Salt pannes and pools
Encyclopedia
Salt pannes and pools are water retaining depressions located within salt
and brackish marsh
es. Pools tend to retain water during the summer months between high tides, whereas pannes generally do not. Salt pannes generally start when a mat of organic debris known as wrack, is deposited upon existing vegetation killing it. This creates a slight depression in the surrounding vegetation which retains water for varying periods of time. Upon successive cycles of inundation and evaporation the panne develops an increased salinity
greater than that of the larger body of water. This increased salinity dictates the type of flora and fauna able to grow within the panne. Salt pools are also secondary formations, though the exact mechanism(s) of formation are not well understood; some have predicted they will increase in size and abundance in the future due to rising sea levels.
Salt pannes and pools are unique microhabitats dominated by various species of halophyte
s, benthic plants and varying estuarine marine life that vary considerably in composition due to a variety of factors:
These factors affect the types of species which can survive within the various types of salt pannes and pools.
Variants of salt pannes and pools:
Low salt marsh
Usually devoid of vegetation, that may be present include smooth cordgrass (Spartina alterniflora
), marine algae such as knotted wrack (Ascophyllum nodosum
) and rockweeds (Fucus spp.). The substrate is typically soft, silty mud.
High salt marsh
Briefly flooded, very shallow with a moderate amount of vegetation usually dominated by Arrow grass (Triglochin maritimum), with the deeper sections possibly remaining unvegetated.
Shallow anaerobic depressions with poor drainage, poor water quality due to low nutrient levels and high concentrations of sulfide
s and similar compounds which inhibit plant growth. Short form (6-12" tall)smooth cord-grass (Spartina alterniflora) is the dominant plant species. Typically found on the high salt marsh, but can occasionally be found on the upper margins of low salt marsh.
Salt marsh mosquito panne
Minimal vegetation often found on the upper half of the high salt marsh. It is typically deeper than forb and smooth cord-grass pannes. Usually flooded by the higher of the two spring tides, retains water for 2–3 weeks later until drying out. The female eastern salt marsh mosquito (Aedes sollicitans
) lays eggs on the exposed surface. The eggs lay dormant until the next time the panne floods.
Widgeon grass (Ruppia maritima
) - marsh minnow deepwater pool
Pools on the high salt marsh that are semi-permanently and permanently flooded. They are able to sustain populations of Sheephead minnow (Cyprinodon variegatus variegatus)
, Mummichogs, (Fundulus heteroclitus)
, and other species of small fish which may become trapped in the pools and benthic species of vegetation. Occasioanally can be found at the upper edge of the low salt marsh.
) an invasive exotic species.
Shallow depressions flooded for only for a brief time and are characterized by a variable mix of graminoids and forbs. Frequent herbs include three-square rush (Scirpus pungens
), stout bulrush (S. robustus), arrow-grass, marsh creeping bent-grass (Agrostis stolonifera
), salt-loving spike-rush (Eleocharis halophila
). Growing with less frequency are red fescue (Festuca rubra
), New York aster (Symphyotrichum novi-belgii
) silverweed, saltmeadow cordgrass (Spartina patens
), and salt marsh rush.
Saturated, mud dominated pannes are occasionally found in the transition zone next to forested uplands where they are shaded by overhanging tree branches thus inhibiting evaporation. This is the preferred habitat for the uncommon seaside crowfoot (Ranunculus cymbalaria
), where prostrate colonies may form small patches over the soil surface. Other graminoids and forbs scattered across the mud, or more often around the panne edge, include Virginia wild rye (Elymus virginicus
), chaffy salt sedge (Carex paleacea
) seaside goldenrod (Solidago sempervirens
), marsh creeping bent grass, New York aster and smooth cordgrass.
Salt marsh
A salt marsh is an environment in the upper coastal intertidal zone between land and salt water or brackish water, it is dominated by dense stands of halophytic plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh...
and brackish marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
es. Pools tend to retain water during the summer months between high tides, whereas pannes generally do not. Salt pannes generally start when a mat of organic debris known as wrack, is deposited upon existing vegetation killing it. This creates a slight depression in the surrounding vegetation which retains water for varying periods of time. Upon successive cycles of inundation and evaporation the panne develops an increased salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
greater than that of the larger body of water. This increased salinity dictates the type of flora and fauna able to grow within the panne. Salt pools are also secondary formations, though the exact mechanism(s) of formation are not well understood; some have predicted they will increase in size and abundance in the future due to rising sea levels.
Salt pannes and pools are unique microhabitats dominated by various species of halophyte
Halophyte
A halophyte is a plant that grows where it is affected by salinity in the root area or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs, and seashores. An example of a halophyte is the salt marsh grass Spartina alterniflora . Relatively few plant species are...
s, benthic plants and varying estuarine marine life that vary considerably in composition due to a variety of factors:
- SubstrateSubstrate (marine biology)Stream substrate is the material that rests at the bottom of a stream. There are several classification guides. One is:*Mud – silt and clay.*Sand – Particles between 0.06 and 2 mm in diameter.*Granule – Between 2 and 4 mm in diameter....
type: affects the ability of the depression to hold water. - depth and diameter: affect water temperature and evaporation rate in the depression. A shallow and wide pool will evaporate at a greater rate than a pool of the same volume of water which is deeper and has a smaller surface area. Evaporation rate also affects salinity, the higher the evaporation rate the higher the salinity, with rates as high as a third greater than ocean water.
- location within the intertidal zone, whether high marshHigh marshHigh marsh is a tidal marsh zone located above the Mean Highwater Mark which, in contrast to the low marsh zone, is inundated infrequently during periods of extreme high tide and storm surge associated with coastal storms...
or low marshLow marshLow marsh is a tidal marsh zone. It is characterized as being flooded daily....
and distance from the mean low tide mark which affects the length and duration of inundation until the depression is subject to evaporation as well as length of time until the rising tide replenishes the water volume.
These factors affect the types of species which can survive within the various types of salt pannes and pools.
Variants of salt pannes and pools:
Low salt marsh
- Low salt marsh panne
Usually devoid of vegetation, that may be present include smooth cordgrass (Spartina alterniflora
Spartina alterniflora
Spartina alterniflora is a perennial deciduous grass which is found in intertidal wetlands, especially estuarine salt marshes. It grows 1-1.5 m tall, and has smooth, hollow stems which bear leaves up to 20-60 cm long and 1.5 cm wide at their base, which are sharply tapered and bend down...
), marine algae such as knotted wrack (Ascophyllum nodosum
Ascophyllum nodosum
Ascophyllum nodosum is a large, common brown alga in the family Fucaceae, being the only species in the genus Ascophyllum. It is seaweed of the northern Atlantic Ocean, also known as rockweed, Norwegian kelp, knotted kelp, knotted wrack or egg wrack...
) and rockweeds (Fucus spp.). The substrate is typically soft, silty mud.
High salt marsh
- Arrow-grass (forb) panne
Briefly flooded, very shallow with a moderate amount of vegetation usually dominated by Arrow grass (Triglochin maritimum), with the deeper sections possibly remaining unvegetated.
- Smooth cord-grass (short form) panne
Shallow anaerobic depressions with poor drainage, poor water quality due to low nutrient levels and high concentrations of sulfide
Sulfide
A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.- Properties :...
s and similar compounds which inhibit plant growth. Short form (6-12" tall)smooth cord-grass (Spartina alterniflora) is the dominant plant species. Typically found on the high salt marsh, but can occasionally be found on the upper margins of low salt marsh.
Salt marsh mosquito panne
Aedes sollicitans
Aedes sollicitans, the eastern saltmarsh mosquito , is a species of mosquito native to the eastern seaboard of the United States and Canada as well as the entire Gulf coast and is also present in the Bahamas and Greater Antilles...
) lays eggs on the exposed surface. The eggs lay dormant until the next time the panne floods.
Widgeon grass (Ruppia maritima
Ruppia maritima
Ruppia maritima is a species of aquatic plant known by the common name wigeongrass. Despite its Latin name, it is not a marine plant; is perhaps best described as a salt-tolerant freshwater species.-Distribution:...
) - marsh minnow deepwater pool
Pools on the high salt marsh that are semi-permanently and permanently flooded. They are able to sustain populations of Sheephead minnow (Cyprinodon variegatus variegatus)
Sheepshead minnow
The sheepshead minnow is a subspecies of killifish found in salt marsh estuary environments....
, Mummichogs, (Fundulus heteroclitus)
Mummichog
The mummichog is a killifish also known as mummies, gudgeons, and mud minnows are found in brackish and coastal waters along the eastern seaboard of the United States as well as Atlantic Canada. It is noted for its hardiness and for being a popular research subject in embryological, physiological,...
, and other species of small fish which may become trapped in the pools and benthic species of vegetation. Occasioanally can be found at the upper edge of the low salt marsh.
Brackish water marsh
Brackish marsh panne variants occur in brackish marshes (short graminoid variant), one of the native dominant species is spike grass (Distichlis spicata), some brackish marsh pannes are dominated by the narrow-leaved cattail (Typha angustifoliaTypha angustifolia
Typha angustifolia L., , is a perennial herbaceous plant of genus Typha. This cattail is an "obligate wetland" species that is commonly found in the northern hemisphere in brackish locations...
) an invasive exotic species.
- Mixed graminoid - forbForbA forb is a herbaceous flowering plant that is not a graminoid . The term is used in biology and in vegetation ecology, especially in relation to grasslands and understory.-Etymology:...
panne
Shallow depressions flooded for only for a brief time and are characterized by a variable mix of graminoids and forbs. Frequent herbs include three-square rush (Scirpus pungens
Scirpus pungens
Schoenoplectus pungens is a species of flowering plant in the sedge family known by the common name Common Three-Square. It is a herbaceous emergent plant that is native to the Americas, Europe, Australasia, and elsewhere....
), stout bulrush (S. robustus), arrow-grass, marsh creeping bent-grass (Agrostis stolonifera
Agrostis stolonifera
Agrostis stolonifera is a perennial grass species in the Poaceae family. It is stoloniferous and may form mats or tufts...
), salt-loving spike-rush (Eleocharis halophila
Eleocharis halophila
Eleocharis halophila is a perennial halophytic plant endemic to salt marshes in eastern Canada, in Ontario in Hudson Bay and James Bay, Quebec in the St. Lawrence Seaway as far as the city of Quebec, Newfoundland and Nova Scotia and in the United States from Maine to North Carolina...
). Growing with less frequency are red fescue (Festuca rubra
Festuca rubra
Festuca rubra is a species of grass known by the common name red fescue. It is found worldwide and can tolerate many habitats and climates; it generally needs full sun to thrive...
), New York aster (Symphyotrichum novi-belgii
Symphyotrichum novi-belgii
Symphyotrichum novi-belgii also known as New York Aster is the type species for Symphyotrichum, a genus of the family Asteraceae whose species were once considered to be Asters and an ornamental plant native to Canada and the United States....
) silverweed, saltmeadow cordgrass (Spartina patens
Spartina patens
Spartina patens , also known as salt marsh hay, is a species of cordgrass native to the Atlantic coast of the Americas, from Newfoundland south along the eastern United States to the Caribbean and northeast Mexico...
), and salt marsh rush.
- Sparsely vegetated panne
Saturated, mud dominated pannes are occasionally found in the transition zone next to forested uplands where they are shaded by overhanging tree branches thus inhibiting evaporation. This is the preferred habitat for the uncommon seaside crowfoot (Ranunculus cymbalaria
Ranunculus cymbalaria
Ranunculus cymbalaria is a species of buttercup known by the common names alkali buttercup and seaside buttercup. It is native to much of Eurasia and parts of North and South America, where it grows in many types of habitat, especially in moist to wet areas such as marshes, bogs, and moist spring...
), where prostrate colonies may form small patches over the soil surface. Other graminoids and forbs scattered across the mud, or more often around the panne edge, include Virginia wild rye (Elymus virginicus
Elymus virginicus
Elymus virginicus, or Virginia wildrye, is a perennial bunchgrass located in Virginia and the eastern United States....
), chaffy salt sedge (Carex paleacea
Carex paleacea
Carex paleacea is one of the 579 species of Carex. The Wetland Indicator Status for the species is classified as "obligate wetland" , occurring 99% of the time in a typical salt marsh environment when conditions are favorable....
) seaside goldenrod (Solidago sempervirens
Solidago sempervirens
Solidago sempervirens is a plant species in the genus Solidago of the Asteraceae family. It is native to eastern North America and parts of the Caribbean. It is an introduced species in the Great Lakes region and the Azores....
), marsh creeping bent grass, New York aster and smooth cordgrass.