L
LAGOONS
Andrzej Osadczuk
Institute of Marine and Coastal Sciences, University of
Szczecin, Szczecin, Poland
Definition
The term lagoon is derived from the Latin lacun and the
later Italian laguna, which originally referred to the shallow water body around Venice (Skeat, 1893). Although
there are many definitions of lagoon, they differ only in
details. A lagoon is defined as a body of brackish, marine
or hypersaline water impounded by a sandy barrier and
having an inlet connecting with the open ocean (Phleger,
1981) or water areas separated from the sea by narrow
and low-laying land strips and usually differing from the
sea in salinity (Kaplin, 1982) or a shallow coastal water
body separated from the ocean by a barrier, connected
at least intermittently to the ocean by one or more
restricted inlets, and usually oriented shore-parallel
(Kjerfve, 1994). A full overview of the definitions of the
term “lagoon” in relation to various coastal environments
has been given by Tagliapietra et al. (2009).
Key features and variety of lagoons
Coastal lagoons represent about 11 % of the world’s coastlines and are widespread all along the world’s ocean coasts
(Nichols and Boon, 1994). However, lagoons develop on
aggrading or formerly aggraded coastal plains which are
gently sloping seaward. They are most common in
microtidal environments, although many examples of
lagoons can be found in mesotidal and even macrotidal
environments (Hayes, 1979; Nichols and Boon, 1994).
Many lagoons are well developed on coasts of
mid-latitudes, especially along the Atlantic coast of the
North and South America (Figure 1). Also, many lagoons
occur on southern coast of Europe, on southern shores of
the North Sea, and in some enclosed seas, such as Black
Sea, Caspian Sea, and southern Baltic. Lagoons can also
be found in low (tropical) and high (polar) latitude zones.
In the first case, lagoons in particular are common along
both coasts of Middle America (Gulf of Mexico, Caribbean Sea). On the other hand, along the shores of Alaska
and the Chukchi Peninsula, we can find many examples
of arctic lagoons (e.g., Kasegaluk Lagoon, Elson Lagoon,
Kunergvin Lagoon). The size of coastal lagoons varies
greatly, from about a hectare to more than 10,000 km
2
(Bird, 2008). Some lagoons extend over 200 km, e.g.,
Lagoa dos Patos (Brazil) and Laguna Madre (Gulf of
Mexico).
With respect to hydrodynamics and water exchange
with the adjacent open sea, coastal lagoons are often classified as closed, partly closed, open, and estuarine
(Nichols and Allen, 1981) (Figure 2) or choked, restricted,
and leaky (Kjerfve, 1986). A closed lagoon is produced by
intermediate to high waves, and strong longshore drift.
Such lagoon has no entrance channel, but that does not
mean that there is no water exchange with the sea. Water
flow, although very limited, can take place through the
permeable sediments of the barrier. Washovers or winds
across the barrier are the leading processes of sediment
influx. Organic production or chemical precipitation is
often a chief sediment-producing process in such conditions. In a partly closed lagoon, high wave energy acting
on the nearshore bed or headlands and strong longshore
currents build an extensive barrier island with prominent
flood delta and poorly developed ebb delta. Over long
periods, tidal currents and wave power may reach a
dynamic balance. Ocean-lagoon exchange is poor, and
entrapment of both sandy and muddy sediments is good.
An open lagoon is a result of wave action in combination
with moderate tidal action and river inflow. High waves
and longshore drift build short barrier islands, while tidal
J. Harff et al. (eds.), Encyclopedia of Marine Geosciences, DOI 10.1007/978-94-007-6238-1,
© Springer Science+Business Media Dordrecht 2016
LAGOONS
Andrzej Osadczuk
Institute of Marine and Coastal Sciences, University of
Szczecin, Szczecin, Poland
Definition
The term lagoon is derived from the Latin lacun and the
later Italian laguna, which originally referred to the shallow water body around Venice (Skeat, 1893). Although
there are many definitions of lagoon, they differ only in
details. A lagoon is defined as a body of brackish, marine
or hypersaline water impounded by a sandy barrier and
having an inlet connecting with the open ocean (Phleger,
1981) or water areas separated from the sea by narrow
and low-laying land strips and usually differing from the
sea in salinity (Kaplin, 1982) or a shallow coastal water
body separated from the ocean by a barrier, connected
at least intermittently to the ocean by one or more
restricted inlets, and usually oriented shore-parallel
(Kjerfve, 1994). A full overview of the definitions of the
term “lagoon” in relation to various coastal environments
has been given by Tagliapietra et al. (2009).
Key features and variety of lagoons
Coastal lagoons represent about 11 % of the world’s coastlines and are widespread all along the world’s ocean coasts
(Nichols and Boon, 1994). However, lagoons develop on
aggrading or formerly aggraded coastal plains which are
gently sloping seaward. They are most common in
microtidal environments, although many examples of
lagoons can be found in mesotidal and even macrotidal
environments (Hayes, 1979; Nichols and Boon, 1994).
Many lagoons are well developed on coasts of
mid-latitudes, especially along the Atlantic coast of the
North and South America (Figure 1). Also, many lagoons
occur on southern coast of Europe, on southern shores of
the North Sea, and in some enclosed seas, such as Black
Sea, Caspian Sea, and southern Baltic. Lagoons can also
be found in low (tropical) and high (polar) latitude zones.
In the first case, lagoons in particular are common along
both coasts of Middle America (Gulf of Mexico, Caribbean Sea). On the other hand, along the shores of Alaska
and the Chukchi Peninsula, we can find many examples
of arctic lagoons (e.g., Kasegaluk Lagoon, Elson Lagoon,
Kunergvin Lagoon). The size of coastal lagoons varies
greatly, from about a hectare to more than 10,000 km
2
(Bird, 2008). Some lagoons extend over 200 km, e.g.,
Lagoa dos Patos (Brazil) and Laguna Madre (Gulf of
Mexico).
With respect to hydrodynamics and water exchange
with the adjacent open sea, coastal lagoons are often classified as closed, partly closed, open, and estuarine
(Nichols and Allen, 1981) (Figure 2) or choked, restricted,
and leaky (Kjerfve, 1986). A closed lagoon is produced by
intermediate to high waves, and strong longshore drift.
Such lagoon has no entrance channel, but that does not
mean that there is no water exchange with the sea. Water
flow, although very limited, can take place through the
permeable sediments of the barrier. Washovers or winds
across the barrier are the leading processes of sediment
influx. Organic production or chemical precipitation is
often a chief sediment-producing process in such conditions. In a partly closed lagoon, high wave energy acting
on the nearshore bed or headlands and strong longshore
currents build an extensive barrier island with prominent
flood delta and poorly developed ebb delta. Over long
periods, tidal currents and wave power may reach a
dynamic balance. Ocean-lagoon exchange is poor, and
entrapment of both sandy and muddy sediments is good.
An open lagoon is a result of wave action in combination
with moderate tidal action and river inflow. High waves
and longshore drift build short barrier islands, while tidal
J. Harff et al. (eds.), Encyclopedia of Marine Geosciences, DOI 10.1007/978-94-007-6238-1,
© Springer Science+Business Media Dordrecht 2016