284
S. Dittmann and J.A. Vargas
higher in some, but not all of the studied tropical tidal flats compared with
their temperate counterparts, which agrees with a concept by Alongi (1989).
Low macrobenthic abundances in tropical tidal flats support a previous comparison by Reise (1991). Species composition and abundances were sitespecific and varied as much within the tropics as between latitudes.
13.4 Community Structure and Distribution
13.4.1 Spatial Zonation Along Environmental Gradients
The macro- and megafauna occur in several distinct assemblages throughout
tropical tidal flats in Australia (Dittmann 1995). These distribution patterns
are related to environmental parameters and biotic interactions and are in
agreement with zoned distributions found for benthic fauna in temperate
tidal flats (Dittmann 2000). The spatial distribution of life forms and benthic
assemblages is less well known from Central America. Therefore, the comparison depicted in Fig. 13.4 remains preliminary until further tropical tidal
flats are surveyed with the same sampling design. So far there are indications
of some similarities in the spatial distributions of life forms, e. g. the occurrence of surface-deposit-feeding tube-worms in the mid-intertidal muddy
sandflats and sand dollars and hermit crabs in the lower intertidal sandflats.
Brachiopods occur in the mid-intertidal: Glottidia audebarti at Cocorocas,
Costa Rica, and Lingula anatina in Hinchinbrook Channel, Australia.
Furthermore, there are site-specific variations in habitat ranges of benthic
organisms that partly result from varying habitat diversities in each tidal flat.
Macnae and Kalk (1962) have already pointed out that the predominance of
benthic associations is related to the extent of their habitat.
While no temporal variation in spatial zonations and community composition was found by Dittmann (2000) in an Australian tidal flat, Vargas (1988,
1989) recorded within-site differences in community composition over time.
These were mainly due to the varying abundances of the single species
described above.
13.4.2 Trophic Groups
In most tidal flats studied in Central America and Australia, about two-thirds
of the macrobenthic organisms were deposit feeders (Fig. 13.5). A distinction
between surface- and subsurface-deposit-feeders showed that surfacedeposit-feeders were more abundant in the Haughton estuary and the
S. Dittmann and J.A. Vargas
higher in some, but not all of the studied tropical tidal flats compared with
their temperate counterparts, which agrees with a concept by Alongi (1989).
Low macrobenthic abundances in tropical tidal flats support a previous comparison by Reise (1991). Species composition and abundances were sitespecific and varied as much within the tropics as between latitudes.
13.4 Community Structure and Distribution
13.4.1 Spatial Zonation Along Environmental Gradients
The macro- and megafauna occur in several distinct assemblages throughout
tropical tidal flats in Australia (Dittmann 1995). These distribution patterns
are related to environmental parameters and biotic interactions and are in
agreement with zoned distributions found for benthic fauna in temperate
tidal flats (Dittmann 2000). The spatial distribution of life forms and benthic
assemblages is less well known from Central America. Therefore, the comparison depicted in Fig. 13.4 remains preliminary until further tropical tidal
flats are surveyed with the same sampling design. So far there are indications
of some similarities in the spatial distributions of life forms, e. g. the occurrence of surface-deposit-feeding tube-worms in the mid-intertidal muddy
sandflats and sand dollars and hermit crabs in the lower intertidal sandflats.
Brachiopods occur in the mid-intertidal: Glottidia audebarti at Cocorocas,
Costa Rica, and Lingula anatina in Hinchinbrook Channel, Australia.
Furthermore, there are site-specific variations in habitat ranges of benthic
organisms that partly result from varying habitat diversities in each tidal flat.
Macnae and Kalk (1962) have already pointed out that the predominance of
benthic associations is related to the extent of their habitat.
While no temporal variation in spatial zonations and community composition was found by Dittmann (2000) in an Australian tidal flat, Vargas (1988,
1989) recorded within-site differences in community composition over time.
These were mainly due to the varying abundances of the single species
described above.
13.4.2 Trophic Groups
In most tidal flats studied in Central America and Australia, about two-thirds
of the macrobenthic organisms were deposit feeders (Fig. 13.5). A distinction
between surface- and subsurface-deposit-feeders showed that surfacedeposit-feeders were more abundant in the Haughton estuary and the