An evaluation of periphyton community structure and function on tile and cobble substrata in experimental stream mesocosms

Abstract

Periphyton communities are an ecologically important source of information when conducting experimental stream ecotoxicological studies . Experimental stream studies often utilize unreplicated systems in order to understand dose-response phenomena . The objective of this study was to examine the robustness of such a dose-response investigation . Autotrophic and heterotrophic periphyton were evaluated in replicated control experimental streams with open recruitment (once-through flow design) . Measurements of population and community structure and community function over an eleven week colonization period were made on unglazed clay tile and cobble substrata . Several measures were significantly different during the study ; however, most of these were a result of initial stochastic colonization events or associated with relatively rare algal populations . During the latter half of the study autotrophic and heterotrophic community measurements on tile and cobble substrata displayed similar trends in both control streams . Population and community metrics were significantly different for approximately 5% of the 400 measurements made after the initial sampling . These results strongly suggest that the driving forces behind structuring aquatic population and community responses will be test chemical exposure and not spuriously developed stream ecosystems with individual trajectories . Recruitment in these open systems is evenly distributed across the replicated experimental stream ecosystems .

Literature Review and Analysis of Biological Complexity in Model Stream Ecosystems: Influence of Size and Experimental Design

“…It is essential that model ecosystems are in approximately the same ecological state prior to chemical exposure . In addition to the ''selective pressure'' applied to the model by the test chemical, use of natural waters in flow-through designs carrying biota appears to result in lotic model systems being less divergent (stream-to-stream) in long-term experiments than has been observed for lentic model ecosystems (Hill et al, 1994;Rodgers et al, 1996;Lowe et al, 1996). Note.…”

“…Kania et al (1976) in a long-term study of mercury exposure in large experimental channels found abundance of periphyton and invertebrates to differ on glass slides, glass dishes, ceramic, and cement substrates; however, the overall interpretation of ecological responses was the same regardless of substrate. Similarly, Lowe et al (1996) and Guckert (1996) have found that periphyton on cobble and gravel substrates responded qualitatively, and to a large degree quantitatively, the same during surfactant exposures in model ecosystems. The less uniform gravel was slightly more taxonomically diverse than the laminar surface of the tile.…”

Effects of atrazine and nicosulfuron on periphytic diatom communities in freshwater outdoor lentic mesocosms

“…Periphytic diatoms have been extensively studied during the last 10 years, and they have been used as indicators of water system qua lity (Lecointe et al 1993, Prygiel et al 1996, Whitton & Rott 1996, Vinebrooke & Graham 1997. Some of their most interesting properties are very fast growth, high taxonomic and physiological diversity, and thenpresence in all aquatic ecosystems (Lowe et al 1996).…”

Stream Periphytic Biodegradation of the Anionic Surfactant C12-Alkyl Sulfate at Environmentally Relevant Concentrations

“…The community grew again through Week 6 and then growth dramatically increased (over an order of magnitude) from Week 6 to 8. The density of cells on the tiles seen from Weeks 0 through 6 are what one would expect if the tile was covered with a monolayer of cells of ''standard'' bacterial size of approximately 1 × 2 m. The increases in cell density at Week 8 occurred concurrently with the development of filamentous algae observed to colonize the tiles at that time (Lowe et al, 1996).…”