Ocean acidification and high irradiance stimulate growth of the Antarctic cryptophyte <i>Geminigera cryophila</i>

Abstract

<p><strong>Abstract.</strong> Ecophysiological studies on Antarctic cryptophytes to assess whether climatic changes such as ocean acidification and enhanced stratification affect their growth in Antarctic coastal waters in the future are lacking so far. This is the first study that investigated the combined effects of increasing availability of pCO<sub>2</sub> (400 and 1000 µatm) and irradiance (20, 200 and 500 μmol photons m<sup>−2</sup> s<sup>−1</sup>) on growth, elemental composition and photophysiology of the Antarctic cryptophyte <i>Geminigera cryophila</i>. Under ambient pCO<sub>2</sub>, this species was characterized by a pronounced sensitivity to increasing irradiance with complete growth inhibition at the highest light intensity. Interestingly, when grown under high pCO<sub>2</sub> this negative light effect vanished and it reached highest rates of growth and particulate organic carbon production at the highest irradiance compared to the other tested experimental conditions. Our results for <i>G. cryophila</i> reveal beneficial effects of ocean acidification in conjunction with enhanced irradiance on growth and photosynthesis. Hence, cryptophytes such as <i>G. cryophila</i> may be potential winners of climate change, potentially thriving better in more stratified and acidic coastal waters and contributing in higher abundance to future phytoplankton assemblages of coastal Antarctic waters.</p>

The interacting effect of prolonged darkness and temperature on photophysiological characteristics of three Antarctic phytoplankton species

“…Numerous studies have aimed to explain how irradiance and other factors influences the composition of Southern Ocean phytoplankton (e.g., Alderkamp et al, 2012;Arrigo et al, 2010;Camoying et al, 2022;Trimborn et al, 2019). In addition to their findings, fitness after long darkness may be a factor that influences early spring phytoplankton composition due to species-specific responses to long darkness.…”