The objective of the project was to develop species-specific or strain-specific assays for harmful algal species.  Polyclonal antibodies (PAbs) to Alexandrium tamarense were produced and were then affinity purified to minimize cross-reactions. The initial production of PAbs was highly successful. Affinity purification required two different approaches, i.e., positive selection of the anti-Alexandrium antibodies and negative adsorption with subsequent removal of the cross-reacting antibodies. The negative adsorption method appeared to be the best approach; however, even after adsorption, significant cross-reactions with Pyrodinium remained. Therefore, negative adsorption proved to be as challenging and unfruitful as the positive selection methods for purified antibodies. Despite considerable effort, the project did not result in a usable, purified polyclonal antibody.  It is now clear that monoclonal antibodies offer the best chance of producing highly specific antibodies to Alexandrium.