As we continue to move westward and away from the coastal upwelling zone the sky is changing and temperatures are very slowly starting to rise. We are sampling about 10° south of the equator so the air is warm; when surface waters cooled by upwelling encounter warm air, condensation in the lower atmosphere causes cloudy skies.
Tonight a break in the clouds revealed a blanket of stars, matched by the sparkling of bioluminescence in the churning waters behind our moving ship. If you’ve ever seen a firefly, you’ve seen bioluminescence. Chemical reactions within certain organism produce a flash of light, the purpose is often illusive but thought to be a form of communication, a way to find prey or warn off predators (in fireflies bioluminescence is hypothesized to be a form of courtship). There are many bacteria, phytoplankton and larger organisms in the ocean with the ability to luminesce. As the propellers of our ship cut through the water tiny organisms become agitated, invoking a sparkly response in the spinning waters left behind by our wake.