LINKING BENTHIC ALGAL BIOMASS TO STREAM SUBSTRATUM TOPOGRAPHY¹

Abstract

The physical properties of substrata significantly influence benthic algal development. We explored the relationships among substratum surface texture and orientation with epilithic microphytobenthic biomass accumulation at the whole-substratum and micrometer scales. Unglazed clay tiles set at three orientations (horizontal, vertical, and 45°), and six substrata of varying surface roughness were deployed in a prairie stream for 3 weeks. Substrata were analyzed for loosely attached, adnate, and total benthic algal biomass as chl a, and confocal laser scanning microscopy was used to measure substrata microtopography (i.e., roughness, microscale slope angles, and three-dimensional surface area). At the whole-substratum level, vertical substrata collected significantly (P < 0.05) less algal biomass, averaging 34% and 36% less than horizontal and 45°substrata, respectively. Benthic algal biomass was also significantly less on smoother surfaces; glass averaged 29% less biomass than stream rocks. At the microscale level, benthic algal biomass was the greatest at intermediate values, peaking at a mean roughness of approximately 17 lm, a mean microscale slope of 50°, and a projected ⁄ areal surface area ratio of 2:1. The proportion of adnate algae increased with surface roughness (26% and 67% for glass and brick, respectively), suggesting that substratum type changes the efficiency of algal removal by brushing. Individual substrata and microsubstrata characteristics can have a strong effect on benthic algae development and potentially affect reach scale algal variability as mediated by geomorphology.

Influence of substratum surface roughness on periphytic algal community structure in a shallow tropical reservoir

“…On the other hand, algal assemblages were more sensitive to increased surface roughness, especially after 5 days colonization time. The influence of substrate topography on the periphytic community structure was well demonstrated in lotic ecosystems (Bergey, 2005;Murdock and Dodds, 2007). In tropical between control and treatments with rough surface at the level of 20-30%.…”

“…However, the physical properties of the substrate should not be disregarded, especially species composition. To Murdock and Dodds (2007) substrate physical properties should not be ignored in the sampling design, especially when comparing sites using different substrates. As the structural variability of the periphytic community is enormous, we recommend that experimental studies are performed with many repetitions so that we can make generalizations about the relationship between substrate and periphyton in tropical ecosystems.…”

“…The roughness values ranged from 4.49-5.51 µm (mean 5.08; n = 10) in R1 treatment, 7.00-12.95 µm (mean 10.19; n = 10) in R2 treatment and 14.90-16.94 µm (mean 15.61; n = 10) in R3 treatment. Murdock and Dodds (2007) found roughness of 0.87 µm for glass, 17.1 µm for rock and 53.8 µm for brick. Thus, the roughness values created in this study are close to those described for rock.…”

“…In non-living substrates such as rocks, substrate chemical composition may not affect biomass accumulation and species composition (Bergey, 2008). However, the physical characteristics of the substrate, such as microtopography and orientation, may significantly affect the community structure of periphytic algal (Burkholder, 1996;Bergey, 2005;Murdock and Dodds 2007).…”

“…The substrate type can influence the periphytic community structure in the micro-environmental scale (Burkholder, 1996), because physical and chemical characteristics of the substrates often provide more than an inert surface for community (Bergey, 2005;Murdock and Dodds, 2007). In non-living substrates such as rocks, substrate chemical composition may not affect biomass accumulation and species composition (Bergey, 2008).…”