Relationships between reduced gases, nutrients, and fluorescence in surface waters off Baja California

Abstract

Temperature, in vivo fluorescence, silicate, phosphate, dissolved hydrogen, and carbon monoxide were measured in surface waters while crossing the California Current system into San Diego. The measurements were made to define surface water variability and to help understand the causes of variations in H 2 and CO concentrations. Striking changes were observed crossing the current system, with the most dramatic effects occuring within 100 km of the coast. In an attempt to separate the effects of different water histories, the data were subdivided according to ‘water type,’ with four types identified on the basis of temperature. Relations between parameters were distinctly different in the different waters. Over the ‘oceanic’ part of the track all variables were relatively constant. Hydrogen was not correlated with CO or in vivo fluorescence except in the warm, coastal water, where the correlation between hydrogen and fluorescence was strong. Carbon monoxide showed a distinct daily cycle when data from different types were examined separately. The mean concentration of CO for each water type covaried with the mean in vivo fluorescence. Likewise the amplitude of daily CO variation was positively correlated with mean fluorescence. This lends support to the hypothesis that the CO abundance is related both to light intensity and to organic content of the water.