Lagoon#Coastal lagoons

Lagoons are shallow, often elongated bodies of water separated from a larger body of water by a shallow or exposed shoal, coral reef, or similar feature. Some authorities include fresh water bodies in the definition of "lagoon", while others explicitly restrict "lagoon" to bodies of water with some degree of salinity. The distinction between "lagoon" and "estuary" also varies between authorities. Richard A. Davis Jr. restricts "lagoon" to bodies of water with little or no fresh water inflow, and little or no tidal flow, and calls any bay that receives a regular flow of fresh water an "estuary". Davis does state that the terms "lagoon" and "estuary" are "often loosely applied, even in scientific literature".{{cite book |last= Davis | first= Richard A. Jr. |title= The Evolving Coast |year= 1994 |publisher=Scientific American Library |location= New York |isbn= 978-0-7167-5042-0 |pages= [https://archive.org/details/evolvingcoast00davi/page/101 101, 107] |url= https://archive.org/details/evolvingcoast00davi/page/101 }} Timothy M. Kusky characterizes lagoons as normally being elongated parallel to the coast, while estuaries are usually drowned river valleys, elongated perpendicular to the coast.{{cite encyclopedia |year=1990 |title=Lagoon |encyclopedia=Oxford Dictionary of Earth Sciences |publisher=Oxford University Press |location=Oxford |editor=Allaby, Michael |isbn=978-0-19-921194-4}}{{cite encyclopedia |editor=Kusky, Timothy |encyclopedia=Encyclopedia of Earth Sciences |title=Lagoon |url=https://archive.org/details/encyclopediaofea0000kusk/page/245 |year=2005 |publisher=Facts on File |location=New York |isbn=0-8160-4973-4 |page=[https://archive.org/details/encyclopediaofea0000kusk/page/245 245] }}{{cite encyclopedia |editor=Nybakken, James W. |encyclopedia=Interdisciplinary Encyclopedia of Marine Sciences |title=Lagoon |year=2003 |publisher=Grolier Academic Reference |volume=2 G-O |location=Danbury, Connecticut |isbn=0-7172-5946-3 |pages=189–90}}{{Cite book | author=Reid, George K.| title=Ecology of Inland Waters and Estuaries| url=https://archive.org/details/ecologyofinlandw0000reid_r5j1| url-access=registration| publisher=Van Nostrand Reinhold Company|location=New York| year=1961|page=[https://archive.org/details/ecologyofinlandw0000reid_r5j1/page/74 74] |asin=B003MRW6AK}} Coastal lagoons are classified as inland bodies of water.{{cite book|page=263|url=https://books.google.com/books?id=VWnxpAxp6TMC|title=Encyclopedia of coastal science|author=Maurice L. Schwartz|publisher=Springer|year=2005|isbn=978-1-4020-1903-6|access-date=31 March 2012}}{{cite book|pages=1–3|url=https://books.google.com/books?id=MrwTtP0mLjUC|title=Coastal lagoon processes|first=Björn |last=Kjerfve |publisher=Elsevier|year=1994|isbn=978-0-444-88258-5|chapter=Coastal Lagoons}}

When used within the context of a distinctive portion of coral reef ecosystems, the term "lagoon" is synonymous with the term "back reef" or "backreef", which is more commonly used by coral reef scientists to refer to the same area.{{Cite journal | last1 = Aronson | first1 = R. B. | title = Hurricane effects on backreef echinoderms of the Caribbean | doi = 10.1007/BF00334473 | journal = Coral Reefs | volume = 12 | issue = 3–4 | pages = 139–142 | year = 1993 | bibcode = 1993CorRe..12..139A | s2cid = 879073 }}

Many lagoons do not include "lagoon" in their common names. Currituck, Albemarle and Pamlico Sounds in North Carolina,{{cite journal |last=Jia |first=Peng and Ming Li |year=2012 |title=Circulation dynamics and salt balance in a lagoonal estuary |url=http://www.agu.org/pubs/crossref/2012/2011JC007124.shtml |journal=Journal of Geophysical Research: Oceans |volume=117 |issue=C01003 |pages=C01003 |bibcode=2012JGRC..117.1003J |doi=10.1029/2011JC007124 |archive-url=https://web.archive.org/web/20140819170946/http://onlinelibrary.wiley.com/doi/10.1029/2011JC007124/abstract |archive-date=Aug 19, 2014 |access-date=24 March 2012 |doi-access=free}} Great South Bay between Long Island and the barrier beaches of Fire Island in New York,{{cite web|last=Goodbred|first=S. Jr., P. Locicero, V. Bonvento, S. Kolbe, S. Holsinger|title=History of the Great South Bay estuary:Evidence of a catastrophic origin|url=http://dspace.sunyconnect.suny.edu/bitstream/handle/1951/48052/goodbred.pdf;jsessionid=92152E84183F75FD0A4D6181D902AEFE?sequence=1|publisher=State University of New York|access-date=24 March 2012}} Isle of Wight Bay, which separates Ocean City, Maryland from the rest of Worcester County, Maryland,{{cite journal|last=Boynton|first=W. R., J. D. Hagy, L. Murray, C. Stokes, W. M Kemp|title=A Comparative Analysis of Eutrophication Patterns in a Temperate Coastal Lagoon|journal=Estuaries|date=June 1996|volume=19|issue=2B|pages=408–421|url=http://www.gonzo.cbl.umces.edu/documents/water_quality/Est19_408.pdf|access-date=24 March 2012|doi=10.2307/1352459|jstor=1352459|s2cid=14978943}} Banana River in Florida, US,{{cite web |title=Total Maximum Daily Loads for the North and Central Indian River Lagoon and Banana river Lagoon, Florida |url=http://www.epa.gov/waters/tmdldocs/6Final_IRL_NutriDO_TMDLs0407.pdf |archive-url=https://web.archive.org/web/20150924143849/http://www.epa.gov/waters/tmdldocs/6Final_IRL_NutriDO_TMDLs0407.pdf |archive-date=24 September 2015 |access-date=24 March 2012 |publisher=United States Environmental Protection Agency}} Lake Illawarra in New South Wales, Australia,{{cite web|title=Proposed Swimming Enclosure Net, Entrance Lagoon, Lake Illawarra|url=http://www.lia.nsw.gov.au/pdf/studies/Enclosure_Net_REF.pdf|publisher=Lake Illawarra Authority|access-date=24 March 2012|archive-url=https://web.archive.org/web/20110228025307/http://www.lia.nsw.gov.au/pdf/studies/Enclosure_Net_REF.pdf|archive-date=28 February 2011}} Montrose Basin in Scotland,{{cite book|last=Bird|first=Eric C. F.|title=Encyclopedia of the World's Coastal Landforms| volume=1|year=2010|publisher=Springer|location=Dordrecht|isbn=978-1-4020-8638-0|page=485|url=https://books.google.com/books?id=Mfo5TPb7SDsC&q=montrose+basin+lagoon&pg=PA485}} and Broad Water in Wales have all been classified as lagoons, despite their names. In England, The Fleet at Chesil Beach has also been described as a lagoon.

In some languages the word for a lagoon is simply a type of lake: In Chinese a lake is {{Lang|zh-latn|hu}} ({{Lang|zh|湖|italic=no}}), and a lagoon is {{Lang|zh-latn|xihu}} ({{Lang|zh|潟湖|italic=no}}). In the French Mediterranean several lagoons are called étang ("lake"). Contrariwise, several other languages have specific words for such bodies of water. In Spanish, coastal lagoons generically are {{Lang|es|laguna costera}}, but those on the Mediterranean coast are specifically called {{Lang|es|albufera}}. In Russian and Ukrainian, those on the Black Sea are {{Lang|ru-latn|liman}} ({{Lang|ru|лиман|italic=no}}), while the generic word is {{Lang|uk-latn|laguna}} ({{Lang|uk|Лагуна|italic=no}}). Similarly, in the Baltic, Danish has the specific {{Lang|da|{{ill|Nor (landform)|lt=Nor|da|Nor}}}}, and German the specifics {{Lang|de|Bodden}} and Haff, as well as generic terms derived from {{Lang|de|laguna}}. In Poland these lagoons are called zalew ("bay"), and in Lithuania marios ("lagoon, reservoir"). In Jutland several lagoons are known as fjord. In New Zealand the Māori word {{Lang|mi|hapua}} refers to a coastal lagoon formed at the mouth of a braided river where there are mixed sand and gravel beaches, while {{Lang|mi|waituna}}, an ephemeral coastal waterbody, is neither a true lagoon, lake, nor estuary.{{Cite book |last=Kirk, R.M. and Lauder, G.A |title=Significant coastal lagoon systems in the South Island, New Zealand: coastal processes and lagoon mouth closure |publisher=Department of Conservation |year=2000 |isbn=0-478-21947-4 |location=Wellington, N.Z.}}

Some languages differentiate between coastal and atoll lagoons. In French, {{Lang|fr|{{ill|lagon (French)|lt=lagon|fr|lagon}}}} refers specifically to an atoll lagoon, while coastal lagoons are described as {{Lang|fr|{{ill|étang|fr}}}}, the generic word for a still lake or pond.

In Vietnamese, {{Lang|vi|Đầm san hô}} refers to an atoll lagoon, whilst {{Lang|vi|Đầm phá}} is coastal.

In Latin America, the term {{Lang|es|laguna}} in Spanish, which lagoon translates to, may be used for a small fresh water lake in a similar way a creek is considered a small river. However, sometimes it is popularly used to describe a full-sized lake, such as Laguna Catemaco in Mexico, which is actually the third-largest lake by area in the country. The brackish water lagoon may be thus explicitly identified as a "coastal lagoon" ({{Lang|es|laguna costera}}). In Portuguese, a similar usage is found: {{Lang|pt|lagoa}} may be a body of shallow seawater, or a small freshwater lake not linked to the sea.

Lagoon is derived from the Italian {{lang|it|laguna}}, which refers to the waters around Venice, the Venetian Lagoon. Laguna is attested in English by at least 1612, and had been Anglicized to "lagune" by 1673. In 1697 William Dampier referred to a "Lagune or Lake of Salt water" on the coast of Mexico. Captain James Cook described an island "of Oval form with a Lagoon in the middle" in 1769.{{cite encyclopedia |encyclopedia=Oxford English Dictionary |title=Lagoon |edition=Compact |year=1971 |publisher=Oxford University Press |volume=I A-O |location=Oxford, England |page=1560 }}

{{further|List of largest atolls}}

File:Atafutrim.jpg atoll in Tokelau in the Pacific Ocean]]

Atoll lagoons form as coral reefs grow upwards while the islands that the reefs surround subside, until eventually only the reefs remain above sea level. Unlike the lagoons that form shoreward of fringing reefs, atoll lagoons often contain some deep (>{{Convert|20|m|ft|abbr=on}}) portions.{{citation needed|date=March 2025}}

File:Caspian Sea covered with plants near Bandar-e Anzali - Barry Kent.jpg in southwestern Caspian Sea coast, Iran]]

File:Hiddensee (2011-05-21).JPG near Stralsund, Germany. Many similar coastal lagoons can be found around the Western Pomerania Lagoon Area National Park.]]

Coastal lagoons form along gently sloping coasts where barrier islands or reefs can develop offshore, and the sea-level is rising relative to the land along the shore (either because of an intrinsic rise in sea-level, or subsidence of the land along the coast). Coastal lagoons do not form along steep or rocky coasts, or if the range of tides is more than {{convert|4|m|ft}}. Due to the gentle slope of the coast, coastal lagoons are shallow. A relative drop in sea level may leave a lagoon largely dry, while a rise in sea level may let the sea breach or destroy barrier islands, and leave reefs too deep underwater to protect the lagoon. Coastal lagoons are young and dynamic, and may be short-lived in geological terms. Coastal lagoons are common, occurring along nearly 15 percent of the world's shorelines. In the United States, lagoons are found along more than 75 percent of the Eastern and Gulf Coasts.

Coastal lagoons can be classified as leaky, restricted, or choked.{{cite book | last=Kjerfve | first=Björn | author-link=Björn Kjerfve | title=Estuarine Variability | chapter=Comparative oceanography of coastal lagoons | publisher=Elsevier | year=1986 | isbn=978-0-12-761890-6 | doi=10.1016/b978-0-12-761890-6.50009-5 | pages=63–81}}

Coastal lagoons are usually connected to the open ocean by inlets between barrier islands. The number and size of the inlets, precipitation, evaporation, and inflow of fresh water all affect the nature of the lagoon. Lagoons with little or no interchange with the open ocean, little or no inflow of fresh water, and high evaporation rates, such as Lake St. Lucia, in South Africa, may become highly saline. Lagoons with no connection to the open ocean and significant inflow of fresh water, such as the Lake Worth Lagoon in Florida in the middle of the 19th century, may be entirely fresh. On the other hand, lagoons with many wide inlets, such as the Wadden Sea, have strong tidal currents and mixing. Coastal lagoons tend to accumulate sediments from inflowing rivers, from runoff from the shores of the lagoon, and from sediment carried into the lagoon through inlets by the tide. Large quantities of sediment may be occasionally be deposited in a lagoon when storm waves overwash barrier islands. Mangroves and marsh plants can facilitate the accumulation of sediment in a lagoon. Benthic organisms may stabilize or destabilize sediments.

{{Cleanup list|section|date=October 2023}}

{{redirect-distinguish|List of largest lagoons|List of largest atoll lagoons}}

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|File:Lagoa_dos_Patos_PIA03444_lrg.jpg|{{Lang|pt|Lagoa dos Patos|italic=no}}, the largest lagoon in South America, in the Brazilian state of Rio Grande do Sul.|Image:Boraboraluft gerade.jpg|Aerial view of Bora Bora in French Polynesia.

|Image:Kivalina Alaska aerial view.jpg|Aerial view of Kivalina, Alaska from the northwest.

|Image:Kiritimati-EO.jpg|Nearly half the area of Kiritimati is covered with lagoons, some freshwater and some seawater.

|Image:Blue Lagoon,Nusa Lembongan-Bali.jpg|Nusa Lembongan Lagoon, Bali, Indonesia.

|File:LEFKADA Panorama1.jpg|Panoramic view of Lefkada City Lagoon, Lefkada Isl., Ionian Islands Prefecture, Greece.

|File:KALOGRIA Panorama.jpg|Panoramic view of Prokopos Lagoon, Achaia, Western Greece Prefecture, Greece.

|File:Island lagoon in Bacuit Bay, El Nido, Palawan, Philippines.jpg|Tropical lagoon in Bacuit Bay, Palawan, Philippines.

|File:Cartagena, Mar Menor, i Cap de Pals (foto satèl·lit).jpg|Photo of Mar Menor as seen from International Space Station.

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{{Portal|Wetlands}}

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• Aerated lagoon
• Anaerobic lagoon
• Ayre (landform)
• Barachois
• Braided river
• Estuary
• Haff (estuarine lagoon)
• Longshore drift
• Sediment transport

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{{Commons category|Lagoons}}

{{aquatic ecosystem topics|expanded=marine}}

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Category:Coastal and oceanic landforms

Category:Oceanographical terminology

Category:Bodies of water