4
K.Reise
experimental artefacts. As a consequence, knowledge has advanced much
more slowly. However, apart from their spatial extent and being subjected to
many human impacts, sedimentary shores have a number of distinct features
that deserve study, and it should not be regarded as the Cinderella to a rocky
sister, the rugged beauty. Both shore types rely on food supplies from the sea,
and suspension feeders are often prominent. Light allows benthic plants to
develop in both shore types: kelp forms extensive stands on rocky coasts and
seagrasses are common on sedimentary shores. Rocks basically provide a
two-dimensional substrate, while sediments offer a third dimension in which
to live. In this third dimension organic material can be stored and is available
to deposit feeders. The third dimension also offers a buffer against the
physical harshness of the intertidal environment. The slope of sedimentary
shores tends to be gentler than that of rocky shores, so that the former has a
much wider areal extent, and thus provides more food to visiting shrimps, fish
and birds.
There are two key variables for the broad-scale comparison of biotic
richness of sedimentary shores. Firstly, the external supplies of nutrients and
organic material, mostly from the sea, but in estuaries also from the land.
Secondly, the morpho dynamics of the shore, determined by wave energy, the
tidal regime and the sediment particles available. The broad-scale composition of shore biota further depends on salinity, the temperature regime and
the biogeographic province.
Except for salinity, intermediate states of the above factors and their
combinations seem to be the most favorable for the biota of the sedimentary
shores. Too great an external food supply may result in anoxia, and too little
will exclude the suspension feeders. Strong hydrodynamic forces and a coarse
sediment grain render a sedimentary environment very unstable and only a
few species are capable of coping with this combination. In embayments and
the shallow subtidal these forces are often appreciably ameliorated by biogenic sediment stabilization. Shallow stagnant waters also require specialized
adaptations. Without flow there may be little buffer against the high physical
fluctuations of the surrounding terrestrial environment. Species richness of
the shore increases from high to low latitudes, and is highest in the Indo-West
Pacific province. On the other hand, benthic zoomass seems to be highest at
mid-latitudes, presumably because under conditions of pronounced seasonality more phytoplankton escapes the pelagic algivores and is left as food for
the zoobenthos (Ricciardi and Bourget 1999).
The ecological patterns and processes of almost all shores have been
modified by humans. The past and present imprint of human activities on the
shore biota not only has to be kept in mind when global comparisons are conducted, but in itself deserves comparative evaluation. On a global scale, the
physical changes resulting from land-use practices, planned and unplanned
coastal engineering have the most important effects. Often there is a habitat
K.Reise
experimental artefacts. As a consequence, knowledge has advanced much
more slowly. However, apart from their spatial extent and being subjected to
many human impacts, sedimentary shores have a number of distinct features
that deserve study, and it should not be regarded as the Cinderella to a rocky
sister, the rugged beauty. Both shore types rely on food supplies from the sea,
and suspension feeders are often prominent. Light allows benthic plants to
develop in both shore types: kelp forms extensive stands on rocky coasts and
seagrasses are common on sedimentary shores. Rocks basically provide a
two-dimensional substrate, while sediments offer a third dimension in which
to live. In this third dimension organic material can be stored and is available
to deposit feeders. The third dimension also offers a buffer against the
physical harshness of the intertidal environment. The slope of sedimentary
shores tends to be gentler than that of rocky shores, so that the former has a
much wider areal extent, and thus provides more food to visiting shrimps, fish
and birds.
There are two key variables for the broad-scale comparison of biotic
richness of sedimentary shores. Firstly, the external supplies of nutrients and
organic material, mostly from the sea, but in estuaries also from the land.
Secondly, the morpho dynamics of the shore, determined by wave energy, the
tidal regime and the sediment particles available. The broad-scale composition of shore biota further depends on salinity, the temperature regime and
the biogeographic province.
Except for salinity, intermediate states of the above factors and their
combinations seem to be the most favorable for the biota of the sedimentary
shores. Too great an external food supply may result in anoxia, and too little
will exclude the suspension feeders. Strong hydrodynamic forces and a coarse
sediment grain render a sedimentary environment very unstable and only a
few species are capable of coping with this combination. In embayments and
the shallow subtidal these forces are often appreciably ameliorated by biogenic sediment stabilization. Shallow stagnant waters also require specialized
adaptations. Without flow there may be little buffer against the high physical
fluctuations of the surrounding terrestrial environment. Species richness of
the shore increases from high to low latitudes, and is highest in the Indo-West
Pacific province. On the other hand, benthic zoomass seems to be highest at
mid-latitudes, presumably because under conditions of pronounced seasonality more phytoplankton escapes the pelagic algivores and is left as food for
the zoobenthos (Ricciardi and Bourget 1999).
The ecological patterns and processes of almost all shores have been
modified by humans. The past and present imprint of human activities on the
shore biota not only has to be kept in mind when global comparisons are conducted, but in itself deserves comparative evaluation. On a global scale, the
physical changes resulting from land-use practices, planned and unplanned
coastal engineering have the most important effects. Often there is a habitat