Veränderungen in der Struktur und Funktion pelagischer Bakterien während und nach der Restauration des Tiefwarensees
Final Report Abstract
This project aimed to consistently follow bacterial dynamics, in particular of the dominant freshwater Actinobacteria cluster acIb, after restauration of eutrophic Lake Tiefwaren. All physico-chemical parameters demonstrate that nutrient load has been successfully reduced by the injection of sodium aluminate and calcium hydroxide into the hypolimnion of the lake. These changes in lake chemistry led to pronounced changes in phytoplankton biomass (as indicated by Chl a) and community composition. Changes in zooplankton were mainly reflected by differences in community composition. Our study – for the first time – shows that BCC, in particular of free-living bacteria, did not change much in relation to lake restauration. In contrast, seasonal changes in temperature but also pH and Chl a were reflected by changes in community composition of mainly particle-attached bacteria. This indicates a tight coupling of attached bacteria to particle quality and also quantity (as indicated by algal biomass (Chl a)) related to seasonal changes in phytoplankton composition. Thereby, temperature (and most likely light) seems to be the most important factor controlling seasonal phytoplankton and also bacterial community dynamics. Seasonal changes in BCC closely followed those of phytoplankton but little those of chemical parameters as a consequence of lake restauration. Unfortunately, we could not measure bacterial parameters before and during early lake restauration and thus we may have missed initial changes due to the treatment. However, in the nutrient limited TW (after treatment) free-living bacteria showed a rather consistent annual pattern which was not affected by the observed changes in chemical parameters during the observation period. Our study reveals that freshwater Actinobacteria of the acIb cluster largely dominated BCC in TW and that their community composition changes seasonally as indicated by a succession in specific phylotypes. In contrast, dynamics of BCC of particle-associated bacteria was much more pronounced and closely related to changes in particle type and quantity which could be related to phytoplankton development. Our on-going in depth-studies on genetic features and physiology of the dominant Actinobacteria of the acI cluster will allow for better predictions of their biogeochemical role. This information is needed to better evaluate potential effects of sudden changes in environmental parameters, e.g. in temperature which seems to be a major driving forces for seasonal bacterial succession in TW. Overall, our study shows that bacterial dynamics in the epilimnion seem to be little affected by the injection of sodium aluminate and calcium hydroxide into the lake’s hypolimnion. This indicates that this type of lake restauration has little site effects on bacterial dynamics and presumably on biogeochemical processes. Since we have missed the first 2 years of the treatment, these results need to be validated in the future, e.g. by following the same restauration procedure in Lake Haus. Based on these results we expect valuable information for lake reaturation and management strategies.
Publications
- Diversity and abundance of freshwater Actinobacteria along environmental gradients in the brackish northern Baltic Sea.
Environmental Microbiology, Vol. 11.2009, Issue 8, pp. 2042–2054.
Holmfeldt, K., Dziallas, C., Titelman, J., Pohlmann, K., Grossart, H.-P., Riemann, L.
(See online at https://dx.doi.org/10.1111/j.1462-2920.2009.01925.x) - Hydrostatic pressure affects physiology and community structure
of marine bacteria during settling to 4000 m - an experimental approach. Marine Ecology Progress Series, Vol. 390. 2009, pp. 97-104.
Grossart, H.-P., Gust, G.
(See online at https://doi.org/10.3354/meps08201) - Substrate incorporation patterns of bacterioplankton populations in stratified and mixed waters of a humic lake. Environmental Microbiology, Vol. 11. 2009, Issue 7, pp. 1854–1865.
Buck, U., Grossart, H.-P., Amann R., Pernthaler, J.
(See online at https://dx.doi.org/10.1111/j.1462-2920.2009.01910.x) - Ecological consequences of bacterioplankton lifestyles: Changes in
concepts are needed. Environmental Microbiology Reports, Vol. 2. 2010, Issue 6, pp. 706–714.
Grossart, H.-P.
(See online at https://dx.doi.org/10.1111/j.1758-2229.2010.00179.x) - www.aquaticmicrobial.net. Communicative & Integrative Biology, Vol. 3. 2010, Issue 6, pp. 491-494.
Grossart, H.-P., Tang, K.
(See online at https://dx.doi.org/10.4161/cib.3.6.12975) - Effects of pollen leaching and microbial degradation on organic carbon and nutrient availability in lake water. Aquatic Sciences, Vol. 74. 2012, Issue 1, pp. 87–99.
Rösel, S., Rychla, A., Wurzbacher, C., Grossart, H.-P.
(See online at https://doi.org/10.1007/s00027-011-0198-3)
