Types of Lagoons – Leaky, Restricted & Choked YouTube Lecture Handouts

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Watch video lecture on YouTube: 3 Types of Coastal Lagoons: Choked, Restricted and Leaky; Lagoons vs. Estuary 3 Types of Coastal Lagoons: Choked, Restricted and Leaky; Lagoons vs. Estuary
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Coastal Lagoons

Inner waterbody oriented parallel to coastline separated from ocean and connected to ocean by one or more restricted inlets – Pheleger

Kjerfev added that ocean entrance can be closed because of sediment deposition as a result of wave action and littoral drift

Most productive ecosystem on earth

Shallow brackish marine bodies separated from ocean by Barrier Island or spit

Term applies only when width of inlet at high tide is less than 20% of total length of enclosing barrier (as given by Bird)

Coastal lagoons have depth less than 2 m

Appear in low-lying areas, parallel to coast & occupy 13% coastal area worldwide

  • Africa coastline – 17.9%

  • North America 17.6%

  • Asia – 13.8%

  • South America – 12.2%

  • Australia – 11.4%

  • Europe – 5.3%

Most extensive stretch – Atlantic and Gulf coast of USA – 2800 km

Other Areas – S. America, India, S. Britain, W. France, W. Africa, SE Australia

Anthropogenic effects has led to alteration – overused for fisheries, salt extraction, transportation, energy production and human activities

Classification of Lagoons

Usually have estuarine circulation with surface outflow (restricted to discharge channels while flood oriented currents are dominant at top of sand banks) and inflow at the bottom

By Kjerfev – based on water exchange with Open Ocean.

  • Choked

  • Restricted

  • Leaky

Image of Classification of Lagoons

Image of Classification of Lagoons

Image of Classification of Lagoons

Characteristics

  • Origin depends on sea level history. Rising sea level during Holocene promoted this growth.

  • Shoreface dynamics and tidal range also play important role in the same

  • With restricted flushing and protracted water residence times, lagoons are susceptible to nutrient enrichment and eutrophication

  • Seasonal closure changes salinity – oligohaline to limnetic conditions in high precipitation and riverine inflow

  • Mesohaline to hypersaline during drought, low inflow and evaporation – have anti-estuarine circulation with outflow at bottom of inlet