Effects of elevated pCO 2 on the photosynthetic performance of the sea ice diatoms Navicula directa and Navicula glaciei

• Published in: Journal of Applied Phycology
• Main Authors: Salleh, S, Abdul Mubin, NAA, Darif, NAM, Mohammad, M, McMinn, A
• Format: Article in Journal/Newspaper
• Language: English
• Published: Kluwer Academic Publ 2022
• Subjects: Biological Sciences; Ecology; Marine and estuarine ecology (incl. marine ichthyology); ice algae; Sea ice
• Online Access: https://doi.org/10.1007/s10811-022-02709-y; http://ecite.utas.edu.au/150145

Sea ice algal communities are generally dominated by pennate diatoms, which commonly occur at the ice-water interface and in brine channels. They also make a significant contribution to higher trophic levels associated with sea ice habitats. Here, the photosynthetic responses of two sea ice diatom species, Navicula directa and Navicula glaciei , to changes in pCO 2 under controlled laboratory conditions were compared. pCO 2 (390ppm and 750ppm) was manipulated to simulate a shift from present levels (1990) to predicted IPCC year 2100 worst-case scenario levels. To investigate these effects, a pulse-amplitude modulation (PAM) fluorometer was used to measure the photosynthetic performance. The ability of the sea ice algae to grow and photosynthesize within physio-chemical gradients in the sea ice suggests that both sea ice species are likely to be well adapted to cope with changes in pCO 2 concentrations. Lower pH and higher pCO 2 for 7days resulted in increased biomass, especially for N. directa . However, a decline in photosynthetic capacity (rETR max ) was observed for both species (highest value 11.375 0.163, control; and 8.322 1.282, treatment). Navicula glaciei showed significant effects of elevated pCO 2 ( p < 0.05) on its photosynthetic response, while N. directa did not. Future changes in CO 2 and pH may thus not significantly affect all diatoms but may lead to changes in the photosynthetic activities in some species.