Dataset: Respiration and Gross Photosynthesis Rates of Galápagos Macroalgae from 2022 to 2025

We quantified the metabolic responses of subtidal seaweed beds to varying thermal conditions during field trials conducted in June 2022, March 2024, October 2024, and January 2025. Using the Community In Situ Metabolism instrument (CISME), we measured dark respiration and gross photosynthesis rates of macroalgal patches in the rocky subtidal zone at approximately six meters depth in Tijeretas Bay, San Cristóbal Island. Measurements were conducted via SCUBA across a rocky platform covered with macroalgal beds. To isolate individual seaweed patches, we used a hose clamp adjusted to the same diameter (56 mm) as the CISME head, selecting 5 to 7 patches and clearing the surrounding seaweed. We then positioned the bottom surface of the CISME head over each target patch and secured it to the substrate using three adjustable retractor hooks. This setup enabled the soft foam ring at the base of the head to seal and isolate the patch within a closed chamber, where 88 mL of seawater recirculated between the chamber and the head during incubation. We ran the R+P program and quantified oxygen saturation under dark (respiration) and light (photosynthesis) conditions for each patch, measuring each process for 4 to 6 minutes.

To normalize rates to macroalgal biomass, we calculated the dry mass (g) of each patch by scraping and vacuuming samples into individual collection mesh bags. These were transported to the Marine Ecology Laboratory at the Galapagos Science Center, where they were weighed, dried at 60 °C for 24 hours, and weighed again.