Cryopreservation represents a key strategy for the long-term conservation and of macroalgae. However, optimized protocols remain scarce for ecologically important species, while most advances have focused on commercially valuable macroalgae. Giant kelp (Macrocystis pyrifera) is a foundation species that sustains highly productive coastal ecosystems. Therefore, the development of reliable cryopreservation protocols is essential for its conservation. In this study, we report preliminary results on the cryopreservation of M. pyrifera using three different devices and cooling rates.
Spores were suspended in DMSO and trehalose and cooled in a: (1) 3D printed device CryoKit V2.4.7 (-15°C/min), (2) CryoRack (-37°C/min), or (3) vitrificated (plunged directly into liquid nitrogen). Post-thaw cell viability (SYTOX Blue) and oxidative stress (CellROX Green) were assessed by flow cytometry, and further development was evaluated by culturing spores for 35 days. Initial analysis indicates cell density and viability differences among the treatments (Table 1). Cryopreservation using a 3D printed device is in progress.
Vitrification was the method with the highest initial viability percentage (79±2%), as analyzed by flow cytometry (Figure 1). However, cell density and germination varied among treatments. The freezing rack showed the highest recovery (1.4 × 105 cells/mL) and germination (41%). These results suggest that the type of device and the cooling rate are critical factors influencing the success of kelp spore cryopreservation. While initial viability provides valuable information, the ability of cells to recover and undergo normal development is ultimately decisive in evaluating cryopreservation success. These results constitute a first step toward establishing reproducible protocols for the cryopreservation of M. pyrifera germplasm, providing essential tools for biodiversity preservation and the long-term resilience of giant kelp forests under changing environmental conditions.