TY  - JOUR
A1  - Attermeyer, Katrin
A1  - Hornick, T.
A1  - Kayler, Z. E.
A1  - Bahr, A.
A1  - Zwirnmann, E.
A1  - Grossart, Hans-Peter
A1  - Premke, K.
T1  - Enhanced bacterial decomposition with increasing addition of autochthonous to allochthonous carbon without any effect on bacterial community composition
JF  - Biogeosciences
N2  - Dissolved organic carbon (DOC) concentrations - mainly of terrestrial origin - are increasing worldwide in inland waters. Heterotrophic bacteria are the main consumers of DOC and thus determine DOC temporal dynamics and availability for higher trophic levels. Our aim was to study bacterial carbon (C) turnover with respect to DOC quantity and chemical quality using both allochthonous and autochthonous DOC sources. We incubated a natural bacterial community with allochthonous C (C-13-labeled beech leachate) and increased concentrations and pulses (intermittent occurrence of organic matter input) of autochthonous C (phytoplankton lysate). We then determined bacterial C consumption, activities, and community composition together with the C flow through bacteria using stable C isotopes. The chemical analysis of single sources revealed differences in aromaticity and low-and high-molecular-weight substance fractions (LMWS and HMWS, respectively) between allochthonous and autochthonous C sources. Both DOC sources (allochthonous and autochthonous DOC) were metabolized at a high bacterial growth efficiency (BGE) around 50%. In treatments with mixed sources, rising concentrations of added autochthonous DOC resulted in a further, significant increase in bacterial DOC consumption of up to 68% when nutrients were not limiting. This rise was accompanied by a decrease in the humic substance (HS) fraction and an increase in bacterial biomass. Changes in DOC concentration and consumption in mixed treatments did not affect bacterial community composition (BCC), but BCC differed in single vs. mixed incubations. Our study highlights that DOC quantity affects bacterial C consumption but not BCC in nutrient-rich aquatic systems. BCC shifted when a mixture of allochthonous and autochthonous C was provided simultaneously to the bacterial community. Our results indicate that chemical quality rather than source of DOC per se (allochthonous vs. autochthonous) determines bacterial DOC turnover.
Y1  - 2014
U6  - https://doi.org/10.5194/bg-11-1479-2014
SN  - 1726-4170
SN  - 1726-4189
VL  - 11
IS  - 6
SP  - 1479
EP  - 1489
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Brothers, Soren M.
A1  - Koehler, J.
A1  - Attermeyer, Katrin
A1  - Grossart, Hans-Peter
A1  - Mehner, T.
A1  - Meyer, N.
A1  - Scharnweber, Inga Kristin
A1  - Hilt, Sabine
T1  - A feedback loop links brownification and anoxia in a temperate, shallow lake
JF  - Limnology and oceanography
N2  - This study examines a natural, rapid, fivefold increase in dissolved organic carbon (DOC) concentrations in a temperate shallow lake, describing the processes by which increased DOC resulted in anoxic conditions and altered existing carbon cycling pathways. High precipitation for two consecutive years led to rising water levels and the flooding of adjacent degraded peatlands. Leaching from the flooded soils provided an initial increase in DOC concentrations (from a 2010 mean of 12 +/- 1 mg L-1 to a maximum concentration of 53 mg L-1 by June 2012). Increasing water levels, DOC, and phytoplankton concentrations reduced light reaching the sediment surface, eliminating most benthic primary production and promoting anoxia in the hypolimnion. From January to June 2012 there was a sudden increase in total phosphorus (from 57 mg L-1 to 216 mg L-1), DOC (from 24.6 mg L-1 to 53 mg L-1), and iron (from 0.12 mg L-1 to 1.07 mg L-1) concentrations, without any further large fluxes in water levels. We suggest that anoxic conditions at the sediment surface and flooded soils produced a dramatic release of these chemicals that exacerbated brownification and eutrophication, creating anoxic conditions that persisted roughly 6 months below a water depth of 1 m and extended periodically to the water surface. This brownification-anoxia feedback loop resulted in a near-complete loss of macroinvertebrate and fish populations, and increased surface carbon dioxide (CO2) emissions by an order of magnitude relative to previous years.
Y1  - 2014
U6  - https://doi.org/10.4319/lo.2014.59.4.1388
SN  - 0024-3590
SN  - 1939-5590
VL  - 59
IS  - 4
SP  - 1388
EP  - 1398
PB  - Wiley-Blackwell
CY  - Hoboken
ER  -