Influence of elevated temperature and pCO2 on the marine periphytic diatom Navicula distans and its associated organisms in culture

Influence of temperature and pCO2, reflecting the future climatic scenario, on the marine periphytic diatom (Navicula distans) and its associated organisms was evaluated. Navicula distans along with its associated picoperiphyte and heterotrophic bacteria were exposed to two temperatures (30°C—present day, and 34°C—projected for year 2100) and pCO2 levels (~500 µatm—present day, and ~1500 µatm—projected for year 2100) in a 2 × 2 factorial design. It was observed that rising temperature reduced the abundance of N. distans and picoperiphyte, but increased that of heterotrophic bacteria. On the other hand, rising pCO2 favoured the growth of N. distans and picoperiphyte and had no significant effect on the bacterial growth. Synergistically, rising temperature and pCO2 had a negative effect on N. distans, and a positive effect on picoperiphyte and heterotrophic bacteria. Additionally, this also resulted in the reduction of diatom cell size. This study suggests that in the future climatic scenario, increased abundance of picoperiphyte and heterotrophic bacteria along with smaller N. distans cells might influence the carbon budget and may have a cascading effect on higher trophic levels.