Growth characterization of non-photosynthetic diatoms, Nitzschia spp., inhabiting estuarine mangrove forests of Ishigaki Island, Japan

Abstract

The non-photosynthetic diatoms Nitzschia spp. are known to have evolved from photosynthetic species to heterotrophic species by the loss of photosynthesis. We investigated their ability to tolerate wide ranges of temperatures and salinities. Nitzschia spp. were capable of surviving or thriving even at 5°C and 35°C. In addition, these diatoms were also capable of surviving at salinities of 0.5 and 12.0, while thriving at those from 1.0 to 9.0. Such tolerance to a wide range of temperatures and salinities would allow these non-photosynthetic diatoms to thrive in mangrove estuaries, where environmental conditions often drastically fluctuate. Our experiments revealed that the growth rates of the non-photosynthetic diatoms were larger than those estimated based on cell volumes and temperature, suggesting that these non-photosynthetic diatoms may be an important group of organisms contributing to material circulation by growing heterotrophically in mangrove estuaries.