effects of inundation, evaporation, transpiration, and sediment types. The increasing salinity can be locally diluted
by freshwater seepage from the margin of the hinterland,
beaches, and spits and cheniers.
Estuarine tidal flat biota comprise plants, resident fauna,
invading and temporary fauna, and microbiota. At the overarching scale, biogeography and climate are major determinants of the composition of tidal flat biota. Tidal flat biota
includes mangroves and their associated fauna in tropical
and subtropical climates, and rushes, sedges, samphire,
and other saltmarsh plants and their associated fauna in
tropical, subtropical, and temperate climates. Mangrove
and saltmarsh emergent vegetation conspicuously exhibits
species zonation. A range of mollusc, crustacean, and polychaete fauna occurs in tidal flat habitats, the composition of
which is related to tidal zones, substrate type, substrate
moisture, and salinity, and commonly results in species
zonation. The resident fauna of tidal flats can be diverse
and complex in composition and its internal population
dynamics and ecological dynamics. It can be categorized
as epifauna, infauna, or alternating infauna/epifauna and
is biogeography specific, climate specific, and substrate
specific in composition and structure. The invading or temporary fauna of tidal flats are variable in terms of taxonomic
group; they include fish (including rays), crabs, reptiles,
and octopus that invade tidal flats on a high tide to feed;
birds, reptiles, and mammals that invade tidal flats on
a low tide to feed; and the birds that use the saltmarsh vegetation and mangrove canopy for a variety of activities.
A special resident fauna on tidal flats of mussels, or
oysters, or serpulid worms can form dense colonies
resulting in skeletal structures that cover tidal flats as
reefal biostromes or locally emerge as reefal bioherms.
Where hard surfaces are developed, encrusting organisms
and (micro-scaled) hard-surface communities of oysters,
hydrozoans, anthozoans, bryozoans, and algae can
develop.
Microbiota of tidal flats includes diatoms, foraminifera,
amoebae, bacteria, fungi, and small-scaled invertebrates
that are abundant in tidal flat sediments, often zonally distributed, and vertically mobile with the fluctuation of the
tide and groundwater of tidal flats. They are commonly
the food source for grazing and sediment foraging
invertebrates.
Ecologically, tidal flats are complex systems, even if
substrates appear relatively uniform (e.g., wholly muddy
tidal flats or wholly sandy tidal flats). Complexity is
underpinned by inundation gradients and salinity which
will determine zonation and hence microecology processes. Where substrates are graded, or where there is variable low-relief geomorphic expression, and where
freshwater is discharging into the tidal flat, the complexity
of tidal flats increases. Occurring in the coastal zone, as a -
low-gradient interface between ocean, land, atmosphere,
and groundwater, they support a diversity of biota and
a diversity of physical, chemical, and biological processes,
and they function as a storage system for living and
decaying biomass and for biochemical/geochemical
products. As coastal systems bridging the environments
of ocean and land and in estuarine settings bridging freshwater and marine water, tidal flats also provide
a multiplicity of ecological functions. As major zones of
primary and secondary productivity, they are important
food sources for marine and terrestrial animals.
On tidal flats, there is primary production carried out by
benthic plant life such as mangroves, saltmarsh vegetation,
seagrasses, algae, and diatoms and, during the high tide in
the water column, by phytoplankton. Plant biomass is
cycled though the ecosystem by herbivory and/or nectivory,
leaf litter fall, decay of plant matter, and filter feeding by
invertebrates. Following incorporation of biomass and
detritus by primary consumers, predators carry the biomass
into higher trophic levels. Tidal flats are major feeding
grounds for nekton and demersal fish on the high tide and
for reptiles, mammals, and avifauna on the low tide. Tidal
flats, and in particular mangroves, saltmarsh, and seagrass,
also provide nurseries and sanctuaries for fauna.
Bibliography
Able, K. W., 2005. A re-examination of fish estuarine dependence:
evidence for connectivity between estuarine and ocean habitats.
Estuarine, Coastal and Shelf Science, 64, 5–17.
Adam, P., 1990. Saltmarsh Ecology. Cambridge: Cambridge University Press.
Albrecht, A. S., 1998. Soft bottom versus hard rock: community
ecology of macro-algae on intertidal mussel beds in the Wadden
Sea. Journal of Experimental Marine Biology and Ecology, 229,
85–109.
Ambrose, W. G., 1984. Role of predatory infauna in structuring
marine soft-bottom communities. Marine Ecology Progress
Series, 17(2), 109–115.
Attrill, M. J., Stafford, R., and Rowden, A. A., 2001. Latitudinal
diversity patterns in estuarine tidal flats: indications of global
cline. Ecography, 24, 318–324.
Backwell, P. R. Y., O’Hara, P. D., and Christy, J. H., 1998. Prey
availability and selective foraging in shorebirds. Animal Behaviour, 55, 1659–1667.
Baker, R., and Sheaves, M., 2005. Redefining the piscivore assemblage of shallow estuarine nursery habitats. Marine Ecology Progress Series, 291, 197–213.
Baker, R., and Sheaves, M., 2007. Shallow-water refuge paradigm:
conflicting evidence from tethering experiments in a tropical
estuary. Marine Ecology Progress Series, 349, 13–22.
Bell, S., and Coull, B., 1978. Field evidence that shrimp predation
regulates meiofauna. Oecologia, 35, 141–148.
Beukema, J. J., 1976. Biomass and species richness of the macrobenthic animals living on the tidal flats of the Dutch Wadden
Sea. Netherlands Journal of Sea Research, 10, 236–261.
Beukema, J. J., 1981. The role of the larger invertebrates in the
Wadden Sea ecosystem. In Dankers, N., et al. (eds.), Invertebrates of the Wadden Sea. Rotterdam: A. A. Balkema,
pp. 211–221.
Beukema, J. J., 1992. Dynamics of juvenile shrimp Crangon
crangon in a tidal-flat nursery of the Wadden Sea after
mild and cold winters. Marine Ecology Progress Series, 83,
157–165.
Beukema, J. J., Essink, K., Michaelis, H., and Zwarts, L., 1993.
Year-to-year variability in the biomass of macrobenthic animals
on tidal flats of the Wadden Sea: How predictable is this food
source for birds? Journal of Sea Research, 31, 319–330.
TIDAL FLAT
675
by freshwater seepage from the margin of the hinterland,
beaches, and spits and cheniers.
Estuarine tidal flat biota comprise plants, resident fauna,
invading and temporary fauna, and microbiota. At the overarching scale, biogeography and climate are major determinants of the composition of tidal flat biota. Tidal flat biota
includes mangroves and their associated fauna in tropical
and subtropical climates, and rushes, sedges, samphire,
and other saltmarsh plants and their associated fauna in
tropical, subtropical, and temperate climates. Mangrove
and saltmarsh emergent vegetation conspicuously exhibits
species zonation. A range of mollusc, crustacean, and polychaete fauna occurs in tidal flat habitats, the composition of
which is related to tidal zones, substrate type, substrate
moisture, and salinity, and commonly results in species
zonation. The resident fauna of tidal flats can be diverse
and complex in composition and its internal population
dynamics and ecological dynamics. It can be categorized
as epifauna, infauna, or alternating infauna/epifauna and
is biogeography specific, climate specific, and substrate
specific in composition and structure. The invading or temporary fauna of tidal flats are variable in terms of taxonomic
group; they include fish (including rays), crabs, reptiles,
and octopus that invade tidal flats on a high tide to feed;
birds, reptiles, and mammals that invade tidal flats on
a low tide to feed; and the birds that use the saltmarsh vegetation and mangrove canopy for a variety of activities.
A special resident fauna on tidal flats of mussels, or
oysters, or serpulid worms can form dense colonies
resulting in skeletal structures that cover tidal flats as
reefal biostromes or locally emerge as reefal bioherms.
Where hard surfaces are developed, encrusting organisms
and (micro-scaled) hard-surface communities of oysters,
hydrozoans, anthozoans, bryozoans, and algae can
develop.
Microbiota of tidal flats includes diatoms, foraminifera,
amoebae, bacteria, fungi, and small-scaled invertebrates
that are abundant in tidal flat sediments, often zonally distributed, and vertically mobile with the fluctuation of the
tide and groundwater of tidal flats. They are commonly
the food source for grazing and sediment foraging
invertebrates.
Ecologically, tidal flats are complex systems, even if
substrates appear relatively uniform (e.g., wholly muddy
tidal flats or wholly sandy tidal flats). Complexity is
underpinned by inundation gradients and salinity which
will determine zonation and hence microecology processes. Where substrates are graded, or where there is variable low-relief geomorphic expression, and where
freshwater is discharging into the tidal flat, the complexity
of tidal flats increases. Occurring in the coastal zone, as a -
low-gradient interface between ocean, land, atmosphere,
and groundwater, they support a diversity of biota and
a diversity of physical, chemical, and biological processes,
and they function as a storage system for living and
decaying biomass and for biochemical/geochemical
products. As coastal systems bridging the environments
of ocean and land and in estuarine settings bridging freshwater and marine water, tidal flats also provide
a multiplicity of ecological functions. As major zones of
primary and secondary productivity, they are important
food sources for marine and terrestrial animals.
On tidal flats, there is primary production carried out by
benthic plant life such as mangroves, saltmarsh vegetation,
seagrasses, algae, and diatoms and, during the high tide in
the water column, by phytoplankton. Plant biomass is
cycled though the ecosystem by herbivory and/or nectivory,
leaf litter fall, decay of plant matter, and filter feeding by
invertebrates. Following incorporation of biomass and
detritus by primary consumers, predators carry the biomass
into higher trophic levels. Tidal flats are major feeding
grounds for nekton and demersal fish on the high tide and
for reptiles, mammals, and avifauna on the low tide. Tidal
flats, and in particular mangroves, saltmarsh, and seagrass,
also provide nurseries and sanctuaries for fauna.
Bibliography
Able, K. W., 2005. A re-examination of fish estuarine dependence:
evidence for connectivity between estuarine and ocean habitats.
Estuarine, Coastal and Shelf Science, 64, 5–17.
Adam, P., 1990. Saltmarsh Ecology. Cambridge: Cambridge University Press.
Albrecht, A. S., 1998. Soft bottom versus hard rock: community
ecology of macro-algae on intertidal mussel beds in the Wadden
Sea. Journal of Experimental Marine Biology and Ecology, 229,
85–109.
Ambrose, W. G., 1984. Role of predatory infauna in structuring
marine soft-bottom communities. Marine Ecology Progress
Series, 17(2), 109–115.
Attrill, M. J., Stafford, R., and Rowden, A. A., 2001. Latitudinal
diversity patterns in estuarine tidal flats: indications of global
cline. Ecography, 24, 318–324.
Backwell, P. R. Y., O’Hara, P. D., and Christy, J. H., 1998. Prey
availability and selective foraging in shorebirds. Animal Behaviour, 55, 1659–1667.
Baker, R., and Sheaves, M., 2005. Redefining the piscivore assemblage of shallow estuarine nursery habitats. Marine Ecology Progress Series, 291, 197–213.
Baker, R., and Sheaves, M., 2007. Shallow-water refuge paradigm:
conflicting evidence from tethering experiments in a tropical
estuary. Marine Ecology Progress Series, 349, 13–22.
Bell, S., and Coull, B., 1978. Field evidence that shrimp predation
regulates meiofauna. Oecologia, 35, 141–148.
Beukema, J. J., 1976. Biomass and species richness of the macrobenthic animals living on the tidal flats of the Dutch Wadden
Sea. Netherlands Journal of Sea Research, 10, 236–261.
Beukema, J. J., 1981. The role of the larger invertebrates in the
Wadden Sea ecosystem. In Dankers, N., et al. (eds.), Invertebrates of the Wadden Sea. Rotterdam: A. A. Balkema,
pp. 211–221.
Beukema, J. J., 1992. Dynamics of juvenile shrimp Crangon
crangon in a tidal-flat nursery of the Wadden Sea after
mild and cold winters. Marine Ecology Progress Series, 83,
157–165.
Beukema, J. J., Essink, K., Michaelis, H., and Zwarts, L., 1993.
Year-to-year variability in the biomass of macrobenthic animals
on tidal flats of the Wadden Sea: How predictable is this food
source for birds? Journal of Sea Research, 31, 319–330.
TIDAL FLAT
675