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.
 Due to the slight detected interaction between light and PO4–P concentration, both factors were analysed as co-variate of the other. The results suggested that light did not have a significant influence on PO4–P effects on spore recruitment (One-way ANOVA; F=0.1005; pN0.05). On the contrary, PO4–P concentration had a highly significant influence on light effects on the biomass of spores (One-way ANOVA; F=59.960; pb0.0001). This suggests that the spore biomass seems to be more affected by lower PO4–P supplies than by lower light intensities. In fact, spore recruitment was not statistically different among light levels within the lower levels of PO4–P supply (2 μmol l−1 and 0.8 μmol l−1), while it was significantly different among PO4–P concentrations within all light levels. Nevertheless, it should be noted that there is a slightly interaction between light and PO4–P levels, which explains the increasing tendency in spore biomass with the increase of these variables.