EXTREMELY HIGH GROWTH RATE OF THE SMALL DIATOM CHAETOCEROS SALSUGINEUM ISOLATED FROM AN ESTUARY IN THE EASTERN SETO INLAND SEA, JAPAN¹

Abstract

Small single-celled Chaetoceros sp. are often widely distributed, but frequently overlooked. An estuarine diatom with an extremely high growth potential under optimal conditions was isolated from the Shinkawa-Kasugagawa estuary in the eastern part of the Seto Inland Sea, western Japan. It was identified as Chaetoceros salsugineum based on morphological observations. This strain had a specific growth rate of 0.54 h(-1) at 30°C under 700 μmol · m(-2) · s(-1) (about 30% of natural maximal summer light) with a 14:10 L:D cycle; there was little growth in the dark. However, under continuous light it grew at only 0.35 h(-1) or a daily specific growth rate of 8.4 d(-1) . In addition, cell density, chlorophyll a, and particulate organic carbon concentrations increased by about 1000 times in 24 h at 30°C under 700 μmol · m(-2) · s(-1) with a 14:10 L:D cycle, showing a growth rate of close to 7 d(-1) . This very rapid growth rate may be the result of adaptation to this estuarine environment with high light and temperature. Thus, C. salsugineum can be an important primary producer in this estuary in summer and also an important organism for further physiological and genetic research.

Irradiance modulates thermal niche in a previously undescribed low-light and cold-adapted nano-diatom

“…In vivo fluorescence was used as a proxy for photosynthetic biomass, because it allowed efficient daily measurements of a large number of simultaneously maintained cultures (as many as 90 at a time). All well-acclimated replicates were kept in the same nutrient conditions, and growth rates were calculated from in-vivo fluorescence of each individual replicate measured relative to itself over time (9,(18)(19)(20)(21). Although In-vivo fluorescence was never used to compare biomass across different light and temperature treatments, in a pilot study we observed that fluorescence and cell counts increased linearly even across different light and temperature treatments ( Figure S1).…”

Demonstrating the need for chemical exposure characterisation in a microplate test system: toxicity screening of sixteen pesticides on two marine microalgae

“…Hence, the time-effective aspect of the microplate-based assay would no longer be an advantage compared with culture flasks. As a linear relationship exists between chlorophyll fluorescence and cell density in steady experimental conditions (Ichimi et al, 2012), using either of these methods should not bias the growth rate calculation. However, this is only true when chlorophyll fluorescence of individual microalgal cells is not modified by the substance they are exposed to, relative to the control culture.…”

Prospects for commercial production of diatoms

“…The longer the time required for plant growth, the less efficient is the plant’s ability to utilize the total available solar energy and land area during its life cycle. A diatom like Chaetoceros has a very short growth cycle [34]. Under sub-tropical conditions as mentioned above, Wang and his group have demonstrated (unpublished work) that using 20% of the diatoms produced during the previous day as seed inoculum, their growth test systems (see Fig.…”