TY  - JOUR
A1  - Engel, Anja
A1  - Piontek, Judith
A1  - Grossart, Hans-Peter
A1  - Riebesell, Ulf
A1  - Schulz, Kai Georg
A1  - Sperling, Martin
T1  - Impact of CO2 enrichment on organic matter dynamics during nutrient induced coastal phytoplankton blooms
JF  - Journal of plankton research
N2  - A mesocosm experiment was conducted to investigate the impact of rising fCO(2) on the build-up and decline of organic matter during coastal phytoplankton blooms. Five mesocosms (similar to 38 mA(3) each) were deployed in the Baltic Sea during spring (2009) and enriched with CO2 to yield a gradient of 355-862 A mu atm. Mesocosms were nutrient fertilized initially to induce phytoplankton bloom development. Changes in particulate and dissolved organic matter concentrations, including dissolved high-molecular weight (> 1 kDa) combined carbohydrates, dissolved free and combined amino acids as well as transparent exopolymer particles (TEP), were monitored over 21 days together with bacterial abundance, and hydrolytic extracellular enzyme activities. Overall, organic matter followed well-known bloom dynamics in all CO2 treatments alike. At high fCO(2,) higher Delta POC:Delta PON during bloom rise, and higher TEP concentrations during bloom peak, suggested preferential accumulation of carbon-rich components. TEP concentration at bloom peak was significantly related to subsequent sedimentation of particulate organic matter. Bacterial abundance increased during the bloom and was highest at high fCO(2). We conclude that increasing fCO(2) supports production and exudation of carbon-rich components, enhancing particle aggregation and settling, but also providing substrate and attachment sites for bacteria. More labile organic carbon and higher bacterial abundance can increase rates of oxygen consumption and may intensify the already high risk of oxygen depletion in coastal seas in the future.
KW  - mesocosm
KW  - ocean acidification
KW  - phytoplankton
KW  - organic matter
KW  - TEP
Y1  - 2014
U6  - https://doi.org/10.1093/plankt/fbt125
SN  - 0142-7873
SN  - 1464-3774
VL  - 36
IS  - 3
SP  - 641
EP  - 657
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Glombitza, Clemens
A1  - Stockhecke, Mona
A1  - Schubert, Carsten J.
A1  - Vetter, Alexandra
A1  - Kallmeyer, Jens
T1  - Sulfate reduction controlled by organic matter availability in deep sediment cores from the saline, alkaline Lake Van (Eastern Anatolia,Turkey)
JF  - Frontiers in microbiology
N2  - As part of the International Continental Drilling Program deep lake drilling project Paleo Van, we investigated sulfate reduction (SR) in deep sediment cores of the saline, alkaline (salinity 21.4%0, alkalinity 155 m mEq-1, pH 9.81) Lake Van, Turkey. The cores were retrieved in the Northern Basin (NB) and at Ahlat Ridge (AR) and reached a maximum depth of 220 m. Additionally, 65-75 cm long gravity cores were taken at both sites. SR rates (SRR) were low (<22 nmol cm-3 day-1) compared to lakes with higher salinity and alkalinity, indicating that salinity and alkalinity are not limiting SR in Lake Van. Both sites differ significantly in rates and depth distribution of SR. In NB, SRR are up to 10 times higher than at AR. SR could be detected down to 19 mblf (meters below lake floor) at NB and down to 13 mblf at AR. Although SRR were lower at AR than at NB, organic matter (OM) concentrations were higher. In contrast, dissolved OM in the pore water at AR contained more macromolecular OM and less low molecular weight OM.VVe thus suggest, that OM content alone cannot be used to infer microbial activity at Lake Van but that quality of OM has an important impact as well. These differences suggest that biogeochemical processes in lacustrine sediments are reacting very sensitively to small variations in geological, physical, or chemical parameters over relatively short distances.
KW  - saline lake
KW  - alkaline lake
KW  - sulfate reduction
KW  - deep biosphere
KW  - organic matter
Y1  - 2013
U6  - https://doi.org/10.3389/fmicb.2013.00209
SN  - 1664-302X
VL  - 4
IS  - 28
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Musolff, Andreas
A1  - Selle, Benny
A1  - Buttner, Olaf
A1  - Opitz, Michael
A1  - Tittel, Jörg
T1  - Unexpected release of phosphate and organic carbon to streams linked to declining nitrogen depositions
JF  - Global change biology
N2  - Reductions in emissions have successfully led to a regional decline in atmospheric nitrogen depositions over the past 20 years. By analyzing long-term data from 110 mountainous streams draining into German drinking water reservoirs, nitrate concentrations indeed declined in the majority of catchments. Furthermore, our meta-analysis indicates that the declining nitrate levels are linked to the release of dissolved iron to streams likely due to a reductive dissolution of iron(III) minerals in riparian wetland soils. This dissolution process mobilized adsorbed compounds, such as phosphate, dissolved organic carbon and arsenic, resulting in concentration increases in the streams and higher inputs to receiving drinking water reservoirs. Reductive mobilization was most significant in catchments with stream nitrate concentrations < 6 mg L-1. Here, nitrate, as a competing electron acceptor, was too low in concentration to inhibit microbial iron(III) reduction. Consequently, observed trends were strongest in forested catchments, where nitrate concentrations were unaffected by agricultural and urban sources and which were therefore sensitive to reductions of atmospheric nitrogen depositions. We conclude that there is strong evidence that the decline in nitrogen deposition toward pre-industrial conditions lowers the redox buffer in riparian soils, destabilizing formerly fixed problematic compounds, and results in serious implications for water quality.
KW  - atmospheric deposition
KW  - carbon cycle
KW  - nitrogen biogeochemistry
KW  - organic matter
KW  - riparian zone
KW  - streamwater chemistry
Y1  - 2017
U6  - https://doi.org/10.1111/gcb.13498
SN  - 1354-1013
SN  - 1365-2486
VL  - 23
SP  - 1891
EP  - 1901
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Zhang Chengjun, 
A1  - Fan Rong, 
A1  - Li Jun, 
A1  - Mischke, Steffen
A1  - Dembele, Blaise
A1  - Hu Xiaolan, 
T1  - Carbon and oxygen isotopic compositions - how lacustrine environmental factors respond in northwestern and northeastern China
JF  - Acta geologica Sinica : english edition
N2  - Surface lake sediments, 28 from Hoh Xil, 24 from northeastern China, 99 from Lake Bosten, 31 from Ulungur and 26 from Heihai were collected to determine C-13 and O-18 values. Considering the impact factors, conductivity, alkalinity, pH, TOC, C/N and carbonate-content in the sediments, Cl, P, S, and metal element ratios of Mg/Ca, Sr/Ca, Fe/Mn of bulk sediments as environmental variables enable evaluation of their influences on C-13 and O-18 using principal component analysis (PCA) method. The closure and residence time of lakes can influence the correlation between C-13 and O-18. Lake water will change from fresh to brackish with increasing reduction and eutrophication effects. Mg/Ca in the bulk sediment indicates the characteristic of residence time, Sr/Ca and Fe/Mn infer the salinity of lakes. Carbonate formation processes and types can influence the C-13-O-18 correlation. O-18 will be heavier from Mg-calcite and aragonite formed in a high-salinity water body than calcite formed in freshwater conditions. When carbonate content is less than 30%, there is no relationship with either C-13 or O-18, and also none between C-13 and O-18. More than 30%, carbonate content, however, co-varies highly to C-13 and O-18, and there is also a high correlation between C-13 and O-18. Vegetation conditions and primary productivity of lakes can influence the characteristics of C-13 and O-18, and their co-variance. Total organic matter content (TOC) in the sediments is higher with more terrestrial and submerged plants infilling. In northeastern and northwestern China, when organic matter in the lake sediments comes from endogenous floating organisms and algae, the C-13 value is high. C-13 is in the range of -4%o to 0 parts per thousand when organic matter comes mainly from floating organisms (C/N<6); in the range of -4 parts per thousand to 8 parts per thousand when organic matter comes from diatoms (C/N=6 to 8); and -8 parts per thousand to -4 parts per thousand when organic matter comes from aquatic and terrestrial plants (C/N>8).
KW  - Limnology
KW  - isotopic analysis
KW  - carbonates
KW  - organic matter
KW  - PCA
KW  - Tibet
KW  - Xinjiang
KW  - Northeastern China
Y1  - 2013
U6  - https://doi.org/10.1111/1755-6724.12133
SN  - 1000-9515
SN  - 1755-6724
VL  - 87
IS  - 5
SP  - 1344
EP  - 1354
PB  - Wiley-Blackwell
CY  - Hoboken
ER  -