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Email the author (Login required) Microphytoplankton communities associated with deep thermoclines in the southwestern Gulf of Mexico during a “Nortes” storm season
Submited: 2026-01-13 12:13:43 | Published: 2026-06-30 22:44:54
DOI: https://doi.org/10.3856/vol54-issue3-fulltext-3613
Abstract
The ocean thermocline acts as a critical transition layer that regulates the vertical distribution of chemical compounds and microorganisms. Because its depth is highly variable, ranging from a few meters to over 100 m, it influences the vertical distribution of species. This study evaluates microphytoplankton communities associated with deep thermoclines off the coast of Veracruz in the southwestern Gulf of Mexico. Data and samples were collected during a multidisciplinary research cruise in February 2023, coinciding with a "Nortes" storm season. Using a CTD-Rosette system, we obtained high-resolution hydrographic profiles and water samples for taxonomic analysis. Our results identified deep thermoclines (ranging from 80 to 140 m depth) that supported a total of 110 species across all sampling stations, comprising 57 diatoms, 48 dinoflagellates, 2 cyanobacteria, 2 silicoflagellates, and 1 ciliate. Diatoms were the most abundant group (20,060 cells L-1), followed by dinoflagellates (17,720 cells L-1). Mesodinium rubrum, Pseudo-nitzschia pseudodelicatissima, Trichodesmium hildebrandtii, Heterocapsa orientalis, and Dictyocha fibula emerged as the most abundant taxa. Ecological indices, including Margalef richness (DMg = 10.17) and Shannon-Weaver diversity (H’ = 4.03), indicate high community complexity, confirming that the thermocline serves a pivotal niche for microphytoplankton. These findings enhance our oceanographic understanding of the southwestern Gulf of Mexico by characterizing microphytoplankton at specific depths during a season that has historically been underrepresented in research due to the navigational challenges posed by stormy weather.
