Algal cell viability assessment: The role of environmental factors in phytoplankton population dynamics

The viability of algal cells is one of the most fundamental issues in marine ecological research. In this work, a method was designed to identify algal cell viability based on digital holography and deep learning, which divided algal cells into three categories: active, weak, and dead cells. This method was applied to measure algal cells in surface waters of the East China Sea in spring, revealing about 4.34 %-23.29 % weak cells and 3.98 %-19.47 % dead cells. Levels of nitrate and chlorophyll a were the main factors affecting the viability of algal cells. Furthermore, algal viability changes during the heating and cooling were observed in laboratory experiments: high temperatures led to an increase in weak algal cells. This may provide an explanation for why most harmful algal blooms occur in warming months. This study provided a novel insight into how to identify the viability of algal cells and understand their significance in the ocean.

Automated summary

A method using digital holography and deep learning was designed to identify the viability of algal cells, categorizing them into active, weak, and dead cells. This method was applied to measure algal cells in the East China Sea, revealing a range of 4.34%-23.29% weak cells and 3.98%-19.47% dead cells in the spring. Nitrate and chlorophyll a levels were found to be the main factors affecting algal cell viability. Additionally, laboratory experiments showed that high temperatures led to an increase in weak algal cells, potentially explaining the occurrence of harmful algal blooms in warming months. Overall, this study provides a novel insight into identifying algal cell viability and understanding their significance in the ocean.