Narrow Results

The high flow rates of the connecting channel between Lake Huron and Lake Erie allow the channel to absorb massive quantities of chemicals and waste materials without an apparent immediate impact. A study carried out in the late 1980s by the USEPA/Environment Canada pointed to the potentially profound impacts on downstream living systems of continuing the uses that then prevailed. The paper reviews the major changes which have taken place since the earlier study was completed and outlines pieces of the scientific case to be made for needed changes in the ways in which the Great Lakes are being managed.

World Heart Day – At the Heart of Health

That Gut Feeling: How A Healthy Digestive System Has Everything To Do With It

Although extensive research on annual cycles of phytoplankton communities in the open sea has been conducted, there have been less continuous measurements on short term variations in semi-enclosed bays. To estimate the conditions necessary for red tide occurrences in an area affected by eutrophication, we carried out continuous field measurements in the inner part of Tokyo Bay at three stations where red tides have often been observed in Spring. The blooms of phytoplankton occur under high solar radiation conditions. Mixed layer thickness and the vertical distribution of PAR are also significant in accounting for the levels of phytoplankton blooms. Under optimum conditions of mixed-layer thickness and the euphotic zone, phytoplankton increased rapidly even under average solar radiation. At this time, north-wind induced outflow and vertical mixing result in diluting phytoplankton and terminating blooms. These bloom conditions will not continue due to self shading of phytoplankton, even if there isn't a strong wind. Therefore, these physical conditions are significant in controlling the levels of blooms in an area affected by eutrophication. Following the phytoplankton blooms, dissolved oxygen and phosphate concentrations show greater temporal variability through decomposition processes of the phytoplankton.

We consider a general growth mechanism, which acts at cellular level and above (organs, systems and whole organisms). Using its mathematical representation, the growth equation, we study the growth and division mechanisms of amoeba and fission yeast Schizosaccharomyces pombe. We show how this mechanism, together with biomolecular machinery, governs growth and reproduction of cells, and these organisms in particular. This mechanism provides revealing answers to fundamental questions of biology, like why cells grow and divide, why and when cells’ growth stops. It also sheds light on questions like why and how life originated and developed. Solving the growth equation, we obtain analytical expression for the growth curve of fission yeast as a function of geometrical characteristics and nutrient influxes for RNA and protein synthesis, and compare the computed growth curves with 85 experiments. Statistical evaluation shows that these growth curves correspond to experimental data significantly better than all previous approximations. Also, using the general growth mechanism, we show how metabolic characteristics of cells, their size and evolutionary traits relate, considering fission yeast. In particular, we found that fission yeast S. pombe consumes about 16–18 times more nutrients for maintenance needs than for biomass synthesis.

One of the major characteristics of living organisms is metabolic rate — the amount of energy produced per unit of time. When the mass of organisms increases, the metabolic rate also increases (as a power function of mass), but usually slower than mass. This effect is called metabolic allometric scaling. Its causes are considered unknown. The effect has important implications for individual and population organismal development. It was shown in the first part of this study, presented in a separate paper, that in the case of multicellular organisms, this effect is a consequence of natural selection and optimization of nutrient distribution between the species of a food chain, sharing resources of a common habitat. Here, in the second part that studies unicellular organisms, we discover that the same principle of natural selection guided by optimization of nutrient distribution between the species of a food chain defines also metabolic allometric scaling of unicellular organisms. To find that, we consider the metabolic properties of Amoeba proteus, fission yeast Schizosaccharomyces pombe, Escherichia coli, Bacillus subtilis, Staphylococcus. The sharing of nutrients is optimized in such a way that bigger microorganisms have progressively bigger nutrient influx per unit of surface. This evolutionary arrangement secures the stability of a food chain by providing certain metabolic advantages for bigger organisms. Accounting for this regular increase of nutrient influx with mass increase, we obtained allometric exponents and their ranges close to experimental values, thus proving that metabolic allometric scaling of both multicellular and unicellular organisms is defined by the same fundamental evolutionary principle of optimized sharing of nutrients between the species of a food chain.

A compilation of general information available on existing international standards and studies on this issue is developed in this chapter.We performed a critical evaluation of technologies for wastewater treatment currently recommended for reuse in agricultural irrigation. The productive use of such treated water is an important alternative for agricultural irrigation because of its high content of nutrients and organic matter, which could facilitate an increase in crops and soil improvement.

The most widely recommended treatment technology is the stabilization lagoons, but it is also recognized that there are other available technologies and the need to consider a final stage of disinfection to achieve compliance of the international guidelines that regulate the wastewater quality for reuse. Ozonation of wastewater treatment is an attractive method due to its oxidative and bactericidal power, so its combination with other treatment processes such as coagulation– flocculation allows a considerable reduction of physicochemical and microbiological pollution of municipal wastewater, enabling its reuse in agricultural irrigation.

To identify the distribution and variation of soil nutrients in arable land is significant to Hainan Island, which is the base of tropical crop products in China. Qiongzhong Li Autonomous County (Qiongzhong County) was selected as study area for the purpose of researching the distribution of soil pH, Organic matters, available nutrients (N, P, K, Ca, Mg, Zn). The arable land soil has acid in the research area, and the average pH was 4.5. The contents of organic matters and available N were relative rich in Qiongzhong County, while the available P and K were deficient. The contents of available Ca and Mg are 508.9 and 82.8 mg kg-1 in soil, which are deficient and unevenly distributed. The content of available Zn is as high as 4.72 mg kg-1, however, potentiality of Zn pollution exists because of high acid degree in arable land soils of Qiongzhong.