Book excerpt: Marine ecosystems are open and dissipative systems that rely on an external energy source – light – for their sustenance. The magnitude of the light flux and the spectral quality of the light field (which determines colour) determine the rate of marine photosynthesis by phytoplankton in the ocean, and the types of phytoplankton communities that flourish in different parts of the ocean and in different seasons. Ocean colour – determined by the spectral quality of light scattered out of the sea and back into the atmosphere – can be monitored using satellite sensors, and used to map the distribution of the major phytoplankton pigment, chlorophyll-a, at global scales. Remote sensing of ocean colour, first realised in 1977, has revolutionised the field of biological oceanography. Over the years, the quality of satellite products has continued to improve, and the range of products available has extended beyond chlorophyll concentration to encompass many variables of interest to biological oceanography and ocean biogeochemistry. However, it is well recognized that satellite observations have to be integrated with, and complemented by, field measurements and modelling, to obtain the full picture. The research topic proposed will cover a range of recent developments in ocean colour remote sensing and allied fields.