Algae such as rockweeds are a fundamental part of marine ecosystems, providing habitat and food to many other marine organisms while also providing ecosystem services like oxygenation of the water. In turn, algae depend on bacteria to maintain their normal shapes and health. New sequencing methods are illuminating the relationships between marine bacteria and marine algae, as demonstrated in research by 15 scientists from countries across the North Atlantic. The published study contributes to the understanding how sensitive important algae are to the changing environment.