The abundance and composition of periphyton in rivers is constrained by flow, water chemistry (e.g., nutrients), light, temperature, and substrate and, hence, is affected by surrounding land use (Biggs and Smith 2002, Pan et al. 2004, O’Brien and Wehr 2010, Klose et al. 2012).
However, Phormidium mats do not follow this pattern and tend to proliferate at low to moderate nutrient concentrations (DIN > 0.1–0.2 mg/L and DRP < 0.01 mg/L; Heath et al. 2015, McAllister et al. 2016).
Internal processes also may play a role in maintaining growth once mats are established (Wood et al. 2015