Articulated Coralline Ecology
Nudibranchs crawl over an articulate and some neighboring algae.
Articulates have a biogeographic distribution covering most of the marine world. Geniculate corallines have been observed all the way from from the icy cold Arctic and Antarctic zones to more tropical equatorial areas. As with most types of organisms, species composition changes with latitude and climate with genera or sister species being replaced by similar relatives. Some species are very prolific and have distribution ranges through a variety of temperature zones. For example, Bossiella and Calliarthron have been observed along the entire Pacific coast of North America.
Environmental conditions play an integral role in determining whether or not a certain articulate will be successful in a given habitat. Spores released by reproductive plants best colonize rocky, uneven surfaces. Seasonality often determines when conceptacle formation will initiate. In addition, temperature and light have strong effects on growth rate, developmental patterning, and location of corallines. Like other primary producers, coralline algae need good light to photosynthesize and produce energy.
An articulated coralline washed ashore with the beachrack.
Although some corallines grow in the high intertidal, most are located in the low intertidal or subtidal. A primary reason for this is that the articulates desiccate very quickly and easily. Surprisingly, water motion is also very important to the development of articulates. Thus, corallines are generally constrained to relatively shallow marine areas; this is not to say that they cannot be found in the ocean's deep though.
The articulated corallines are benthic. Although they generally prefer to grow on abiotic substrate, some species can grow as epiphytes on other organisms. Geniculates are present in most marine ecosystems. Just like all other community members, they must compete for limited space to grow on the coastal rocks and seafloor. And in heavily human impacted areas, developing thalli are usually extremely susceptible to trampling and other damage. For these reasons and as expected, some areas are more densely populated with articulates than others.
© 2001 Ian Ehrenreich. All rights reserved.