The oceans are the Earth's largest ecosystem, covering 70% of our planet and providing goods and services for the majority of the world's population. Understanding the complex abiotic and biotic processes on the micro- to macroscale is the key to protect and sustain the marine ecosystem. Marine microorganisms are the 'gatekeepers' of the biotic processes that control the global cycles of energy and organic matter. A multinational, multidisciplinary approach, bringing together research on oceanography, biodiversity and genomics, is now needed to understand and finally predict the complex responses of the marine ecosystem to ongoing global changes. Such an integrative approach will not only bring better understanding of the complex interplay of the organisms with their environment, but will reveal a wealth of new metabolic processes and functions, which have a high potential for biotechnological applications. This potential has already been recognized by the European commission which funded a series of workshops and projects on marine genomics in the sixth and seventh framework programme. Nevertheless, there remain many obstacles to achieving the goal – such as a lack of bioinformatics tailored for the marine field, consistent data acquisition and exchange, as well as continuous monitoring programmes and a lack of relevant marine bacterial models. Marine ecosystems research is complex and challenging, but it also harbours the opportunity to cross the borders between disciplines and countries to finally create a rewarding marine research era that is more than the sum of its parts.