Synthesis: Comparative Ecology
of Sedimentary Shores
K. REISE
In the biota of sedimentary shores a few dominant species often manage to
transform the coastal ecotone. Examples are the reefs or beds of suspension
feeders, seagrass beds and algal mats. Dominant bioturbating worms, crabs
and sometimes vertebrates may modify topography, hydrodynamics, sediment properties, and alter the habitat structure and nutrient cycling. The rest
of the species are relegated to niches positioned relative to these dominants.
Trophic pathways are short, usually in three steps from micro algae to invertebrates to fish or birds.
Suspension Feeders
Suspension feeders tend to aggregate in dense patches, beds or reefs on sedimentary shores and dominate the benthic fauna (Dame et aI., Chap. O. These
suspension feeders sit smugly in the sediment and are served all their lives by
the tidal waters once their pelagic dispersal stages have settled among conspecifics. Currents and waves import food, oxygen and competent larvae and
disperse waste and propagules. Suspension feeders take advantage of the
shallow coastal conditions where the phytoplankton of the photic zone
approaches the bottom and benthic micro algae are stirred up in mixed water
masses. By stretching out above the bottom, by being epibenthic or by generating hummocks or reefs, the aggregated suspension feeders themselves
enhance turbulent mixing. On a small scale and moderate density, this
positive effect of crowding on the food supply may outweigh competition for
food, at least along the edges of suspension-feeder patches (Green et aI.1998).
Where the exchange rates of water masses between nearshore and offshore
are low, as in estuaries and lagoons, suspension feeders significantly graze
down phytoplankton with cascading effects on the pelagic food web. By
facilitating the quick remineralization of nutrients, there is also a positive
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001
of Sedimentary Shores
K. REISE
In the biota of sedimentary shores a few dominant species often manage to
transform the coastal ecotone. Examples are the reefs or beds of suspension
feeders, seagrass beds and algal mats. Dominant bioturbating worms, crabs
and sometimes vertebrates may modify topography, hydrodynamics, sediment properties, and alter the habitat structure and nutrient cycling. The rest
of the species are relegated to niches positioned relative to these dominants.
Trophic pathways are short, usually in three steps from micro algae to invertebrates to fish or birds.
Suspension Feeders
Suspension feeders tend to aggregate in dense patches, beds or reefs on sedimentary shores and dominate the benthic fauna (Dame et aI., Chap. O. These
suspension feeders sit smugly in the sediment and are served all their lives by
the tidal waters once their pelagic dispersal stages have settled among conspecifics. Currents and waves import food, oxygen and competent larvae and
disperse waste and propagules. Suspension feeders take advantage of the
shallow coastal conditions where the phytoplankton of the photic zone
approaches the bottom and benthic micro algae are stirred up in mixed water
masses. By stretching out above the bottom, by being epibenthic or by generating hummocks or reefs, the aggregated suspension feeders themselves
enhance turbulent mixing. On a small scale and moderate density, this
positive effect of crowding on the food supply may outweigh competition for
food, at least along the edges of suspension-feeder patches (Green et aI.1998).
Where the exchange rates of water masses between nearshore and offshore
are low, as in estuaries and lagoons, suspension feeders significantly graze
down phytoplankton with cascading effects on the pelagic food web. By
facilitating the quick remineralization of nutrients, there is also a positive
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001