The relationship between macroalgal morphological complexity and hydraulic conditions in stream habitats

Abstract

The effects of habitat complexity have been considered important factors for the evolution of morphological complexity in organisms. We assessed the possible relationship between hydraulic niche conditions and the morphological complexity of algal filaments by sampling four species of macroalgae inhabiting different hydraulic niches in two freshwater streams. These algal species exhibit different fractal dimensions, which were measured by applying a grid method. The results showed that morphological differences are a function of hydraulic niche for stream macroalgae. Algae with complex shape (Nitella wrightii and Batrachosperum puiggarianum) were established in slower flows, while algae with simpler filament shape (Vaucheria sp. and Oedogonium sp.) were more likely to occur in faster water currents. The sites where the species occurred are a reflection of their ability to hold position, which is ultimately driven by their morphology. The influence of flow in stream habitats is an important factor for lotic macroalgae settlement and its effects can be related to evolutionary adjustment of body shape in these environments. We suggest that the morphological structure (here as fractal dimension) of freshwater macroalgae can be considered an adaptation to the costs and benefits exhibited by different hydraulic niches.

Comparison of periphyton communities on natural and artificial macrophytes with contrasting morphological structures

“…The periphyton Chl-a on HA was obviously higher than on HN. This is possibly due to the differences in leaf fractal dimension between HN (1.37) and HA (1.30), suggesting that higher morphological complexity means greater surface area (Mcabendroth, Ramsay, Foggo, Rundle, & Bilton, 2005;Thomaz, Dibble, Evangelista, Higuti, & Bini, 2008;Tonetto, Cardoso-Leite, Novaes, & Guillermo-Ferreira, 2015). Therefore, the differences in the abundance and composition of periphyton between natural and artificial plants showed a complex pattern, confirming that the periphyton community may be affected by the morphological architecture (and metabolic activity) of a particular macrophyte (Grutters et al, 2017;Tunca et al, 2014).…”

Substratum simplification reduces beta diversity of stream algal communities

“…The roughness provided by the crevices on the surface of the substrata was, therefore, responsible for the higher beta diversity among complex than among simplified substrata when species richness was accounted for. Indeed, the streambed in natural lotic systems is composed of various irregularities (Taniguchi & Tokeshi, ) that provide refuges against grazing and physical disturbances such as high‐discharge and desiccation events for periphytic algae (DeNicola & McIntire, ; Taniguchi & Tokeshi, ; Schneck, Schwarzbold & Melo, ; Tonetto et al ., , ). Complex substrata provide suitable conditions to a large set of species and might favour the occurrence of stochasticity in colonisation/establishment history.…”

“…1 legend for additional details. Taniguchi & Tokeshi, 2004;Schneck, Schwarzbold & Melo, 2013;Tonetto et al, 2014Tonetto et al, , 2015. Complex substrata provide suitable conditions to a large set of species and might favour the occurrence of stochasticity in colonisation/establishment history.…”

Macroalgas de riachos na Serra do Japi, sudeste do Estado de São Paulo, Brasil

“…Sendo assim, nos últimos anos, principalmente no Brasil, trabalhos envolvendo levantamentos taxonômicos de espécies de macroalgas lóticas têm sido ainda escassos. Os trabalhos mais recentes têm envolvido principalmente abordagens experimentais (Branco et al 2010, Tonetto et al 2014, 2015 ou ecológicas (Oliveira et al 2013, Peres et al 2017.…”