Stress-induced alterations in ecosystem function: the role of acidification in lotic metabolism and biogeochemistry

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dc.contributor.authorEly, Damon Thomasen
dc.contributor.committeechairValett, H. Mauriceen
dc.contributor.committeecochairJones, Robert H.en
dc.contributor.committeememberBurger, James A.en
dc.contributor.committeememberDaniels, W. Leeen
dc.contributor.committeememberWebster, Jackson R.en
dc.contributor.departmentBiologyen
dc.date.accessioned2017-04-06T15:42:22Zen
dc.date.adate2010-06-14en
dc.date.available2017-04-06T15:42:22Zen
dc.date.issued2010-03-31en
dc.date.rdate2016-09-27en
dc.date.sdate2010-05-07en
dc.description.abstractI investigated how anthropogenic acidification influences stream metabolism and nitrogen (N) cycling by considering the stress response of microbial compartments responsible for these ecosystem processes. Microcosm incubations of leaf biofilms from streams of differing pH revealed greater rates of fungal biomass-specific respiration (i.e. the stress metric <i>q</i>CO₂) and biomass-specific N uptake (i.e. <i>q</i>N) with increasing acidity. The positive relationship between <i>q</i>CO₂ and <i>q</i>N indicated alternate fates for N other than structural biomass, possibly related to increased exoenzyme production as part of the stress response. Whole-stream ¹⁵N experiments and measurements of respiration and fungal standing crop across the pH gradient resulted in similar patterns in <i>q</i>CO₂ and <i>q</i>N found in microcosm experiments, supporting <i>q</i>CO₂ as an ecosystem-level stress indicator and providing insight towards controls over N cycling across the pH gradient. Fungal biomass and ecosystem respiration declined with increasing acidity while N uptake metrics were not related to pH, which suggested <i>q</i>N in acid streams was sufficiently high to counteract declines in fungal abundance. During spring, chlorophyll <i>a</i> standing crops were higher in more acidic streams despite lower nutrient concentrations. However, N uptake rates and gross primary production differed little between acid and circumneutral streams. Reduced heterotrophy in acid streams was apparent in lower whole-stream respiration rates, less ability to process organic carbon, and little response of N uptake to added carbon resources. Overall, acid-induced stress in streams was found to impair decomposer activity and caused a decoupling of carbon and nitrogen cycles in these systems.en
dc.description.degreePh. D.en
dc.identifier.otheretd-05072010-214046en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-05072010-214046/en
dc.identifier.urihttp://hdl.handle.net/10919/77067en
dc.language.isoen_USen
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectaquatic fungien
dc.subjectDINen
dc.subject¹⁵Nen
dc.subjectspiralingen
dc.subjectqCO₂en
dc.subjectnitrogen uptakeen
dc.subjectrespirationen
dc.subjectchlorophyll aen
dc.subjectstream metabolismen
dc.titleStress-induced alterations in ecosystem function: the role of acidification in lotic metabolism and biogeochemistryen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineBiologyen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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