Figure 2. Microbial abundance as determined by direct counts, including virus-like particles (VLPs), total bacterial counts (TBCs), heterotrophic nanoflagellates (HNFs), and autotrophic nanoflagellates (ANFs).

Microbes were counted in samples of seawater (SW) and in ballast-water surface (BWS) and bottom (BWB) samples. The mid-ocean ballast-water exchange occurred on day 5 (Exchange). Day 5 water samples were collected after the water exchange. No ANFs were detected in bottom ballast water after day 4 or in surface ballast water after day 6.