Editing Limnology

{{Short description|Science of inland aquatic ecosystems}}
[[File:Lake Hawea, New Zealand.jpg|thumb|upright=1.3|[[Lake Hāwea]], New Zealand]]

'''Limnology''' ({{IPAc-en|l|ɪ|m|ˈ|n|ɒ|l|ə|dʒ|i}} {{respell|lim|NOL|ə|jee}}; {{etymology|grc|''{{Wikt-lang|grc|λίμνη}}'' ({{grc-transl|λίμνη}})|lake||''{{Wikt-lang|grc|-λογία}}'' ({{grc-transl|[[-logy|-λογία]]}})|study of}}) is the study of inland [[aquatic ecosystems]].<ref>{{cite book |url=https://books.google.com/books?id=JIw76nEh0aoC&q=limnology+definition&pg=PR11 |title=Fundamentals of Limnology |last=Kumar|first=Arvind |date=2005 |publisher=APH Publishing |isbn=9788176489195}}</ref> 
It includes aspects of the [[biology|biological]], [[chemistry|chemical]], [[physics|physical]], and [[geology|geological]] characteristics of [[fresh water|fresh]] and [[saline water|saline]], natural and man-made [[body of water|bodies of water]]. This includes the study of [[lake]]s, [[reservoir]]s, [[pond]]s, [[river]]s, [[Spring (hydrosphere)|springs]], [[stream]]s, [[wetland]]s, and [[groundwater]].<ref name="Wetzel" >{{cite book |last=Wetzel|first=R. G. |year=2001 |title=Limnology: Lake and River Ecosystems |edition=3rd |publisher=[[Academic Press]] |isbn=0-12-744760-1}}){{page needed|date=December 2020}}</ref> Water systems are often categorized as either running ([[river ecosystem|lotic]]) or standing ([[lake ecosystem|lentic]]).<ref>{{cite book |last1=Marsh|first1=G. Alex |chapter=Lentic and lotic ecosystems |date=1999 |url=https://doi.org/10.1007/1-4020-4494-1_204 |title=Environmental Geology |pages=381–388 |place=Dordrecht |publisher=Springer Netherlands |language=en |doi=10.1007/1-4020-4494-1_204 |isbn=978-1-4020-4494-6 |access-date=2022-04-21 |last2=Fairbridge|first2=Rhodes W.}}</ref>

Limnology includes the study of the drainage basin, movement of water through the basin and biogeochemical changes that occur en route. A more recent sub-discipline of limnology, termed [[landscape limnology]], studies, manages, and seeks to conserve these [[ecosystem]]s using a landscape perspective, by explicitly examining connections between an aquatic ecosystem and its [[drainage basin]]. Recently, the need to understand global inland waters as part of the [[Earth system science|Earth system]] created a sub-discipline called global limnology.<ref>{{cite journal |last1=Downing|first1=John A. |title=Global limnology: up-scaling aquatic services and processes to planet Earth |journal=SIL Proceedings, 1922-2010 |date=January 2009 |volume=30 |issue=8 |pages=1149–1166 |doi=10.1080/03680770.2009.11923903 |bibcode=2009SILP...30.1149D |s2cid=131488888}}</ref> This approach considers processes in inland waters on a global scale, like the role of inland aquatic ecosystems in global [[biogeochemical cycle]]s.<ref>{{cite journal |last1=Cole |first1=J. J. |last2=Prairie |first2=Y. T. |last3=Caraco |first3=N. F. |last4=McDowell |first4=W. H. |last5=Tranvik |first5=L. J. |last6=Striegl |first6=R. G. |last7=Duarte |first7=C. M. |last8=Kortelainen |first8=P. |last9=Downing |first9=J. A. |last10=Middelburg |first10=J. J. |last11=Melack |first11=J. |title=Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget |journal=Ecosystems |date=23 May 2007 |volume=10 |issue=1 |pages=172–185 |doi=10.1007/s10021-006-9013-8 |bibcode=2007Ecosy..10..172C |citeseerx=10.1.1.177.3527 |s2cid=1728636 }}</ref><ref>{{cite journal |last1=Tranvik |first1=Lars J. |last2=Downing |first2=John A. |last3=Cotner |first3=James B. |last4=Loiselle |first4=Steven A. |last5=Striegl |first5=Robert G. |last6=Ballatore |first6=Thomas J. |last7=Dillon |first7=Peter |last8=Finlay |first8=Kerri |last9=Fortino |first9=Kenneth |last10=Knoll |first10=Lesley B. |last11=Kortelainen |first11=Pirkko L. |last12=Kutser |first12=Tiit |last13=Larsen |first13=Soren |last14=Laurion |first14=Isabelle |last15=Leech |first15=Dina M. |last16=McCallister |first16=S. Leigh |last17=McKnight |first17=Diane M. |last18=Melack |first18=John M. |last19=Overholt |first19=Erin |last20=Porter |first20=Jason A. |last21=Prairie |first21=Yves |last22=Renwick |first22=William H. |last23=Roland |first23=Fabio |last24=Sherman |first24=Bradford S. |last25=Schindler |first25=David W. |last26=Sobek |first26=Sebastian |last27=Tremblay |first27=Alain |last28=Vanni |first28=Michael J. |last29=Verschoor |first29=Antonie M. |last30=von Wachenfeldt |first30=Eddie |last31=Weyhenmeyer |first31=Gesa A. |title=Lakes and reservoirs as regulators of carbon cycling and climate |journal=Limnology and Oceanography |date=November 2009 |volume=54 |issue=6part2 |pages=2298–2314 |doi=10.4319/lo.2009.54.6_part_2.2298 |bibcode=2009LimOc..54.2298T |hdl=10852/11601 |doi-access=free }}</ref><ref>{{cite journal |last1=Raymond |first1=Peter A. |last2=Hartmann |first2=Jens |last3=Lauerwald |first3=Ronny |last4=Sobek |first4=Sebastian |last5=McDonald |first5=Cory |last6=Hoover |first6=Mark |last7=Butman |first7=David |last8=Striegl |first8=Robert |last9=Mayorga |first9=Emilio |last10=Humborg |first10=Christoph |last11=Kortelainen |first11=Pirkko |last12=Dürr |first12=Hans |last13=Meybeck |first13=Michel |last14=Ciais |first14=Philippe |last15=Guth |first15=Peter |title=Global carbon dioxide emissions from inland waters |journal=Nature |date=21 November 2013 |volume=503 |issue=7476 |pages=355–359 |doi=10.1038/nature12760 |pmid=24256802 |bibcode=2013Natur.503..355R |s2cid=4460910 |url=http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-213816 }}</ref><ref>{{cite journal |last1=Engel |first1=Fabian |last2=Farrell |first2=Kaitlin J. |last3=McCullough |first3=Ian M. |last4=Scordo |first4=Facundo |last5=Denfeld |first5=Blaize A. |last6=Dugan |first6=Hilary A. |last7=de Eyto |first7=Elvira |last8=Hanson |first8=Paul C. |last9=McClure |first9=Ryan P. |last10=Nõges |first10=Peeter |last11=Nõges |first11=Tiina |last12=Ryder |first12=Elizabeth |last13=Weathers |first13=Kathleen C. |last14=Weyhenmeyer |first14=Gesa A. |title=A lake classification concept for a more accurate global estimate of the dissolved inorganic carbon export from terrestrial ecosystems to inland waters |journal=The Science of Nature |date=26 March 2018 |volume=105 |issue=3 |pages=25 |doi=10.1007/s00114-018-1547-z |pmid=29582138 |pmc=5869952 |bibcode=2018SciNa.105...25E }}</ref><ref>{{cite journal |last1=O'Reilly |first1=Catherine M. |last2=Sharma |first2=Sapna |last3=Gray |first3=Derek K. |last4=Hampton |first4=Stephanie E. |last5=Read |first5=Jordan S. |last6=Rowley |first6=Rex J. |last7=Schneider |first7=Philipp |last8=Lenters |first8=John D. |last9=McIntyre |first9=Peter B. |last10=Kraemer |first10=Benjamin M. |last11=Weyhenmeyer |first11=Gesa A. |last12=Straile |first12=Dietmar |last13=Dong |first13=Bo |last14=Adrian |first14=Rita |last15=Allan |first15=Mathew G. |last16=Anneville |first16=Orlane |last17=Arvola |first17=Lauri |last18=Austin |first18=Jay |last19=Bailey |first19=John L. |last20=Baron |first20=Jill S. |last21=Brookes |first21=Justin D. |last22=Eyto |first22=Elvira de |last23=Dokulil |first23=Martin T. |last24=Hamilton |first24=David P. |last25=Havens |first25=Karl |last26=Hetherington |first26=Amy L. |last27=Higgins |first27=Scott N. |last28=Hook |first28=Simon |last29=Izmest'eva |first29=Lyubov R. |last30=Joehnk |first30=Klaus D. |last31=Kangur |first31=Kulli |last32=Kasprzak |first32=Peter |last33=Kumagai |first33=Michio |last34=Kuusisto |first34=Esko |last35=Leshkevich |first35=George |last36=Livingstone |first36=David M. |last37=MacIntyre |first37=Sally |last38=May |first38=Linda |last39=Melack |first39=John M. |last40=Mueller-Navarra |first40=Doerthe C. |last41=Naumenko |first41=Mikhail |last42=Noges |first42=Peeter |last43=Noges |first43=Tiina |last44=North |first44=Ryan P. |last45=Plisnier |first45=Pierre-Denis |last46=Rigosi |first46=Anna |last47=Rimmer |first47=Alon |last48=Rogora |first48=Michela |last49=Rudstam |first49=Lars G. |last50=Rusak |first50=James A. |last51=Salmaso |first51=Nico |last52=Samal |first52=Nihar R. |last53=Schindler |first53=Daniel E. |last54=Schladow |first54=S. Geoffrey |last55=Schmid |first55=Martin |last56=Schmidt |first56=Silke R. |last57=Silow |first57=Eugene |last58=Soylu |first58=M. Evren |last59=Teubner |first59=Katrin |last60=Verburg |first60=Piet |last61=Voutilainen |first61=Ari |last62=Watkinson |first62=Andrew |last63=Williamson |first63=Craig E. |last64=Zhang |first64=Guoqing |title=Rapid and highly variable warming of lake surface waters around the globe |journal=Geophysical Research Letters |date=2015 |volume=42 |issue=24 |pages=10,773–10,781 |doi=10.1002/2015gl066235 |bibcode=2015GeoRL..4210773O |doi-access=free |hdl=10289/10465 |hdl-access=free }}</ref>

Limnology is closely related to [[aquatic ecology]] and [[hydrobiology]], which study aquatic organisms and their interactions with the abiotic (non-living) environment. While limnology has substantial overlap with freshwater-focused disciplines (e.g., [[freshwater biology]]), it also includes the study of inland salt lakes.

==History==
The term limnology was coined by [[François-Alphonse Forel]] (1841–1912) who established the field with his studies of [[Lake Geneva]]. Interest in the discipline rapidly expanded, and in 1922 [[August Thienemann]] (a German zoologist) and [[Einar Naumann]] (a Swedish botanist) co-founded the [[International Society of Limnology]] (SIL, from [[Societas Internationalis Limnologiae]]).  Forel's original definition of limnology, "the [[oceanography]] of lakes", was expanded to encompass the study of all inland waters,<ref name="Wetzel"/> and influenced [[Benedykt Dybowski]]'s work on [[Lake Baikal]].

Prominent early American limnologists included [[G. Evelyn Hutchinson]] and [[Edward Smith Deevey, Jr.|Ed Deevey]].<ref>Frey, D.G. (ed.), 1963. Limnology in North America. University of Wisconsin Press, Madison</ref> At the [[University of Wisconsin–Madison|University of Wisconsin-Madison]], [[Edward Ashael Birge|Edward A. Birge]], [[Chancey Juday]], [[Charles R. Goldman]], and [[Arthur D. Hasler]] contributed to the development of the [[Center for Limnology]].<ref>{{Cite web|url=https://uwdc.library.wisc.edu/collections/uw/uwmadison/limnhist/|title=History of Limnology – UW Digital Collections|language=en-US|access-date=2019-05-02}}</ref><ref name="Beckel">{{Cite journal|last=Beckel|first=Annamarie L.|date=1987|title=Breaking new waters : a century of limnology at the University of Wisconsin. Special issue | journal=Transactions of the Wisconsin Academy of Sciences, Arts and Letters |url=https://search.library.wisc.edu/digital/A44N2KX6ER3XFM9A|language=en-US}}</ref>

==General limnology==

===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"/>

===Chemical properties===
The chemical composition of water in aquatic ecosystems is influenced by natural characteristics and processes including [[precipitation]], underlying [[soil]] and [[bedrock]] in the [[drainage basin]], [[erosion]], [[evaporation]], and [[sedimentation]].<ref name="limnology book"/> All bodies of water have a certain composition of both [[Organic compound|organic]] and [[Inorganic compound|inorganic]] elements and compounds. Biological reactions also affect the chemical properties of water. In addition to natural processes, human activities strongly influence the chemical composition of aquatic systems and their water quality.<ref name="water quality book" />

''Allochthonous'' sources of carbon or nutrients come from outside the aquatic system (such as plant and soil material).  Carbon sources from within the system, such as algae and the microbial breakdown of aquatic particulate [[organic carbon]], are ''autochthonous''. In aquatic food webs, the portion of biomass derived from allochthonous material is then named "allochthony".<ref>Grosbois, G., del Giorgio, P.A. & Rautio, M. (2017). [http://onlinelibrary.wiley.com/wol1/doi/10.1111/fwb.12879/full ''Zooplankton allochthony is spatially heterogeneous in a boreal lake'']. Freshwat. Biol., 62, 474-490</ref> In streams and small lakes, allochthonous sources of carbon are dominant while in large lakes and the ocean, autochthonous sources dominate.<ref>Eby, G.N., 2004, Principles of Environmental Geochemistry: Thomson Brooks/Cole, Pacific Grove, CA., 514 pp.</ref>

==== Oxygen and carbon dioxide ====
[[Oxygen saturation|Dissolved oxygen]] and dissolved [[carbon dioxide]] are often discussed together due their coupled role in [[Cellular respiration|respiration]] and [[photosynthesis]]. Dissolved oxygen concentrations can be altered by physical, chemical, and biological processes and reaction. Physical processes including wind mixing can increase dissolved oxygen concentrations, particularly in surface waters of aquatic ecosystems. Because dissolved oxygen solubility is linked to water temperatures, changes in temperature affect dissolved oxygen concentrations as warmer water has a lower capacity to "hold" oxygen as colder water.<ref name=":0">{{Cite book|title=Freshwater ecology : concepts and environmental applications of limnology|last=Dodds|first=Walter K.|date=2010|publisher=Academic Press|others=Whiles, Matt R.|isbn=9780123747242|edition= 2nd|location=Burlington, MA|oclc=784140625}}{{page needed|date=December 2020}}</ref> Biologically, both photosynthesis and aerobic respiration affect dissolved oxygen concentrations.<ref name="water quality book"/> Photosynthesis by [[Autotroph|autotrophic organisms]], such as [[phytoplankton]] and aquatic [[algae]], increases dissolved oxygen concentrations while simultaneously reducing carbon dioxide concentrations, since carbon dioxide is taken up during photosynthesis.<ref name=":0" /> All [[aerobic organism]]s in the aquatic environment take up dissolved oxygen during aerobic respiration, while carbon dioxide is released as a byproduct of this reaction. Because photosynthesis is light-limited, both photosynthesis and respiration occur during the [[daylight]] hours, while only respiration occurs during [[Night|dark]] hours or in dark portions of an ecosystem. The balance between dissolved oxygen production and consumption is calculated as the [[Lake metabolism|aquatic metabolism rate]].<ref>{{cite journal |last1=Cole |first1=Jonathan J. |last2=Caraco |first2=Nina F. |title=Carbon in catchments: connecting terrestrial carbon losses with aquatic metabolism |journal=Marine and Freshwater Research |date=2001 |volume=52 |issue=1 |pages=101 |doi=10.1071/mf00084 |bibcode=2001MFRes..52..101C |s2cid=11143190 }}</ref>
[[File:Lake metabolism cross section.png|thumb|upright=2.2|Lake cross-sectional diagram of the factors influencing lake metabolic rates and concentration of dissolved gases within lakes. Processes in gold text consume oxygen and produce carbon dioxide while processes in green text produce oxygen and consume carbon dioxide.]]
Vertical changes in the concentrations of dissolved oxygen are affected by both wind mixing of surface waters and the balance between photosynthesis and respiration of [[organic matter]]. These vertical changes, known as profiles, are based on similar principles as thermal stratification and light penetration. As light availability decreases deeper in the water column, photosynthesis rates also decrease, and less dissolved oxygen is produced. This means that dissolved oxygen concentrations generally decrease as you move deeper into the body of water because of photosynthesis is not replenishing dissolved oxygen that is being taken up through respiration.<ref name="water quality book" /> During periods of thermal stratification, water density gradients prevent oxygen-rich surface waters from mixing with deeper waters. Prolonged periods of stratification can result in the depletion of bottom-water dissolved oxygen; when dissolved oxygen concentrations are below 2 milligrams per liter, waters are considered [[Hypoxia (environmental)|hypoxic]].<ref name=":0" /> When dissolved oxygen concentrations are approximately 0 milligrams per liter, conditions are [[Anoxic waters|anoxic]]. Both hypoxic and anoxic waters reduce available habitat for organisms that respire oxygen, and contribute to changes in other chemical reactions in the water.<ref name=":0" />

==== Nitrogen ====
[[Nitrogen]] is a nutrient central for the function of aquatic ecosystems. Nitrogen is generally present as a [[gas|dissolved gas]] ([[Nitrogen gas|N<sub>2</sub>]]) in aquatic ecosystems, however due to the high energy requirement of utilising N<sub>2</sub> most organisms tend not to use it.<ref name=":3">{{Citation |last1=Dodds |first1=Walter K. |title=Nitrogen, Sulfur, Phosphorus, and Other Nutrients |date=2010 |work=Freshwater Ecology |pages=345–373 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780123747242000143 |access-date=2025-04-24 |publisher=Elsevier |language=en |doi=10.1016/b978-0-12-374724-2.00014-3 |isbn=978-0-12-374724-2 |last2=Whiles |first2=Matt R.|url-access=subscription }}</ref> Therefore, most water quality studies tend to focus on [[nitrate]], [[nitrite]] and [[ammonia]] levels.<ref name="limnology book"/><ref name=":3" /> Most of these dissolved nitrogen compounds follow a seasonal pattern with greater concentrations in the [[Autumn|fall]] and [[winter]] months compared to the [[Spring (season)|spring]] and [[summer]].<ref name="limnology book"/> 

==== Phosphorus ====
Another important nutrient in aquatic systems is [[phosphorus]]. Phosphorus has a different role in aquatic ecosystems as it is a limiting factor in the growth of phytoplankton because of generally low concentrations in the water.<ref name="limnology book" /> Dissolved phosphorus is also crucial to all living things, is often very limiting to primary productivity in freshwater, and has its own distinctive ecosystem [[Phosphorus cycle|cycling]].<ref name="water quality book" />

===Biological properties===
[[File:Lake George from village beach.jpg|thumb|[[Lake George (lake), New York|Lake George]], [[New York (state)|New York]], United States, an [[oligotrophic lake]]]]

====Role in ecology====
Lakes "are relatively easy to sample, because they have clear-cut boundaries (compared to terrestrial ecosystems) and because field experiments are relatively easy to perform.", which make then especially useful for ecologists who try to understand ecological dynamics.<ref>Lampert, W., & Sommer, U. 2007. Limnoecology.</ref>

====Lake trophic classification====
One way to classify lakes (or other bodies of water) is with the [[trophic state index]].<ref name="Wetzel"/> An oligotrophic lake is characterized by relatively low levels of [[primary production]] and low levels of [[nutrient]]s. A eutrophic lake has high levels of primary productivity due to very high nutrient levels. [[Eutrophication]] of a lake can lead to [[algal blooms]]. [[Dystrophic lake|Dystrophic]] lakes have high levels of [[humic matter]] and typically have yellow-brown, tea-coloured waters.<ref name="Wetzel"/>  These categories do not have rigid specifications; the classification system can be seen as more of a spectrum encompassing the various levels of aquatic productivity.{{Citation needed|date=March 2024}}

== Tropical limnology ==
Tropical limnology is a unique and important subfield of limnology that focuses on the distinct physical, chemical, biological, and cultural aspects of freshwater systems in [[Tropics|tropical regions]].<ref name=":1">{{Cite journal |last=Lewis |first=William M. |date=1987 |title=Tropical Limnology |url=https://www.jstor.org/stable/2097129 |journal=Annual Review of Ecology and Systematics |volume=18 |issue=1 |pages=159–184 |doi=10.1146/annurev.es.18.110187.001111 |jstor=2097129 |bibcode=1987AnRES..18..159L |issn=0066-4162|url-access=subscription }}</ref> The physical and chemical properties of tropical aquatic environments are different from those in [[Temperate climate|temperate regions]], with warmer and more stable temperatures, higher nutrient levels, and more complex ecological interactions.<ref name=":1" /> Moreover, the [[biodiversity]] of tropical freshwater systems is typically higher, human impacts are often more severe, and there are important cultural and socioeconomic factors that influence the use and management of these systems.<ref name=":1" />

== Professional organizations ==
People who study limnology are called limnologists. These scientists largely study the characteristics of inland fresh-water systems such as lakes, rivers, streams, ponds and wetlands. They may also study non-oceanic bodies of salt water, such as the Great Salt Lake. There are many professional organizations related to limnology and other aspects of the aquatic science, including the [[Association for the Sciences of Limnology and Oceanography]], the [[:es:Asociación Ibérica de Limnología|Asociación Ibérica de Limnología]], the [[International Society of Limnology]], the [[Polish Limnological Society]], the Society of Canadian Limnologists, and the [[Freshwater Biological Association]].{{Citation needed|date=March 2024}}

==See also==
{{portal|Lakes|Rivers|Wetlands}}
{{div col}}
* {{annotated link|Hydrology}}
* {{annotated link|Lake ecosystem|aka=Lentic ecosystems}}
* {{annotated link|Limnoforming}}
* {{annotated link|Limnological tower}}
* {{annotated link|River ecosystem|aka=Lotic ecosystems}}
* {{annotated link|Paleolimnology}}
{{div col end}}

== References ==
{{Reflist}}

== Further reading ==
* Gerald A. Cole, ''Textbook of Limnology'', 4th ed. (Waveland Press, 1994) {{ISBN|0-88133-800-1}}
* Stanley Dodson, ''Introduction to Limnology'' (2005), {{ISBN|0-07-287935-1}}
* A.J.Horne and C.R. Goldman: ''Limnology'' (1994), {{ISBN|0-07-023673-9}}
* [[George Evelyn Hutchinson|G. E. Hutchinson]], ''A Treatise on Limnology'', 3 vols. (1957–1975) - classic but dated
* H.B.N. Hynes, ''The Ecology of Running Waters'' (1970)
* Jacob Kalff, ''Limnology'' ([[Prentice Hall]], 2001)
* B. Moss, ''Ecology of Fresh Waters'' ([[Wiley-Blackwell|Blackwell]], 1998)
* Robert G. Wetzel and [[Gene E. Likens]], ''Limnological Analyses'', 3rd ed. ([[Springer Science+Business Media|Springer-Verlag]], 2000)
* Patrick E. O'Sullivan and Colin S. Reynolds ''The Lakes Handbook: Limnology and limnetic ecology'' {{ISBN|0-632-04797-6}}

{{aquatic ecosystem topics|state=expanded}}
{{aquatic organisms}}
{{Physical geography topics}}

{{Authority control}}

[[Category:Limnology| ]]
[[Category:Freshwater ecology|.01]]
[[Category:Hydrography]]
[[Category:Lakes]]
[[Category:Rivers]]
[[Category:Systems ecology]]
[[Category:Aquatic ecology]]
[[Category:Water]]