Prof Dr. Corina Brussaard

Microbiologist Corina Brussaard investigates viruses in the seas and oceans. ‘There are many viruses; one glass of seawater easily contains 150 million virus particles. But how significant is their ecological effect?’

Unknown territory

‘It is often said that we know more about the surface of the moon than about life in the ocean. That could certainly be the case for these marine viruses. At present, we are only investigating the tip of the iceberg. A large number of novel viruses have been found, amongst which giant viruses and viruses that infect other viruses.’ Who these viruses infect, how effective they are, and what the consequences are for the marine food web needs further study. We have found for example, that algal mortality due to viruses is considerable, and even comparable to losses by grazing of algae by other organisms. The effect on the structure and efficiency of the food chain is, however, completely different. It should therefore be investigated how important these viral infections are, not only for the specific host species but also for the entire ecosystem. Especially now, in a period when the oceans are undergoing so many changes.’

Long live the viruses

‘Viruses have a bad reputation; after all, they make you ill! But that is just one side of the story. The majority of living biomass in the sea consists of microorganisms. Sooner or later, those billions of virus particles cause the unicellular host cells to die following the infection (due to the release of the newly produced progeny viruses), as result of which the host cell contents end up in the surrounding water and will be decomposed by bacteria. As there are so many of these microorganisms, the viruses worldwide jointly have a significant influence on the carbon and nutrient cycles in the oceans. Due to their specific preferences who to infect, viruses also ensure considerable biodiversity of species and strains: after all, the death of one gives another the chance to grow. Therefore, paradoxically, viruses contribute to sustaining life in the sea.’