18 April 2022

Respirometry - Photosynthesis and Respiration

To measure photosynthesis and respiration for the timepoint 4 fragments (n=24) we followed the Putnam Lab respirometer manual. Since our set up in Mo’orea has two six chamber respirometer stands, we did three separate runs with n=8 fragments with one blank on each stand for a total of n=10 chambers per run. We first took molecular samples of each fragment with one ~0.5-1 cm biopsy preserved in 1 mL of RNA/DNA shield and one ~0.5-1 cm biopsy snap frozen in liquid nitrogen and stored in the Gump Molecular -40 C freezer. We set our light levels to ~610 μmol photons m−2 s−1 (51% on the AI lights) following our PI cuvre calculations to measure photosynthesis for ~20 minutes or until a consistent reading was achieved and then we turn off the lights and conducted light-enhanced dark respiration for ~20 minutes or until a consistent reading was achieved. After each trial was completed, volumes were measured from the chambers and the physiological fragments were snap frozen and stored in the Gump Molecular -40 C freezer in whirl paks.

Heatwave

Danielle started the eighteenth and last day of the heatwave period and the decline for the corals to to experience a diel fluctuation in the heated treatement of 28.9 °C to 29.6 °C. Through our heatwave analyses, the climatological data shows that in Mo’orea at our site in the backreef, temperatures above 29.6 °C longer than a five day period is considered a heatwave.

Daily measurements

Danielle recorded bleaching score and survivorship for the fragments and colonies and completed a daily measurements of light, temperature, salinity and pH. She also cleaned the tanks.

Bleaching score processing

Following Emma Strands Bleaching Score Protocol Emma, Hollie, Kristen, and Danielle have started processing the daily colony photos to track when the ambient and hot colonies start to differ in bleaching score. They have been updating the Photographic Bleaching Script often to make these comparisons and consult on moving forward.

It appears that the bleaching score in the colonies experiencing the heat stress have continued to decline. We see a significant difference in the interaction between treatment and day.

Histological processing

Following the histological processing protocol Danielle checked the histological samples and saw that many had completely been decalcified within 48 hours. She checked that the samples were still acidic and left them longer.

Data tracking

All daily measurements, bleaching score, and survivorship tracking for the colonies and fragments can be found on the Heatwave Google Drive and Gametogenesis GitHub.