o c e a n   a c i d i f i c a t i o n

25% of CO2 emitted from man-made sources currently enters the ocean, which then reacts with water to produce carbonic acid, thus decreasing levels of carbonate. Carbonate is important for maintaining biological systems with organisms that use calcium carbonate for their skeletons or shells.

Coral reefs under rapid climate change and ocean acidification. O. Hoegh-Guldberg et al. 2017.


Shallow-reef corals are not the only ones sensitive to changing ocean pH; cold-water, or deep-sea, corals have also been shown to have reduced rates of calcification when seawater is more acidic.

Calcification of the cold-water coral Lophelia pertusa under ambient and reduced pH. Maier et al. 2009.


A recent study compared the effects of increased ocean CO2 concentrations on dominant (kelp) and subordinate (turf algae) species of seaweed. The authors reported that high CO2 had a negligible effect on kelp, increased productivity in turf algae and suppressed turf algae consumption by sea urchins. Even though the increased CO2 caused no direct damage to kelp, it was still displaced by turf algae due to the rise of more favorable conditions for the turf. Understanding interactions like these are crucial for predicting ocean ecosystem shifts in the face of a changing climate.

The duality of ocean acidification as a resource and a stressor. Connell et al. 2018.

Photo by Ellie Jones