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The role of nutrient variability in aquatic ecosystems

Butzler, Julia M (2002) The role of nutrient variability in aquatic ecosystems. Master's Thesis, University of Pittsburgh. (Unpublished)

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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.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Butzler, Julia Mjmbst56@pitt.eduJMBST56
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairChase, Jonathanjchase@pitt.eduJCHASE
Committee MemberRelyea, Rickyrelyea@pitt.eduRELYEA
Committee MemberKalisz, Susankalisz@pitt.eduKALISZ
Date: 16 July 2002
Date Type: Completion
Defense Date: 28 November 2001
Approval Date: 16 July 2002
Submission Date: 3 May 2002
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: aquatic systems; community structure; environmental variability; nutrient input; rate; timing; trophic state
Other ID:, etd-05032002-143502
Date Deposited: 10 Nov 2011 19:43
Last Modified: 15 Nov 2016 13:43


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