Development of Benthic Algal Assemblages Subjected to Differing Near-Substrate Hydrodynamic Regimes

Abstract

Recent research concerning benthic algae in streams suggests that the near-substrate hydrodynamic regime may affect the composition of benthic algal assemblages. Algae from local streams were allowed to colonize laboratory flumes containing substrates of different sizes under two velocity regimes to determine whether benthic algal assemblages were affected by substrate size or hydrodynamics. While all hydrodynamic parameters except for local velocity diverged among flumes with different substrate sizes, cell counts per unit area of substrate and the relative proportions of different forms of algae remained similar overall. Much of the similarity appears to be attributable to the dominant filamentous algae. "Blooms" of one or two species were detected on occasion, but did not affect overall similarity (though they may affect local recolonization). The results, if extrapolated, suggest that hydrodynamic conditions alone may not be responsible for the variation in algal assemblages seen in the field, and that the morphological form of the alga may be more important than the species of alga when determining its response to hydrodynamic conditions.

Changes in diatom-dominated biofilms during simulated improvements in water quality: implications for diatom-based monitoring in rivers

“…To assess the changes of growth form abundances during the transfers, the diatoms were clustered into six groups (Table S1, see supplemental material available at: http://www.informaworld.com/mpp/uploads/tejp_a _420025_supp.pdf) according to Whitford (1956), Stevenson (1983), Roemer et al (1984), Planas et al (1989), Rieter (1989), Tanaka & Watanabe (1990), Katoh (1992), Molloy (1992) and to SEM photos of the dehydrated biofilms: adnate (Figs 7, 13) (Achnanthidium, Amphora, Cocconeis, Planothidium, Psammothidium), stalked (Figs 7, 8) (Cymbella, Encyonema, Encyonopsis, Gomphonema, Reimeria, Rhoicosphenia), motile (Figs 10, 11a, b, 12a, b, 16) (among others Navicula sensu lato, most Nitzschia, Surirella), planktonic (Nitzschia acicularis, centric diatoms, except Melosira varians), filamentous (Diatoma vulgaris, Melosira varians, Staurosirella pinnata) and rosette forming (Ulnaria ulna, Meridion circulare). This classification should not be considered as adaptable to every situation, but at least corresponded to what was observed with light and electron microscopy in the samples of the present study.…”

Interaction between local hydrodynamics and algal community in epilithic biofilm

“…where U(z) is the mean (above the roughness sublayer) or double-average longitudinal velocity (inside the roughness sublayer), U• is the friction velocity, k. the Nikuradse's equivalent sand roughness, d the displacement height, K the Karman constant (K = 0.41), H the flow height and c, and Du are empirical constants (C, = 1 and Du = 2.3). Observations on the interaction between water flow and biofilms (Reiter, 1989a(Reiter, , 1989bNikora et al, 1997Nikora et al, , 1998Labiod et al, 2007) have shown that friction velocity U• (which measures the drag of the flow at the bottom layer) could increase with the growth of epilithic biofilm, leading to the conclusion that stream biofilm increased bed roughness. However, Biggs and Hickey (1994) , Moulin et al (2008) and Graba et al (2010) have found that stream biofilm decreased the drag forces and the roughness.…”

A prospectus for periphyton: recent and future ecological research

“…For communities that exceed these maxima, drag forces will exceed attachment strength and initiate sloughing. Circumstantial evidence for such equilibrium states come from comparisons of developing periphyton communities in which different starting values of shear stress and hydraulic roughness converge over time as the communities mature (Reiter 1989).…”