Marshes and mangrove swamps

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Marshes and mangrove swamps

Tidal marshes and mangrove swamps represent transitional regions between marine/brackish water and terrestrial environments. Tidl marshes occur in temperate areas, whereas the mangrove swamp is characteristic for tropics

Murray (1972) lists the following characteristics of these environments :

1. It is developed in the upper part of the intertidal zone
2. During much of each tidal cycle it is exposed to the atmosphere
3. It spends a smaller part of the tidal cycle submerged beneath sea or estuarine water
4. It is subject to the more dramatic fluctuations in temperature of the atmosphere
5. Fresh water is periodically introduced from rain showers
6. There is usually high organic productivity by the marsh plants and microflora
7. The fauna comprises few permanent indigenous species although migratory terrestrial animals are sometimes common

Tidal marshes can be subdivided in three groups according to salinity;

1. Hyposalina marshes
2. Normal marine marshes
3. Hypersaline marshes

Species diversity is highest in hyposaline marshes, although the general diversity is low.

The hyposaline marshes are characterized by the predominance of arenaceous species (Miliammina sp., Ammotium sp., Trochammina inflate) and rotaliids ( Elphidium spp.) and the absence of miliolids

Normal marine marshes are inhabited by dominantly arenaceous species with minor miliolieds and rotaliids.

In hypersaline marshes the percentage of arenaceous species, miliolids and rotaliids is about equal.

Typical cosmopolitan marsh species are:

- Ammotium salsum

- Arenoparrella Mexicana

- Miliammina fusca

- Taclammina macrescens

Interpreting an ancient marsh environment may be difficult. Due to reducing conditions calcareous test are easily destroyed after death. After complete solution of calcareous species, it is impossible to distinguish between the various marsh environments. Only the low diversity and an assemblage consisting of small arenaceous species such as Trochammina sp.. Haplophragmoides sp., Ammobaculites sp. points to a marsh origin. If Miliammina sp is present in this assemblage, a hyposaline lagoon could also be indicated.

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