Environmental Engineering Reference
In-Depth Information
exchangeable Ca, K and Mg, total N and available P grouped together with minimum
difference in their nature. Soil organic carbon and soil organic matter was highly
correlated factors so that they are grouped together. Other factors like water salinity, soil
salinity and water transparency showed similar distribution pattern in the study area
which clustered together with minimum euclidean distance level.
I
NTRODUCTION
Salt marshes are defined as areas with alluvial sediments deposited on the shore by the
sea and subjected to tidal or weather effected inundation by more or less diluted sea water
(Beeftink, 1977). Coastal salt marsh areas vegetated by herbs, grasses, and low shrubs
bordering saline water bodies are unique ecosystems universally recognized for their
exceptional ecological value (Mitsch and Gosselink, 1993; Kent, 1994; Alongi, 1998; Eisma,
1998). These are not only rank among the most highly productive ecosystems on earth but
also provide critically important habitat for numerous aquatic and terrestrial organisms, many
of which are of significant commercial and recreational value. Salt marshes occur on
intertidal shores in mid and high latitude regions worldwide. They commonly flourish around
high tide level in sheltered coastal embayments of the temperate zone where wave energy,
tidal regime, and substrate conditions are favorable for their development (Chapman, 1974).
Within their geographical range, salt marshes are influenced by a array of local factors that
control their development, most notably tidal characteristics, surface drainage, pedological
conditions, sediment accretion, wave and current action, erosion, freshwater inflow, salinity,
nutrient concentrations, shoreline structure, and marsh topography (Clark and Patterson,
1985; Frey and Basan, 1985; Mitsch and Gosselink, 1993; Lewis, 1994; Eisma, 1998). Salt
marshes can develop in a variety of settings, provided the hydrology, sediment and biological
conditions are suitable. They usually form in coastal areas that are emerging or which are
stable relative to sea level. Salt marshes develop on intertidal mudflats that have developed
vertically to the point where the elevation of the mudflat surface equals or exceeds mean high
water level and which has consolidated enough to allow for the colonization of the mudflat
surface by salt-tolerant plants (Gonni and Thomas, 2000; Hatcher and Patriquin, 1981;
Nordstorm and Roman, 1996).
Intertidal saltmarshes are considered ecotones due to their positions between the
terrestrial and marine or estuarine ecosystems. In the saltmarshes, the environmental
conditions (e.g. tide, exposure time, temperature, salinity) are constantly changing. Due to the
constantly changing environment several factors may influence the habitat value of
saltmarshes for biotic communities (Hampel, 2003). However, several typical features
characterize the salt marshes. Hydrology is considered the single most important factor in the
development and functioning of saltmarshes (Mitsch and Gosselink, 1993; Reed, 1993). Salt
marshes are affected by both the above-ground and underground water regime. Tides and
rainfall affect the conditions above ground. The rainfall is an important factor as it inundates
enclosed depressions and influences the salinity of the surface soil. Tides influence the
zonation pattern of the vegetation in local or regional (Beeftink, 1977). The flow of water
within the salt marsh system influences the sedimentation, distribution of suspended
materials, flux rates of materials between the saltmarsh and the adjacent water, movement of
the biota and erosional processes (Vernberg, 1993; Rozas, 1995). The soil type influences the
