A daily cycle of fluorescence in vivo was strikingly apparent in surface waters of the central equatorial Pacific between latitudes 4N and 10S, but not in waters to the north or south of this zone. These changes in fluorescence did not represent changes in chlorophyll-a concentration, but rather a photoinhibition of fluorescence by ambient light. Higher nutrient and chlorophyll-a concentrations were found in the region where cycling occurred....
Setser, Patrick J., Norman L. Guinasso, and David R. Schink. 1982. "Daily patterns of fluorescence in vivo in the central equatorial Pacific." Journal of Marine Research 40, (2). https://elischolar.library.yale.edu/journal_of_marine_research/1592