Microbial dynamics in acetate-enriched ballast water at different temperatures

Acetate breakdown indeed occurred faster at higher temperatures. At 25 °C the highest bacteria growth, fastest nutrient and oxygen consumption and highest DOC reduction occurred. On the other hand, at −1 °C bacterial growth was strongly delayed, only starting to increase after 12 days. Furthermore, at 25 °C the acetate pool was not depleted, probably due to nutrient and oxygen limitation. This means that not all acetate will be broken down in ballast water tanks, even during long voyages in warm waters. In addition, at low temperatures acetate breakdown in ballast water tanks and in discharged water will be extremely slow. Therefore, regular discharge of acetate enriched ballast water in harbors and bays may cause eutrophication and changes in the microbial community, especially in colder regions.