Toxic algae; Taxonomy, Quantification and Early Warning. TOXALGAEHarmful algal blooms (HAB) cause large economic losses to the shellfish and fish farming industries. Of the about 5000 described marine microalgal species about 100 have been found to be tox ic and about 20 toxic algal species are recorded in Norwegian waters. Toxic algae are found within a number of taxonomic groups such as the diatoms, dinoflagellates, haptophytes, raphidophytes and dictyochophytes. In the light microscope many of the toxic algae are difficult to distinguish from closely related species. Some of these similar species are not known to be toxic (e.g. species of Pseudo-nitzschia and Chattonella), which make precise species identifications essential. TOXALGAE wants to develop m icroscopy methods for better description and species discrimination of fragile ichthytoxic flagellates of the genera Prymnesium, Chrysochromulina, Karenia, Karlodinium, Pseudochattonella, Dictyocha, Heterosigma and Chattonella, and molecular methods such as Quantitative PCR (polymerase chain reaction) and microarray detection that can identify and quantify both the fragile ichthytoxic flagellates and the species of the genera Alexandrium, Dinophysis, Azadinium, Prorocentrum and Pseudo-nitzschia that are responsible for shell fish poisoning. We will adapt and develop QPCR probes and probes for microarray detection (the latter in collaboration with the EU project MIDTAL: microarray detection of toxic algae) and use them to map the spatial distribution of h armful algae in Norwegian waters, including the Norwegian and Barents Sea. We will identify and describe species that are new to our waters and science. Monitoring of harmful algae in coastal waters is important in assessing the potential for blooms and m onitoring programs have been set up in several countries. At present most monitoring programs rely on light microscopy cell counts. By developing and taking into use methods such as QPCR and microarray detection.