Particle-associated and free-living microbial assemblages are distinct in a permanently redox-stratified freshwater lake

Microbial assemblages associated with biogenic particles are phylogenetically distinct from free-living counterparts, yet biogeochemically coupled. Compositions may vary with organic carbon and inorganic substrate availability and with redox conditions, which determine reductant and oxidant availability. To explore microbial assemblage compositional responses to steep oxygen and redox gradients and seasonal variability in particle and substrate availability, we analyzed taxonomic compositions of particle-associated (PA) and free-living (FL) bacteria and archaea in permanently redox-stratified Fayetteville Green Lake. PA and FL assemblages (> 2.7 μm and 0.2-2.7 μm) were surveyed at the peak (July) and end (October) of concurrent cyanobacteria, purple and green sulfur bacteria blooms that result in substantial vertical fluxes of particulate organic carbon. Assemblage compositions varied significantly among redox conditions and size fractions (PA or FL). Temporal differences were only apparent among samples from the mixolimnion and oxycline, coinciding with seasonal hydrographic changes. PA assemblages of the mixolimnion and oxycline shifted from aerobic heterotrophs in July to fermenters, iron-reducers, and denitrifiers in October, likely reflecting seasonal variability in photoautotroph biomass and inorganic nitrogen. Within a light-scattering layer spanning the lower oxycline and upper monimolimnion, photoautotrophs were more abundant in July than in October, when Desulfocapsa, a sulfate-reducing and sulfur-disproportionating bacterium, and Chlorophyte chloroplasts were abundant in PA assemblages. In this layer, microbial activity and cell concentrations were also highest. Below, the most abundant resident taxa were sulfate-reducing bacteria and anaerobic respirers. Results suggest PA and FL assemblage niche partitioning interconnects multiple elemental cycles that involve particulate and dissolved phases.

Anoxic depositional overprinting of 238U/235U in calcite: When do carbonates tell black shale tales?

The fidelity of uranium isotopes (δ238U) in marine carbonates as a paleoredox proxy relies on whether carbonates can record and preserve seawater δ238U. Although modern carbonate sediments deposited under oxic conditions have been shown to track seawater δ238U, it remains unknown whether this is true for carbonates deposited under anoxic conditions. This is a crucial question because many ancient carbonates were likely deposited or reworked under anoxic bottom waters. To better understand the behavior of uranium isotopes under this scenario, we investigated U isotope geochemistry in the meromictic Fayetteville Green Lake (FGL; New York, USA), where primary calcite is precipitated from oxic surface waters, sinks past the chemocline, and is deposited under anoxic bottom waters. We observed significant depletions of dissolved U concentration (from 2.7 to 0.9 ppb) and δ238U (from –0.55‰ to –0.96‰) below the chemocline in FGL. Parallel with these depletions, δ238U of sediment traps increased progressively from –0.51‰ to –0.16‰, suggesting that U(VI) reduction was occurring in the anoxic water column. Carbonate sediments deposited under anoxic bottom waters were enriched in U by 6–18× compared to primary calcite. Our data suggest that such significant authigenic U enrichments resulted from U(VI) reduction in the anoxic water column and below the sediment-water interface. The δ238U value in the top 0.25 cm of sediments was –0.29‰ ± 0.10‰, overprinting original δ238U in primary calcite (–0.51‰ ± 0.02‰). Future applications of carbonate δ238U as a paleoredox proxy should consider depositional environments (oxic vs. anoxic) of carbonates.

Basin-specific records of lake oligotrophication during the middle-to-late Holocene in boreal northeast Ontario, Canada

Descriptions of regional climate expression require data from multiple lakes, yet little is known of how variation in records within morphometrically complex lakes may affect interpretations. In northeast Ontario (Canada), this issue was addressed using records of pollen, pigments, and diatoms in three sediment cores from two small boreal lakes spanning the last ~6000 years. Pollen analysis suggested warm conditions between ~6000 and ~4000 cal yr BP, coherent with previous assessments from boreal eastern Ontario and western Quebec. Analysis of phototrophic communities from fossil pigments and diatom valves suggested relatively eutrophic conditions with lower lake-levels during this interval. Generalized additive model trends identified significant regional changes in pollen assemblages and declines in pigment concentrations after ~4000 cal yr BP consistent with cooler and wetter climate conditions that resulted in regional lake oligotrophication and increased lake levels during the late-Holocene. Despite contemporaneous changes in pollen and pigment biomarkers across lakes, cores collected from adjacent basins of the same lake (Green Lake) did not show similar trends in fossil pigments likely reflecting preferential deposition of clay-rich allochthonous material in the deeper central basin and suggesting that regional signals in climate may be complicated by lake- or basin-specific catchment processes.

Lake Qooqa as a Narrative: Finding Meanings in Social Memory (A Narrative Inquiry)

Lake Qooqa in Oromia/Ethiopia started out as a man-made lake back in the 1960s, formed by the damming of the Awash River and other rivers for a practical function, i.e., for hydroelectric power. The lake flooded over the surrounding picturesque landscape, shattered sacred sites and the livelihoods of the Siiba Oromo, and damaged the ecosystem in the area, which was later resuscitated to have an aesthetic function for tourists. Available sources showed that people used the lake for irrigation, washing, fishing, and drinking, while tanneries, flower farms, and manufacturing facilities for soap and plastic products were set up along the banks without enough environmental impact assessment and virtually with no regulations on how to get rid of their effluents, which contained dangerous chemicals such as arsenic, mercury, chromium, lead, and cadmium, giving the lake a blue and green color locally called bulee; hence, the name the “Green Lake”. In the present study, following a string of “narrative turns” in other disciplinary fields of humanities and social sciences (folklore, history, and anthropology), I use social memory and life hi/story narratives from Amudde, Arsi, Oromia/Ethiopia, to consider a few methodological and theoretical questions of folkloric and ecological nature in doing a narrative study: What is social memory? What does social memory reveal about the people and the environment in which they live? Is a personal narrative story folklore? Where do stories come from? What should the researcher do with the stories s/he collected? Hence, this study aims to tackle two objectives: first, using social memory data as a means to connect social identity and historical memory set in a social context in which people shape their group identity and debate conflicting views of the past, I explore the Green Lake as a narrative, which is, in its current situation, a prototypical image of degradation and anthropogenic impacts, and trace trajectories and meanings of social memory about the shared past, i.e., the historical grief of loss that people in the study area carry in their memory pool. Second, toward this end, I use people’s stories from the research site, particularly Amina’s story about the loss of seven members of her family from complications related to drinking the polluted water, as evidence to show, sharing Sandra Dolby Stahl’s claim, that the narrative of personal experience belongs in folklore studies to the established genre of the family story.

IMPLEMENTASI DATA MINING UNTUK MENGETAHUI POLA PEMBELIAN OBAT MENGGUNAKAN ALGORITMA APRIORI

Competition in the business world requires entrepreneurs to think of finding a way or method to increase the transaction of goods sold. The purpose of this research is to provide drug stock data that is widely purchased by pharmacy customers at Kimia Farma, Green Lake branch in Jakarta. The algorithm used in this study is a priori to determine the relationship between the frequency of sales of drug brands most frequently purchased by customers. The association pattern formed with a minimum support of 40% and a minimum value of 70% confidence produces 17 association rules. The strong rules obtained are that if you buy a 500Mg Ponstan KPL @ 100, you will buy an Incidal OD 10Mg Cap with a support value of 59% and a confidence value of 84%. A priori algorithm can be used by companies to develop marketing strategies in marketing products by examining consumer purchasing patterns.