During November 2005, a dense bloom of Dinophysis spp. dominated (>97%) by Dinophysis acuta in the Galician Rías Baixas (NW Spain), provided a unique opportunity to describe the full toxin profile - including toxins that represent a low percentage and escape detection in analyses of single-cell isolates - in plankton concentrates rich in this species. Detection and identification of toxins were carried out by liquid chromatography coupled to mass spectrometry (LC-MS/MS), a method that is based on their retention times (RT) and the fragmentation patterns of their mass spectra. OA-D8 diol-ester and PTX11 were detected in co-occurrence with okadaic acid analogues (OA, DTX2) and PTX2 in plankton concentrates dominated by D. acuta. The presence of a PTX11-isomer, which was suggested to be PTX13 or a novel PTX11-isomer, released in the sea water, was also confirmed in samples obtained after deployment of passive samplers (SPATT) in situ at the time of the D. acuta bloom maximum. The amount of PTX11 per cell of D. acuta, estimated as PTX2 equivalents, ranged between not detected and 2.2pg cell(-1), and represented a maximum of 2.9% of the total toxin content. The variation in PTX11 content per cell of D. acuta, during a daily cycle, followed the same pattern than that of PTX2, with maxima at 21:00 and 03:00h (dark hours), but the amounts per cell were one order of magnitude lower. This is the first report of PTX11, together with the confirmation of OA-D8 diol-ester in D. acuta populations from Europe.