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Benthic Macroalgae (Biotic Subclass)

Component: Biotic

Unique Identifier: 433

Biotic Setting Benthic/Attached Biota
Biotic Class Aquatic Vegetation Bed
Biotic Subclass Benthic Macroalgae
Biotic Group Calcareous Algal Bed
Canopy-Forming Algal Bed
Coralline/Crustose Algal Bed
Filamentous Algal Bed
Leathery/Leafy Algal Bed
Mesh/Bubble Algal Bed
Sheet Algal Bed
Turf Algal Bed

Definition Aquatic beds dominated by macroalgae attached to the substrate, such as kelp (Figure 8.14), intertidal fucoids, and calcareous algae. Macroalgal communities can exist at all depths within the photic zone, on diverse substrates, and across a range of energy and water chemistry regimes. In the CMECS framework, macroalgae that dominate the benthic environment and form a vegetated cover fall within this subclass. Macroalgal communities (typically coralline/crustose algae) that build substrate in a reef setting are categorized in the BC Reef Biota Class instead.

Many macroalgal types and communities have low temporal persistence and can bloom and die-back within short periods. This aspect of macroalgae is reflected with the temporal persistence modifier, which allows further description of the units in this subclass.

While many researchers organize macroalgae based on their pigmentation, CMECS takes a growth morphology approach to defining benthic algal biotic groups. This decision was driven by the fact that macroalgal assemblages often include a variety of co-existing algal species, making delineations of individual species difficult. This approach also captures the influence that the algal growth structure has in shaping the local environment—by providing shelter, shade, and detrital material to an area, which is important to associated fauna.

The Biotic Group level of classification here is a modification of the "Littler functional-form model" for marine macroalgae, as described by Littler, Littler, and Taylor (1983) and promoted by Lobban and Harrison (1997). The Littler functional form groups are the sheet group, filamentous group, coarsely branched group, thick leathery group, jointed calcareous group, and crustose group. Littler, Littler, and Taylor (1983) discuss the morphological, metabolic, and ecological significance of each group, and they point out that these groups are best considered as recognizable points along a continuum (rather than as discrete bins). Biotic Groups and Communities defined by macroalgae generally also include a diversity of associated fauna, including many that consume macroalgae (e.g., sea urchins and mollusks); these may be characterized as Modifiers: Associated Taxa, or Co-occurring Elements.