Abstract
Intertidal algae have to cope with diurnally and seasonally fluctuating environmental factors such as salinity, temperature, dehydration, and light. In New Zealand, solar radiation, including the ultraviolet wavelengths, is also an important stress factor for such algae. Therefore, two native (Bostrychia arbuscula W.H.Harvey [Ceramiales], Champia novae-zelandiae (J.D.Hooker & Harvey) Harvey [Rhodymeniales]) and one introduced red algal taxon (Schizymenia spp. J. Agardh [Nemastomatales]) were investigated over 12 months in terms of stress metabolites which contribute to ultraviolet radiation (UVR) and salinity tolerance. Mycosporine-like amino acids (MAAs), which act as sunscreens, and organic osmolytes were qualitatively and quantitatively analyzed. Porphyra-334, shinorine, and palythine were the most dominant MAAs yet distributed differently among the species. B. arbuscula showed a correlation between photosynthetically active radiation (PAR)/UVR and slightly higher MAA concentrations in summer. In contrast, C. novae-zelandiae displayed the lowest level of MAAs in summer, and no correlation was found between MAA values and solar radiation. In Schizymenia spp., the highest MAA amounts were found in summer, and for most months, a correlation with PAR/UV radiation was visible. While digeneaside and sorbitol were the dominant organic osmolytes in B. arbuscula, floridoside occurred in C. novae-zelandiae and Schizymenia spp. Only B. arbuscula exhibited higher organic osmolyte concentrations in summer. In contrast, floridoside contents in C. novae-zelandiae and Schizymenia spp. were low and highly variable over the course of the seasons. Our data indicate that both native red algal species are well acclimated to the intertidal zone. For the introduced Schizymenia spp., a more narrow salinity tolerance can be assumed, while the high MAA values may explain its establishment in New Zealand.
Highlights
The intertidal zone is influenced by changing and fluctuating environmental factors, such as radiation, temperature, salinity, and mechanical forces, resulting in numerous physicochemical gradients (Lüning 1990)
The mean daily global radiation, the mean daily photosynthetically active radiation (PAR), and the mean daily ultraviolet B (UVB) radiation were highest in Wellington summer (December–February) and decreased continuously toward winter
Our results showed that Bostrychia arbuscula contained a larger number of different mycosporine-like amino acids (MAAs) in contrast to Champia novae-zelandiae and Schizymenia spp., which had only two different MAAs
Summary
The intertidal zone is influenced by changing and fluctuating environmental factors, such as radiation, temperature, salinity, and mechanical forces, resulting in numerous physicochemical gradients (Lüning 1990). Macroalgae living in this zone have to tolerate these diurnally and seasonally changing environmental conditions (Davison and Pearson 1996; Bischof et al 2006; Diehl et al 2019), because they often act as. The most common biochemical acclimation of red algae against UVR is the biosynthesis and accumulation of mycosporine-like amino acids (MAAs) as UV-protective molecules (Carreto and Carignan 2011). The formation and accumulation of MAAs in intertidal red algae is a species-specific process (Hoyer et al 2001, 2002)
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