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In this thesis, I investigated the factors influencing the growth and vertical distribution of planktonic algae in extremely acidic mining lakes (pH 2-3). In the focal study site, Lake 111 (pH 2.7; Lusatia, Germany), the chrysophyte, Ochromonas sp., dominates in the upper water strata and the chlorophyte, Chlamydomonas sp., in the deeper strata, forming a pronounced deep chlorophyll maximum (DCM). Inorganic carbon (IC) limitation influenced the phototrophic growth of Chlamydomonas sp. in the upper water strata. Conversely, in deeper strata, light limited its phototrophic growth. When compared with published data for algae from neutral lakes, Chlamydomonas sp. from Lake 111 exhibited a lower maximum growth rate, an enhanced compensation point and higher dark respiration rates, suggesting higher metabolic costs due to the extreme physico-chemical conditions. The photosynthetic performance of Chlamydomonas sp. decreased in high-light-adapted cells when IC limited. In addition, the minimal phosphorus (P) cell quota was suggestive of a higher P requirement under IC limitation. Subsequently, it was shown that Chlamydomonas sp. was a mixotroph, able to enhance its growth rate by taking up dissolved organic carbon (DOC) via osmotrophy. Therefore, it could survive in deeper water strata where DOC concentrations were higher and light limited. However, neither IC limitation, P availability nor in situ DOC concentrations (bottom-up control) could fully explain the vertical distribution of Chlamydomonas sp. in Lake 111. Conversely, when a novel approach was adopted, the grazing influence of the phagotrophic phototroph, Ochromonas sp., was found to exert top-down control on its prey (Chlamydomonas sp.) reducing prey abundance in the upper water strata. This, coupled with the fact that Chlamydomonas sp. uses DOC for growth, leads to a pronounced accumulation of Chlamydomonas sp. cells at depth; an apparent DCM. Therefore, grazing appears to be the main factor influencing the vertical distribution of algae observed in Lake 111. The knowledge gained from this thesis provides information essential for predicting the effect of strategies to neutralize the acidic mining lakes on the food-web.
Das Weisungsrecht nach Art. 85 Abs. 3 GG : Inhalt, Grenzen und haftungsrechtliche Dimensionen
(2003)
Dringliche Rechte am Wohnungseigentum und Rechtsgeschäfte der Wohnungseigentümer untereinander
(2003)
Eigennamen referieren - Referieren mit Eigennamen : zur Kontextinvarianz der namentlichen Bezugnahme
(2003)
Verbales Arbeitgedächtnis und die Verarbeitung lexikalisch ambiger Wörter in Wort- und Satzkontexten
(2003)
Rechtsgrundlagen und Grenzen zulässiger Maßnahmen bei der Durchsuchung von Wohn- und Geschäftsräumen
(2003)
Fisch oder Karpfen ? : lexikale Aktivierung von Benennungsalternativen bei der Objektbenennung
(2003)
Die ungarische Gesellschaft mit beschränkter Haftung : mit Gemeinsamkeiten zur deutschen GmbH
(2003)
Der Ausstellungsvertrag
(2003)