Rl. Lowe et al., AN EVALUATION OF PERIPHYTON COMMUNITY STRUCTURE AND FUNCTION ON TILE AND COBBLE SUBSTRATA IN EXPERIMENTAL STREAM MESOCOSMS, Hydrobiologia, 328(2), 1996, pp. 135-146
Periphyton communities are an ecologically important source of informa
tion when conducting experimental stream ecotoxicological studies. Exp
erimental stream studies often utilize unreplicated systems in order t
o understand dose-response phenomena. The objective of this study was
to examine the robustness of such a dose-response investigation. Autot
rophic and heterotrophic periphyton were evaluated in replicated contr
ol experimental streams with open recruitment (once-through flow desig
n). Measurements of population and community structure and community f
unction over an eleven week colonization period were made on unglazed
clay tile and cobble substrata. Several measures were significantly di
fferent during the study; however, most of these were a result of init
ial 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 dis
played similar trends in both control streams. Population and communit
y 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 spuriou
sly developed stream ecosystems with individual trajectories. Recruitm
ent in these open systems is evenly distributed across the replicated
experimental stream ecosystems.