Salt Marsh Flora

Salt marshes are challenging habitats for plants and the plants that thrive their have unusual adaptations, making them fascinating subjects of study. Here we review a few such species growing together as a single community on a single salt marsh. This is the second part of this article, the first part covered glassworts.

Greater Sea-spurrey (Campion Family, Caryophyllaceae)

Spergularia media

The Greater Sea-Spurrey (Spergularia media) has striking, though very small (8 to 12 mm across) pinkish-white flowers (the camera has made them look whiter than in life but a pink tinge is visible). In Greater Sea-spurrey, the stems are creeping to ascending and up to 30 cm long. This species is perennial. The leaves are fleshy and somewhat succulent.

Seed dispersal shows some fascinating adaptations! The fruit ('seeds') shown below, are distinguishable from other species of Sea-spurrey in usually having a large membranous wing around the entire circumference. This aids dispersal of the enclosed seed in open habitats. However, some individual flowers may produce wingless fruit and some may produce both. It has been shown that these plants will produce more winged seeds if they are growing in open habitats, where wind can easily scatter the seeds (Telenius, 1992). However, in crowded habitats, winged seeds are more likely to be trapped by vegetation while wingless seeds disperse more easily (Telenius and Torrstensson, 1989) and so the plants produce fewer winged seeds when crowded!

Spergularia media - fruit

Spergularia media

The fruit is a capsule which opens via three valves.

Grass-leaved Orache (Atriplex littoralis): Chenopodiaceae

Orache

Orache

The genus Atriplex includes the Oraches and Sea-purslane and belongs to the Goosefoot family (Chenopodiaceae). These plants have very reduced flowers which reveal their secrets under the microscope! Oraches are often fleshy and somewhat succulent in appearance. In Oraches the male and female flowers are separate. The female flowers lack sepals and are enclosed within a pair of triangular bracteoles that enlarge in the fruit. Grass-leaved Orache is an erect annual up to 1 m tall with narrow 'lanceolate' (narrow and pointed) leaves. It occurs on coasts, shores and salt-marsh edges, sea walls and spreads inland along salted roads.

Orache - salt glands

Orache - salt glands

Above: Pairs of trianglar bracteoles, covered in protuberances and trichomes, enclosing the female flowers.

Under the microscope, much of the plant and the pair of triangular bracteoles in particular, are covered with many
trichomes which look like beautiful tiny stalked vases of crystal glass (the photograph does not fully capture the spectacle as seen under the microscope by eye). These are salt bladders or salt glands. They accumulate excess salt that the plant has absorbed from the salty soil and secreted. They swell with salty liquid before bursting to release their salt to the outside. They can accumulate salt at up to 60 times the concentration of that in the rest of the plant tissues and thereby prevent salts accumulating within the tissues to toxic concentrations. This presumably accounts for the mealy appearance of many Oraches (waxy secretions can also account for mealyness in plants).

Annual Sea-blite (Suaeda maritima)

Suaeda maritima

Suaeda maritima

Suaeda maritima (Chenopodiaceae) is an annual salt-marsh plant with succulent leaves (like half cylinders) with pointed tips and slightly tapered bases. (The related perennial Shrubby sea-blite, Suaeda vera (Suaeda fruticosa) is larger and has more cylindrical leaves with rounded tips and less tapered bases). The stems are either green or flushed red and may be upright or prostrate.

Below: a series of three close-up photomicrographs in different focal planes. Note the 5 fleshy sepals on each flower.

Suaeda maritima - up-close

Suaeda maritima - up-close

Suaeda maritima - up-close

Suaeda maritima - up-close

Suaeda maritima - up-close

Annual Sea-blite

Annual Sea-blite growing among glassworts and Sea Purslane.

Annual Sea-blite

Sea-purslane (Atriplex portulacoides)

Atriplex portulacoides

This plant is a perennial (unlike other Oraches) and is a low shrub with a mealy appearance. The bracteoles enclose the female flowers and developing fruits and have broad 3-lobed tips and are fused together over much of their length (protecting the sexual parts from dehydration).

Atriplex portulacoides - up-close Atriplex portulacoides - up-close

Sea Purslane

Sea-Purslane

Sea Beet (Beta vulgaris): Chenopodiaceae

Sea Beet, Beta vulgaris, up-close

Sea Beet is similar in superficial appearance to a Goosefoot or an Orache, with spikes of fairly inconspicuous and dull-coloured flowers. However, The flowers are more conspicuous to the naked eye with the 5 fleshy sepals quite distinct. The coastal form is usually subspecies maritimum. The cultivated form, which produces the swollen taproot that is eaten as beetroot, is subspecies vulgaris, which can sometimes also be found growing wild along coasts.

Sea Beet

Above: Sea Beet growing in a different location (on a sea wall). The seaside plant is usually subspecies maritima, though the form cultivated for its root, subspecies vulgaris occurs along coasts as well.

Golden Samphire (Inula crithmoides): Asteraceae

Inula crithmoides

Golden Samphire (family: Asteraceae) is found on the upper drier banks of salt marshes (and also on shingle beaches and sea cliffs). Note the fleshy leaves: an adaptation to salty habitats.

Inula crithmoides

The picture below was taken on a coastal promenade rather than a salt marsh; the lilac flowers of Rock Sea-lavendar (Limonium binervosum agg., Plumbaginaceae: the Sea-lavendar family) can also be seen interspersed with the Golden Samphire:

Inula crithmoides


Seaweeds of Salt Marshes

At the base of runnels in the lower salt marsh seaweeds are also to be found, in particular the Bladder Wrack (Fucus vesiculosus) and the Knotted Wrack (Ascophyllum nodusum). Much of the soil on the bottom and sides of the runnels is stained green. Microscopical examination revealed that this was due to an unidentified filamentous green alga, forming chains of cells or filaments one-cell thick, and numerous filaments of blue-green cyanobacteria of the Oscillatoria type (actually prokaryotes). A sample of this green-tinged soil, about 1 square cm and only a few millimeters thick also contained about 30 aquatic oligochaete annelids (Tubificids) each about 1 cm long. This is a phenomenal density, the entire sample of surface soil was a living matrix!

Cyanobacteria

Above: Oscilatoria type cyanobacteria from the bottom of a salt marsh runnel.


Exercise: How many plants can you identify below?

Click images to view full size.

salt marsh

salt marsh

salt marsh

salt marsh

salt marsh



Bibliography and Further Reading

Davy, A.J., G.F. Bishop, H. Mossman, S. Redondo-Gomez, J.M. Castillo, E.M. Castellanos, T. Luque and M.E. Figueroa, 2006. Biological Flora of the British Isles: Sarcocornia perennis (Miller) A.J. Scott. Journal of Ecology 94: 1035-1048.

Mozafar, A. and Goodin, J.R. 1970. Vesiculated Hairs: A Mechanism for Salt Tolerance in Atriplex halimus L. Plant Physiol. 45: 62-65.

Telenius, A. 1992. Seed heteromorphism in a population of
Spergularia media in relation to the
ambient vegetation density. Plant Biology 41: 305-318.

Telenius, A. and P. Torstensson, 1989. The seed dimorphism of of
Spergularia marina in relation to dispersal by wind and water. Oceologia 80: 206-210.


Article created: 13 Sep 2016

Article updated: 15 Sep 2018
Article updated: 14 Sep 2019 (determinations of glassworts revised)
Article updated: 2/11/2019
Article updated: 14/12/2019