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Using both temporal and spatial versions of PE, together with mutual information-based functional networks, we identify coherent dynamical regimes and ecological boundaries that are difficult to detect with classical linear methods. Temporal PE at the annual time scale reveals two well-separated low-entropy regions corresponding to the North Atlantic Subtropical and Subpolar Gyres, divided by a sharp zonal boundary consistent with a transition between light-limited and nutrient-limited phytoplankton regimes. Area-Weighted Connectivity maps further suggest that the Subpolar bloom region is itself divided into two dynamically distinct subregions in the Labrador and Irminger Seas. Analysis of spatial PE uncovers a characteristic entropy\u2013chlorophyll cycle in which bloom growth occurs during periods of high spatial disorder, while the recession phase is associated with the emergence of large-scale meridional Chl-a gradients. Mutual information between Chl-a and physical drivers reveals seasonal, predominantly non-linear coupling with SST and MLD, with SST exhibiting a significant negative correlation during spring and autumn and MLD showing surprisingly weak local control during the bloom phase. Our results demonstrate the potential of ordinal-pattern methods as a complementary, model-free framework for characterizing the interplay between ocean physics and marine ecosystem dynamics from remote sensing observations.<\/jats:p>","DOI":"10.1063\/5.0336325","type":"journal-article","created":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T13:10:54Z","timestamp":1790082654000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Permutation entropy reveals coherent structures and ecological boundaries in North Atlantic phytoplankton blooms"],"prefix":"10.1063","volume":"36","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8028-9005","authenticated-orcid":false,"given":"Giulio","family":"Tirabassi","sequence":"first","affiliation":[{"name":"Department of Computer Science, Applied Mathematics and Statistics, Universitat de Girona 1 , Girona,","place":["Spain"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7473-394X","authenticated-orcid":false,"given":"Daniele","family":"Iudicone","sequence":"additional","affiliation":[{"name":"Stazione Zoologica Anton Dohrn 2 , Naples,","place":["Italy"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2994-9514","authenticated-orcid":false,"given":"Enrico","family":"Ser-Giacomi","sequence":"additional","affiliation":[{"name":"IFISC (CSIC-UIB), Institute for Cross-Disciplinary Physics and Complex Systems 3 , Palma de Mallorca,","place":["Spain"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"317","published-online":{"date-parts":[[2026,9,22]]},"reference":[{"key":"2026092209104313700_c1","doi-asserted-by":"publisher","first-page":"174102","DOI":"10.1103\/PhysRevLett.88.174102","article-title":"Permutation entropy: A natural complexity measure for time series","volume":"88","year":"2002","journal-title":"Phys. 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