Seagrass (Zostera marina L.) bed recolonisation after anoxia-induced full mortality

Recolonisation of Zostera marina, following complete destruction caused by an anoxic crisis, was studied in the Than lagoon (French Mediterranean Sea) from February 1998 to September 1999. The recolonisation took place surprisingly rapidly as biomasses similar to those from untouched areas were reached only nine months after seed germination. The recolonisation success was partly due to a high seedling survival rate as well as a rapid vegetative recruitment (ranging from 0.012 to 0.042 per day). Two phases of recovery could be observed: a rapid multiplication of shoots during the first 3 months was followed by an increase in biomass due to elongation of leaves. During the first year of recolonisation no flowering shoot was observed whilst reproductive effort was considerable during the second year. In case of two consecutive anoxic crises at the same site, the recovery would have probably been much slower, since the annual seedbank would have been depleted. (C) 2003 Elsevier B.V. All rights reserved.