3.2.2. Dinophysis and Prorocentrum and DSP Toxins
The non-toxic species Dinophysis tripos was counted in sample 1A (20 cells·L−1) and the toxic species D. caudata in sample 6A (30 cells·L−1, Table 4). No other Dinophysis species was identified by using light microscopy. Only the top genus-level probe in the hierarchy for Dinophysis (DphyGS03_25_dT) was detected with the microarray in sample 6A, but no species-specific probes were detected with the microarray in sample 6A. This result suggests that the microarray threshold for D. caudata species probe is above 30 cells. 
Cells from the potentially toxic genus Prorocentrum (group of P. minimum, balticum, and cordatum) were counted in samples 2A and 4A (both with 400 cells·L−1, Table 4). In addition, two planktonic usually considered harmless species, P. micans (sample 2A) and P. triestinum (sample 3A, 4A and 6A), were also identified by light microscopy with abundances ≤800 cells·L−1 (Table S1). No Prorocentrum species were counted in sample 1A. None of the planktonic clade-level probe for Prorocentrum ProroFBS02_25_dT and the species-specific probes for P. minimum (PminiD01_25_dT) and P. micans (PmicaD02_25_dT) of the microarray detected the presence of these taxa. It is likely that they require higher cell numbers to achieve a signal. With the third generation of the MIDTAL microarray new probes for Prorocentrum (two clade-level and six species-level probes) were tested, but without the poly dT_15 spacer region to raise the probes higher above the surface because they were still under testing for specificity. The new planktonic Prorocentrum probe ProroFPS01 was detected in samples 1A, 2A and 6A whereas the benthic Prorocentrum probe ProroFBS01 was detected in samples 4A and 6A (Figure 4(a)). New species-specific probes were made for the benthic species P. belizeanum, maculosum, rathymum and mexicanum. The probe PbeliS01 specific for P. belizeanum was detected with the microarray in samples 4A and 6A and the probe PrathD01 specific for P. rathymum and mexicanum was detected in sample 6A (Figure 4(a)). As for both samples, the higher probe ProroFBS01 (benthic Prorocentrum) was detected; the species-specific probes are not false positives and point out the limitation of microscopic cell counting. The specificity of theses Prorocentrum species has only been tested against a limited number of species and it is also likely that these probes are cross-reacting to another species present in the sample. P. rathymum is found in Malaysia and in the Mediterranean and P. mexicanum has a Caribbean distribution. More work is needed to clarify the taxon that is reacting with this probe. One way to achieve this is to use the probe as a FISH probe and sort the labeled cells or look at them in the microscope.
Okadaic acid was detected by ELISA in all samples except for the first (sample 1A), and the Multi SPR gave no signal at all. We presume that because Prorocentrum was more abundant than Dinophysis; its species is the source of this toxin.
Figure 4  (a) Normalized signal of Prorocentrum-level probes (ProroFPS01 and ProroFBS01) and the species-level probes PrathD01 and PbeliS01. (b) Normalized signal of the Alexandrium genus-level probe AlexGD01_25_dT.

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