Abstract

Phytoplankton are important components of aquatic ecosystems. A dramatic way that certain phytoplankton affect these ecosystems, and human health, is by undergoing an annual cycle of bloom and crash. This involves a rapid growth of a large population and its subsequent rapid death. Algal bloom can be harmful to the environment so it is important to know the ending process. However, it is uncertain if the crash is caused by nutrient deprivation or programmed cell death. Previous experiments showed a similar crash in synchronized culture of Chlamydomonas reinhardtii in the lab. In this study, we used synchronized culture to simulate the crash of a natural blooming algal population and to determine the cause of the crash. Moreover, programmed cell death in mammalian cells was found to be regulated by cytoplasmic stress granules. Previous studies in our lab reported similar RNA-containing stress granules in the chloroplast of C. reinhardtiiand the localization of oxidized RNA to the pyrenoid. Thus, another objective of this study was to detect RNA in the pyrenoid and determine if that was associated with the rapid death. My results suggest that synchronized culture is an effective model to simulate natural bloom and crash in algal population and the crash was mainly caused by nutrient deprivation, although some possible toxins produced by algal cells might be another factor. Accumulation of RNA during light phase of the diel cycle was observed but the attempt to extract RNA from pyrenoid was unsuccessful. My results are preliminary and further investigation is necessary, however, they could still serve as a start for future studies.