About Rachel Golda

I am a second year Ph.D. student at Oregon Health and Sciences University. My degree track is Environmental Sciences and Engineering, with a focus on Estuary and Ocean Systems.

This Is It!

Well, this is it folks! My year as an Oregon Sea Grant scholar has come to a close. Between my last blog and now, I have made great strides in my work.

First off, the chemostat works beautifully! After many false starts, George is finally functioning as it should, readjusting the pH of the culture vessel by bubbling the media with CO2 gas. The LabVIEW program monitors and regulates everything, and I am going to write a function into it that will allow it to send a warning to my phone when something goes wrong, any time of the day or night (I’m not sure if I should be excited about this…).

Aided by my intrepid undergraduate intern, Maria, I ran an experiment this summer to test the effect that a range of pHs would have on saxitoxin production of A. catenella. I compiled growth data, PAM fluorescence data, ran numerous reactive oxygen species (ROS) assays to determine the level of physiological stress in the dinoflagellates, and ran an intracellular saxitoxin ELISA assay. I plan to do the extracellular ELISA in the very near future.

I am still in the process of data processing, statistical analysis, finishing the other ELISAs, doing back-up lab work, etc. However, I can tell you that my preliminary data processing seems to indicate that my original hypotheses are correct: stress induced by low pH is linked with increased saxitoxin production in A. catenella.

For the actual results – well, you’ll just have to read the papers.

I’ve learned a lot this year, and seen much work come to fruition that may not have been possible without this scholarship. I’m very blessed to have had the opportunity and ability to do this research. If the new Malouf scholars have as much fun as I did this year, they will count themselves lucky to be scientists. :)

The Hills Are Alive With the Sound of… Bubbling?

NOTE – This entry was meant for posting in May. Please forgive the late entry.


Happy Spring! When the flowers bloom… and so do the phytoplankton. :) 

I am in the rhythm of chemostat building and am proud to announce the creation of a necessary portion of my chemostat system: the Conditioning Electronically-Operated Relay Grouping (GEORG – “Sound of Music,” anyone?), affectionately known as “George.”

George was built over the course of two 16-hour days and boasts six independently-controlled solid-state relays. These relays will act as switches that will control the solenoid valves on the pneumatic manifold. In short, George will allow me to control the amount of CO2 gas that will be bubbled into the system to control the pH of the chemostat system.

A feature of George that I am particularly pleased with came from a suggestion that a family member made to “idiot-proof” the system. Thus, I customized George’s DB15 ports and Molex connectors so that they cannot be mixed up or connected to the wrong connector (which would render the system temporarily useless), or ports (which would short circuit poor George and cause a major setback – and possible a small fire).

But before I get too excited – George must be thoroughly tested and connected to both the pneumatic manifold and the Labview program – which is still in the de-bugging phase.

This has been an intense month as I build George and finish up the preliminary pH experiments on Alexandrium catenella. I have also been going through the process to select an undergraduate intern to help me this summer. I am excited, as this will be my first experience mentoring. I have narrowed the field to four possible interns, and will make my final decision this week.

Vessels, Pumps and VIs – Oh My!

Since my last post I have completely re-designed my chemostat system. Take a look at my last blog post to see a picture of the previous system (aka Cv1.0). Although good in theory (autoclavable culture vessel, large culture volume, inexpensive to implement), many problems came out in the test culture phase.

To begin with, although the culture vessel itself was indeed autoclavable, the bulkhead fittings that connected tubing to the vessel were not. The silicone sealant used to close off gaps was also not autoclavable.

Additionally, the peristaltic pumps for this system quickly became very unreliable and refused to stay synchronized. Since the principle of a chemostat system is dependent on constant, synchronized influx and efflux of media, lack of synchronization in the input/output pumps leads to serious problems such as excessive dilution of the culture or (far worse) draining the culture vessel dry.

The culture vessel for Cv1.0 was also far too large. Topping out at 4 liters, it required an enormous amount of media to keep the culture at steady state.

Because of these problems I have decided to adopt a new system design (Cv2.0). Instead of the previous two pump chemostat system (one input pump and one output pump), the new system is an overflow chemostat. This simply means that the culture vessel has an open port in the side of the flask that drains excess media when the media level rises to the overflow level. This has the great benefit of requiring only one media pump (the input pump) since the overflow port drains media at the same rate that it is being pumped into the system. This new culture vessel is also much smaller (2L media capacity), so media demands should be less. Upgrading to a better quality peristaltic pump seems to have solved the flow inconsistency problems experienced in the previous system.

I have also begun the process of writing a LabVIEW VI (virtual instrument) to control the gas manifold (see picture) in response to culture pH. Slowly but surely, progress is being made.

Gas manifold with solenoid valves and non-compressible gas lines

In between working over my chemostat I have been writing my thesis proposal. It looks like I’ll be defending my proposal sometime in March or April, so I’ve also been working on some preliminary data to relate Alexandrium cellular health to pH. Hopefully I’ll be including this in my next post.

Happy 2013! :)



Greetings oceanophiles! As this is my first blog post as a Sea Grant scholar, I feel I should give a little background about myself. I am just beginning my second year as a Ph.D. student with Drs. Tawnya Peterson and Joseph Needoba at Oregon Health & Science University in Beaverton, OR. My degree track is Environmental Science and Engineering, with a focus on Estuary and Ocean Systems. I have always loved the Pacific Northwest, and am constantly amazed that I get to study it for a living.

So what am I actually doing? The goal of my research is to identify links between pH and pCO2 concentration in the water and population dynamics of harmful algal blooms (HABs) in the northern California Current system. My research specifically focuses on the marine dinoflagellate Alexandrium. This little guy is the alga that is primarily responsible for paralytic shellfish poisoning (PSP) events off the west coast of North America. Alexandrium produces saxitoxin, an extremely potent neurotoxin. Shellfish are filter feeders, and accumulate toxins when they feed on HAB species in the surrounding water. When there is an increased number of Alexandrium in the water (as frequently happens in the summer months), saxitoxin builds up to dangerous levels in the shellfish and can cause paralysis in humans and animals. What I want to do is discover whether there is a link between the pH/pCO2 content of the water and population dynamics and toxin production of Alexandrium.

I expect to be spending a lot of time on boats in the next few years, stalking the wild Alexandrium through the Columbia River estuary and out on the coast, but I will probably spend far more time in the lab. To that end, I am in the process of building a chemostat culture system, which will grow algae at a constant rate in a nutritionally static environment. Influx and efflux of media to and from the culture vessel are synchronized to the growth rate of the algae to maintain a constant growth rate.


The constant influx of fresh media and efflux of waste will ensure that the nutrient load of the culture vessel remains constant. I also designed the system to automatically monitor and control pH using a custom made pneumatic manifold that will change the pH of the culture vessel by bubbling it with CO2 gas. The monitoring will be accomplished by a Labview program that will also allow for remote monitoring of the system, and send will me alarms if/when something goes wrong. I have already finished the first iteration of the chemostat system and am in the process of working out the bugs (waste overflows, variable pump rates, etc.).

I’m excited to see where this year will take me and to see what new adventures lie in wait, both in the lab and out on the water. Tallyho!