why is there a low nitrate level in lakes?
601562
If there were high nitrate levels... the lake would eventually become a wetland or swamp.  Plants like nitrates... aquatic life does not.  Some lakes are suffering from nitrate run-off (it usually comes from farmers fields or where other types of nitrogen rich fertilizers or substances aren't kept in check)  Those nitrates then in turn generate weed growth.  The weed growth will then choke off the lake.  Ever notice the wierd shade of green in a pond next to houses or apartment complexes.  They're using chemicals to keep the water's P-H on the acidic side to curb vegetation and maintain the proper aesthetics that they want of open water.  If you want further information pertaining to your more immediate area... contact your local county agricultural agent.  He or she should be listed in the white pages under county government.
219448
The warm waters of the Gulf Stream are nutrient-poor compared to more fertile waters closer to shore; hence, the reason they are clear and blue.  Warm, tropical waters are nutrient-poor in general.
429160
At a higher elevation the pressure on the water is less therefore it will boil at a lower temperature than it would at sea level.\n\nA liquids state of matter depends on pressure and temperature to make something from liquid to gas you use high temperature and low pressure.
836580
Salt water has a lower freezing point than fresh water.
694763
because ice is less dense than water, therefore it floats, this helps the species of the lake survive in winter time because the ice acts as an insulator
732287
Most nitrates are fertilizers for plants .
22175
Some rivers dont they can finish in a lake thats inland. Water just flows downhill till its at the lowest level it can find which is usually the sea
518328
nutrient depletion in overly eutrophic bodies of water
561534
Your question is a bit ambiguous, but let's see if we can answer and clarify:\n\n(1) There is a lake with a certain amount of water, thus establishing a water level with respect to the ground.\n(2) There is a boat with a coin inside it on the lake. The boat sinks into the lake to a level that you can mark on the side of the boat.\n(3) The coin is tossed into the lake, thus reducing the total weight of the boat and this will cause the "water level" wrt to the boat to change, i.e. the "water level" will decrease a bit since the boat will have risen a bit higher from the water surface.\n(4) When the boat with the coin inside it is floating on the lake, the lake's water level wrt to the ground will rise a bit, because the boat has displaced the lake's water.\n(5) When the coin is tossed into the lake, the water level wrt to the ground does change, but we do not know how because now the lake's water is being displaced by the coin's physical volume, not by its weight, as it was the case when it was inside the boat.
372176
Sounds like you've got too much time on your hands to me!  The ions in solution keep the water molecules farther apart from eachother on average than they would be in pure water.  Therefore the hydrogen bonds are weaker and the water will boil at a lower energy level.  At least that's what I'd guess.
845869
High nitrate levels can be caused by runoff from human and animal waste, manure and fertilizers from farms, leaking underground tanks, landfills, unsafe disposal of industrial waste and organic waste.
546630
Absolutely not. But there have been cases where subtherapeutic levels of fluoride have been added to the water, too little to do any good. Happened in my town.
568488
lack of water\navailaible water is not clean\nratio of popuation to water availaible is high
868418
# Anoxic autotrophs: Obtain hydrogen from chemicals such as sulfur.\n[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[Dead Zones are areas where the bottom water (the water at the sea floor) is anoxic, meaning that it has very low (or completely zero) concentrations of dissolved oxygen.]]]]]]]]]]]]]]]]]]]]]]]]]\nDead Zones are areas where the bottom water (the water at the sea floor) is anoxic, meaning that it has very low (or completely zero) concentrations of dissolved oxygen. These dead zones are occurring in many areas along the coasts of major continents, and they are spreading over larger areas of the sea floor. Because very few organisms can tolerate the lack of oxygen in these areas, they can destroy the habitat in which numerous organisms make their home.\n\nThe cause of anoxic bottom waters is fairly simple: the organic matter produced by phytoplankton at the surface of the ocean (in the euphotic zone) sinks to the bottom (the benthic zone) where it is subject to breakdown by the action of bacteria, a process known as bacterial respiration. The problem is, while phytoplankton use carbon dioxide and produce oxygen during photosynthesis, bacteria use oxygen and give off carbon dioxide during respiration. The oxygen used by bacteria is the oxygen dissolved in the water, and that’s the same oxygen that all of the other oxygen-respiring animals on the bottom (crabs, clams, shrimp, and a host of mud-loving creatures) and swimming in the water (zooplankton, fish) require for life to continue.\n\nThe "creeping dead zones" are areas in the ocean where it appears that phytoplankton productivity has been enhanced, or natural water flow has been restricted, leading to increasing bottom water anoxia. If phytoplankton productivity is enhanced, more organic matter is produced, more organic matter sinks to the bottom and is respired by bacteria, and thus more oxygen is consumed. If water flow is restricted, the natural refreshing flow of "oxic" waters (water with normal dissolved oxygen concentrations) is reduced, so that the remaining oxygen is depleted faster.\n\nMany of the areas where increasing bottom water anoxia has recently been observed are near the mouths of major river systems. While Satellite images can’t see the bottom of the ocean, they can see the surface, where sediments from rivers mix with ocean waters. The images shown here are Satellite images (SeaWiFS) observations of the Mississippi River delta, the Yangtze River mouth in China (The Yangtze River mouth is not currently identified as an area with an associated dead zone, but such conditions could develop there in the future), and the Pearl River mouth in China, near Hong Kong.\n\nSeaWiFS can also observe areas where water flow is restricted, such as the Baltic Sea in Europe. The image on the left features Denmark after strong storms caused flooding and increased sediment suspension in the Baltic. On the right is an overview of the Baltic Sea, including a plankton bloom in the Skagerrak just north of Denmark.\n\nThe apparent cause of the creeping dead zones is agriculture, specifically fertilizer. While fertilizer is necessary to foster bumper agricultural crops, it also runs off the fields into the streams and rivers of a watershed. When the fertilizer reaches the ocean, it just becomes more nutrients for the phytoplankton, so they do what they do best: they grow and multiply. Which leads to more organic matter reaching the bottom, more bacterial respiration, and more anoxic bottom water.\n\nThese effects can be magnified by catastrophe. When the heavy rains of Hurricane Floyd caused extensive flooding in North Carolina in September 1999, the heavy load of nutrients (from dead animals, flooded animal waste ponds, and numerous other sources) reached the sounds that lie between the coast and the Outer Banks, oxygen levels in the water plummeted. The picture at the top of the page shows the heavy load of sediments flowing into Pamlico Sound. SeaWiFS captur
104763
well, i do know there's this blue chemical called biochemical oxygen demand(BOD) which is used to see how polluted water is from different sources. like, if you compare drain water and pond water. so if you put few drops in each water, and wait for one day, you'll realise that drain water isnt as blue as pond water coz drain water is more polluted. since there are more waste compared to pond water, so there'll be less oxygen. so yeah.
201692
because this "lake" is below ocean level, the river supply the lake with salty water. As there is no way how to carry the water out again, the only chance to maintain the level constant is to evaporate the water, but the salt remains inside.\n----------------------------------------------------------\n\n"The Dead Sea (Arabic البحر الميت, Hebrew ים המלח) is the lowest exposed point on the Earth's surface. It is on the border between the West Bank, Israel, and Jordan on the Jordan Rift Valley. This endorheic body of water is the deepest hypersaline lake in the world.\n\nThe Dead Sea is 67 km long, up to 18 km wide and 799 m below sea level in depth at its deepest point. While the surface elevation of the Dead Sea continues to fluctuate, the Dead Sea valley contains the lowest land point on the face of the earth: an elevation of 394 m (1291 ft) below sea level. "
929747
Nitrogen runoff from farm fertilizers, sewage, and air pollution is one of the big causes of ocean dead zones. When the nitrogen flows to the sea, it acts as a fertilizer to plankton. The abundant plankton use up all the ocean's oxygen. \nMitigation: \nReducing the discharge of nitrogen to rivers by reducing runoff, using less fertilizer, reducing nitrogen emissions from cars and factories, treating sewage better.