For individual organisms to complete their life cycles, a series of developmental stage transitions need to be achieved without major interruptions.  A developmental threshold model predicts the rate of development from one life stage to another under a dynamically changing environmental condition. The model would allow ecologists to examine the timing of developmental events (phenology) and further estimate the spatial distribution of suitable habitats (biogeography) that allow successful transitioning of developmental stages. This type of model has been increasingly applied to study terrestrial populations in recent years, but not so much for marine populations. In this presentation, I will introduce the concept of developmental threshold modeling, explain the linkage between phenology and biogeography, and discuss the model’s applicability in marine systems.  I will present a case study on the zooplankton populations in the Arctic Ocean to illustrate how critical development thresholds can be linked to the biogeography of different species, and how climate change can impact the probability of successful developmental transitions.