seawater surrounding the kelp farm, indicating that L. elsbetiae is not fertile or disperses at a very small scale in Northern Brittany during the deployment time of young kelps. Our results suggest that infections of cultivated S. latissima with the endophyte L. elsbetiae might be a minor problem in kelp farms in Northern Brittany if the seeding production is kept under controlled conditions without external contamination.

Modulation of physiological performance by temperature and salinity in the sugar kelp Saccharina latissima

“…2012; Bernard et al . 2019). In Roscoff, Brittany, S. latissima is exposed to high tidal coefficients (Gévaert et al .…”

“…Namely, certain kelp pigments, such as carotenoids, and mannitol are relevant for human health (Iwamoto & Shiraiwa 2005;Wells et al 2017). S. latissima has been traditionally harvested and it is recently also commercially cultivated in Brittany, France (Mesnildrey et al 2012;Bernard et al 2019). In Roscoff, Brittany, S. latissima is exposed to high tidal coefficients (Gévaert et al 2003) and low tides might lead to exposure to low salinity during rain and hyperosmotic stress when desiccated (Lüning 1990).…”

18S rDNA gene metabarcoding of microeukaryotes and epi‐endophytes in the holobiome of seven species of large brown algae

“…The nutrient‐rich surfaces of brown algae and other seaweeds harbor a wide diversity of microbial epibionts and endobionts, comprising eukaryotes (Armstrong et al, 2000; Bernard, Rousvoal, et al, 2019; Bernard, Strittmatter, et al, 2019; Gachon et al, 2009; Zuccaro et al, 2008), prokaryotes (Capistrant‐Fossa et al, 2021; Egan et al, 2013; Goecke et al, 2013; Hollants et al, 2013; Singh & Reddy, 2015), and viruses (Lachnit et al, 2016; McKeown et al, 2017; McKeown et al, 2018; Müller et al, 1998), i.e., the symbiome. These, together with the host, are collectively referred to as the seaweed holobiont and can be considered a localized ecosystem living on and in a host (Egan et al, 2013; Margulis & Fester, 1991; Skillings, 2016; van der Loos et al, 2019).…”

“…Previous studies demonstrate that a broad taxonomic diversity of microeukaryotes is associated with brown algae, including surface‐dwelling heterotrophic diatoms, dinoflagellates, and ciliates (Armstrong et al, 2000), naked amoebae (Rogerson, 1991), epiphytic and endophytic diatoms (Baardseth, 1969; Lam et al, 2008; Totti et al, 2009), and algal epi‐endophytes (Bernard et al, 2017; Bernard, Rousvoal, et al, 2019; Bringloe et al, 2021; Rinkel et al, 2012) in addition to parasitic or saprotrophic labyrinthulids (Raghukumar, 2002; Raghukumar & Damare, 2011), oomycetes (Gachon et al, 2009, 2017; Strittmatter et al, 2013), phytomyxids (Goecke et al, 2012; Murúa et al, 2017; Neuhauser et al, 2014), and fungi (Küpper & Müller, 1999; Tourneroche et al, 2020; Vallet et al, 2018; Zuccaro et al, 2003, 2008). The nature of these microeukaryote–host relationships is mostly unknown, although some symbionts can have detrimental effects on their macroalgal hosts, for example, phytomyxids (Goecke et al, 2012; Murúa et al, 2017; Neuhauser et al, 2014), oomycetes (Gachon et al, 2009, 2017; Strittmatter et al, 2013), chytridiomycete fungi (Küpper et al, 2006; Küpper & Müller, 1999), and phaeophycean parasites and pathogens (Bernard et al, 2017; Bernard, Rousvoal, et al, 2019; Bernard, Strittmatter, et al, 2019; Bringloe et al, 2021; Heesch et al, 2008). Other microeukaryotes are suspected to have a beneficial effect on their hosts, for example, fungal mutualists (Garbary & MacDonald, 1995; Toxopeus et al, 2011; Zuccaro et al, 2008) and endophytes that might protect seaweeds against pathogenic protists (Vallet et al, 2018).…”

“…These epi‐/endophytes can have negative effects, such as imposing physical and physiological stress on their host, or positive ecosystem effects, such as increasing available habitats and food for both macroscopic and microscopic life (Potin, 2012). As macroalgal symbiomes comprise multicellular algae as epiphytes (Bjærke & Fredriksen, 2010; Fredriksen et al, 2005) and potentially pathogenic endophytes (Amsler et al, 2009; Bernard, Rousvoal, et al, 2019; Bernard, Strittmatter, et al, 2019; Bringloe et al, 2021; Ellertsdóttir & Peters, 1997; Heesch et al, 2008; Murúa et al, 2018) in addition to microeukaryotes, the almost complete lack of knowledge of these eukaryotes in a holobiont context is a fundamental knowledge gap which needs to be filled in order to improve our understanding of brown algal holobionts. Consequently, there is a need for studies that apply comprehensive high‐throughput sequencing (HTS) techniques to explore seaweed‐associated microbiomes (Bringloe et al, 2021; van der Loos et al, 2019).…”