The spore biomass increased with light and with PO4–P concentration and the interaction between these factors was slightly statistically significant ( pb0.05) (Fig. 2B; Tables 2-4, 3 and 4). PO4–P concentration had a highly significant influence on algal recruitment ( pb0.0001). Significantly different spore biomasses were obtained at the different used PO4–P concentrations, within each light level, with the exception of 6.4 and 2 μmol l−1 PO4–P at 20 μE m−2 s−1, where spores biomass were not statistically different (Table 4). For a PO4–P concentration of 6.4 μmol l−1, spore biomasses at 90 and at 40 μE m−2 s−1 were statistically different from that at 20 μE m−2 s−1. There were no statistically differences among light levels when PO4–P concentration was 2 μmol l−1, but for a PO4–P concentration of 0.8 μmol l−1, spore biomass at 40 μE m−2 s−1 was statistically different from that at 90 μE m−2 s−1.