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Allochthonous and autochthonous carbon sources of lake bacterioplankton

Kritzberg, Emma LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

Pelagiska bakterier använder löst organiskt material som kol- och energikälla. Det lösta materialet kan ha sitt ursprung i intern (autokton) eller terrester (allokton) primärproduktion. Den här avhandlingen handlar om hur bakterier använder autoktont och alloktont producerat kol. Dessutom undersöker jag om det finns en koppling mellan kolkällans ursprung och strukturen och funktionen hos bakteriesamhället.



Trots liten tillförsel av alloktont kol, så indikerar hög respiration:primärproduktion och bakterieproduktion:primärproduktion att fem oligotrofa klarvatten sjöar på Färöarna var nettoheterotrofa, d v s respirationen överstiger produktionen, och att det heterotrofa... (More)
Popular Abstract in Swedish

Pelagiska bakterier använder löst organiskt material som kol- och energikälla. Det lösta materialet kan ha sitt ursprung i intern (autokton) eller terrester (allokton) primärproduktion. Den här avhandlingen handlar om hur bakterier använder autoktont och alloktont producerat kol. Dessutom undersöker jag om det finns en koppling mellan kolkällans ursprung och strukturen och funktionen hos bakteriesamhället.



Trots liten tillförsel av alloktont kol, så indikerar hög respiration:primärproduktion och bakterieproduktion:primärproduktion att fem oligotrofa klarvatten sjöar på Färöarna var nettoheterotrofa, d v s respirationen överstiger produktionen, och att det heterotrofa planktonsamhället understöddes av alloktont kol. Förekomsten av nettoheterotrofi säger emellertid ingenting om vad som händer med det alloktona kolet. Betydelsen av alloktont kol undersöktes istället genom inmärkning av den autoktona produktionen genom tillsatser av 13C till hela sjöar (Norra Wisconsin). Det autoktona kolet kunde spåras i bakteriererna. Det alloktona kolets betydelse för bakterieproduktionen varierade mellan 40 och 80 % mellan eutrofa, icke-humösa och oligotrofa, humösa sjöar. Bakterierna visade en preferens för autoktont kol, även om selektiviteten inte var total. I en annan, korrelativ studie som utfördes i samma område framkom det att bakterier dessutom använder det autoktona kolet effektivare, vilket innebär att autoktont kol i högre utsträckning kan föras vidare till högre nivåer i födokedjan. Resultaten från isoptoptillsatserna och den korrelativa studien simulerades med hjälp av en enkel steady state model över bakteriell användning av autoktont och alloktont kol. Det visade sig att en högre preferens för och effektivare använding av autoktont kol kan förklara varför bakterieproduktionen är kopplad till autoktont kol även i nettoheterotrofa sjöar där bakterierna omsätter mycket alloktont kol. Slutligen, så tycktes kolkällans ursprung påverka både bakteriesamhällets sammansättning och generella funktion (produktion, respiration, tillväxteffektivitet och kolförbrukning). Sammanfattningsvis så kan förekomsten av olika subkulturer inom bakterisamhället växa olika fort på substrat med olika ursprung, och det kan förklara varför vi observerar en selektiv användning av autoktont kol när vi studerar bakteriesamhället som en enhet. (Less)
Abstract
Organic substrates for pelagic bacteria are derived from dissolved organic carbon (DOC) in the water column that originates either from primary production from within the lake itself (autochthonous), or import of organic matter from the terrestrial watershed (allochthonous production). This thesis addresses the utilization of allochthonous versus autochthonous carbon (C) sources by lake bacterioplankton. In addition, I examine the connection between the source of the organic matter and the structure and function of the bacterial community.



In spite of low allochthonous C inputs, high respiration:primary production and bacterial:primary production suggested that five oligotrophic clear-water lakes on the Faroe Islands... (More)
Organic substrates for pelagic bacteria are derived from dissolved organic carbon (DOC) in the water column that originates either from primary production from within the lake itself (autochthonous), or import of organic matter from the terrestrial watershed (allochthonous production). This thesis addresses the utilization of allochthonous versus autochthonous carbon (C) sources by lake bacterioplankton. In addition, I examine the connection between the source of the organic matter and the structure and function of the bacterial community.



In spite of low allochthonous C inputs, high respiration:primary production and bacterial:primary production suggested that five oligotrophic clear-water lakes on the Faroe Islands were net heterotrophic (respiration exceeded primary production) and that the heterotrophic plankton were subsidized by allochthonous organic C. While the occurence of net heterotrophy does not reveal anything about the fate of the allochthonous C, the importance of autochthonous versus allochthonous DOC in supporting bacterial production was examined by whole-lake additions of 13C (Forest lakes in Northern Wisconsin), and tracing its subsequent uptake by phytoplankton and on to bacteria. Bacterial production in lakes ranging from eutrophic and low-humic to oligotrophic and humic, consisted of 40 ? 80 % allochthonous C, confirming the often stated hypothesis that autochthonous carbon alone does not support bacterial production. Yet, autochthonous DOC was preferentially utilized relative to terrestrial DOC, although the preference for autochthonous C was not complete. Furthermore, based on a correlative study of ten lakes in the same area, bacteria seemed to grow more efficiently on autochthonous C, suggesting that this C is more effectively transferred to higher organisms. The results of the lake survey and the whole-lake isotope additions were simulated by a simple steady state model of bacterial utilization of autochthonous and allochthonous dissolved organic C. This showed that a higher preference and greater growth efficiency of bacteria on autochthonous C could explain why bacterial production was coupled to autochthonous production also in net heterotrophic ecosystems where the use of allochthonous C by bacteria was high. Finally, the source of the organic substrate (autochthonous and allochthonous) appeared to influence the bacterial community composition as well as general bacterial functions (production, respiration, growth yield and substrate utilization). Hence, bacterial sub-populations growing at different rates on substrates of differing origin, might explain why we observe a selective utilization of autochthonous C by the total bacterial community. (Less)
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author
supervisor
opponent
  • Associate Professor del Giorgio, Paul, Département des sciences biologiques, Université du Québec à Montréal (UQÀM), CP 8888, succursale Ce
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Marinbiologi, limnologi, akvatisk ekologi, aquatic ecology, marine biology, Hydrobiology, bacterial community composition, bacterial growth efficiency, bacterioplankton, carbon subsidy, dissolved organic carbon, limnology
pages
96 pages
publisher
Department of Ecology, Lund University
defense location
Blå hallen, Ekologihuset, Sölvegatan 37
defense date
2005-03-18 09:30
ISBN
91-7105-215-1
language
English
LU publication?
yes
id
421ab469-1243-4477-bb0f-b7bfa5145951 (old id 544416)
date added to LUP
2007-10-13 12:34:27
date last changed
2016-09-19 08:45:08
@phdthesis{421ab469-1243-4477-bb0f-b7bfa5145951,
  abstract     = {Organic substrates for pelagic bacteria are derived from dissolved organic carbon (DOC) in the water column that originates either from primary production from within the lake itself (autochthonous), or import of organic matter from the terrestrial watershed (allochthonous production). This thesis addresses the utilization of allochthonous versus autochthonous carbon (C) sources by lake bacterioplankton. In addition, I examine the connection between the source of the organic matter and the structure and function of the bacterial community.<br/><br>
<br/><br>
In spite of low allochthonous C inputs, high respiration:primary production and bacterial:primary production suggested that five oligotrophic clear-water lakes on the Faroe Islands were net heterotrophic (respiration exceeded primary production) and that the heterotrophic plankton were subsidized by allochthonous organic C. While the occurence of net heterotrophy does not reveal anything about the fate of the allochthonous C, the importance of autochthonous versus allochthonous DOC in supporting bacterial production was examined by whole-lake additions of 13C (Forest lakes in Northern Wisconsin), and tracing its subsequent uptake by phytoplankton and on to bacteria. Bacterial production in lakes ranging from eutrophic and low-humic to oligotrophic and humic, consisted of 40 ? 80 % allochthonous C, confirming the often stated hypothesis that autochthonous carbon alone does not support bacterial production. Yet, autochthonous DOC was preferentially utilized relative to terrestrial DOC, although the preference for autochthonous C was not complete. Furthermore, based on a correlative study of ten lakes in the same area, bacteria seemed to grow more efficiently on autochthonous C, suggesting that this C is more effectively transferred to higher organisms. The results of the lake survey and the whole-lake isotope additions were simulated by a simple steady state model of bacterial utilization of autochthonous and allochthonous dissolved organic C. This showed that a higher preference and greater growth efficiency of bacteria on autochthonous C could explain why bacterial production was coupled to autochthonous production also in net heterotrophic ecosystems where the use of allochthonous C by bacteria was high. Finally, the source of the organic substrate (autochthonous and allochthonous) appeared to influence the bacterial community composition as well as general bacterial functions (production, respiration, growth yield and substrate utilization). Hence, bacterial sub-populations growing at different rates on substrates of differing origin, might explain why we observe a selective utilization of autochthonous C by the total bacterial community.},
  author       = {Kritzberg, Emma},
  isbn         = {91-7105-215-1},
  keyword      = {Marinbiologi,limnologi,akvatisk ekologi,aquatic ecology,marine biology,Hydrobiology,bacterial community composition,bacterial growth efficiency,bacterioplankton,carbon subsidy,dissolved organic carbon,limnology},
  language     = {eng},
  pages        = {96},
  publisher    = {Department of Ecology, Lund University},
  school       = {Lund University},
  title        = {Allochthonous and autochthonous carbon sources of lake bacterioplankton},
  year         = {2005},
}