Long-term seagrass meadow monitoring near Perth, Western Australia

For 17 and 12 years, respectively, the density and diversity of seagrass co ver were described along two transects, 375 and 280 m long, in winter and s ummer in a temperate Western Australian seagrass meadow. The results indica ted that, of the nine species in five genera present, two genera were domin ant - Posidonia (four species) and Amphibolis (two species). Two minor spec ies, Heterozostera tasmanica and Halophila ovalis, generally increased in c over in summer and were sometimes washed out by winter storms. Posidonia me adows changed little in cover over the 17 years and in this time the positi on of the P. sinuosa meadow at the lee edges of blowouts did not move. Spec ies tended to grow in monospecific stands but occasional associations betwe en species did occur. Transects through seagrass meadows can be powerful mo nitoring tools if the limitations to this method are realised and they are used to answer well-defined questions. (C) 2000 Elsevier Science B.V. All r ights reserved.