5.S BIOtiC Interactions in a Lal1icc-Tldal Flat
161
decline of M. lunulata after the die-off of Lanice following an extremely cold
winter in the Dutch Wadden Sea.
The empty Lanice tubes still present after the ice winter 1995/96 had no effect
on the benthos. But six weeks after the recolonization of Lanice in the tidal fiats in
summer 1996, increased benthos abundances were recorded, showing a high elasticity of this distribution pattern. The colony-forming diatom Amphipleura rutilans
and green algae were frequent that summer on sites where Lanice had settled and
on the artificial tube fields. Both probably facilitated the settlement of juvenile
bivalves and polychaetes (Dauer et al. 1982).
The benthic colonization of Lanice-patches can be active (Armonies 1994) or
passive (Eckman 1979). A passive accumulation was confirmed by the experiments using artificial tubes. The effect of small-scale topography as such on benthos distributions was shown by the higher benthos abundances in mounds with or
without Lanice compared to depressions. The biogenic structure of the worm tubes
can reduce current velocities near the sediment surface and thus create favourable
hydrodynamic conditions for the settlement of larvae as well as dispersing macroand meiobenthic organisms (see also Chap. 5.3 and 5.4). Positive correlations
between the structural complexity of worm tubes and meiofauna distributions were
found by Bell (1985) and Sach & van Bernem (1996). Mangrove-derived tannins
(Alongi 1987) and other natural bromophenol sources (Steward et al. 1992) can
have inhibitory effects on associated benthic nematodes. No such effect was demonstrated for bromophenols potentially leaching from Lanice tubes (Goerke &
Weber 1990).
The higher densities of infaunal predators in Lanice-patches could be a response to the higher meio- and macrobenthic densities at these sites (Zuhlke et al.
1998). While previous studies discussed the increased benthos abundances in natural and artificial tube fields as a result of a reduced rate of epibenthic predation or
an increase of shelter (Woodin 1978; Dauer et al. 1982), the studies in ELA W AT
indicate more complex mechanisms. The association of benthic organisms to
polychaete tubes also varies over time (Bell & Woodin 1984). The interactions and
trophic relations between Lanice and its associated fauna should thus be studied
further.
Acknowledgements
This chapter is based on the studies in ELA WAT by Hans-Peter Baumer, Carlo
van Bernem, Dietrich Blome, Michael Grotjahn, Hermann Michaelis, Roswitha
Keuker-Rudiger, Heidrun Ortleb, Dietmar Pfeifer, Georg Ramm, 10m Reichert,
Gunther Sach, Ulrike Schleier, lurgen Steuwer and Ruth Zuhlke. Their studies
were published as cited in the text, and further unpublished data were kindly provided by Dietrich Blome, Jorn Reichert, Jurgen Steuwer and Ruth Zuhlke. I thank
the reviewer for helpful comments on the manuscript. The project was funded by
the German Bundesministerium fUr Bildung, Wissenschaft, Forschung und Technologie (BMBF) under grant number 03FO 112 A and B. The responsibility for the
contents of the publication rests with the author.
161
decline of M. lunulata after the die-off of Lanice following an extremely cold
winter in the Dutch Wadden Sea.
The empty Lanice tubes still present after the ice winter 1995/96 had no effect
on the benthos. But six weeks after the recolonization of Lanice in the tidal fiats in
summer 1996, increased benthos abundances were recorded, showing a high elasticity of this distribution pattern. The colony-forming diatom Amphipleura rutilans
and green algae were frequent that summer on sites where Lanice had settled and
on the artificial tube fields. Both probably facilitated the settlement of juvenile
bivalves and polychaetes (Dauer et al. 1982).
The benthic colonization of Lanice-patches can be active (Armonies 1994) or
passive (Eckman 1979). A passive accumulation was confirmed by the experiments using artificial tubes. The effect of small-scale topography as such on benthos distributions was shown by the higher benthos abundances in mounds with or
without Lanice compared to depressions. The biogenic structure of the worm tubes
can reduce current velocities near the sediment surface and thus create favourable
hydrodynamic conditions for the settlement of larvae as well as dispersing macroand meiobenthic organisms (see also Chap. 5.3 and 5.4). Positive correlations
between the structural complexity of worm tubes and meiofauna distributions were
found by Bell (1985) and Sach & van Bernem (1996). Mangrove-derived tannins
(Alongi 1987) and other natural bromophenol sources (Steward et al. 1992) can
have inhibitory effects on associated benthic nematodes. No such effect was demonstrated for bromophenols potentially leaching from Lanice tubes (Goerke &
Weber 1990).
The higher densities of infaunal predators in Lanice-patches could be a response to the higher meio- and macrobenthic densities at these sites (Zuhlke et al.
1998). While previous studies discussed the increased benthos abundances in natural and artificial tube fields as a result of a reduced rate of epibenthic predation or
an increase of shelter (Woodin 1978; Dauer et al. 1982), the studies in ELA W AT
indicate more complex mechanisms. The association of benthic organisms to
polychaete tubes also varies over time (Bell & Woodin 1984). The interactions and
trophic relations between Lanice and its associated fauna should thus be studied
further.
Acknowledgements
This chapter is based on the studies in ELA WAT by Hans-Peter Baumer, Carlo
van Bernem, Dietrich Blome, Michael Grotjahn, Hermann Michaelis, Roswitha
Keuker-Rudiger, Heidrun Ortleb, Dietmar Pfeifer, Georg Ramm, 10m Reichert,
Gunther Sach, Ulrike Schleier, lurgen Steuwer and Ruth Zuhlke. Their studies
were published as cited in the text, and further unpublished data were kindly provided by Dietrich Blome, Jorn Reichert, Jurgen Steuwer and Ruth Zuhlke. I thank
the reviewer for helpful comments on the manuscript. The project was funded by
the German Bundesministerium fUr Bildung, Wissenschaft, Forschung und Technologie (BMBF) under grant number 03FO 112 A and B. The responsibility for the
contents of the publication rests with the author.