Natural gas is closely related to crude oil. Both substances are thought to have formed in the earth's crust as a result of transformation of organic matter due to the heat and pressure of the overlying rock. All oil deposits contain natural gas, although natural gas is often found without oil. Gas hydrocarbons can also be produced as a result of microbial decomposition of organic substances and, less often, due to reduction of mineral salts. …showed first 75 words of 2286 total…

…showed last 75 words of 2286 total…From the physiological perspective, such a phenomenon is explained by the fact that the level of hemoglobin in fish blood and the rate of blood circulation through the gills increase under oxygen deficit. Clearly, such effects are of special interest when interpreting the data on fish response to natural gas in situations of significant change in the oxygen regime (e.g., during eutrophication of water bodies or seasonal and weather variations of the oxygen content).