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The basal metabolic rate (BMR) is the mininum amount of energy the living thing use for the maintenance of life. The BMR of a healthy young woman is about 150 kJ per square meter of body surface per hour.
If any of the physical condition, health condition or enviornmental condition is changed, the metabolic rate of the individual would be changed.
In the graph it is shown that the arctic fox can keep the basal metabolic rate at the environmental temperature as low as - 40oC. Water temperature has been defined as the “abiotic master factor” by JR Brett due to its effect on aquatic organisms 15. Considered alone, water temperature can affect the metabolic rates and biological activity of aquatic organisms14. Temperature fluctuations can also affect the behavior choices of aquatic organisms, such as moving to warmer or cooler water after feeding, predator-prey responses and resting or migrating routines 16. In addition to its effects on aquatic organisms, high water temperatures can increase the solubility and thus toxicity of certain compounds 1. Ammonia is known for its toxicity at high pH levels, but temperature can also influence acute and chronic criteria concentrations 21.
However, for every 10°C increase in temperature, the ratio of unionized ammonia to ammonium doubles 21. Water temperature affects viscosity, which in turn affects ionic activity and conductivity. Conductivity increases approximately 2-3% per 1°C increase in temperature, though in pure water it will increase approximately 5% per 1°C 11. This lack of data is due to the difficulty in identifying and measuring every redoxing species that could be present in any given water source. Water temperature can alter the number ions present, changing the pH of the solution without making it more acidic or basic. However, that does not mean that temperature changes will make a solution more acidic or basic.
Water freezes from the surface down, allowing organisms to survive the winter below the ice cover.
It is important to note that salinity not only affects water density but it can shift the maximum density and freezing points of water.
The coldest recorded natural seawater temperature was -2.6°C, recorded beneath an Antarctic glacier 38. Stratification is the division of a water column into strata, or layers, of water with different properties. Lake stratification – the different layers are separated by thermoclines, or temperature gradients.
When referring to temperature and density strata within a lake, the layers are usually called the epilimnion, metalimnion and hypolimnion from top to bottom 14. Below the epilimnion is a layer of water with a rapidly changing temperature range known as the metalimnion 32. A flowchart of Hutchinson and Loffler’s classification of lakes based on stratification and circulation patterns. As warned in some recipes, cooking times are longer at higher elevations, due to a shift in water’s boiling point. If a body of water is deep enough to stratify, sunlight will only transfer heat through the photic zone (light-reaching).
Groundwater, streams and rivers can alter the temperature of the body of water into which they flow. Thermal pollution from municipal and industrial effluents can negatively affect water quality.
Man-made influences on water temperature include thermal pollution, runoff, deforestation and impoundments. Thermal pollution is any discharge that will dramatically alter the temperature of a natural water source 48. Runoff from parking lots and other impervious surfaces are another form of thermal pollution.
The McKenzie dam altered the water temperature pattern downstream, affecting fish behaviors, particularly reproduction. Shifting the temperature pattern can affect the migration, spawning and hatching of local fish species 9. Water temperature can vary from frozen ice to near boiling, so what determines a “typical” temperature? Rivers and streams tend to experience greater, more rapid and temperature fluctuations than lakes and oceans 14. Oceanic temperatures also vary by season, latitude, depth, ocean currents and convection 51. The temperature of the ocean plays an important role in atmospheric conditions across the globe. Maximum recommended temperature levels for different fish species at various lifetime stages. Water that is too warm is usually considered to be more dangerous to aquatic life than cold water.
Water temperature’s impact on a variety of other parameters make it a subtle, but vital, factor in determining water quality.
As temperature measures thermal energy, scales have been developed to give temperature values meaning relative to other values.
The Fahrenheit and Celsius scales are defined by the degrees at which water freezes and boils 3. Contact the seller- opens in a new window or tab and request a shipping method to your location. As hot and cold are both arbitrary terms, temperature can further be defined as a measurement of the average thermal energy of a substance 5.
Heat flow and the fluctuation of temperature determine what species will live and thrive in a body of water.
In addition to its own effects, temperature influences several other parameters and can alter the physical and chemical properties of water. In general, algal photosynthesis will increase with temperature, though different species will have different peak temperatures for optimum photosynthetic activity 14. These elements include heavy metals such as cadmium, zinc and lead as well as compounds like ammonia 19,20. This means that colder lakes and streams can hold more dissolved oxygen than warmer waters.
As conductivity is measured by the electrical potential of ions in solution, it is affected by the concentration, charge and mobility of those ions 11. This variation is why many professionals use a standardized comparison of conductivity, known as specific conductance, that is temperature corrected to 25°C 10. The redoxing species in calibration solutions are quantitatively known, and thus temperature’s effect can be measured.
The effect that temperature has on ORP values depends on the chemical species (atoms, molecules and ions) present in the solution 25.
As these species are difficult to know and quantitatively define in environmental studies, most ORP electrodes will not automatically compensate for temperature. At a pH of 7, the hydrogen and hydroxyl ions have equal concentrations, 1 x 10-7 M, keeping the solution neutral 27. That means if the temperature of water increases, the equation will shift to the left to reach equilibrium again.
Because the ratio of hydrogen and hydroxyl ions remains the same, the acidity of water does not change with temperature 28. If water was most dense at its freezing point (0 °C) then it would sink to the bottom, freezing a body of water from the bottom up, killing all of the organisms living within it 29.


As the salt concentration increases, both maximum density and the freezing point will decrease 14.
That does not sound like a large difference, but it is enough to keep ice floating on top of water and allows aquatic organisms to survive the winter. When saltwater begins to freeze, the water molecules begin to form a crystal lattice (just like they do in freshwater). Older ice structures, called multiyear ice, have no brine left and are fresh enough to drink once melted 41. These divisions are usually defined by temperature and density, though other parameters such as salinity and chemical distinctions can also be used 31. The upper layer, the epilimnion, is exposed to solar radiation and thermal contact with the atmosphere, keeping it warmer.
This strata is usually too deep to be affected by wind, solar radiation and atmospheric heat exchanges 31.
There are six types of holomictic lakes, with definitions based on average temperature and how frequently temperatures align 14. As heat always flows from a higher temperature to a lower temperature, this transfer can go both ways 6. If a spring or groundwater source is colder than the river it flows into, the river will become cooler.
Water that flows off of these surfaces absorb much of their heat and transfer it to a nearby stream or river, elevating the temperature 9.
Water that is shaded by vegetation and other objects will not absorb as much heat as sunlit water 14.
While a dam does not directly contribute heat to the water, it can affect the natural patterns of water temperature warming and cooling 9. The temperature pattern will shift if the reservoir stratifies and the dam release is too high or too low, releasing unusually cool or unusually warm water into the stream 9.
Typical temperatures are dependent on 1) type of water body 2) depth 3) season 4) latitude 5) surrounding environment. Surface water will vary more with season and latitude than deeper waters, and show diurnal (daily) fluctuations due to solar radiation and wind 53. Hurricanes, cyclones, thunderstorms and other weather events can form depending on the temperature of the ocean 53.
During La Nina conditions, a band of cold water is pushed west along the equator, while during El Nino conditions, warm temperatures dominate. These lakes are usually saline, meromictic lakes, which means that when they stratify, only the upper layer of the water will mix 14. The EPA and some states, including Alaska, Idaho, Oregon and Washington, have recommended maximum seasonal and regional temperatures49.
Today, water temperature is commonly measured on one of three scales: Celsius, Fahrenheit or Kelvin 2.
The Celsius scale is also referred to as centigrade because there is a 100 degree interval between the two defined points (freezing and boiling of water) 2. If you reside in an EU member state besides UK, import VAT on this purchase is not recoverable. Thermal energy is the kinetic energy of atoms and molecules, so temperature in turn measures the average kinetic energy of the atoms and molecules 5. Some organisms, particularly aquatic plants flourish in warmer temperatures, while some fishes such as trout or salmon prefer colder streams 8. For most fish, a 10°C increase in water temperature will approximately double the rate of physiological function 16. Tropical plants in particular will show restricted growth and dormancy in water temperatures below 21°C 17. Water temperature can not only increase the solubility of toxic compounds, but it can also influence an organism’s tolerance limit 19.
The more viscous it is, the less fluid it is; molasses and mercury are more viscous than water. In addition, there are a few salts that become less soluble at warmer temperatures, and thus will negatively affect conductivity 22.
Temperature-dependence data charts are usually available for calibration solutions, but not for field samples 25. However, temperature can still alter a reading and should be recorded with each measurement considered when analyzing the data 26. This is a unique relationship in that unlike most materials, the density of pure water decreases approximately 9% when it freezes 29.
Instead, this property ensures that the bottom of a body of water will remain at least 4°C, and thus unfrozen 30. Average seawater has a salinity level of 35 PPT (parts per thousand) and has a shifted maximum density of -3.5°C 14. In both cases, hydrostatic pressures allowed water to remain liquid at such cold temperatures 38. This drop in density occurs because the hydrogen bonds in water create an open hexagonal lattice, leaving space between the molecules 42.
These crystals only include water molecules, not salt ions, and the formation is known as brine exclusion 43. Stratification occurs because work (force and displacement) is required to mix liquids of different densities 14. The epilimnion will extend as far as sunlight and wind will allow, and is usually deeper in lakes with greater surface areas 14. In other words, when the water temperature begins to significantly drop, the thermocline has been crossed.
This bottom layer is known as the monimolimnion, and is usually divided from the collective layers above it (mixolimnion) by a halocline (salinity-based cline)31. At high elevations (lower pressure), there is a slight increase in the freezing point, but the change in pressure is not enough to significantly affect the point 30.
This energy is then transferred to a water’s surface as heat, increasing the temperature of the water.
Recalling the rules of heat transfer (energy flows from hot to cold), the river loses energy to the cooler water as it warms it up 6. If the temperature of discharge is significantly warmer than the natural water, it can negatively affect water quality. When trees or riparian canopies are removed, a body of water can become unusually warm, altering its natural cycle and habitats 48. An operational dam without a sliding gate assembly can alter the water temperatures downstream of the dam, which can affect local fish population behaviors. While a specific body of water can have a general pattern that it follows annually, there is no definitive “typical” temperature for water.
Due to the shifting angle of solar radiation and the effects of atmospheric heat transfer, water temperatures will vary seasonally 44.
Monsoons can occur when there is a large temperature differential between land and sea, causing cyclical precipitation and storms 35.
Hot springs, also known as hydrothermal springs, are fed by groundwater that is significantly warmer than other flows 50. As discussed in the stratification section, the layers are separated by a halocline, with the mixolimnion remaining fairly fresh and the lower monimolimnion containing a higher salt concentration 14.
Water that is too cold will affect the biological processes and metabolic rates of aquatic organisms 14. Other states offer no numerical value, and instead state “no measurable change from natural conditions”1. While dormancy is appropriate for surviving a cold winter, warmer temperatures are required for most plants to flourish. Mortality rates for zinc are significantly higher at temperatures above 25°C than at temperatures below 20°C 19. The inverse relationship between temperature and viscosity means that an increase in temperature will decrease viscosity 14.
As warm water can dissolve several minerals and salts more easily than cold water, the ionic concentration is often higher 9. As the temperature increases or decreases, the ion concentrations will also shift, thus shifting the pH value 27. Likewise, if the temperature were to decrease, the equation would shift to the right, increasing the ionic concentration and decreasing pH.
This is more than a 7° difference from freshwater and is below seawater’s freezing point of 1.9°C 14.


Average seawater has a salinity level of 35 PPT (parts per thousand), which shifts the freezing point to -1.9°C 14. As the ice structure grows, pockets of concentrated saltwater can be trapped inside the ice, but are not incorporated into its structure.
Thermal stratification is usually seasonal, with clear delineations between layers during the summer, narrower layers in winter, and a “turnover” in the spring and fall when temperature is fairly uniform throughout the water column 32. In addition, the metalimnion can fluctuate in thickness and depth due to weather conditions and seasonal changes 14. This plane is generally accepted as the depth at which temperature decreases at a rate greater than 1°C per meter 14.
In deeper lakes, the mixing can be minimal and the hypolimnion will remain near maximum density, or 4°C 14.
Meromictic conditions can occur in a holomictic lake when unusual weather conditions cause the lake to stratify before it has time to completely mix 14. On the other side of the scale, at higher pressures (such as in a pressure cooker), water will boil at a higher temperature 34.
The heat is then transferred from the particles to water molecules, increasing the temperature of the surrounding water 47. If the inflow is large or fast enough, the equilibrium temperature of the water will be close to the temperature of the inflow 1. There are several significant consequences of thermal pollution, including diminished dissolved oxygen levels, fish kills and influxes of invasive species 48. Even a specific body of water can vary due to any of these sources; a lake might freeze over one winter, but it might not freeze the following year due to a warm winter. As solar radiation is more intense near the equator, water at lower latitudes wills to be warmer than water at higher latitudes 44. Due to its massive size and the high specific heat of water, the ocean has an equally large heat capacity 14. Hurricanes and cyclones develop over warm water, where the heat can be rapidly transferred to the air via convection 54. On the other side of the scale, water that is too warm can cause excessive respiration rates, stressing fish. On the Kelvin scale, the unit is a kelvin, but it is the same magnitude as a Celsius degree 2.
There are three characteristics in the survival temperature curve for a well-adapted animal.
Heat transfer, whether from the air, sunlight, another water source or thermal pollution can change the temperature of water. Increased metabolic function can be noticed in respiration rates and digestive responses in most species.
This occurs because tissue permeability, metabolic rate and oxygen consumption all increase with increased water temperature 19. The increased mineral and ion content can be noticed in natural hot springs, which tout their “healing” abilities 50. As surface water temperature approaches the maximum density temperature, it sinks and is replaced by warmer, lighter water 42. As seasons progress, sunlight, wind, ambient temperature and ice (in winter) cause the lake to restratify 32.
As temperature and density are related, a second cline, known as a pycnocline exists at the same depths.
Atmospheric pressure does not affect the temperature of the water itself, but only its ability to become vapor, thus shifting the boiling to the left or right. The depth of the photic zone is based on the amount of solids and other light-scattering elements present in the water.
Glacial fed streams will keep conjoining rivers cooler near the source of the flow than further downstream 1. It follows the same warming cooling pattern both years, but it does not reach the same temperatures.
Shaded streams will not be as influenced by solar radiation as their exposed counterparts and can remain cooler. This means that fluctuations between seasons or due to unusual events will only have a slight impact 51. In a similar vein, lake-effect snow and other heavy precipitation conditions can form when cold air flows over a large, warmer body of water 55. This heat transfer can come from groundwater flows that run deep enough into the Earth’s crust, or that come into contact with magma in volcanic zones 50. Warm water also cannot hold as much dissolved oxygen as cold water, so there is less oxygen available for uptake by organisms 14. The more historical data that is available, the more abnormal fluctuations can be detected and addressed.
Increased respiration rates at higher temperatures lead to increased oxygen consumption, which can be detrimental if rates remain raised for an extended period of time. Any change to a system at equilibrium, such as adding a reactant or altering the temperature, will shift the system until it reaches equilibrium again 28. Water at temperatures above and below this, including superheated and supercooled water, will float on 4°C water. Instead, the process on convection simply circulates the cooling water until the entire surface water column reaches the freezing point 42.
The temperature of water below the photic zone is generally only altered when the water is mixed 37.
Bodies of water that are influenced by groundwater flow or a glacial fed stream will also be cooler 1. Studies have shown the ocean has warmed approximately 0.1 degrees Celsius in the past century 52.
Hot springs remain much warmer than the ambient ground temperature, with some volcanic hot springs even reaching boiling temperatures 50. This heat cannot escape because the density of the saline lower layer is not significantly affected by increasing temperatures 14.
Furthermore, temperatures above 35°C can begin to denature, or breakdown, enzymes, reducing metabolic function 18.
As the phase boundary between liquid and solid requires the proper pressure as well as temperature, ice only beings to form on the surface 30. The result is a daily fluctuation in water temperature based on the amount of sunlight received by the water. Thus shallower bodies of water tend to warm quicker and reach higher temperatures than deeper water bodies 1. While this number seems small, it is quite considerable in regards to the size of the ocean. El Nino describes the warming of the Pacific Ocean due to a lack of wind, which alters the depth of the thermocline.
The result is a heat trap at the halocline, where temperatures can easily reach 50°C and higher 14. This convection pattern allows water both warmer and colder than 4°C (and at potentially different dissolved oxygen concentrations) to intermix 30. Hot Lake in Washington is one example of a heliothermic lake, where the halocline remains near 30°C even when the lake is covered in ice 14.
Salmon and trout prefer to swim in colder rivers, while largemouth and smallmouth bass can tolerate much warmer waters for both growth and spawning 8. When the enviornmental temperature reaches to a certain point, the individual cannot affort and die.
This process occurs seasonally in holomictic (mixing) lakes, as the water temperature (and thus other parameters) reach equilibrium 14. La Nina is the opposite condition of the ocean, where temperatures are cooler than normal, typically with reverse impacts on the weather 35. They can last anywhere from 9 months to a couple years, depending on the strength of the episode 35.



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