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Dead zones are hypoxic (low-oxygen) areas in the world's oceans and large lakes. Hypoxia occurs when dissolved oxygen (DO) concentration falls to or below 2 ml of O 2 /liter. [2] When a body of water experiences hypoxic conditions, aquatic flora and fauna begin to change behavior in order to reach sections of water with higher oxygen levels.
In temperate lakes, fall-season cooling of surface water results in turnover of the water column, where the thermocline is disrupted, and the lake temperature profile becomes more uniform. In cold climates, when water cools below 4 o C (the temperature of maximum density) many lakes can experience an inverse thermal stratification in winter. [ 18 ]
The driving force in stratification is gravity, which sorts adjacent arbitrary volumes of water by local density, operating on them by buoyancy and weight.A volume of water of lower density than the surroundings will have a resultant buoyant force lifting it upwards, and a volume with higher density will be pulled down by the weight which will be greater than the resultant buoyant forces ...
Following Henry's law, as water becomes warmer, oxygen becomes less soluble in it. This property leads to daily anoxic cycles on small geographic scales and seasonal cycles of anoxia on larger scales. Thus, bodies of water are more vulnerable to anoxic conditions during the warmest period of the day and during summer months.
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is essential for recycling the finite matter that occupies physical space in the biosphere .
A fresh pig carcass. At this stage the remains are usually intact and free of insects. The corpse progresses through algor mortis (a reduction in body temperature until ambient temperature is reached), rigor mortis (the temporary stiffening of the limbs due to chemical changes in the muscles), and livor mortis (pooling of the blood on the side of the body that is closest to the ground).
Limestone is the raw material for production of lime, primarily known for treating soils, purifying water and smelting copper. Lime is an important ingredient used in chemical industries. [ 110 ] Limestone and (to a lesser extent) marble are reactive to acid solutions, making acid rain a significant problem to the preservation of artifacts made ...
Many species have a higher density than water, which should cause them to sink inadvertently down into the benthos. To combat this, phytoplankton have developed density-changing mechanisms, by forming vacuoles and gas vesicles , or by changing their shapes to induce drag, thus slowing their descent. [ 9 ]