In almost any Atlantic coastal area of Europe where there is a suitable substratum and adequate water quality, one or more species of kelp may be found. Their high productivity and complex biological structure make kelps especially important members of their communities, particularly when present in dense stands known as "kelp forests". Currently, these species are subject to important novel constraints of physical and anthropogenic origins that can strongly modify their sustainability, their distribution and the biodiversity of associated species. Along the Portuguese coastline there is a perception by the local and scientific communities that some kelp species abundance is declining, particularly at the southern coast. Nevertheless, no large-scale spatial study of kelp abundance and diversity has been done. With the acronym Findkelp, this study aimed to assess from May to August 2008, the Portuguese kelp conservation status through community participation, field-based observations and large-scale Geographic Information System (GIS) technology. A communication strategy towards scuba divers and other coastal zone users was made to build and educate a team of informed volunteers that worked as independent observers, reporting georeferenced data in an electronic data-base available on the project's website. At randomly underwater chosen locations (n=56) from the volunteers reported sites (n=388), structural descriptors of kelp populations were groundtruthed, by means of non-destructive sampling techniques (3x50m belt-transects). By crossing the volunteer's reported data with the groundtruthed data, using error matrices and Kappa statistics with concordance agreement scales, a Portuguese coast line GIS map with perfect agreement (K=0.827) was made including the current distribution, diversity and conservation status of 6 kelp species.