Abstract
Ocean acidification and warming are affecting polar regions with particular intensity. Rocky shores of the Antarctic Peninsula are dominated by canopy-forming Desmarestiales. This study investigates the physiological and transcriptomic responses of the endemic macroalga Desmarestia anceps to a combination of different levels of temperature (2 and 7 °C), dissolved CO2 (380 and 1000 ppm), and irradiance (65 and 145 µmol photons m-2 s-1). Growth and photosynthesis increased at high CO2 conditions, and strongly decreased at 2 °C plus high irradiance, in comparison to the other treatments. Photoinhibition at 2 °C plus high irradiance was evidenced by the photochemical performance and intensive release of dissolved organic carbon. The highest number of differentially regulated transcripts was observed in thalli exposed to 2 °C plus high irradiance. Algal 13C isotopic discrimination values suggested an absence of down-regulation of carbon-concentrating mechanisms at high CO2. CO2 enrichment induced few transcriptomic changes. There was high and constitutive gene expression of many photochemical and inorganic carbon utilization components, which might be related to the strong adaptation of D. anceps to the Antarctic environment. These results suggest that increased temperature and CO2 will allow D. anceps to maintain its productivity while tolerating higher irradiances than at present conditions.
Highlights
Global change is affecting polar regions to a larger extent than any other region on Earth (Intergovernmental Panel on Climate Change, 2013)
Young sporophytes of Desmarestia anceps Montagne were raised from Alfred Wegener Institute (AWI) stock cultures of female and male gametophytes, established from spores of fertile sporophytes collected at Potter Cove (King George Island, South Shetland Islands, Antarctica; 62°14ʹS, 58°38ʹW) using the cultivation methods described by Wiencke and tom Dieck (1989)
Sporophytes were transferred to 5 l beakers at a photon fluence rate (PFR) of 50–55 μmol photons m−2 s−1 provided by white light fluorescent tubes (L58W/965; Osram, Germany); PFR was measured in the water in the middle of the beaker using a spherical micro quantum sensor (US-SQS/L; Walz, Germany) connected to a radiometer (LiCor-250A; Li-Cor Biosciences, USA)
Summary
Global change is affecting polar regions to a larger extent than any other region on Earth (Intergovernmental Panel on Climate Change, 2013). The retreat of sea-ice cover in coastal areas as a consequence of global warming will result in increased irradiance levels in the water column. A recent reduction in phytoplankton productivity in the northern Antarctic Peninsula region has been observed as a consequence of reduced ice cover (Montes-Hugo et al, 2009), probably owing to less stratified conditions in response to an increase in wind mixing. This decline in phytoplankton may result in a significant rise in subtidal irradiance in areas of low turbidity
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