Crustose coralline algae (CCA) are pink, calcifying macroalgae that act as the ?glue? to hold the carbonate framework of a coral reef together and they act as a ?landing strip? for the larvae of several invertebrate species, including corals, and thus are a key component to a healthy tropical reef ecosystem. But CCA have been shown to be highly susceptible to rising seawater temperatures and acidity in laboratory experiments, causing concern that these important reef-builders will be among the first to be impacted by climate change and ocean acidification. The proposed underlying mechanism for the adverse response to acidity in particular is presumed to be the concentration of magnesium incorporated into the calcite crystalline structure, which increases solubility of the calcium carbonate skeleton. The somewhat controversial conclusion that certain species of tropical CCA deposit dolomite, an insoluble form of high Mg calcite that would make them more resilient to ocean acidification than supposed, has been supported by this study. However, deposition of dolomite does not appear to render the CCA immune to the impacts of ocean acidity and temperature and certain species appear to be highly plastic in their response to environmental condition. This is the first study to quantify several biological metrics for particular CCA species across a large latitudinal gradient. Last Modified: 02/14/2017 Submitted by: Nichole N Price