Observations of a mass occurrence of Macoma balthica larvae in midsummer

In 1995 the seasonal development of concentrations of both phytoplankton and larvae of the bivalve Macoma balthica was studied in the coastal zone behind the back-barrier island of Spiekeroog (German Wadden Sea). In July/August larvae reached maximum concentrations of about 1000 to 4200 ind. m⁻³ (depending on the sampling site and tidal period), probably in relation to a phytoplankton bloom in July. This observation of an unusually late maximum of Macoma larvae is discussed in detail in connection with the recent literature available about spawning of M. balthica in the Wadden Sea.