Elevated Contribution of Low Nucleic Acid Prokaryotes and Viral Lysis to the Prokaryotic Community Along the Nutrient Gradient From an Estuary to Open Ocean Transect

Prokaryotes represent the largest living biomass reservoir in aquatic environments and play a crucial role in the global ocean. However, the factors that shape the abundance and potential growth rate of the ecologically distinct prokaryotic subgroups [i.e., high nucleic acid (HNA) and low nucleic acid (LNA) cells] along varying trophic conditions in the ocean remain poorly understood. This study conducted a series of modified dilution experiments to investigate how the abundance and potential growth rate of HNA and LNA prokaryotes and their regulating factors (i.e., protozoan grazing and viral lysis) change along a cross-shore nutrient gradient in the northern South China Sea. The results showed that the abundance of both HNA and LNA cells was significantly positively correlated with the abundance of heterotrophic nanoflagellates and viruses, whereas only HNA abundance exhibited a significant positive correlation with nutrient level. With a decreasing nutrient concentration, the potential growth rate of the HNA subgroup declined significantly, while that of the LNA subgroup was significantly enhanced, leading to an elevated relative potential growth rate of the LNA to HNA subgroup under decreasing nutrient levels. Furthermore, our data revealed different regulatory roles of protozoan grazing and viral lysis on the HNA and LNA subgroups, with HNA suffering higher mortality pressure from grazing than from lysis in contrast to LNA, which experienced equivalent pressures. As the nutrient levels declined, the relative contribution of lysis to the mortality of the HNA subgroup increased significantly, in contrast to the insignificant change in that of the LNA subgroup. Our results indicated the elevated role of LNA cells in the prokaryotic community and the enhanced viral lysis pressure on the total prokaryotes under oligotrophic conditions. This implies a weakened efficiency of carbon cycling within the microbial loop and enhanced viral lysis to shunt more carbon and energy flow in the future ocean, in which oligotrophication will be strengthened due to global warming.

Determination the influence of liming with oilshale ashes to the changes of water extractable plant nutrients in acidic soils

<p>The acidification process influences mostly soils used agriculturally. It causes yield decrease and loss of plant nutrients from soil via leaching and also rise in concentration of undesibrable, harmful for plant roots ions ( Al<sup>3+</sup>) in soil solution.</p><p>To overcome the negative effects of acidification to agricultural plant production, liming of agriculturally managed soils is widely in use. 40% of agriculturally used lands in Estonia needs periodic liming and approximately 130 000 tons of liming material will be needed for neutralizing acidic soils every year.  Typically different naturally occouring carbonatic materials , as limestone and dolomite, is used for this purpose.  In Estonia more than 9 million tons of ash has been produced as waste byproduct in Estonian power plants every year. Only 1,9% of this byproduct has been reused in building materials industry and agriculture. The amounts of oilshale ash used as liming material by farmers is increasing from year to year.  </p><p>The oilshale fly ash is higly alkaline material with high content of Ca (20 – 33% ), K ( 2,6 – 10%), Mg (2 – 4%) and several microlelement (Zn, Cu, Mo, Mn). Due to modernization of powerplants the new burning technology (CFB) was introduced. Therefore the the fly ash with new chemical and physical properties appeared on the market of liming agents for farmers.</p><p>The aim of the research was to investigate the change of water soluble plant nutrient  (P, K, Mg, Ca) content in acidic soils as a result of liming with oilshale fly ash.  Experiment was conducted as a pot experiment  with five different soils and three fly ashes and two types of granulated ashes and powdered limestone.  The influence of soil organic carbon, soil acidity, texture, to the water soluble  nutrient gradient in soil was investigated. </p><p>The differences between oilshale ashes to the changes in nutrient gradient was found. The Nutrient gradient depends from oilshale ash as well from soil properties.   </p>

Stoichiometric homeostasis of wetland vegetation along a nutrient gradient in a subtropical wetland. Understanding stoichiometric mechanisms of nutrient retention in wetland macrophytes

Nutrient homeostasis relates ambient stoichiometric conditions in an environment to the stoichiometry of living entities of the ecosystem. In wetland ecosystems, vegetation can be a large, highly variable and dynamic sink of nutrients. This study investigated stoichiometric homeostasis of dominant emergent and submerged aquatic vegetation (EAV and SAV, respectively) within two treatment flow-ways (FW) of Everglades Stormwater Treatment Area 2 (STA-2). These FW encompass a large gradient in plant nutrient availability. The hypotheses of this study is that wetland vegetation is non-homeostatic relative to ambient nutrients and consequently nutrient resorption will not vary along the nutrient gradient. We developed a framework to investigate how vegetation uptake and resorption of nutrients contribute separately to homeostasis. Overall, the wetland vegetation in this study was non-homeostatic with respect to differential uptake of nitrogen (N) vs. phosphorus (P). Resorption evaluated for EAV was high for P and moderate for N, resorption efficiency did not significantly vary along the gradient and therefore did not affect overall homeostatic status. Nutrient addition experiments may help to compensate for some of the limitation of our study, especially with respect to resolving the primary nutrient source (organic vs. inorganic sources, water vs. soil compartment) and nutrient utilization rates.