Introduction: Microplastics are present throughout the global ocean and can be ingested by many species, including zooplankton. Although they fall within the size range of zooplankton prey, there are few in situ studies on microplastic ingestion. Objective: To evaluate the bioavailability and bioconcentration of microplastics in seven representative taxonomic groups of zooplankton within a Marine Protected Area (MPA) in the Caribbean. Methods: To elucidate the biodisponibility of microplastics, twelve stations were sampled with oblique towns using mini-bongo net during two contrasting hydroclimatic seasons in 2022. In the laboratory, we analyzed size, shape and polymer compositions of microplastics at each water sample using stereoscopy and FTIR-ATR with 4 cm- 1 resolution. Seven dominant zooplankton groups were selected from different trophic levels to assess the ingestion encounter rate and bioaccumulation of microplastics. Results: A median bioavailability of microplastics of 0.091 microplastics/m³ was recorded (mainly polyester and PET fibers and fragments), with significant differences between seasons (Kruskal-Wallis, p = 1.5 ×10-⁹). Zooplankton mainly ingested black fragments with an Encounter Rate of 0 to 0.22 microplastics/ind., and the observed bioconcentration in the taxonomic groups was > 1, indicating direct or indirect bioaccumulation. Conclusion: The bioavailability of microplastics in the MPA is lower than in other regions of the world, and the temporal variability is modulated by the Caribbean's oceanographic dynamics and river inputs into the coastal zone. Six of the seven analyzed zooplankton groups accumulate microplastics, with Paracalanidae showing the highest bioconcentration factor. These findings highlight the need to monitor and mitigate the effects of microplastics on marine ecosystems to protect both the affected species and the ecosystem services they provide.