CorallineAlgae

Coralline Algae

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Description

Coralline algae are usually pink or red but they can be other colors as well, including gray, green, blue, yellow, and purple.

This alga takes two main morphological forms. These forms are called branching (geniculate or articulated) and encrusting (non-geniculate or non-articulated). The branching form protrudes from the substrate on which the alga is situated whereas the encrusting form grows along the surface of the substrate.

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Classification

Kingdom: Protista

Division: Rhodophyta (red algae)

Class: Rhodophyceae

Subclass: Florideae

Order: Corallinales

Family: Coralinaceae (Coralline algae)

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Habitat/Location

Coralline algae inhabit intertidal and subtidal coastal areas. It is necessary for the algae to perform photosynthesis, so the algae's habitat is limited to the depth of light penetration in water (depth of 0-270 meters). Because coralline algae is crucial for the construction of reefs, this partly explains why reefs are predominantly found in shallow depths of water.

Non-geniculate algae must live on an area that provides them with support. They are most commonly found on bedrock in the ocean, but they can also live on other types of substrate, such as an animal shells or on top of other algae. Geniculate algae also commonly live on substrates, but unlike non-geniculate algae they have the ability to be partially unattached. As long as they are anchored so some part of the substrate, the rest of the algae can be independent.

Algae can tolerate varying levels of water salinity. They do not live in freshwater; only in salinated water. Coralline algae can also be found in aquariums and are very popular accessories for decorative or functional tanks.

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Biology

Coralline algae can reproduce either asexually or sexually. This is evolutionarily advantageous for the algae because they do not require seed fertilization in order to proliferate; they can perform budding as well.

As a reef builder, one of coralline algae's most important functions is the excretion of calcite. The excretion of calcite binds reefs together into a contiguous entity. Calcite is a soft mineral composed of CaCO3 and Mg as well.

One unique biological function coralline algae performs, is called fouling. Fouling is the sloughing off outer layer of cells and is done for several reasons. It is advantageous for algae to do this in order to compete with algae attempting to grow on top of preexisting coralline algae. Algae may also do this to eliminate burrowing organisms in the outer layer, and renew damaged tissue and reproductive cells.

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Ecology

This type of algae typically falls in the category of epiphytes (plants that grow on top of other plants). Because of their exposed placement, coralline algae is susceptible to organisms such as parrot fish and mollusks which feed on the coralline algae.

Coralline algae interacts with its environment in a unique way by promoting the settlement of herbivores and invertebrates. The algae produces chemicals that attract herbivore larval settlement. After larval development into mature stages, the coralline algae serves yet another supportive function by providing habitat for small reef animals and invertebrates.

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Environmental Significance

Coralline algae form their habitat on reefs, reefs are becoming endangered. The algae is susceptible to threats such as coral bleaching, which impedes the alga's ability to produce calcite-- coralline algae's key function in binding reefs together. Without this supportive structure being replenished by coralline algae, reefs are more susceptible to the turbulence of the ocean and destruction of habitat becomes more likely. This would negatively impact not just the coralline algae, but also all the creatures that inhabit reefs. Reefs are some of the most biologically diverse areas in the world, so many species are at stake.

Coralline algae is further threatened by extraction for economic use. Geniculate algae are especially targeted for their use in soil conditioner, animal food additive, pharmaceutical products.

Beyond the threats they face, coralline algae are environmentally significant because they can be used for fossil dating.

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Sources

Cabioch, J. "Morphogenesis and Generic Concepts in Coralline Algae — a Reappraisal." Helgoländer Meeresuntersuchungen Helgolander Meeresunters 42.3-4 (1988): 493-509. Web.

"Coralline Algae." Coralline Algae. California State University, Fullerton, n.d. Web. 01 Mar. 2016

Johansen, H. William. Morphology and Systematics of Coralline Algae with Special Reference to Calliarthron. Berkeley: U of California, 1969. Print.

Keats, D.w., M.a. Knight, and C.m. Pueschel. "Antifouling Effects of Epithallial Shedding in Three Crustose Coralline Algae (Rhodophyta, Coralinales) on a Coral Reef." Journal of Experimental Marine Biology and Ecology 213.2 (1997): 281-93. Web.

Martin, Sophie. "Marine Coralline Algae." Marine Coralline Algae. The Encyclopedia of Earth, 15 June 2014. Web. 01 Mar. 2016.

Steneck, R. "The Ecology of Coralline Algal Crusts: Convergent Patterns and Adaptative Strategies." Annual Review of Ecology and Systematics 17.1 (1986): 273-303. Web. 1 Mar. 2016.

Woelkerling, W. J. M.H. Foslie and the Corallinaceae: An Analysis and Indexes. Vaduz: J. Cramer, 1984. Print.