Resource-limited control of stream periphyton
| dc.contributor.author | Nickolichuk, Kevin John | en_US |
| dc.date.accessioned | 2024-08-15T16:33:45Z | |
| dc.date.available | 2024-08-15T16:33:45Z | |
| dc.date.copyright | 1995 | en_US |
| dc.date.issued | 1995 | |
| dc.degree.department | Department of Biology | |
| dc.degree.level | Master of Science M.Sc. | en |
| dc.description.abstract | Stream periphyton can undergo dramatic cycles of biomass accrual, senescence, decay and export. Since deterioration of stream water quality can occur when biomass accrual reaches nuisance levels, an understanding of the abiotic and biotic factors leading to these biomass levels are important for management of stream water quality. This study sought to determine the relative importance of the abiotic factors - water velocity, nutrient flux and ratios, light and their interactions - as determinants of excessive periphyton production. Two experiments were conducted in an outdoor, experimental stream-trough system within a southern Vancouver Island watershed. The stream-troughs provided a compromise between the need for realism with respect to natural systems and the need for a replicated experimental design. Using this system it was possible to manipulate the effects of specific parameters (e.g. velocity and nutrients) on biomass production in the presence of unmodified parameters (e.g. temperature, light), enabling the work to be more applicable to natural systems. In the first experiment, the effects of velocity and nutrient flux (μg N and P·time-1) interactions on periphyton biomass accumulation and species composition were examined at velocities below 15 cm·sec-1. Periphyton biomass was positively correlated with velocity in the absence of nutrient manipulation. Treatments receiving supplemental nitrogen and phosphorus, to mimic the nutrient fluxes of the highest velocity, yielded the greatest biomass accrual. The latter periphyton community structure consisted of large, floating, chlorophyte dominated mats. The second experiment examined the effects of N:P ratios at low and high nitrogen and phosphorus concentrations on periphyton community structure. In single nutrient manipulation treatments (either N or P added), biomass accrual was greatest at a ratio of 15 compared with that at 5, even though the latter treatment had a greater P concentration. Taxonomic composition remained relatively consistent with differing N:P ratios, except for higher numbers of a filamentous Cyanophyte at low N:P ratios and high P concentrations. The latter results confirm the findings reported by other workers. A third study examined the interactions of light- and nutrient-limitation on periphyton structure within a stream (Rithet Creek) whose riparian canopy had been partially harvested. The experimental design used nutrient-diffusing substrata (agar filled clay pots) at two shaded and two unshaded sites. Unlike other studies which found only light to be the limiting resource in forested streams and nutrients the limiting factor in unshaded streams, the results of this study suggested a dual resource limitation affected periphyton biomass accrual. Light was the primary factor limiting periphyton development given that biomass accrual was an order of magnitude greater at unshaded sites compared with shaded sites. Light was an important determinant of the taxonomic composition of the periphyton, with filamentous chlorophytes dominant under high light conditions. Nitrogen was found to be a secondary limiting factor as evidenced by an 8 fold increase in biomass accrual on treatments receiving added N&P compared to the controls or treatments receiving added P only. Nutrient concentration only affected the relative proportion and numerical abundance of the species present. | |
| dc.format.extent | 117 pages | |
| dc.identifier.uri | https://hdl.handle.net/1828/19128 | |
| dc.rights | Available to the World Wide Web | en_US |
| dc.title | Resource-limited control of stream periphyton | en_US |
| dc.type | Thesis | en_US |
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