7 Competitive Bioturbators on Intertidal Sand
Flats in the European Wadden Sea and Ariake
Sound in Japan
E. FLACH and A. TAMAKI
7.1 Introduction
Distribution patterns and changes in abundance of macrozoobenthic species
on intertidal sand flats have often been interpreted in terms of the physical
environment, such as tidal level, sediment composition and salinity. More
recently, however, biotic interactions have been recognised to be a significant
structuring force for intertidal sand flat communities (Reise 1985; Posey
1987). There are several kinds of biotic interactions (Arthur and Mitchell
1989). The most frequently studied is competition (mainly for food), a - -
interaction where there are effects on both species. The reverse of competition
is mutualism, in which both species profit from the interaction (+ +); this is,
however, not often observed on intertidal sand flats. The other often observed
interaction is predation, which is a + - interaction, termed contramensalism
by Arthur and Mitchell (1989). In this case, only one species benefits. In
addition to these interactions in which both species are influenced, there are
also interactions in which only one species is influenced. This could be either
commensalism (+ 0 interaction) or amensalism (- 0 interaction). For this
type of interaction the size of the animals often determines the outcome of
the interaction (Wilson 1981). An example of this is the mobility-mode
hypothesis of Posey (1987), which states that dense aggregations of large
organisms or those with strong sedimentary effects may exclude smaller
species through modifications related to their mobility type. In this chapter
we will concentrate on one type of these interactions, the either positive
and/or negative effects of two large bioturbating species on the benthic community at two intertidal sand flats on different sides of the world.
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001
Flats in the European Wadden Sea and Ariake
Sound in Japan
E. FLACH and A. TAMAKI
7.1 Introduction
Distribution patterns and changes in abundance of macrozoobenthic species
on intertidal sand flats have often been interpreted in terms of the physical
environment, such as tidal level, sediment composition and salinity. More
recently, however, biotic interactions have been recognised to be a significant
structuring force for intertidal sand flat communities (Reise 1985; Posey
1987). There are several kinds of biotic interactions (Arthur and Mitchell
1989). The most frequently studied is competition (mainly for food), a - -
interaction where there are effects on both species. The reverse of competition
is mutualism, in which both species profit from the interaction (+ +); this is,
however, not often observed on intertidal sand flats. The other often observed
interaction is predation, which is a + - interaction, termed contramensalism
by Arthur and Mitchell (1989). In this case, only one species benefits. In
addition to these interactions in which both species are influenced, there are
also interactions in which only one species is influenced. This could be either
commensalism (+ 0 interaction) or amensalism (- 0 interaction). For this
type of interaction the size of the animals often determines the outcome of
the interaction (Wilson 1981). An example of this is the mobility-mode
hypothesis of Posey (1987), which states that dense aggregations of large
organisms or those with strong sedimentary effects may exclude smaller
species through modifications related to their mobility type. In this chapter
we will concentrate on one type of these interactions, the either positive
and/or negative effects of two large bioturbating species on the benthic community at two intertidal sand flats on different sides of the world.
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001