Stress metabolite pattern in the eulittoral red alga Pyropia plicata (Bangiales) in New Zealand – mycosporine-like amino acids and heterosides

© 2018 Intertidal rocky shore ecosystems are affected by steep environmental gradients such as fluctuating solar irradiation and salinity along the marine-terrestrial interface. The eulittoral red alga Pyropia plicata (Bangiales) is endemic and abundant to coastal regions of New Zealand and almost unstudied in terms of ecophysiological performance under radiation and salinity stress. Therefore, the acclimation potential of this species against enhanced ultraviolet radiation (UVR) and osmotic stress was evaluated in a combination of field and laboratory experiments with an emphasis on stress metabolite concentrations (UV-sunscreens, organic osmolytes). Samples of P. plicata were collected at the same site in the intertidal zone of Wellington, New Zealand over three seasons (April–November 2016) and used in independent UV and salt stress experiments under controlled conditions. The mycosporine-like amino acids (MAA) shinorine and porphyra-334 were the quantitatively dominant UV-sunscreen compounds, and the total concentrations varied over the year between 5 and 14 mg g−1 dry weight (DW), but neither UVR nor PAR had a significant impact on the total or individual MAA concentrations. A UV radiation stress experiment was conducted, but the total MAA concentrations of 6–8 mg g−1 DW did not change, neither did the contents of shinorine (~ 3 mg g−1 DW) nor that of porphyra-334 (4–5 mg g−1 DW). This suggests, that P. plicata has sufficiently high UV-sunscreen amounts and hence does not respond to changes in UV radiation. Pyropia plicata contained three heterosides (floridoside, D- and L-isofloridoside), which act as organic osmolytes. Seasonally the total concentrations of these compounds varied between 203 and 1226 mmol kg−1 DW, with L-isofloridoside quantitatively dominating all samples. A salt stress experiment showed an increase in the total heteroside concentrations in P. plicata with increasing salinities. However, floridoside was the most up-regulated heteroside under hypersaline conditions indicating its key role in osmotic acclimation. Our data indicate that P. plicata always contains various stress metabolites in consistently high concentrations which mitigate against environmental changes typical of the intertidal zone of New Zealand

Molecular phylogeny and taxonomic revision of the genus Wittrockiella (Pithophoraceae, Cladophorales), including the descriptions of W. australis sp. nov. and W. zosterae sp. nov

© 2017 Phycological Society of America Wittrockiella is a small genus of filamentous green algae that occurs in habitats with reduced or fluctuating salinities. Many aspects of the basic biology of these algae are still unknown and the phylogenetic relationships within the genus have not been fully explored. We provide a phylogeny based on three ribosomal markers (ITS, LSU, and SSU rDNA) of the genus, including broad intraspecific sampling for W. lyallii and W. salina, recommendations for the use of existing names are made, and highlight aspects of their physiology and life cycle. Molecular data indicate that there are five species of Wittrockiella. Two new species, W. australis and W. zosterae, are described, both are endophytes. Although W. lyallii and W. salina can be identified morphologically, there are no diagnostic morphological characters to distinguish between W. amphibia, W. australis, and W. zosterae. A range of low molecular weight carbohydrates were analyzed but proved to not be taxonomically informative. The distribution range of W. salina is extended to the Northern Hemisphere as this species has been found in brackish lakes in Japan. Furthermore, it is shown that there are no grounds to recognize W. salina var. kraftii, which was described as an endemic variety from a freshwater habitat on Lord Howe Island, Australia. Culture experiments indicate that W. australis has a preference for growth in lower salinities over full seawater. For W. amphibia and W. zosterae, sexual reproduction is documented, and the split of these species is possibly attributable to polyploidization