Editing Limnology (section)

===Physical properties===
Physical properties of aquatic ecosystems are determined by a combination of heat, currents, waves and other seasonal distributions of environmental conditions.<ref name="limnology book">{{cite book|last1=Horne|first1=Alexander J|last2=Goldman|first2=Charles R|title=Limnology|date=1994|publisher=McGraw-Hill|location=United States of America|isbn=978-0-07-023673-8|edition= Second}}{{page needed|date=December 2020}}</ref> The [[Morphometrics|morphometry]] of a body of water depends on the type of feature (such as a lake, river, stream, wetland, estuary etc.) and the structure of the earth surrounding the body of water. [[Lake#Limnology|Lakes]], for instance, are classified by their formation, and zones of lakes are defined by water depth.<ref>{{cite book|last1=Welch|first1=P.S.|title=Limnology (Zoological Science Publications)|date=1935|publisher=McGraw-Hill|location=United States of America|isbn=978-0-07-069179-7}}{{page needed|date=December 2020}}</ref><ref name="Seekell 2021 e2021GL093366">{{Cite journal|last1=Seekell|first1=D.|last2=Cael|first2=B.|last3=Lindmark|first3=E.|last4=Byström|first4=P.|date=2021|title=The Fractal Scaling Relationship for River Inlets to Lakes|url=http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-183511|journal=Geophysical Research Letters|language=en|volume=48|issue=9|pages=e2021GL093366|doi=10.1029/2021GL093366|bibcode=2021GeoRL..4893366S |s2cid=235508504 |issn=1944-8007}}</ref> [[River]] and [[stream]] system morphometry is driven by underlying geology of the area as well as the general velocity of the water.<ref name="limnology book"/>  Stream morphometry is also influenced by topography (especially slope) as well as precipitation patterns and other factors such as vegetation and land development. Connectivity between streams and lakes relates to the landscape [[drainage density]], [[List of lakes by area|lake surface area]] and [[Shoreline development index|lake shape]].<ref name="Seekell 2021 e2021GL093366"/> 
  
Other types of aquatic systems which fall within the study of limnology are [[estuaries]]. Estuaries are bodies of water classified by the interaction of a river and the ocean or sea.<ref name="limnology book"/> [[Wetland]]s vary in size, shape, and pattern however the most common types, marshes, bogs and swamps, often fluctuate between containing shallow, freshwater and being dry depending on the time of year.<ref name="limnology book"/> The volume and quality of water in underground aquifers rely on the vegetation cover, which fosters recharge and aids in maintaining water quality.<ref name=":2" />

====Light interactions====
Light zonation is the concept of how the amount of sunlight penetration into water influences the structure of a body of water.<ref name="limnology book"/> These zones define various levels of productivity within an aquatic ecosystems such as a lake. For instance, the depth of the water column which sunlight is able to penetrate and where most plant life is able to grow is known as the [[Photic zone|photic or euphotic]] zone. The rest of the water column which is deeper and does not receive sufficient amounts of sunlight for plant growth is known as the [[aphotic zone]].<ref name="limnology book"/> The amount of solar energy present underwater and the spectral quality of the light that are present at various depths have a significant impact on the behavior of many aquatic organisms. For example, zooplankton's vertical migration is influenced by solar energy levels.<ref name=":2">{{Cite book |last1=Tundisi |first1=Jose Galizia |url=https://www.taylorfrancis.com/books/9780203803950 |title=Limnology |last2=Tundisi |first2=Takako Matsumura |date=2012-01-27 |publisher=CRC Press |isbn=978-0-203-80395-0 |edition=0 |language=en |doi=10.1201/b11386}}</ref>

====Thermal stratification====
Similar to light zonation, thermal [[Lake stratification|stratification]] or thermal zonation is a way of grouping parts of the water body within an aquatic system based on the temperature of different lake layers. The less [[Turbidity|turbid]] the water, the more light is able to penetrate, and thus heat is conveyed deeper in the water.<ref name="water quality book">{{cite book|title=Water Quality: An Introduction|date=2015|publisher=Springer|isbn=978-3-319-17445-7|edition= Second|location=Switzerland|last1=Boyd|first1=Claude E.}}{{page needed|date=December 2020}}</ref> Heating declines exponentially with depth in the water column, so the water will be warmest near the surface but progressively cooler as moving downwards. There are three main sections that define thermal stratification in a lake. The [[epilimnion]] is closest to the water surface and absorbs long- and shortwave radiation to warm the water surface. During cooler months, wind shear can contribute to cooling of the water surface. The [[thermocline]] is an area within the water column where water temperatures rapidly decrease.<ref name="water quality book" /> The bottom layer is the [[hypolimnion]], which tends to have the coldest water because its depth restricts sunlight from reaching it.<ref name="water quality book" />  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<sup>o</sup>C (the temperature of maximum density) many lakes can experience an inverse thermal stratification in winter.<ref>{{Cite journal|last1=Yang|first1=Bernard|last2=Wells|first2=Mathew G.|last3=McMeans|first3=Bailey C.|last4=Dugan|first4=Hilary A.|last5=Rusak|first5=James A.|last6=Weyhenmeyer|first6=Gesa A.|last7=Brentrup|first7=Jennifer A.|last8=Hrycik|first8=Allison R.|last9=Laas|first9=Alo|last10=Pilla|first10=Rachel M.|last11=Austin|first11=Jay A.|date=2021|title=A New Thermal Categorization of Ice-Covered Lakes|url=http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-440176|journal=Geophysical Research Letters|language=en|volume=48|issue=3|pages=e2020GL091374|doi=10.1029/2020GL091374|bibcode=2021GeoRL..4891374Y |s2cid=233921281 |issn=1944-8007}}</ref> These lakes are often [[Dimictic lake|dimictic]], with a brief spring overturn in addition to longer fall overturn. The [[relative thermal resistance]] is the energy needed to mix these strata of different temperatures.<ref name="auto">Wetzel, R. G. (2001). Limnology: Lake and river ecosystems. San Diego: Academic Press.{{page needed|date=December 2020}} p74, 86</ref>

====Lake Heat Budget====
An annual heat budget, also shown as θ<sub>a</sub>, is the total amount of heat needed to raise the water from its minimum winter temperature to its maximum summer temperature. This can be calculated by integrating the area of the lake at each depth interval (A<sub>z</sub>) multiplied by the difference between the summer (θ<sub>sz</sub>) and winter (θ<sub>wz</sub>) temperatures or <math>\displaystyle \int</math>A<sub>z</sub>(θ<sub>sz</sub>-θ<sub>wz</sub>)<ref name="auto"/>