Ocean darkening and ocean acidification have long been growing concerns when it has come to the health of our oceans and marine ecosystems, and I am primarily interested in better understanding the interactions between these two phenomena. Ocean darkening is caused by excess phytoplankton blooms, which are fed by increased nutrient and sediment runoff. They become a major source of dissolved organic matter (DOM), and it is chromophoric dissolved organic matter (CDOM) specifically that absorbs light, causing a decrease in the depth of the ocean's photic zone. Through my research, I aim to study how these scientific processes are affected by a reduction in pH, and whether or not this change will alter the production output of CDOM by Chaetoceros muelleri, my selected diatom of choice. This work could provide valuable information that would increase the current understanding of phytoplankton biology and there responses to environmental events. 

Over the past weeks, I've been working towards establishing my first Chaetoceros muelleri cultures and preparing the necessary materials beforehand. Prior to the arrival of the starter cultures from the phytoplankton suppliers, I diluted my Guillard's f/2 medium, a widely-used nutrient formula for phytoplankton, in artificially-mixed salt water to create the culture medium that will be used to grow my Chaetoceros muelleri cultures throughout the month. I also made a dilute sodium silicate solution, added in addition to the f/2 medium to provide the silicate that diatoms need to build their cell walls. In preparation for pH reduction, I gained access to 0.5 M HCl and 0.5 NaOH, as well as an aquatic pH meter. Due to issues obtaining my phytoplankton and culturing them during the first month of research, I was only able to establish my first round of cultures this past week after some alterations to my experimental design. Overall, despite some delays to my research, I look forward to progressing with my project. 

During my first attempt to culture Chaetoceros muelleri, a ran into some unexpected setbacks that caused some delays in my research. I couple days after transferring the diatoms from 15 mL test tubes to glass beakers, their culture medium completely evaporated and ultimately killed the cells. After further research, I discovered that this evaporation was potentially accelerated by my inclusion of an aeration system, which consisted of an air pump and tubing. Thus, I altered my culture setup, in which I scrapped an automatic, constant aeration system and instead will manually swirl my cultures daily. I also changed the cover of cultures from tin foil to plastic wrap and reduced the size of the culture vessels. Furthermore, I made sure to this time place my "backup" cultures in the fridge, slowing their growth process and maintaining them for longer in the case that problems arise with my current active culture.