46
:l Study Area
3.6.2
Lanice conchilega
In sandy tidal tlats of the Wadden Sea and in the ambient subtidal areas of the
North Sea, the tube building polychaete Lanice conchilega may reach a high abundance combined with high biomass values. In the East Frisian Wadden Sea the
highest abundance of 2800 ind m" was recorded from the Dornumer Nacken. In
the Spiekerooger backbarrier tidal tlats, on the Neuharlingersieler Nacken, a
maximum abundance of 1600 ind m' was observed, and at the Groninger Plate
150-1800 ind m'. The highest abundance ever reported in the literature was more
than 10 000 ind m' in a subtidal estuarine population (Buhr 1979).
In the intertidal area, L. conchilega preferentially occurs in sandy sediments and
feeds on suspended algae as well as detritus (Hartmann-Schroder 1996). In the
Wadden Sea, this species may reach an age of 1-2 years (Beukema et al. 1978).
As for other tube building polychaetes, it may be assumed that the tubes of
L. conchilega, protruding 2-3 cm from the sediment surface, strongly affect the
hydrodynamical regime in the benthic boundary layer and thus the distribution of
co-occurring biota (e.g. Eckman et al. 1981; Eckman 1985; Carey 1983, 1987).
During the pilot phase of ELA WAT, studies revealed that the aggregation of a
harpacticoid copepod was significantly correlated with the occurrence of
L. conchi/ega tubes (Pfeifer et al. 1996). More interactions with other taxa such as
meiofauna (nematodes) and macrofauna were investigated during the main phase
of ELA W A T (Chap. 5.5).
In summary, this polychaete species is an "ecosystem engineer" (sensu Jones et
al. 1994) and as such a central key to the understanding of the community dynamics in Lanice flats. ELA W AT results proved that L. conchilega does not build up a
characteristic association of its own, but enriches an Arenicola-dominated sandflat
association in abundance and species numbers due to a reduction of current velocities by its tubes (Zuhlke et al. 1998). Its effect on the ambient area varies with the
density of tubes, which itself is determined by recruitment success of L. conchilega
(reproduction and initial settlement) (Chaps. 5.3 and 5.4). In the long-term, the
population-dynamics of this cold sensitive species are determined by the frequency
of cold winters in the Wadden Sea. Directly after cold winters, L. conchilega can
no longer be observed in the intertidal. Onset of recovery of the intertidal parts of
the population will occur the next summer due to recruitment processes (Chap. 5.3;
Ziegelmeier 1964; Beukema et al. 1978). High standing stocks of L. conchilega in
the intertidal develop in periods of several successive mild winters (Beukema et al.
1978; Beukema 1992).
Acknowledgements
The data used in this chapter from ELA W AT are based on the studies by W.-E.
Arntz, Alexander Bartholoma, Brigitte Behrends, Carlo van Bernem, Dietrich
Blome, Monique Delafontaine, Burghard Flemming, Carmen-Pia Gunther, Gunther Hertweck, Jens Heuers, Sandra Jaklin, Ingrid Kroncke, Gerd Liebezeit, Jorn
Reichert, Gunther Sach and Ruth Zuhlke. We thank the reviewer for helpful comments on the manuscript. The project was funded by the German Bundesministe-
:l Study Area
3.6.2
Lanice conchilega
In sandy tidal tlats of the Wadden Sea and in the ambient subtidal areas of the
North Sea, the tube building polychaete Lanice conchilega may reach a high abundance combined with high biomass values. In the East Frisian Wadden Sea the
highest abundance of 2800 ind m" was recorded from the Dornumer Nacken. In
the Spiekerooger backbarrier tidal tlats, on the Neuharlingersieler Nacken, a
maximum abundance of 1600 ind m' was observed, and at the Groninger Plate
150-1800 ind m'. The highest abundance ever reported in the literature was more
than 10 000 ind m' in a subtidal estuarine population (Buhr 1979).
In the intertidal area, L. conchilega preferentially occurs in sandy sediments and
feeds on suspended algae as well as detritus (Hartmann-Schroder 1996). In the
Wadden Sea, this species may reach an age of 1-2 years (Beukema et al. 1978).
As for other tube building polychaetes, it may be assumed that the tubes of
L. conchilega, protruding 2-3 cm from the sediment surface, strongly affect the
hydrodynamical regime in the benthic boundary layer and thus the distribution of
co-occurring biota (e.g. Eckman et al. 1981; Eckman 1985; Carey 1983, 1987).
During the pilot phase of ELA WAT, studies revealed that the aggregation of a
harpacticoid copepod was significantly correlated with the occurrence of
L. conchi/ega tubes (Pfeifer et al. 1996). More interactions with other taxa such as
meiofauna (nematodes) and macrofauna were investigated during the main phase
of ELA W A T (Chap. 5.5).
In summary, this polychaete species is an "ecosystem engineer" (sensu Jones et
al. 1994) and as such a central key to the understanding of the community dynamics in Lanice flats. ELA W AT results proved that L. conchilega does not build up a
characteristic association of its own, but enriches an Arenicola-dominated sandflat
association in abundance and species numbers due to a reduction of current velocities by its tubes (Zuhlke et al. 1998). Its effect on the ambient area varies with the
density of tubes, which itself is determined by recruitment success of L. conchilega
(reproduction and initial settlement) (Chaps. 5.3 and 5.4). In the long-term, the
population-dynamics of this cold sensitive species are determined by the frequency
of cold winters in the Wadden Sea. Directly after cold winters, L. conchilega can
no longer be observed in the intertidal. Onset of recovery of the intertidal parts of
the population will occur the next summer due to recruitment processes (Chap. 5.3;
Ziegelmeier 1964; Beukema et al. 1978). High standing stocks of L. conchilega in
the intertidal develop in periods of several successive mild winters (Beukema et al.
1978; Beukema 1992).
Acknowledgements
The data used in this chapter from ELA W AT are based on the studies by W.-E.
Arntz, Alexander Bartholoma, Brigitte Behrends, Carlo van Bernem, Dietrich
Blome, Monique Delafontaine, Burghard Flemming, Carmen-Pia Gunther, Gunther Hertweck, Jens Heuers, Sandra Jaklin, Ingrid Kroncke, Gerd Liebezeit, Jorn
Reichert, Gunther Sach and Ruth Zuhlke. We thank the reviewer for helpful comments on the manuscript. The project was funded by the German Bundesministe-