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Abstract:
Particulate organic matter, POM, consists of living material and organic detritus found in the water column. The elemental ratios that make up the POM are important for understanding global patterns of nutrient cycling and the composition of the microbial communities in the ocean. While crossing the Subtropical South Pacific Gyre (SPG), onboard the TFS Sonne (SO245), from Antofagasta, Chile to Wellington, New Zealand, samples for particulate organic carbon (POC), nitrogen (PON), and sulfur (POS) were taken, and compared to hydrographic and chemical measurements (i.e. nutrient concentrations, Chl a, temperature, salinity) that were taken in parallel. There was a deepening of the deep chlorophyll maximum, nutricline, and thermocline in the center of the SPG. A low ratio of chlorophyll a to POC (<0.01 μg Chl a: μg C) in the surface waters of the SPG indicates that the community in the surface waters of the gyre is different than that of the deep chlorophyll maximum. Concentrations of POC and PON in the surface waters of the SPG were (2-3 μM) and (0.2 μM) respectively, with concentrations staying close to 1 μM POC and 0.15 μM PON in deeper waters. The concentration of POS was low (0.2 μM) in the SPG and increased as the cruise progressed westward towards New Zealand, with maximums of 3-4 μM POS. POS, as opposed to POC and PON, increased with depth in the westward waters of the SPG. The average C: N ratio for the upper 500 m of the SPG is 11.8. The dataset generated from this Master’s thesis composes the second set of POC and PON concentrations measured in the SPG and the first set of POS concentrations from the SPG. This information, in addition with cell counts and ecological studies performed onboard the SONNE will be combined in the future to provide one of the most comprehensive reports to date on the SPG, the world’s most understudied –but largest– ocean gyre.
