Phosphorus (P) is a limiting nutrient responsible for the eutrophication of surface waters and marine coasts. Wastewater treatment technologies are being stressed to achieve low P effluents and national effluent P limits are expected in the coming years. This research investigates how different algae, as individual species and a mixed culture, utilize bioavailable phosphorus (BAP) when examined by the standard algal species Raphidocelis subcapitata along with Chlorella vulgaris and Chlamydomonas reinhardtii as additional test species. It also investigates how different P-species contribute to BAP using the standard algal species. Results show there is no significant difference in %(BAP/total dissolved P) among the cultures studied and that all P-species contributed to BAP. BAP is an important parameter in determining effluent contributions to eutrophication; this research demonstrates that the current standard algal species is a reliable species for BAP bioassays and that certain P-species may be used to determine BAP estimates.