Saltmarshes are areas of land which are regularly submerged in sea water. They found in sheltered bays and estuaries and are composed of a muddy substrate. Saltmarshes are typically found in temperate regions in the northern and southern hemispheres. Saltmarshes are divided up into different zones: pioneer, low, mid and high marsh. These zones are defined be the dominant species of plants that live there which, in turn, are usually restricted to each zone by the period of time they are inundated by seawater.
The plants which colonize saltmarshes are specially adapted to the live in salt water. Different species have different adaptations to deal with the environmental conditions. Salicornia (Glasswort, Pickle Weed or Samphire) has modified leaves which form bulbous structures on its stem that are less likely to be damaged than regular leaves. It can withstand being completely submerged for most of the day. Salicornia can range form green or red or purple in the colouration of it’s fleshly, segmented stem. It is usually small, less than 30 cm tall.
Salicornia europaea is found in Africa, Europe and North America. Within the saltmarsh it can be found in low marsh and in depressions, salt pans and open creek sides. It is an annual plant, flowering in August to October. It flowers in groups of three. Its leaves stick out as small protrusions from the main stem.
Salicornia europaea grows very differently depending on whether it comes from a population in the upper or lower marsh. In the lower marsh, S. europaea – and the rest of the lower marsh – is completely covered by sea water expect during neap tides. Lower marsh S. europaea grows at a linear rate through out May to August. Upper marsh S. europaea grows very slowly between May and June before growing rapidly during August. S. europaea from an upper marsh population which was transplanted to the lower marsh did not show a linear growth rate. It continued to grow slowly until August when the growth rate increased. S. europaea from a lower marsh population that was transplanted to the upper marsh continued to grow at a linear rate. However, the lower marsh S. europaea did not grow as well in the upper marsh. This indicates that the growth rates of the two populations are phenotypic variation. This means the growth rate of S. europaea is partly determined by specific alleles (DNA sequences).
Salicornia europaea seedlings germinate in late April to early May. The plants grow slowly until the middle of July. During this time of vegetative growth, a period when the saltmarsh is most likely to become hypersaline, additions of seawater or nitrogen salts do not inhibit or otherwise effect plant growth. The addition of nitrogen salts does, however, increase plant growth after flowering. This increase in growth is much more represented in plants from the upper marsh where growth increased by about 500%. Plants in the lower marsh only increased by about 30%. The massive increase in the upper mash S. europaea indicates that nitrogen is a limiting factor in its growth.
R. L. Jefferies, A. J. Davy, T. Rudmik (1981) Population Biology Of The Salt Marsh Annual Salicornia Europaea. Journal of Ecology, 69, 17-31 Available through: British Ecological Society website <http://www.britishecologicalsociety.org/documents/publications/journal_of_ecology/jefferies_virtual_issue/69_1_pp_17-31.pdf> [Accessed 18 October 2012]
McGraw, Dacid C.; Ungar Irwin A. (May, 1981) Growth and Survival of the Halophyte Salicornia Europaera L. Under Saline Field Conditions. The Ohio Journal of Science. v81, n3, 109-113 Available through: Knowledge Bank website <http://hdl.handle.net/1811/22776> [Accessed 18 October 2012]
Irwin A. Ungar, David K. Benner and David C. McGraw (April, 1979) The Distribution and Growth of Salicornia Europaea on an Inland Salt Pan. Ecology, Vol. 60, No. 2, pp. 329-336 Available through: JSTOR website <http://www.jstor.org/stable/1937662> [Accessed 18 October 2012]
W. G. Beeftink (20 June 1985) Population Dynamics of Annual Salicornia Species in the Tidal Salt Marshes of the Oosterschelde, the Netherlands. Vegetatio, Vol. 61, No. 1/3, pp. 127-136 Available through: JSTOR website <http://www.jstor.org/stable/20146240> [Accessed 18 October 2012
Joint Nature Conservation Committee. 1310 Salicornia and other annuals colonising mud and sand [online] Available at:<http://jncc.defra.gov.uk/protectedsites/sacselection/habitat.asp?FeatureIntCode=H1310> [Accessed 18 October 2012]