SUFFOCATION OF A LITTORAL ZOSTERA BED BY ENTEROMORPHA-RADIATA

A large (about 10 ha), mixed bed of the seagrasses Zostera marina L. (narrow morph) and Zostera noltii Hornem. on the intertidal flats of Langstone Harbour, Hayling Island (Hampshire, UK), has been monitored annually since 1986. No noticeable changes took place in the period 1986-1990. In September 1991 this seagrass bed appeared to be largely destroyed by a thick blanket of the chlorophyte Enteromorpha radiata J. Apadh; most still living Zostera plants were in a bad condition. In August 1992 not a single specimen of Zostera was found growing in the area.