Development of benthic macrofauna

In total, 20 taxa were determined in the 16 samples, 10 taxa belonging to the Annelida, 5 to Arthropoda and, 4 to Mollusca, and 1 to Nemertea. On average, 10,1 ± 0,8 taxa per station were observed. The most common species was the mud shrimp Corophium volutator, observed in all 16 stations (Table 6). Other common species included the polychaetes Polydora cornuta and Pygospio elegans, the bivalve Macoma balthica and Nemertea and Oligochaeta. The total average density was 14990 ± 2890 ind.m^-2, with Corophium volutator (13083 ± 2113 ind.m^-2) by far the most dominant species in terms of density (see table 1).

Table 1: Observed species/taxon in Perkpolder with their occurrence (% of the 16 samples observed) and the average density of each species/taxon observed.
Species/taxon	Occurrence %	Density ± SE (ind.m^-2)
Corophium volutator	100	13083 ± 2113
Polydora cornuta	94	584 ± 134
NEMERTEA	88	85 ± 15
OLIGOCHAETA	88	586 ± 259
Macoma balthica	81	130 ± 31
Pygospio elegans	81	127 ± 41
Eteone longa	56	45 ± 12
Aphelochaeta sp	50	34 ± 12
Alitta succinea	50	80 ± 33
Crangon crangon	44	29 ± 11
Hypereteone foliosa	44	37 ± 12
Streblospio shrubsolii	44	34 ± 13
Heteromastus filiformis	38	29 ± 13
Peringia ulvae	38	16 ± 5
Chironomus salinarius	31	19 ± 8
Cyathura carinata	31	40 ± 18
NUDIBRANCHIA	19	8 ± 4
INSECTA	13	13 ± 11
Hediste diversicolor	13	5 ± 4
Scrobicularia plana	6	5 ± 5

Figure 1: Relation between the sedimentation and the total density of the benthic macrofauna observed at each station (Boersema et al. 2016).

A relation was observed between the amount of sedimentation and the total density of the benthic macrofauna, with higher densities observed at higher sedimentation rates (figure 1).

Conclusion

A fast recovery of the benthic macrofauna was observed in Perkpolder. Already five to six months after breaching the dike, twenty benthic taxa were observed in the area, based on a sampling of 16 stations. Also the densities reach high values, especially for the mud shrimp Corophium volutator, a common species for this part of the Western Scheldt This fast recovery is most likely due to the fast sedimentation of fine sediments into the Perkpolder area, forming a fresh new layer of estuarine sediment in which the benthic macrofauna can settle.

Referenties

Perkpolder tidal restauration, one year after realisation, draft progress report, Boersema, M., J. van der werf, P. de Louw, T. Ysebaert, T. Bouma, Centre of expertise Delta Technology, 27 november 2016.

Development of benthic macrofauna

Conclusion

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