Study Systems
Marine forests generally are created by the large, three-dimensional
structure of brown seaweeds in the class Phaeophyceae, primarily the
“kelps” (order Laminariales) and fucoids (order Fucales). Generalized
terms used to describe functional groups within these systems are not
consistent, thus, for the sake of clarity we will use “canopy-forming
species” to describe brown seaweeds that create three-dimensional
habitat. This includes all canopy species referred to as floating,
stipitate, and prostrate canopies in Dayton et al. (1984), also termed
surface, understory, and bottom canopies (Schiel & Foster 2015). Algal
turfs are a diverse functional group that includes species from all
three algal phyla, but refer to shrub-like, filamentous, and branched
species that can be opportunistic and provide very little structure
(Filbee-Dexter & Wernberg 2018). Alternately, algal crusts are
low-lying, prostrate species that closely adhere to the substrate
(Steneck & Dethier 1994). These two functional groups can further be
divided by whether or not the species is calcified (Steneck & Dethier
1994). These delineations result in four functional groups that interact
with canopy-forming species: coralline turf, coralline crust,
non-coralline turf, non-coralline crust. Throughout the manuscript, we
often refer to “turfs”, given their increasing importance in
transforming coastal environments (Filbee-Dexter & Wernberg 2018), but
we consider the interactions of each of these four functional groups
that live below the canopy.