Table 2.

Assignment of traits to diatom taxa in the NRSA 2008–2009 and 2013–2014 datasets using genus-level taxonomy.

Traits	Definition of trait classification	Typical genus examples
Functional
Life-forms
Mobile	Free moving e.g., some species vertically migrate into the sediments to acquire nutrients or through sediments to reach light	Achnanthes, Amphora, Nitzschia
Tube-living colony	Species that form tubes inside which frustules can move	Amphipleura, Encyonema, Frustulia
Colonial	Species are attached by spines, stalks, or mucilage at their poles	Aulacoseira, Eunotia, Tabellaria
Non-colonial	Species are not attached; can be floating or free-moving	Achnanthes, Navicula sensu lato, Nitzschia
Filament colony	Species linked by spines	Aulacoseira, Skeletonema
Zig-zag colony	Pennate species connected by mucilage at their neighbor poles	Diatoma, Tabellaria
Stellate colony	Pennate species connected by mucilage at their opposed poles	Asterionella, Staurosira
Arbuscular colony	Species produce stalks at either pole; stalks diverge from each diatom frustule to form branching colonies	Cymbella, Rhoicosphenia
Rosette colony	Species attached to substrate by a short stalk at one pole; colonies look fan-shaped	Fragilaria, Ulnaria
Ribbon colony	Species attached to one another either by interlocking spines or by mucilage excretions on their valve face, forming long, ribbon-like colonies	Eunotia, Fragilaria, Staurosira
Pedunculate	Species grows upright to substrate, attached by a mucilage pad or stalk	Achnanthes, Gomphonema, Reimeria
Pad	Species grows upright to substrate, attached by a mucilage pad	Fragilaria, Karayevia, Ulnaria
Stalk	Species produce a stalk that sticks to the substrate. The stalk can be simple that is linked to one cell or can be branching stalks linked to several cells	Gomphonema, Psammothidium, Surirella
Adnate	Species grows parallel to substrate, attached by their valve face	Amphora, Cocconeis, Rhopalodia
Ecological guilds
High-profile	Large species, or those that tend to form colonies such as filamentous, branched, chain-forming and tube-living	Diatoma, Eunotia, Gomphonema
Low-profile	Species of short stature, including prostrate, adnate, erect, and slow-moving species	Achnanthidium Achnanthes, Amphora
Motile	Fast-moving species	Epithemia, Navicula sensu lato, Surirella
Planktic	Solitary or colonial species that live in the water column or unattached to substrates	Aulacoseira, Cyclotella, Stephanodiscus
Physiological N-fixers	Atmospheric nitrogen-fixing species	Epithemia, Rhopalodia