Temporal and spatial variation in the epilithic biofilm of an acid stream

Abstract

Summary 1. The extent of spatial and temporal variation, and the taxonomic and biochemical composition of epilithic biofilm were determined in a first‐order, acidic stream in the Ashdown Forest, southern England. 2. The biofilm had an autotrophic component consisting of acidobiontic diatoms, small coccoid green algae, zygnematacean filamentous green algae, and a heterotrophic component of bacteria. Fungi were absent. 3. Diatoms were the dominant algal group in spring. These were succeeded by coccoid green algae in summer. Synchronous variation existed between algae and bacteria, suggesting a strong link between the two groups. 4. Quantitative community descriptors (algal and bacterial densities, chlorophyll, ash‐free dry matter) and biochemical descriptors (protein, lipid and carbohydrate content) of biofilm presented a consistent temporal pattern in which biofilm biomass peaked in spring and early summer and decreased subsequently. 5. Stepwise multiple regression revealed that temporal variation in the quantity of biofilm coating substrata was primarily associated with photosynthetically active radiation. The quantity of biofilm coating the upper surfaces of substrata increased with substratum particle size (small stones, large stones and bedrock). Smothering of algae by fine particulate organic matter, proximal shading by bed sediments, and physical disturbance are proposed as mechanisms that brought about the pattern.

Periphyton Growth on Three Bio-substrates and Its Influence on the Performance of Jaraqui (<i>Semaprochilodus insignis</i>)

“…In the present study, NFE accounted for 53.28-54.44% (Table 4). Ledger and Hildrew (1998) reported 29-33% carbohydrate in periphyton developed on stones. Nielsen et al (1997) observed that the extra-cellular polymeric substances in biofilms are responsible for 50-80% of total organic matter and therefore, large amounts of carbohydrate, which explains the high proportion of carbohydrates in periphyton.…”

Does rock chemistry affect periphyton accrual in streams?

“…Algal biomass is affected by stone location in streams (Matthaei et al, 2003) and algal biomass generally increases with stone size (Ledger and Hildrew, 1998). At the scale of individual stones, orientation and exposure to stream flow affect algal biomass accumulation (Stevenson, 1984).…”

Biological barriers to restoration: testing the biotic resistance hypothesis in an upland stream recovering from acidification

“…The scrubbed surface of each cobble was carefully traced onto an acetate sheet and the area (cm 2 ) subsequently determined from the mass of the tracings (Ledger & Hildrew, 1998). The biofilm samples were later defrosted in the laboratory and made up to 24 ml with water.…”

“…The biofilm samples were later defrosted in the laboratory and made up to 24 ml with water. Estimates of ash-free dry mass (AFDM) were made by placing aliquots of biofilm slurry (5-10 ml) in crucibles for ashing at 500°C for 4 h. AFDM was estimated as the difference between oven-dried (80°C) and ashed crucibles (Ledger & Hildrew, 1998).…”