Early patterns of Caulerpa racemosa recovery in the Mediterranean Sea: the influence of algal turfs

Variability in recovery of the introduced green alga Caulerpa racemosa has been investigated on a subtidal rocky shore in the north-western Mediterranean Sea. Two removal experiments were performed. The first was designed to test the effects of season on the early patterns of recovery of C. racemosa on a rocky bottom and on algal turf. In the second experiment recovery of C. racemosa on the rocky bottom and on algal turf was estimated from July–October 2000, the end of the vegetative period of the alga. Recovery of experimental plots occurred from adjacent populations of C. racemosa by stolon growth. In the first experiment, recovery occurred from August to November in all the experimental units, while no growth was observed during winter and spring. Recovery was significantly higher on algal turf than on rock during all vegetative periods. In both the habitats, recovery was quicker in summer than in autumn, even if differences between dates within each season were also significant. In the second experiment, three months after removal, the mean per cent cover of C. racemosa in algal turf was twice that on rock.