The effects of nutrient input into aquatic systems has been studied frequently; typically, these studies report an increase in algal biomass and a decrease in species diversity in response to an increase of nutrients. However, it is not clear why similar aquatic communities will respond differently to nutrient additions of similar magnitudes, resulting in alternative communities. Because variance in natural ecosystems is pervasive, perhaps it is this variability that helps determine the final community. I proposed that the total amount of nutrient input and the variability of nutrient input would affect the abundances and composition of species. A natural survey was conducted to measure the variable levels of nutrients in several aquatic systems. Experimental ponds were used to test the effects of variable rates and timing of nutrient inputs upon an aquatic community; experimental treatments manipulated the total amount of nutrient input (high v. low), the rate of nutrient input (annually, monthly or weekly), the timing of the nutrient input (early v. mid- season), and the trophic status at which these treatments were imposed (mesotrophic v. eutrophic). The effects of the variability of nutrient input was at least as important as the total amount of the nutrient input. There were large impacts upon species diversity, abundances and composition. Although these effects were manifested in many trophic groups, the response to the variability was most strikingly found within the primary producers, which showed large shifts in abundance and composition.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-05032002-143502 |
| Date | 16 July 2002 |
| Creators | Butzler, Julia M |
| Contributors | Dr. Susan Kalisz, Dr. Ricky Relyea, Dr. Jonathan Chase |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu:80/ETD/available/etd-05032002-143502/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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