Monterey Bay Aquarium Research Institute
Marine Botany

Ulva title imageEcology

Distribution    Biotic Interactions    Nutrients    Bioindicators    


Generally, Ulva species are likely to proliferate in areas where nutrients are high, wave shearing forces are low and herbivory is reduced.They are quite tolerant of stressful conditions, and their presence often indicates freshwater input or pollution.

One place Ulva seem to love in Monterey is the harbor.  The protection from the waves allows them to proliferate.  Not only does the pollution not bother them, but it probably even fertilizes their growth.

As with all algae, the distributions of Ulva are related to their requirements regarding light, temperature and nutrients.How they respond to conditions such as competition, desiccation, different concentrations of nutrients, disturbance and animal interactions affects where Ulva live.   

An Ulva-covered rock in the low intertidal zone.

Ulva generally lives in the middle to low intertidal zone (or eulittoral to high sublittoral zone).The fronds are not situated at the same level throughout the year, however.In the colder months, the algae grow mainly in wide bands in the intertidal.In the warmer months, they grow in a narrower band, lower in the intertidal.  Minimizing the amount of time they spend out of the water, under the hot summer sun, protects them from desiccation.  Ulva are greatly impaired by extreme desiccation (defined as loss of more than 25% original water content).

Ulva exposed to the drying sun at low tide

Ulva show differential photosynthetic responses to light quality at different depths.Because they contain a high concentration of pigments and are therefore able to absorb almost all wavelengths of light, they do better in shallow waters. Fleshy thalloid algae, which are more opaque and contain lower concentrations of pigments, tend to perform better in deep water than membranous algae such as Ulva. Because Ulva, which are largely translucent, absorb most of the incident light, they are optically black even though they look green on the surface. more ecology

 ©Anna Kirby 2001  

Last updated: Feb. 05, 2009