The shape of the thallus of Halosaccion glandiforme creates minimal drag, which allows it to survive in wave-exposed areas despite the fact that they possess a relatively weak stipe (Vogel & Loudon 1985).
This species is also quite resistant to being eaten by most organisms. However, the majority of the herbivory on H. glandiforme that does take place is due to molluscan grazers such as littorine snails (Little & Kitching 1996).
H. glandiforme is able to avoid desiccation stress by retaining seawater within the thallus. Its pores allow for bulk flow of water into and out of the thallus during emersion and immersion periods, respectively (Vogel & Loudon 1985). Retaining seawater during emersion periods also allows it to maintain rates of photosynthesis that are nearly equivalent to the rates that it maintains while submerged (Oates 2008).
Little, C & JA Kitching. 1996. The biology of rocky shores. Oxford University Press: New York, NY
Oates, BR. 2008. Components of photosynthesis in the intertidal saccate alga Halosaccion americanum (Rhodophyta, Palmariales). Journal of Phycology. 22: 217 – 223.
Vogel, S and C Loudon. 1985. Fluid mechanics of the thallus of an intertidal red alga, Halosaccion glandiforme. The Biological Bulletin. 168: 161-174.