Effects of a dynamic uplift in an oligotrophic tropical stratified system on the structure of paralarvae, phyllosomas, and fish larvae assemblages from the epipelagic zone during a late-spring survey

In regions where western boundary currents interact with shelf topography, dynamic uplift can modify the vertical structure of the water column. How these changes shape larval assemblages in stratified tropical oligotrophic systems remains insufficiently understood. The Mexican Caribbean, influenced by the Yucatán Current, provides an ideal setting to investigate these dynamics. We examined the vertical distribution of fish, cephalopod, and lobster larvae across the epipelagic zone, at the surface mixed layer, the deep chlorophyll maximum (DCM), and the halocline core, on the east and west sides of northern Cozumel Island, which differ in uplift intensity. Larvae were collected using a WP2 net (500 μm mesh size) equipped with an opening–closing system. The effects of physical, chemical and biological variables, including chlorophyll-a concentration and the density of phytoplankton groups (i.e. cyanobacteria, dinoflagellates, and diatoms), on larval distribution were assessed using Canonical Correspondence Analysis and Generalized Additive Models. A total of 51 fish families, five paralarvae families, and one phyllosoma family were identified. Larval assemblages differed significantly among depth layers but not between sides of the island. Fish larvae peaked at the DCM, paralarvae dominated the surface layer, and phyllosomas occurred mainly below the DCM. Mesopelagic taxa dominated numerically across layers, whereas neritic families contributed substantially in the upper mixed layer. Temperature and chlorophyll-a were the main drivers of larval distribution, while phytoplankton composition and phosphate also influenced Enoploteuthidae paralarvae. These variables jointly shape depth-specific larval assemblages by reflecting the thermal structure and food availability in the water column.