different growth morphologies are reported for the dominant genera in acidic,
oligotrophic lakes: Brachysira may grow unattached or attached to the
substrate by stalks (Spaulding and Edlund 2009), Frustulia may grow as single
cells or as colonies in tubes (Spaulding and Edlund 2008) and Eunotia may
grow singly, attached to the substrate by stalks or in long colonies (Furey
2010). There are two possible explanations for variations in growth
morphology. Either the growth morphology is species- and not genera-specific,
or it is driven by abiotic and biotic gradients. Hence, the application of
ecological guilds for ecological status assessment should be used with caution,
species-specific growth morphology and the drivers affecting growth
morphology need to be studied further, especially in low pH systems.