18S
6 RccololllZ
Temporal Development of Recolonization
Diatoms were the first organisms to recolonize the disturbed plots. Individuals of
some species survived the defaunation treatment. A similar rapid colonization
within days was recorded by Davis & Lee (1983). Diatoms can be transported by
resuspension in the water column (Baillie & Welsh 1980; Chap. 5.1). Although the
sediment traps implanted at the study site on the Groninger Plate contained mainly
mobile diatoms, colony-forming and sessile species were first to colonize the
disturbed plots. These diatoms were probably transported with lateral sediment
movement. The composition of the diatom assemblage developing in the disturbed
plots depended on the diatoms present in the ambient sediments at the moment of
recolonization.
The rapid colonization of diatoms provided a food source for the subsequent
recolonization by other benthic organisms (Davis & Lee 1983; Reise 1992).
Among the nematodes. who also appeared in the disturbed plots within a few days
and weeks, diatom-feeding species (e.g. Atrochromadora microlaima, innocuonema tentahundum, Paracanthonchus caecus, Chromadoropsis vivipara, Daptonema
normandicum, Daptonema setosum) made up the majority of the first colonizers.
Meiofauna is known to react actively to diatom (Lee et al. 1977) and bacteria
aggregations in the sediment (Thistle 1981; Rieper 1982). The availability of resources can be more decisive for recolonization than dispersal abilities (Fegley
198R). Both emergence and drift as well as passive lateral transport are important
mechanisms for meiofauna recolonization (Bell & Sherman 1980; Sherman &
Coull 1980; Hagerman & Rieger 19R I; Palmer & Brandt 1981; Palmer 1988;
Armonies 1994). The rapid colonization by ostracods could have been an indication for bedload transport in the area.
The first macrofauna organisms recorded in the disturbed plots belonged to
several feeding modes. The most abundant colonizer, Pygospio elegam, has a
versatile feeding strategy (Fauchald &Jumars 1979). Polychaetes proved to be
early recolonizers in many investigations, as they are mobile and often enough
opportunistic (Grass Ie & Grassle 1974; Simon & Dauer 1977; Smith & Brumsickle 1989; Thrush et al. 1996). The settlement of suspension-feeding polychaetes
can be facilitated by the mucus production of microbes and meiofauna (Probert
1984). Furthermore. the developing tube-lawns of spionids can solidify the sediment and thus affect the further recolonization (Probert 1984; Thrush et al. 1996).
Thus, the recruitment success of P. elegans in the experimental plots could have
affected the course of recolonization by other infauna, yet its density did not reach
that of tube-lawns reported in the literature cited above. P. elegam was also the
most dominant small macrobenthic organism in ambient sediments and its abundance in the experimental treatments caused the quick similarity between abundances of disturbed and control plots.
The amphipod Urothoe poseidonis was also among the first colonizers in the
disturbed plots. This species is very mobile and was often recorded in driftnets on
the ambient sandtlats (Steuwer & Heuers, pers. comm). Next to polychaetes, amphipods have been recorded as early colonizers in other investigations (Bess &
Devlin 1993; Thrush et al. 1996). Their colonizing potential depends on their dis-
6 RccololllZ
Temporal Development of Recolonization
Diatoms were the first organisms to recolonize the disturbed plots. Individuals of
some species survived the defaunation treatment. A similar rapid colonization
within days was recorded by Davis & Lee (1983). Diatoms can be transported by
resuspension in the water column (Baillie & Welsh 1980; Chap. 5.1). Although the
sediment traps implanted at the study site on the Groninger Plate contained mainly
mobile diatoms, colony-forming and sessile species were first to colonize the
disturbed plots. These diatoms were probably transported with lateral sediment
movement. The composition of the diatom assemblage developing in the disturbed
plots depended on the diatoms present in the ambient sediments at the moment of
recolonization.
The rapid colonization of diatoms provided a food source for the subsequent
recolonization by other benthic organisms (Davis & Lee 1983; Reise 1992).
Among the nematodes. who also appeared in the disturbed plots within a few days
and weeks, diatom-feeding species (e.g. Atrochromadora microlaima, innocuonema tentahundum, Paracanthonchus caecus, Chromadoropsis vivipara, Daptonema
normandicum, Daptonema setosum) made up the majority of the first colonizers.
Meiofauna is known to react actively to diatom (Lee et al. 1977) and bacteria
aggregations in the sediment (Thistle 1981; Rieper 1982). The availability of resources can be more decisive for recolonization than dispersal abilities (Fegley
198R). Both emergence and drift as well as passive lateral transport are important
mechanisms for meiofauna recolonization (Bell & Sherman 1980; Sherman &
Coull 1980; Hagerman & Rieger 19R I; Palmer & Brandt 1981; Palmer 1988;
Armonies 1994). The rapid colonization by ostracods could have been an indication for bedload transport in the area.
The first macrofauna organisms recorded in the disturbed plots belonged to
several feeding modes. The most abundant colonizer, Pygospio elegam, has a
versatile feeding strategy (Fauchald &Jumars 1979). Polychaetes proved to be
early recolonizers in many investigations, as they are mobile and often enough
opportunistic (Grass Ie & Grassle 1974; Simon & Dauer 1977; Smith & Brumsickle 1989; Thrush et al. 1996). The settlement of suspension-feeding polychaetes
can be facilitated by the mucus production of microbes and meiofauna (Probert
1984). Furthermore. the developing tube-lawns of spionids can solidify the sediment and thus affect the further recolonization (Probert 1984; Thrush et al. 1996).
Thus, the recruitment success of P. elegans in the experimental plots could have
affected the course of recolonization by other infauna, yet its density did not reach
that of tube-lawns reported in the literature cited above. P. elegam was also the
most dominant small macrobenthic organism in ambient sediments and its abundance in the experimental treatments caused the quick similarity between abundances of disturbed and control plots.
The amphipod Urothoe poseidonis was also among the first colonizers in the
disturbed plots. This species is very mobile and was often recorded in driftnets on
the ambient sandtlats (Steuwer & Heuers, pers. comm). Next to polychaetes, amphipods have been recorded as early colonizers in other investigations (Bess &
Devlin 1993; Thrush et al. 1996). Their colonizing potential depends on their dis-