The bivalve lives buried below the surface, maintaining contact with the overlying water by means of the inhalant and exhalant siphons (Brafield & Newell, 1961; Fish & Fish, 1989). M. balthica is capable of deposit as well as suspension feeding (Brafield & Newell, 1961; Wolff, 1973; Fish & Fish, 1989). M. balthica is able to withstand low winter temperatures. In the Dutch Wadden Sea its abundance increases after cold winters (Beukema, 1979; Beukema & Essink, 1986).


The species is an important prey item for birds such as the knot (Zwarts & Blomert, 1992; Zwarts et al., 1992). [details]

Description: A rather thick, broadly oval shell up to 30 mm long. The top of the shell is somewhere in the middle
of the shell. The back is slightly acuminate. The shell surface is smooth with very fine concentric
growth lines. Its colour varies: white, yellow, orange to reddish. They burrow shallowly in fine, muddy sand bottoms and feed on food particles located on top of the sediment that they manage to suck up by means of their very long, individually separated stretchable siphons. [details]

Dimensions: reaches 1.5 to 3.5 cm in size [details]

Distribution: M. balthica occurs from the upper part of the intertidal down to the shallow subtidal zone. In the study area it is confined to the Wadden Sea, the Delta estuaries and a narrow zone along the coast. It has not been recorded from depths over 25 m in the open North Sea. The highest biomasses are found along the Dutch coast and north of Ameland and Schiermonnikoog. [details]

Distribution: Arctic seas to off Georgia [details]

Distribution: Macoma balthica typically occurs in the coastal zone of the Belgian part of the North Sea. In the 1976-1986 period only low densities were observed (up to 10 ind./m2) whereas densities up to 170 ind./m2 were found in the 1994-2001 period. In this period the highest densities seemed to occur near the eastern coastal zone. [details]

Habitat: Macoma balthica tends to prefer very fine sediments (median grain size < 200 μm) with high mud contents (> 20%). The maximum relative occurrence (80%!) is reached in sediments with a median grain size of 0-50 μm and a mud content of 50-60%. [details]

Habitat: Known from the nearshore. [details]

Habitat: intertidal, bathyal, infralittoral and circalittoral of the Gulf and estuary [details]

Habitat: Known from seamounts and knolls [details]

Habitat: M. balthica occurs in muddy sediments with a preference for relatively high silt-clay percentages. [details]

Morphology: M. balthica has a broadly oval shell, somewhat inflated anteriorly. lt is up to 25 mm in length. The shell surface is smooth, sculptured with very fine concentric lines. The growth stages are clearly visible, usually marked by bands of colour. lt is very variable in colour, with shades of white, yellow, pink or purple, often drawn out in concentric bands. The interior of the shell is white or purple, or a shade of the external colour (Tebble, 1966; Fish & Fish, 1989; Hayward & Ryland, 1990). [details]

Reproduction: separate sexes, usually not dimorphic in shell structure; fertilization occurs within the mantle cavity anf young hatch as pelagic larvae (generalized for group) [details]

Spelling: often spelled M. baltica [details]