A study to determine some ecosystem level effects of an aquatic invertebrate grazer, Hyalella azteca, was performed in aquatic ix microcosms. Impact of the grazer was assessed in three general areas: 1) inorganic nutrient levels of the microcosm water column, 2) productivity and respiration of the biotic community, and 3) plant community composition in the microcosms.
The grazing amphipod caused inorganic phosphorus and nitrogen (except ammonia) levels to be elevated in the microcosms. The increase was due, at least partially, to excretion of nutrients into the water by the amphipod. The presence of H. azteca did not significantly alter levels of gross productivity for the whole system nor for the sediment surface. Productivity to respiration ratios were significantly reduced by the grazing amphipod, indicating the amphipod was inhibiting plant biomass accumulation even though gross productivity was not affected.
Systems exposed to amphipod grazing had a twenty-five percent lower plant biomass than controls at the termination of the experiment. Gross productivity to plant biomass ratios were significantly higher in grazed systems, indicating a more actively growing plant community was being maintained by the grazer's activities. Plant community composition was significantly altered by the amphipod. Chara biomass was higher in grazed systems, while filamentous algae, blue-green algal colonies and periphyton had significantly higher biomasses in the control systems. The phosphorus distribution within the grazed microcosms was significantly different from that found in the controls. More phosphorus was incorporated into filamentous algae, blue-green algal colonies and the overall plant compartment in the control, while Chara and the water column contained more phosphorus in the grazed microcosms. The amphipod also caused the percent content of phosphorus to be higher in certain plant categories.
| Identifer | oai:union.ndltd.org:UTAHS/oai:digitalcommons.usu.edu:etd-7455 |
| Date | 01 May 1979 |
| Creators | Werner, Martin D. |
| Publisher | DigitalCommons@USU |
| Source Sets | Utah State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | All Graduate Theses and Dissertations |
| Rights | Copyright for this work is held by the author. Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owner. Responsibility for any use rests exclusively with the user. For more information contact digitalcommons@usu.edu. |
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