Ocean partitions are often based on readily accessible variables, such as abiotic factors and chlorophyll-a concentration, but provide limited insight into biological patterns. This study developed a three-step partitioning strategy prioritizing environmental factors that best described the variability patterns of harmful algal bloom (HAB)-forming taxa off SW Iberia. These included the producers of amnesic shellfish poisoning (ASP), diarrhetic shellfish poisoning (DSP), and paralytic shellfish poisoning (PSP). First, dimensionality reduction and unsupervised classification were applied to three environmental datasets, derived from remote sensing and model outputs, covering a 19-year period. Second, different empirical-statistical models were used to determine which datasets best explained the abundance of HAB-producers, available for an 8-year period in different classified coastal production areas. Finally, the best datasets were used to derive partitions prioritizing the variability of different HAB groups, at a pixel level. The first classifications identified up to 12 regions, with four to five located in the coastal-slope domain, with a variable configuration depending on the dataset. The best predictor datasets and models identified five regions (two inner-shelf, two outer-shelf/slope, and one transitional coastal-ocean region), representative of HAB groups. No clear distinctive partitions were identified for different groups, namely for ASP- and DSP-producers, likely due to the combined influence of upwelling and freshwater discharges, along with submarine topographic features. Our partitioning strategy can be applied to other marine systems and taxonomic groups. Future improvements, including more complete environmental and biological datasets, could enhance the value of biologically informed environmental partitions as proxies for species abundance.
Lima et al. (Fri,) studied this question.