Ecological Associations: Desmarestia ligulata often lives in association with a diversity of other algae, often including other Desmarestia species. In central California studies have shown nongeniculate coralline algae to be the primary substratum on which D. ligulata recruits (1). Common epiphytes on Desmarestia ligulata include Acrochaetium desmarestiae and Ectocarpus acutus.

Acid Release: Desmarestia ligulata throughout its life stores free sulfuric acid within the vacuoles of its cells which results in internal pH levels ranging from 0.8 to 1.8. When stressed by factors such as air exposure (dessication) and temperature, Desmarestia ligulata releases this stored acid which results in the rapid deterioration of not only its own tissue but also any surrounding algae. This fact should be kept in mind when collecting specimens as they can damage other algae placed in the same bucket.

This acid release process also results in the discoloration of the Demarestia tissue as it breaks down, often turning the golden brown tissue green (as can be seen in the photo on the left) but can also turn to yellow or blue. This characteristic results in the nickname the "color changer algae".

Effect of Desmarestia Acid on Urchins: Desmarestia ligulata, along with other acid storing and secreting members of the Desmarestia genus, have been shown to have an erosional effect on the calcium carbonate teeth of urchins that happen to graze on the algae. The sulfuric acid in Desmarestia spp. is thought to serve as an anti-herbivore defense and studies have been done that show that Desmarestia acid causes sea urchins to crawl away. The physical barrier of Desmarestia when it is seasonally abundant is thought to have a seasonal effect on the distribution and grazing patterns of urchin populations. (2)

Demonstration of Acid Release: In our lab, Noemi and I ran a simple experiment to demonstrate acid release of Desmarestia spp. over time when the algae are stressed. We used two species of Desmarestia, D. viridis and D. ligulata and placed them in dishes of lukewarm water. The algae had been air exposure in transport and instantly created a water pH of 5.5. After 15 minutes the pH of the water decreased to 3.0, and after 30 minutes the pH of the water was at 1.0 (refer to photo on the left), showing the gradually increase of acid in the water as it was released from the Desmarestia tissue.