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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 on a cross-shelf cruise in Feb-Mar 2023 aboard the R/V Atlantic Explorer. Elevated concentrations of TDN (>12 µM) and TDP (>0.5 µM) were observed 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).
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Total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) of samples collected on the West Florida Shelf during STING II cruise EN704 on R/V Endeavor from Jul 1 to Jul 12, 2023
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 on a cruise in July of 2023 aboard the R/V Endeavor. Elevated concentrations of TDN (>12 µM) and TDP (>0.5 µM) were observed 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).
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- PAR ID:
- 10675980
- Publisher / Repository:
- Biological and Chemical Oceanography Data Management Office (BCO-DMO)
- Date Published:
- Edition / Version:
- 1
- Subject(s) / Keyword(s):
- West Florida Shelf dissolved organic nitrogen dissolved organic phosphorus Gulf of Mexico
- Format(s):
- Medium: X
- Location:
- Biological and Chemical Oceanography Data Management Office
- Institution:
- Woods Hole Oceanographic Institution
- Sponsoring Org:
- National Science Foundation
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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).more » « less
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The West Florida Shelf (WFS) in the Gulf of America (formerly the Gulf of Mexico) is oligotrophic, with inorganic nitrogen (N) and phosphorus (P) concentrations typically at or below detection limits, and yet significant rates of primary productivity, including blooms of the harmful algal species Karenia brevis, are observed there. Additionally, multiple clades of the cyanobacterial diazotroph Trichodesmium spp. are endemic on the WFS. Consequently, dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) are thought to be the primary sources of assimilative macro nutrients on the WFS. Here we present results from a multidisciplinary study conducted on spring and summer 2023 cruises that 1) quantified rates of N2 fixation on the WFS; 2) characterized the diazotroph community composition; 3) measured dissolved inorganic and organic and suspended particulate organic nutrient concentrations and isotopic compositions; 4) measured trace element concentrations, speciation, and isotopic composition; 5) characterized dissolved organic matter chemical composition; and, 6) quantified fluxes of these elements from submarine groundwater discharge using a radium isotope mass balance model. Additionally, quarterly sampling of the geochemistry of riverine and submarine groundwater wells defined the chemical composition of margin (i.e., riverine and submarine groundwater) inputs. Together, we use these results to understand whether submarine groundwater discharge is the dominant source of bioavailable DON, DOP, dissolved iron, and iron-binding ligands on the WFS. Additionally, we use the results to ask whether the abundance of Karenia brevis and Trichodesmium spp. are associated with enhanced submarine groundwater inputs, and whether rates of N2 fixation carried out by two different Trichodesmium spp. are associated with enhanced submarine groundwater inputs.more » « less
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In lakes, ecosystem structure and processes are influenced by gross primary production (GPP), ecosystem respiration (R), and net ecosystem production (NEP). The rates of these metabolic processes are often controlled by resource availability, which often reflects catchment loads. Although the relationship between catchment loads and in-lake nutrient concentrations may be well defined in specific lakes, we explored how watershed vs. in-lake predictors of metabolism compare across lake types. To do this, we combined stream loads of carbon (C), nitrogen (N), and phosphorus (P) with high frequency in situ monitoring of lake metabolism and in-lake C, N, and P concentrations from 16 lakes spanning a range of latitudes (39 to 64 degrees N), inflowing stream (0 - 6 streams), and trophic status (oligotrophic to eutrophic). The data package includes high-frequency dissolved oxygen, water temperature, wind speed, and solar radiation data as well as daily estimates of GPP, R, and NEP derived from those data. In addition, the data package includes in-lake and stream concentrations of dissolved organic carbon, total nitrogen, and total phosphorus and stream discharge data. The package also includes estimates of daily carbon, nitrogen and phosphorus loading to each lake derived from the stream concentrations and discharge.more » « less
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