Arad'ın resimleri

Taha Toros Arşivi, Dosya No: 43-Agop AradUnutma İstanbul projesi İstanbul Kalkınma Ajansı'nın 2016 yılı "Yenilikçi ve Yaratıcı İstanbul Mali Destek Programı" kapsamında desteklenmiştir. Proje No: TR10/16/YNY/010

Methane production increases with warming and carbon additions to incubated sediments from a semiarid reservoir

<p>Methane production (MP) in aquatic systems is positively related to temperature and trophic state. Global warming and eutrophication are predicted to potentiate MP in freshwater reservoirs. The simultaneous impact of rising temperature and carbon and nutrient additions on MP were examined in a tropical semiarid hydropower reservoir. Sediments cores from 3 locations (profundal, littoral, and intermediate) with differing water depth were sectioned and slurries incubated at 20, 30, and 40 °C with or without additions of carbon, nitrogen, or phosphorus, or all combined. Maximal MP (4.2 μmol g DW⁻¹ d⁻¹), occurred under carbon addition, and mean MP was about twice as high than in the control, independent of temperature. The effect of carbon additions manifested differently at the 3 locations, with enhancement of MP greater in upper sediment layers of the profundal location and in deeper layers (4–8 cm) of littoral and intermediate locations. Without carbon addition, MP was slower and positive effects of warming were more frequent, especially in littoral. These results suggest that the combined effect of warming and land use changes, principally on carbon loads, will increase the MP and methane emissions potential in this semiarid reservoir. Differences in effects are linked to location in the reservoir.</p

DGGE profiles of fungal 18S rRNA gene amplicons derived from the leaf litter of the plant species A: <i>Baccaure ramiflora</i>, B: <i>Hevea brasiliensis</i>, C: <i>Pleioblastus amarus</i> and D: <i>Pometi tomentos</i>.

<p>The numbers of days of incubations are indicated. Each sampling day has two replicates of separate incubations denote by A and B. The arrows indicate the bands that have sequences affiliated to <i>Aspergillus</i> (day 1) and <i>Pleosporales</i> (day 42).</p

Richness and diversity of microbial communities of the leaf litter of 4 plant species during 42 days incubation A: number of bands obtained from DGGE analysis of bacterial 16S rRNA gene PCR amplicons, B: Shannon’s index calculated from bacterial DGGE profiles, C: number of bands obtained from DGGE analysis of fungal 18S rRNA gene PCR amplicons, and D: Shannon’s index calculated from fungal DGGE profiles.

<p>The plant species <i>Baccaure ramiflora, Hevea brasiliensis, Pleioblastus amarus</i> and <i>Pometi tomentos</i> were denoted by Br, Hb, Pa and Pt, respectively.</p

Enhancing Surface Methane Fluxes from an Oligotrophic Lake: Exploring the Microbubble Hypothesis

Exchange of the greenhouse gases carbon dioxide (CO₂) and methane (CH₄) across inland water surfaces is an important component of the terrestrial carbon (C) balance. We investigated the fluxes of these two gases across the surface of oligotrophic Lake Stechlin using a floating chamber approach. The normalized gas transfer rate for CH₄ (<i>k</i>_600,CH4) was on average 2.5 times higher than that for CO₂ (<i>k</i>_600,CO2) and consequently higher than Fickian transport. Because of its low solubility relative to CO₂, the enhanced CH₄ flux is possibly explained by the presence of microbubbles in the lake’s surface layer. These microbubbles may originate from atmospheric bubble entrainment or gas supersaturation (i.e., O₂) or both. Irrespective of the source, we determined that an average of 145 L m^–2 d^–1 of gas is required to exit the surface layer via microbubbles to produce the observed elevated <i>k</i>₆₀₀,_CH4. As <i>k</i>₆₀₀ values are used to estimate CH₄ pathways in aquatic systems, the presence of microbubbles could alter the resulting CH₄ and perhaps C balances. These microbubbles will also affect the surface fluxes of other sparingly soluble gases in inland waters, including O₂ and N₂