Definition
In an estuary, sublittoral refers to the zone immediately
below the eulittoral zone extending outward from the
neap low tide mark at the shoreline. In an ocean, sublittoral refers to the zone extending from the neap low tide
mark at the shoreline to the outer edge of the continental
shelf.
Description
Sublittoral habitats in an estuary lie within the photic zone
and thus are typically highly productive. Numerous flora
and fauna inhabit the sublittoral zone forming rich biotic
communities (Day et al., 2012; Levinton, 2013). This is
a subaqueous environment susceptible to the vagaries of
physical and chemical factors, resulting in variable spatial
and temporal biotic responses (Allaby and Allaby, 1999;
Kennish, 2001).
Bibliography
Allaby, A., and Allaby, A. (eds.), 1999. A Dictionary of Earth
Sciences, 2nd edn. Oxford: Oxford University Press.
Day, J. W., Crump, B. C., Kemp, W. M., and Yanez-Arancibia,
A. (eds.), 2012. Estuarine Ecology, 2nd edn. New York:
Wiley-Blackwell.
Kennish, M. J. (ed.), 2001. Practical Handbook of Marine Science,
3rd edn. Boca Raton: CRC Press.
Levinton, J. S., 2013. Marine Biology: Function, Biodiversity,
Ecology, 4th edn. Oxford: Oxford University Press.
Cross-references
Benthic Ecology
Littoral Zone
Shoreline
SUBMERGED COASTS
Lluís Gómez-Pujol
Universitat de les Illes Baleares, Palma (Balearic Islands),
Spain
Synonyms
Submergent coasts
Definition
Submerged coasts are defined as coasts formed by the relative submergence of a landmass via sea-level rise and/or
by land subsidence or by both factors.
Description
Most early coastal classification schemes are based on the
observation that coastal landforms are largely the product
of sea-level variations. Such classifications distinguish
between emerged and submerged coasts (Johnson,
1919). More sophisticated analyses have attempted to
establish coastal classifications by balancing two sets of
factors in the coastal configuration, one historical and
one contemporary. In the first, the coastal type is controlled by plate tectonics resulting in emergencesubmergence categories. Historic factors must be assessed
such as the nature of the sea-level change over the last
10,000 years of the postglacial transgression. Additionally
variations in wave energy, tidal regime, and biogeographic
agents and processes must be considered. Valentin (1952)
incorporated these factors in an elegant diagram that combined advancing and retreating coasts with emerging and
submerging ones. Most of the submerging coasts correlate
with coastal retreat or land erosion. The main shortcoming
of these early classifications is the emphasis on geological
control that places less significance on the role of hydrodynamic processes.
The coupling mechanisms in coastal submersion are
sea-level rise and land subsidence. Between 20 and 6 kyr
ago, driven by the melting of Northern Hemisphere ice
caps, global sea level increased $120 m. This rise in sea
level caused the rapid submergence of vast areas of the
continental shelf. In the last 6 kyr, global sea level has
remained more or less stable during an interglacial period
(Pirazzoli, 1996). Despite being more variable in time and
space, land subsidence may result from different tectonic
and neotectonic processes or by the accumulation and
compaction of sediments. During the twentieth century,
many coastal areas experienced human-induced land subsidence caused by groundwater withdrawal or oil and gas
extraction, among others. Regulation of river flow and the
construction of breakwaters that cut longshore sediment
supply have also contributed to destruction and sinking
of deltas (Bird, 1993). Climate models, which take into
account increasing greenhouse effects, estimate that the
global temperature may increase 2
C and sea level may
increase 0.11–0.77 m over the next century, which will
cause significant coastal flooding and submergence
(Church et al., 2001).
Typical submerged coasts are drowned river and glacial
valleys, often referred as rias, calas, fiords, fiards, sharms,
and sebkhas. Although many of them can fit within
a broad morphological classification of estuaries, from
a hydrodynamic point of view, drowned valleys are not
necessarily estuaries (Bird, 2008). Inlets formed by partial
submergence of river valleys are known as rias, whereas
fiords are steep-sided inlets at the mouth of valleys that
were formerly glaciated. Inlets generated by Holocene
marine submergence of formerly glaciated valleys and
depressions in low-lying rock landforms are known as
fiards. These steep-sided valleys, incised in limestone
plateaus during low sea-level stages that have been
submerged during the Holocene, are known as calas
or calanques (Gómez-Pujol et al., 2013). Finally, in arid
environments, such as those of the Red Sea and the
Arabian Gulf, wadis developed during the Holocene
marine transgression, leading to the formation of long,
narrow marine inlets termed sharms. When these valleys
exhibit a branched embayment, they are known as sebkhas
(Castaing and Guilcher, 1995).
650
SUBMERGED COASTS
In an estuary, sublittoral refers to the zone immediately
below the eulittoral zone extending outward from the
neap low tide mark at the shoreline. In an ocean, sublittoral refers to the zone extending from the neap low tide
mark at the shoreline to the outer edge of the continental
shelf.
Description
Sublittoral habitats in an estuary lie within the photic zone
and thus are typically highly productive. Numerous flora
and fauna inhabit the sublittoral zone forming rich biotic
communities (Day et al., 2012; Levinton, 2013). This is
a subaqueous environment susceptible to the vagaries of
physical and chemical factors, resulting in variable spatial
and temporal biotic responses (Allaby and Allaby, 1999;
Kennish, 2001).
Bibliography
Allaby, A., and Allaby, A. (eds.), 1999. A Dictionary of Earth
Sciences, 2nd edn. Oxford: Oxford University Press.
Day, J. W., Crump, B. C., Kemp, W. M., and Yanez-Arancibia,
A. (eds.), 2012. Estuarine Ecology, 2nd edn. New York:
Wiley-Blackwell.
Kennish, M. J. (ed.), 2001. Practical Handbook of Marine Science,
3rd edn. Boca Raton: CRC Press.
Levinton, J. S., 2013. Marine Biology: Function, Biodiversity,
Ecology, 4th edn. Oxford: Oxford University Press.
Cross-references
Benthic Ecology
Littoral Zone
Shoreline
SUBMERGED COASTS
Lluís Gómez-Pujol
Universitat de les Illes Baleares, Palma (Balearic Islands),
Spain
Synonyms
Submergent coasts
Definition
Submerged coasts are defined as coasts formed by the relative submergence of a landmass via sea-level rise and/or
by land subsidence or by both factors.
Description
Most early coastal classification schemes are based on the
observation that coastal landforms are largely the product
of sea-level variations. Such classifications distinguish
between emerged and submerged coasts (Johnson,
1919). More sophisticated analyses have attempted to
establish coastal classifications by balancing two sets of
factors in the coastal configuration, one historical and
one contemporary. In the first, the coastal type is controlled by plate tectonics resulting in emergencesubmergence categories. Historic factors must be assessed
such as the nature of the sea-level change over the last
10,000 years of the postglacial transgression. Additionally
variations in wave energy, tidal regime, and biogeographic
agents and processes must be considered. Valentin (1952)
incorporated these factors in an elegant diagram that combined advancing and retreating coasts with emerging and
submerging ones. Most of the submerging coasts correlate
with coastal retreat or land erosion. The main shortcoming
of these early classifications is the emphasis on geological
control that places less significance on the role of hydrodynamic processes.
The coupling mechanisms in coastal submersion are
sea-level rise and land subsidence. Between 20 and 6 kyr
ago, driven by the melting of Northern Hemisphere ice
caps, global sea level increased $120 m. This rise in sea
level caused the rapid submergence of vast areas of the
continental shelf. In the last 6 kyr, global sea level has
remained more or less stable during an interglacial period
(Pirazzoli, 1996). Despite being more variable in time and
space, land subsidence may result from different tectonic
and neotectonic processes or by the accumulation and
compaction of sediments. During the twentieth century,
many coastal areas experienced human-induced land subsidence caused by groundwater withdrawal or oil and gas
extraction, among others. Regulation of river flow and the
construction of breakwaters that cut longshore sediment
supply have also contributed to destruction and sinking
of deltas (Bird, 1993). Climate models, which take into
account increasing greenhouse effects, estimate that the
global temperature may increase 2
C and sea level may
increase 0.11–0.77 m over the next century, which will
cause significant coastal flooding and submergence
(Church et al., 2001).
Typical submerged coasts are drowned river and glacial
valleys, often referred as rias, calas, fiords, fiards, sharms,
and sebkhas. Although many of them can fit within
a broad morphological classification of estuaries, from
a hydrodynamic point of view, drowned valleys are not
necessarily estuaries (Bird, 2008). Inlets formed by partial
submergence of river valleys are known as rias, whereas
fiords are steep-sided inlets at the mouth of valleys that
were formerly glaciated. Inlets generated by Holocene
marine submergence of formerly glaciated valleys and
depressions in low-lying rock landforms are known as
fiards. These steep-sided valleys, incised in limestone
plateaus during low sea-level stages that have been
submerged during the Holocene, are known as calas
or calanques (Gómez-Pujol et al., 2013). Finally, in arid
environments, such as those of the Red Sea and the
Arabian Gulf, wadis developed during the Holocene
marine transgression, leading to the formation of long,
narrow marine inlets termed sharms. When these valleys
exhibit a branched embayment, they are known as sebkhas
(Castaing and Guilcher, 1995).
650
SUBMERGED COASTS