TY - JOUR A1 - Kamjunke, Norbert A1 - Beckers, Liza-Marie A1 - Herzsprung, Peter A1 - von Tümpling, Wolf A1 - Lechtenfeld, Oliver A1 - Tittel, Jörg A1 - Risse-Buhl, Ute A1 - Rode, Michael A1 - Wachholz, Alexander A1 - Kallies, Rene A1 - Schulze, Tobias A1 - Krauss, Martin A1 - Brack, Werner A1 - Comero, Sara A1 - Gawlik, Bernd Manfred A1 - Skejo, Hello A1 - Tavazzi, Simona A1 - Mariani, Giulio A1 - Borchardt, Dietrich A1 - Weitere, Markus T1 - Lagrangian profiles of riverine autotrophy, organic matter transformation, and micropollutants at extreme drought JF - The science of the total environment : an international journal for scientific research into the environment and its relationship with man N2 - On their way from inland to the ocean, flowing water bodies, their constituents and their biotic communities are ex-posed to complex transport and transformation processes. However, detailed process knowledge as revealed by La-grangian measurements adjusted to travel time is rare in large rivers, in particular at hydrological extremes. To fill this gap, we investigated autotrophic processes, heterotrophic carbon utilization, and micropollutant concentrations applying a Lagrangian sampling design in a 600 km section of the River Elbe (Germany) at historically low discharge. Under base flow conditions, we expect the maximum intensity of instream processes and of point source impacts. Phy-toplankton biomass and photosynthesis increased from upstream to downstream sites but maximum chlorophyll con-centration was lower than at mean discharge. Concentrations of dissolved macronutrients decreased to almost complete phosphate depletion and low nitrate values. The longitudinal increase of bacterial abundance and production was less pronounced than in wetter years and bacterial community composition changed downstream. Molecular analyses revealed a longitudinal increase of many DOM components due to microbial production, whereas saturated lipid-like DOM, unsaturated aromatics and polyphenols, and some CHOS surfactants declined. In decomposition exper-iments, DOM components with high O/C ratios and high masses decreased whereas those with low O/C ratios, low masses, and high nitrogen content increased at all sites. Radiocarbon age analyses showed that DOC was relatively old (890-1870 years B.P.), whereas the mineralized fraction was much younger suggesting predominant oxidation of algal lysis products and exudates particularly at downstream sites. Micropollutants determining toxicity for algae (terbuthylazine, terbutryn, isoproturon and lenacil), hexachlorocyclohexanes and DDTs showed higher concentrations from the middle towards the downstream part but calculated toxicity was not negatively correlated to phytoplankton. Overall, autotrophic and heterotrophic process rates and micropollutant concentrations increased from up-to down-stream reaches, but their magnitudes were not distinctly different to conditions at medium discharges. KW - Phytoplankton KW - Nutrients KW - Dissolved organic matter (DOM) KW - bacteria KW - Respiration KW - Micropollutants Y1 - 2022 U6 - https://doi.org/10.1016/j.scitotenv.2022.154243 SN - 0048-9697 SN - 1879-1026 VL - 828 PB - Elsevier CY - Amsterdam 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 - Wölfl, S. A1 - Tittel, Jörg A1 - Zippel, Barbara A1 - Kringel, R. T1 - Occurrence of an algal mass development in an acidic (pH 2.5), iron and aluminium-rich coal mining pond Y1 - 2000 ER - TY - JOUR A1 - Bissinger, Vera A1 - Jander, Jörn A1 - Tittel, Jörg T1 - A new medium free of organic carbon to cultivate organisms from extremely acidic mining lakes (pH 2.7) N2 - An algal culture medium was developed which reflects the extreme chemical conditions of acidic mining lakes (pH 2.7, high concentrations of iron and sulfate) and remains stable without addition of organic carbon sources. It enables controlled experiments e.g. on the heterotrophic potential of pigmented flagellates in the laboratory. Various plankton organisms isolated from acidic lakes were successfully cultivated in this medium. The growth rates of an Chlamydomonas- isolate from acidic mining lakes were assessed by measuring cell densities under pure autotrophic and heterotrophic conditions (with glucose as organic C-source) and showed values of 0.74 and 0.40, respectively. Y1 - 2000 ER - TY - JOUR A1 - Bissinger, Vera A1 - Tittel, Jörg T1 - Process rates and growth limiting factors of planktonic algae (Chlamydomonas sp.) from extremely acidic (pH 2,5 3) mining lakes in Germany Y1 - 2000 ER - TY - JOUR A1 - Koschorreck, Matthias A1 - Frömmichen, René A1 - Herzsprung, Peter A1 - Tittel, Jörg A1 - Wendt-Potthoff, Katrin T1 - Function of straw for in situ remediation of acidic mining lakes Y1 - 2002 SN - 0049-6979 ER - TY - JOUR A1 - Koschorreck, Matthias A1 - Tittel, Jörg T1 - Benthic photosynthesis in an acidic mining lake (pH 2.6). Y1 - 2002 ER - TY - JOUR A1 - Tittel, Jörg A1 - Bissinger, Vera A1 - Zippel, Barbara A1 - Gaedke, Ursula A1 - Bell, Elanor M. A1 - Lorke, Andreas A1 - Kamjunke, Norbert T1 - Mixotrophs combine resource use to outcompete specialists: Implications for aquatic food webs N2 - The majority of species can be grouped into those relying solely on photosynthesis (phototrophy) or those relying solely on the assimilation of organic substances (heterotrophy) to meet their requirements for energy and carbon. However, a special life history trait exists in which organisms combine both phototrophy and heterotrophy. Such 'mixotrophy' is a widespread phenomenon in aquatic habitats and is observed in many protozoan and metazoan organisms. The strategy requires investment in both photosynthetic and heterotrophic cellular apparatus, but the benefits must outweigh these costs. In accordance with the mechanistic resource competition theory, laboratory experiments revealed that pigmented mixotrophs combined light and prey as substitutable resources. Thereby, they reduced prey abundance below the critical food concentration of competing specialist grazers [Rothhaupt, K. O. (1996) Ecology 77, 716-724]. Here, we demonstrate for the first time the important consequences of this strategy for an aquatic community. In the illuminated surface strata of a lake, mixotrophs reduced prey abundance so steeply that grazers from higher trophic levels, consuming both the mixotrophs and their prey, could not persist. Thus, the mixotrophs escaped from both competition and grazing, and remained dominant. Furthermore, the mixotrophs structured the prey abundance along the vertical light gradient creating low densities near the surface and a pronounced maximum of their algal prey at depth. Such deep algal accumulations are typical features of nutrient poor aquatic habitats, previously explained by resource availability. We hypothesize instead that the mixotrophic grazing strategy is responsible for deep algal accumulations in many aquatic environments. Y1 - 2003 UR - www.pnas.org/cgi/doi/10.1073/pnas.2130696100 ER - TY - JOUR A1 - Kamjunke, Norbert A1 - Gaedke, Ursula A1 - Tittel, Jörg A1 - Weithoff, Guntram A1 - Bell, Elanor M. T1 - Strong vertical differences in the plankton composition of an extremely acidic lake N2 - Vertical differences in food web structure were examined in an extremely acidic, iron-rich mining lake in Germany (Lake 111; pH 2.6, total Fe 150mg L-1) during the period of stratification. We tested whether or not the seasonal variation of the plankton composition is less pronounced than the differences observed over depth. The lake was strongly stratified in summer, and concentrations of dissolved organic carbon and inorganic carbon were consistently low in the epilimnion but high in the hypolimnion. Oxygen concentrations declined in the hypolimnion but were always above 2mg L-1. Light attenuation did not change over depth and time and was governed by dissolved ferric iron. The plankton consisted mainly of single-celled and filamentous bacteria, the two mixotrophic flagellates Chlamydomonas sp. and Ochromonas sp., the two rotifer species Elosa worallii and Cephalodella hoodi, and Heliozoa as top predators. We observed very few ciliates and rhizopods, and no heterotrophic flagellates, crustaceans or fish. Ochromonas sp., bacterial filaments, Elosa and Heliozoa dominated in the epilimnion whereas Chlamydomonas sp., single-celled bacteria and Cephalodella dominated in the hypolimnion. Single-celled bacteria were controlled by Ochromonas sp. whereas the lack of large consumers favoured a high proportion of bacterial filaments. The primarily phototrophic Chlamydomas sp. was limited by light and CO2 and may have been reduced due to grazing by Ochromonas sp. in the epilimnion. The distribution of the primarily phagotrophic Ochromonas sp. and of the animals seemed to be controlled by prey availability. Differences in the plankton composition were much higher between the epilimnion and hypolimnion than within a particular stratum over time. The food web in Lake 111 was extremely species-poor enabling no functional redundancy. This was attributed to the direct exclusion of species by the harsh environmental conditions and presumably enforced by competitive exclusion. The latter was promoted by the low diversity at the first trophic level which, in turn, was attributed to relatively stable growth conditions and the independence of resource availability (inorganic carbon and light) from algal density. Ecological theory suggests that low functional redundancy promotes low stability in ecosystem processes which was not supported by our data. Y1 - 2004 ER - TY - JOUR A1 - Tittel, Jörg A1 - Kamjunke, Norbert T1 - Metabolism of dissolved organic carbon by planktonic bacteria and mixotrophic algae in lake neutralisation experiments N2 - 1. Lakes formed in mining pits often contain high concentrations of dissolved ferric iron and sulphate (e.g. 2 and 16 mmol L)1, respectively) and the pH is buffered between 2.5 and 3.5. Efforts to neutralise their water are based on the stimulation of lake internal, bacterial iron- and sulphate reduction. Electron donors may be supplied by organic carbon compounds or indirectly by enhancement of primary production. Here, we investigated the function of mixotrophic algae, which can potentially supplement or deplete the organic carbon pool, in the carbon metabolism and alkalinity budget of an acidic mining lake. 2. Two weeks after organic substrates had been added in a large in situ mesocosm of 30 m diameter, a bloom of Chlamydomonas occurred, reaching a biovolume of 80 mm3 L)1. Growth experiments using filtered lake water showed that the alga reduced the overall dissolved organic carbon (DOC) concentration despite significant photosynthetic activity. However, when Chlamydomonas were grown together with natural bacterioplankton, net DOC consumption did not increase. 3. Uptake experiments using [14C]-glucose indicated that bacteria dominated glucose uptake and remineralisation. Therefore, the DOC leached in the water column was processed mainly by planktonic bacteria. Leached DOC must be regarded as loss, not transferred by larger organisms to the sediment, where reduction processes take place. 4. From phytoplankton biomass and production 2 years after fertilisation we estimated that pelagic photosynthesis does not supply an electron donor capacity capable of reducing more than 2% of actual stock of acidity per year. We estimated that only the benthic primary production was in a range to compensate for ongoing inputs of iron and sulphate. Y1 - 2004 ER -