Increasing species richness of the macrozoobenthic fauna on tidal flats of the Wadden Sea by local range expansion and invasion of exotic species

Table 1 Summary of contributions by various groups of species to long-term (1970–2009) changes in macrozoobenthic species richness on Balgzand, expressed in (changes of) mean number of species per site (n, per 0.95 m²)

N	Group	n	Species
4	Non-indigenous invaders	+~1.5 (Fig. 4b)	See Fig. 5
5	Local invaders	+~0.2 (Fig. 4b)	Crep, Gly, Lep, Ech, Oph ^a
10	Winter-sensitive	+~1.8 (Fig. 4a)	See Fig. 2
6	Upward trend	+~2.0 (Fig. 4c)	Lit, Ner spp., Ete, Uro, Gam, Bal^b
2	Downward trend	−~0.4 (Fig. 4c)	Mag, Scolel ^c
15	No trend, common	~0 (Fig. 4d)	^d
8	No trend, rare	~0 (Fig. 4d)	^e
50	All	+~5.1
Total (see Fig. 1b)	+5.2

N is the number of species allotted to each group
^a Crepidula fornicata, Glycera alba, Lepidochitona cinerea, Echinocardium cordatum, Ophiura ophiura
^bLittorina littorea, Nereis spp. (mostly Alitta succinea), Eteone spp., Urothoe poseidonis, Gammarus locusta, Balanoids (Balanus crenatus, Semibalanus balanoides, Austrominius modestus)
^c Magelona johnstoni, Scolelepis foliosa
^dMacoma balthica, Mya arenaria, Mytilus edulis, Scrobicularia plana, Hydrobia ulvae, Retusa obtusa, Phyllodoce sp. (mostly Ph. mucosa), Arenicola marina, Bylgides sarsi, Heteromastus filiformis, Hediste diversicolor, Scoloplos armiger, Bathyporeia sp., Corophium sp., Anthozoa (mostly Metridium senile and Sagartia troglodytes)
^eAbra alba, Petricola pholadiformis, Spisula subtruncata, Tellina (Angulus) fabula, Littorina obtusata, Pectinaria koreni, Neomysis/Praunus sp., Asterias rubens

ISSN: 1438-3888