Modeling biological pathways connecting surface and deep ocean ecosystem

The deep ocean is home to a vast, diverse, and sparsely sampled ecosystem, and holds the largest carbon pool relevant to climate. Earth System Models provide an essential tool to investigate the impacts of human activities on this remote environment. However, the current generation of Earth System Models focuses mostly on surface layers, and knowledge about impacts on mesopelagic and abyssal zones is still emerging. Here, I review recent advances and challenges in modeling biological pathways that connect the surface and deep ocean realms. These include particle-related processes that support the gravitational biological pump, vertical migrations of zooplankton and nekton, and their interactions with particles. I also discuss developments in the representation of higher trophic levels, including fish, in Earth System Models, their connections to deep ocean biogeochemistry, and their potential responses to climate change and fishing pressure. The complexity and variety of scales involved in these phenomena pose a formidable challenge that will require concerted, interdisciplinary efforts to overcome.