13 Transport and Mixing in Coastal
Ecosystems
13.1 Introduction
The basic mechanisms for transport in the deep ocean and in coastal waters,
namely convection and diffusion, have been examined in Chap. 8. In this
chapter we will describe some examples illustrating the influence of transport
of organic and inorganic matter on the geomorphology and ecology of coastal
ecosystems, being under the constant influence of the adjacent ocean waters.
The rhythms of tides, severe storms and long-term climatic perturbations shape
the coasts. Sediment is continuously moving, being deposited in one place and
eroded in another, as the shoreline attempts to establish an equilibrium with
prevailing hydrodynamic conditions.
A unique and important part of the coastal aquatic environment are the
estuaries, where river flow meets the sea. These areas form the transition zone
between inland areas of freshwater and the sea water lying offshore. Regardless
of type, estuaries are characterized by the mixing of fresh and salt water. As we
showed in Chap. 8, estuarine circulation is complex, and includes a variety of
residual currents that depend on the relative mixing effects of river discharge
and tidal energy. Due to changing gradients in temperature, salinity, and
dissolved chemicals, and due to nutrients supplied by rivers, estuaries are able
to support a thriving and abundant biota.
The energy which enters the biosphere principally in the form of sunlight flows
through estuarine ecosystems, while the chemical constituents of organisms are
continually cycled among organisms, water, sediments and the atmosphere.
The exact nature of the chemical processes occurring in an estuary depends
on the quantity and kind of materials transported by the fresh and salt water
sources, the different chemical reactions that occur in fresh and salt water, and
the residence time of river water in the estuary (Ketchum, 1983; Day et al.,
1989) .
The transport of organic and inorganic matter in any coastal ecosystem is
primarily induced by the advection and diffusion mechanisms. In the next
S. R. Massel, Fluid Mechanics for Marine Ecologists
© Springer-Verlag Berlin Heidelberg 1999
Ecosystems
13.1 Introduction
The basic mechanisms for transport in the deep ocean and in coastal waters,
namely convection and diffusion, have been examined in Chap. 8. In this
chapter we will describe some examples illustrating the influence of transport
of organic and inorganic matter on the geomorphology and ecology of coastal
ecosystems, being under the constant influence of the adjacent ocean waters.
The rhythms of tides, severe storms and long-term climatic perturbations shape
the coasts. Sediment is continuously moving, being deposited in one place and
eroded in another, as the shoreline attempts to establish an equilibrium with
prevailing hydrodynamic conditions.
A unique and important part of the coastal aquatic environment are the
estuaries, where river flow meets the sea. These areas form the transition zone
between inland areas of freshwater and the sea water lying offshore. Regardless
of type, estuaries are characterized by the mixing of fresh and salt water. As we
showed in Chap. 8, estuarine circulation is complex, and includes a variety of
residual currents that depend on the relative mixing effects of river discharge
and tidal energy. Due to changing gradients in temperature, salinity, and
dissolved chemicals, and due to nutrients supplied by rivers, estuaries are able
to support a thriving and abundant biota.
The energy which enters the biosphere principally in the form of sunlight flows
through estuarine ecosystems, while the chemical constituents of organisms are
continually cycled among organisms, water, sediments and the atmosphere.
The exact nature of the chemical processes occurring in an estuary depends
on the quantity and kind of materials transported by the fresh and salt water
sources, the different chemical reactions that occur in fresh and salt water, and
the residence time of river water in the estuary (Ketchum, 1983; Day et al.,
1989) .
The transport of organic and inorganic matter in any coastal ecosystem is
primarily induced by the advection and diffusion mechanisms. In the next
S. R. Massel, Fluid Mechanics for Marine Ecologists
© Springer-Verlag Berlin Heidelberg 1999