The microorganisms in the ocean enjoy the sun and warmth of the equator, just as we scientists do when we are not working. Here in the equatorial upwelling zone, microorganisms grow well because of the extra nutrients that are brought to the ocean’s surface by upwelling (upwards movement) of water from the deep ocean. As a consequence, in certain depths of the water column, oxygen is consumed faster than it is supplied via circulation
Phytoplankton (marine plants) grow in the sunlit surface waters, but when they sink through the water column, they are eaten by other organisms – including microorganisms – that consume oxygen as part of this process. This process leads to oxygen minimum zones (OMZs) in certain depths of the water column. One can compare this process to a poorly-ventilated room full of people: the oxygen is rapidly consumed, so the air becomes bad. At our equator station, the OMZ was at a depth of ca. 400 meters.
Unlike people, who cannot live without oxygen, there are certain types of bacteria that are well-adapted to life without oxygen. They “breath” using other elements that are abundant in the ocean, for example sulfate. Many of these bacteria, however, don’t tolerate oxygen very well, so they are most commonly found in the sediments and soils, where they carry out processes critical for global elemental cycles. Recently, however, scientists have discovered that some of these organisms are also present in OMZs; their role and activities in these zones is not yet well understood.
For this reason, we are trying to cultivate representative organisms of this type on board, in order to take them back to Oldenburg and study them at a molecular level. We are collecting water from the OMZ and adding it to oxygen-free artificial seawater medium to which we have added nutrients. The culture vessels are closed, and have a nitrogen atmosphere instead of an oxygen-containing atmosphere. We prepared these flasks in Oldenburg in January, and fortunately they survived the transport process to New Zealand. Now we have to be patient, hoping that something will grow in our flasks. These special bacteria are known to grow very slowly, but they will be worth the wait!