University Events

Description: The School for Marine Science and Technology
Department of Estuarine and Ocean Sciences
Seminar Announcement

“Distribution of larval fish in the Eastern Tropical North Pacific Oxygen Minimum Zone”

Juan Gutierrez Bravo
Graduate Student
SMAST at UMassD

Wednesday, April 12, 2023
12:30 pm – 1:30 pm
SMAST East, Rooms 101/102
And via Zoom

Abstract:
The three-dimensional distribution of fish larvae and juveniles, in relation to environmental structure and dissolved oxygen gradients, was analyzed from eight key locations in the Eastern Tropical North Pacific Oxygen Minimum Zone (OMZ). The oxic layer depth (>100 umol kg-1) was <50 m in the Costa Rica Dome, ~80 m in the warm pool off Guatemala and Mexico, and ~120 m in two anticyclonic eddies crossed during sampling. The upper-lower boundaries of the OMZ anoxic core (<2 umol kg-1) expanded from 350-500 m off Costa Rica to 100-750 m off central Mexico, displacing the hypoxic layer (10-100 umol kg-1). Larval fish stages were distinctly distributed. Preflexion and flexion stages were restricted to the oxic layer. Postflexion and transformation stages were abundant in the oxic layer but also present in deeper layers, including the anoxic core. Juveniles of meso-bathypelagic species were present along the water column but most abundant below the anoxic core, showing a physiological capacity to cross anoxic waters. Dominant species distribution shows that epipelagic species are restricted to the oxic layer through their development, while meso-bathypelagic species like Diogenichthys laternatus and Cyclothone spp. cross the core to deep hypoxic waters as transformation larvae and juveniles. Thus, expanding OMZs could further restrict the habitat of epipelagic species, while also affecting the displacement of meso-bathypelagic species. We suggest that changes from hypoxic to anoxic conditions could greatly affect the life cycles of keystone species in the world’s OMZs.
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For additional information, please contact Sydney Carreiro at scarreiro1@umassd.edu