[Eoas-seminar] Oceanography Thesis Defense - Zhou Liang - Nov 2, 1:00pm - Zoom

[eoas-seminar at lists.fsu.edu]

Zhou Liang

M.S. Chemical Oceanography Candidate





TITLE: THE ENVIRONMENTAL FACTORS INFLUENCING THE ACCUMULATION AND LOSS OF THE DISSOLVED ORGANIC PHOSPHORUS (DOP) IN THE GLOBAL SURFACE OCEAN
Major Professor:  Dr. Angela Knapp

Date: Monday, November 2, 2020                            Time: 1:00 PM


Location:
Zoom Meeting (URL: https://urldefense.com/v3/__https://fsu.zoom.us/j/96954590850?pwd=SVQvSVhQOFp1TmJJQld5blpWWVkydz09__;!!Epnw_ITfSMW4!4KWdO6ij-BSszU6KVbHehNfSoBrJ3nxy-0NcrryyWSmt8kYtPrOvEfolkyMF9w2YFQ$<https://urldefense.com/v3/__https:/fsu.zoom.us/j/96954590850?pwd=SVQvSVhQOFp1TmJJQld5blpWWVkydz09__;!!Epnw_ITfSMW4!4KWdO6ij-BSszU6KVbHehNfSoBrJ3nxy-0NcrryyWSmt8kYtPrOvEfolkyMF9w2YFQ$>)
Meeting ID: 969 5459 0850
Passcode: 676702


ABSTRACT





Dissolved organic phosphorus (DOP) in the surface ocean has a dual role as both the product of primary production and as a phosphorus substrate for phytoplankton when inorganic forms of phosphorus (P) are scarce. DOP has increasingly been recognized as an important source of P, especially in oligotrophic gyres, where recent modeling work suggests it may support 8% of net primary production and 33% of biological nitrogen (N2) fixation. However, there are few DOP concentration measurements in the global ocean, especially compared to measurements of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON). In particular, there are few DOP concentration measurements from the Indian Ocean and South Pacific Ocean. Consequently, a robust understanding of the role of DOP in supporting primary production and N2 fixation remains data-limited. Here, we present 378 DOP concentration measurements from the 2016 GO-SHIP I08S and I09N cruise in the Eastern Indian Ocean, 204 DOP concentration measurements from the 2017 P06 GO-SHIP cruise in the South Pacific Ocean, and 213 DOP concentration measurements from the 2016 P18 GO-SHIP cruise in the Eastern Pacific Ocean. Additional DOP concentration measurements were made in the Gulf of Alaska (n = 37), South Atlantic (n = 29) and Eastern Tropical South Pacific Ocean (n=119). Together with nitrate+nitrite (NO3), phosphate (PO4), and dissolved organic carbon and nitrogen concentration measurements made in the same samples, we evaluate trends in surface ocean DOP concentration to identify regions of net DOP accumulation and loss. We find that surface ocean DOP stocks are positively correlated with surface ocean chlorophyll a concentration and negatively correlated with iron stress in the Eastern Pacific Ocean, indicating a region of net DOP accumulation. In contrast, surface ocean DOP stocks are negatively correlated with surface ocean chlorophyll a concentration and positively correlated with surface ocean iron stress in the Indian, South Pacific, and Atlantic  Oceans, indicating  net  DOP loss in these regions when iron stress is alleviated. Additionally, surface DOP stocks are significantly negatively correlated with subsurface NO3:PO4 concentration ratios, indicating that PO4 availability plays a key role in regulating surface ocean DOP stocks. Together, these findings significantly expand the global ocean DOP dataset and we provide a mechanism to explain surface ocean DOP distributions, with primary roles for DOP accumulation and loss in the context of phosphate and iron stress in the global scale.



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