Total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) of samples collected from rivers draining onto the West Florida Shelf and submarine groundwater wells on the Western coast of Florida from Nov 2022 to Mar 2024

The West Florida Shelf (WFS) is oligotrophic, with inorganic N and P concentrations typically at or below detection limits, and yet significant rates of primary productivity, including blooms of the cyanobacterial diazotroph Trichodesmium spp. as well as the harmful algal species Karenia brevis, are observed there. Consequently, dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) are thought to be the primary sources of assimilative nutrients on the WFS. Here we report measurements of total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) concentrations made on samples collected quarterly from rivers draining onto the WFS as well as from submarine groundwater wells on three transects extending from the Florida Nature Coast in the north to Venice Headland in the south. Elevated concentrations of TDN (>12 µM) and TDP (>0.5 µM) were observed in riverine and groundwater samples, as well as in the shallow, nearshore region, while to the west concentrations of both TDN and TDP decreased to values typically associated with oligotrophic North Atlantic waters (4 to 5 µM TDN and 0.05 to 0.1 µM TDP).西佛罗里达陆架（West Florida Shelf, WFS）属于贫营养海域，其无机氮与无机磷浓度通常处于或低于检出限，但该海域仍观测到显著的初级生产力，包括固氮蓝细菌束毛藻属（Trichodesmium spp.）水华以及有害藻种短凯伦藻（Karenia brevis）的暴发。因此，学界普遍认为溶解态有机氮（dissolved organic nitrogen, DON）与溶解态有机磷（dissolved organic phosphorus, DOP）是西佛罗里达陆架海域可同化营养盐的主要来源。本研究报道了总溶解态氮（total dissolved nitrogen, TDN）与总溶解态磷（total dissolved phosphorus, TDP）的浓度测定结果：样本按季度采集自汇入西佛罗里达陆架的河流，以及北起佛罗里达自然海岸、南至威尼斯海岬的三条断面上的海底地下水井。研究观测到，河流与地下水样本以及近岸浅水区的TDN浓度（>12 μM）和TDP浓度（>0.5 μM）均显著升高；而向西方向海域的TDN与TDP浓度则降至与贫营养北大西洋水体相当的水平（TDN为4~5 μM，TDP为0.05~0.1 μM）。