Influence of intensified upwelling on two different Corallina officinalis Linneo 1758 populations by exploring direct...

In the perspective of a future ocean, climate change can alter upwelling systems globally. Along the Chilean coast, upwelling becomes intensified, leading to cool temperatures and low pH, which can affect common and widespread calcifying seaweed species such as Corallina officinalis. We measured physiological, biomineralogical, and palatability responses in two distinct populations originating from contrasting upwelling regimes, one from an upwelling area and the other from an upwelling shadow, by exposing them to current and future upwelling conditions. After 20 days of experimentation, photosynthetic responses such as maximum quantum yield (Fv/Fm) remained high (>0.5) across populations. In contrast, maximal photosynthetic efficiency (rETRmax), light saturation point (Ek) and pigment content were higher in individuals exposed to future conditions, while alpha (electron transport efficiency) decreased over time. The carbonate content was higher in individuals exposed to future conditions, while the organic matter content differed between populations, with lower contents in the population originating from the site with higher environmental variability (-1.1 %). Individuals exposed to future upwelling conditions presented higher soluble protein contents (2-3 mg/g wet weight) and were also more consumed by sea urchins (+162.7 %). Our results indicate that the two C. officinalis populations possess strategies that confer tolerance to projected increases in upwelling, demonstrating their capacity to adapt to changing environmental conditions. However, rising herbivory pressure associated with intensified upwelling may exert a stronger influence on ecosystem dynamics, potentially altering future community composition.