Values, Alterations and Degradation of the Natural Landscape 99
An estuary is a semi-closed marine system, as a river mouth in an
oblong bay, where salinity assumes intermediate values and the action of
the tide plays an important role in the regulation of natural parameters
and in the energy supply to the system. Primary production is high and is
due to three categories of organisms: phytoplankton, benthic microflora
and aquatic plants. Thus, favourable conditions for the development of
abundant consumer organisms both in the estuary and the neighbouring
ecosystems are created.
5.3.2 Freshwater Ecosystems
5.3.2.1 Water Course
Lotic ecosystems include big and small rivers, creeks and intermittent
streams. From an ecological point of view, they belong to two categories:
sections of rivers that erode the banks and the bottom, and those that
deposit sediments and therefore have a muddy bottom. A river can generally be divided in three parts: the sections of tributaries near the springs,
where the water is clear and the concentration of nutrients is low, the intermediate sections where biodiversity and photosynthesis are greater, and
the section near the mouth where flow is slow and transparency is low, at
least in big rivers. The lotic ecosystem usually has a lot of particularities
and its various uses by man, such as water supply, waste disposal, energy
production, piscatorial production and flood control can have destructive
consequences and need careful multidisciplinary study.
5.3.2.2 Lake
Lakes are collections of stagnant freshwater or, more rarely, salt water
inside the boundaries of continents. A lake is directly dependent on its
drainage basin; specifically it is dependent on the size, geology, erodibility,
topography, land uses, vegetation cover etc. of its watershed. The chemical
status of a lake depends on the climatic, hydrological and geological conditions as well as the pollution of the drainage basin, in conjunction with the
biological condition of the water ecosystem, which is connected with the
concentrations of dissolved oxygen and nutrients, transparency, primary
production, presence of higher predators etc.
5.3.2.3 Wetland
Wetlands’ ecosystems include marshes, relatively shallow lakes, lagoons and
other coastal aquatic systems, as well as riparian or hygrophilous forests.
Their productivity is generally high, as in the case, for example, of estuaries.
The hydrological function is a determinant for all wetland systems.
An estuary is a semi-closed marine system, as a river mouth in an
oblong bay, where salinity assumes intermediate values and the action of
the tide plays an important role in the regulation of natural parameters
and in the energy supply to the system. Primary production is high and is
due to three categories of organisms: phytoplankton, benthic microflora
and aquatic plants. Thus, favourable conditions for the development of
abundant consumer organisms both in the estuary and the neighbouring
ecosystems are created.
5.3.2 Freshwater Ecosystems
5.3.2.1 Water Course
Lotic ecosystems include big and small rivers, creeks and intermittent
streams. From an ecological point of view, they belong to two categories:
sections of rivers that erode the banks and the bottom, and those that
deposit sediments and therefore have a muddy bottom. A river can generally be divided in three parts: the sections of tributaries near the springs,
where the water is clear and the concentration of nutrients is low, the intermediate sections where biodiversity and photosynthesis are greater, and
the section near the mouth where flow is slow and transparency is low, at
least in big rivers. The lotic ecosystem usually has a lot of particularities
and its various uses by man, such as water supply, waste disposal, energy
production, piscatorial production and flood control can have destructive
consequences and need careful multidisciplinary study.
5.3.2.2 Lake
Lakes are collections of stagnant freshwater or, more rarely, salt water
inside the boundaries of continents. A lake is directly dependent on its
drainage basin; specifically it is dependent on the size, geology, erodibility,
topography, land uses, vegetation cover etc. of its watershed. The chemical
status of a lake depends on the climatic, hydrological and geological conditions as well as the pollution of the drainage basin, in conjunction with the
biological condition of the water ecosystem, which is connected with the
concentrations of dissolved oxygen and nutrients, transparency, primary
production, presence of higher predators etc.
5.3.2.3 Wetland
Wetlands’ ecosystems include marshes, relatively shallow lakes, lagoons and
other coastal aquatic systems, as well as riparian or hygrophilous forests.
Their productivity is generally high, as in the case, for example, of estuaries.
The hydrological function is a determinant for all wetland systems.