Today I tested the effect of CO2 bubbling in seawater on pH for Genevieve’s project.

Set up

All tests conducted in FTR 213.

I found a regulator for the CO2 canister. This regulator will stay on the canister. TO use, we will just barely barely open the top metal valve of the canister, which will allow air to flow through the regulator and to the bubbler.

I then set up two buckets filled approximately half way with seawater from the FTR tanks.

I added the hose with bubbler from the CO2 tank into one bucket and added a regular air bubbler into the other bucket.

CO2 bucket:

Air bucket:

I then measured pH using the multi-probe in the buckets at the start, after 30 minutes, and after 90 minutes.

Observations

Immediately after adding the CO2 bubbler to the bucket I measured the pH. pH quickly dropped to approximately 5.3 in the CO2 bucket and was 8.0 in the control bucket. This was done at the lowest possible bubbling of CO2.

After 45 minutes, the control was at 7.9 and the CO2 bucket was at 5.01 pH.

After 90 minutes, the pH was 5.04. It seems that bubbling reaches this low pH level and remains constant.

If we expose oysters to these conditions, it would be an acute stress exposure for a short period of time.

Working protocol

For future CO2 expsoures, we can add seawater to the buckets and have one bucket bubbling air and one bubbling CO2.

Seawater should be made by filling a bucket with fresh water from the hose and then adding in Instant Ocean salt (in a big in the tank room) until dissolved and a salinity of 24-27 psu is reached. Add salt in small batches to avoid high salinity. Use the refractometer to monitor salinity for making the seawater. The multimeter fancy probe does not need to be used for this.

Oysters can be placed in the buckets for 1-3 as an initial trial to conduct an acute pH stress exposure.

Measure temperature, pH, and salinity in the buckets using the fancy multimeter probe every X minutes during the exposure.

After the exposure, oysters can be returned to their tank in the tank room.

This can be repeated over multiple days followed by thermal tolerance survival testing.