High nutrient requirement on the photosynthetic performance of a diatom species of the genus <i>Nitzschia</i> (<scp>Bacillariophyta</scp>) isolated from the high‐altitude wetland, <scp>Salar</scp> de <scp>Huasco</scp>, <scp>Chile</scp>

<jats:title>SUMMARY</jats:title><jats:p>This study characterizes the ecophysiological responses and growth dynamics of <jats:italic>Nitzschia palea</jats:italic> isolated from Salar de Huasco, Chile, a high‐altitude wetland located at 3800 m above sea level. The culture was maintained at 17°C under cool‐white fluorescent light with a 14:10 h light/dark photocycle and a photon flux of 50 μmol photons m<jats:sup>−</jats:sup><jats:sup>2</jats:sup> s<jats:sup>−1</jats:sup>. The diatom was identified morphologically and genetically, with phylogenetic analysis confirming its close relationship to known <jats:italic>N. palea</jats:italic> strains. Photophysiological responses were measured along with a series of media and temperature conditions in <jats:italic>N. palea</jats:italic> strain. Modified f/2 media supplemented with different concentrations of Si, Se and vitamins were tested. Subsequently, growth in the double‐Si f/2 media was assessed at three different temperatures. Lastly, the diatom strain was incubated at 17°C and 27–29°C in f/2 + double‐Si (NN: non‐extra nutrient addition) and a highly eutrophic state of f/2 (WN: with nutrient enrichment addition). The highest growth was observed using the f/2 media WN at 17°C (day 5, 4.46 × 10<jats:sup>5</jats:sup> ± 3.15 × 10<jats:sup>4</jats:sup> SD cells mL<jats:sup>−1</jats:sup>). Temperature significantly influenced growth; 17°C supported higher cell densities and more stable photosynthetic parameters compared 27–29°C. Nutrient enrichment further enhanced photosynthetic efficiency (αETR) and maximal quantum yield (<jats:italic>F<jats:sub>v</jats:sub></jats:italic>/<jats:italic>F</jats:italic><jats:sub><jats:italic>m</jats:italic></jats:sub>), particularly under control temperature conditions. Photosynthetic performance, assessed via rapid light‐response curves, showed significant temperature and nutrient dependent variation. <jats:italic>Nitzschia palea</jats:italic> cultures at 27–29°C exhibited increased in relative maximal ETR (rETR<jats:sub>max</jats:sub>,184.1 μmol m<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>) compared to control conditions. In nutrient enriched treatments, photosynthetic efficiency peaked on day 5, but declined by day 8. These findings highlight the adaptive capacity of <jats:italic>N. palea</jats:italic> to fluctuating environmental conditions and underscore its potential as a model organism for studying diatom responses to nutrient and temperature stress in extreme ecosystems.</jats:p>