The oceans provide abundant resources that modern society depends on such as fisheries, tourism, transportation and energy. Furthermore, the oceans also regulate the Earth's climate by absorbing anthropogenic carbon dioxide and heat, cycling nutrients, organic carbon and oxygen. It is thus crucial to understand changing oceans as the climate warms. Computational models have played a central role in examining potential future changes. These models are built on mathematical representation of physical and biochemical processes that we currently understand, and they are not perfect and need to be checked and calibrated with observational data. This presentation highlights some recent works using observations and models to understand the cycling of nutrients, iron, oxygen and carbon, and hope to address what we should expect for ocean biogeochemistry in coming decades.