Funding & Acknowledgements

The data used in this analysis is from the Export Standardized Tables in the SEACAR Data Discovery Interface (DDI). Documents and information available through the SEACAR DDI are owned by the data provider(s) and users are expected to provide appropriate credit following accepted citation formats. Users are encouraged to access data to maximize utilization of gained knowledge, reducing redundant research and facilitating partnerships and scientific innovation.

With respect to documents and information available from SEACAR DDI, neither the State of Florida nor the Florida Department of Environmental Protection makes any warranty, expressed or implied, including the warranties of merchantability and fitness for a particular purpose arising out of the use or inability to use the data, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.

This report was funded in part, through a grant agreement from the Florida Department of Environmental Protection, Florida Coastal Management Program, by a grant provided by the Office for Coastal Management under the Coastal Zone Management Act of 1972, as amended, National Oceanic and Atmospheric Administration. The views, statements, findings, conclusions and recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of the State of Florida, NOAA or any of their sub agencies.

Published: 2025-10-08

Threshold Filtering

Threshold filters, following the guidance of Florida Department of Environmental Protection’s (FDEP) Division of Environmental Assessment and Restoration (DEAR) are used to exclude specific results values from the SEACAR Analysis. Based on the threshold filters, Quality Assurance / Quality Control (QAQC) Flags are inserted into the SEACAR_QAQCFlagCode and SEACAR_QAQC_Description columns of the export data. The Include column indicates whether the QAQC Flag will also indicate that data are excluded from analysis. No data are excluded from the data export, but the analysis scripts can use the Include column to exclude data (1 to include, 0 to exclude).

Continuous Water Quality threshold values
Parameter Name Units Low Threshold High Threshold
Dissolved Oxygen mg/L -0.000001 50
Dissolved Oxygen Saturation % -0.000001 500
Salinity ppt -0.000001 70
Turbidity NTU -0.000001 4000
Water Temperature Degrees C -5.000000 45
pH None 2.000000 14
Discrete Water Quality threshold values
Parameter Name Units Low Threshold High Threshold
Ammonia, Un-ionized (NH3) mg/L - -
Ammonium, Filtered (NH4) mg/L - -
Chlorophyll a, Corrected for Pheophytin ug/L - -
Chlorophyll a, Uncorrected for Pheophytin ug/L - -
Colored Dissolved Organic Matter PCU - -
Dissolved Oxygen mg/L -0.000001 25
Dissolved Oxygen Saturation % -0.000001 310
Fluorescent Dissolved Organic Matter QSE - -
Light Extinction Coefficient m^-1 - -
NO2+3, Filtered mg/L - -
Nitrate (NO3) mg/L - -
Nitrite (NO2) mg/L - -
Nitrogen, organic mg/L - -
Phosphate, Filtered (PO4) mg/L - -
Salinity ppt -0.000001 70
Secchi Depth m 0.000001 50
Specific Conductivity mS/cm 0.005000 100
Total Kjeldahl Nitrogen mg/L - -
Total Nitrogen mg/L - -
Total Nitrogen mg/L - -
Total Phosphorus mg/L - -
Total Suspended Solids mg/L - -
Turbidity NTU - -
Water Temperature Degrees C 3.000000 40
pH None 2.000000 13
Quality Assurance Flags inserted based on threshold checks listed in Table 1 and 2
SEACAR QAQC Description Include SEACAR QAQCFlagCode
Exceeds maximum threshold 0 2Q
Below minimum threshold 0 4Q
Within threshold tolerance 1 6Q
No defined thresholds for this parameter 1 7Q

Value Qualifiers

Value qualifier codes included within the data are used to exclude certain results from the analysis. The data are retained in the data export files, but the analysis uses the Include column to filter the results.

STORET and WIN value qualifier codes

Value qualifier codes from STORET and WIN data are examined with the database and used to populate the Include column in data exports.

Value Qualifier codes excluded from analysis
Qualifier Source Value Qualifier Include MDL Description
STORET-WIN H 0 0 Value based on field kit determination; results may not be accurate
STORET-WIN J 0 0 Estimated value
STORET-WIN V 0 0 Analyte was detected at or above method detection limit
STORET-WIN Y 0 0 Lab analysis from an improperly preserved sample; data may be inaccurate

Discrete Water Quality Value Qualifiers

The following value qualifiers are highlighted in the Discrete Water Quality section of this report. An exception is made for Program 476 - Charlotte Harbor Estuaries Volunteer Water Quality Monitoring Network and data flagged with Value Qualifier H are included for this program only.

H - Value based on field kit determiniation; results may not be accurate. This code shall be used if a field screening test (e.g., field gas chromatograph data, immunoassay, or vendor-supplied field kit) was used to generate the value and the field kit or method has not been recognized by the Department as equivalent to laboratory methods.

I - The reported value is greater than or equal to the laboratory method detection limit but less than the laboratory practical quantitation limit.

Q - Sample held beyond the accepted holding time. This code shall be used if the value is derived from a sample that was prepared or analyzed after the approved holding time restrictions for sample preparation or analysis.

S - Secchi disk visible to bottom of waterbody. The value reported is the depth of the waterbody at the location of the Secchi disk measurement.

U - Indicates that the compound was analyzed for but not detected. This symbol shall be used to indicate that the specified component was not detected. The value associated with the qualifier shall be the laboratory method detection limit. Unless requested by the client, less than the method detection limit values shall not be reported

Systemwide Monitoring Program (SWMP) value qualifier codes

Value qualifier codes from the SWMP continuous program are examined with the database and used to populate the Include column in data exports. SWMP Qualifier Codes are indicated by QualifierSource=SWMP.

SWMP Value Qualifier codes
Qualifier Source Value Qualifier Include Description
SWMP -1 1 Optional parameter not collected
SWMP -2 0 Missing data
SWMP -3 0 Data rejected due to QA/QC
SWMP -4 0 Outside low sensor range
SWMP -5 0 Outside high sensor range
SWMP 0 1 Passed initial QA/QC checks
SWMP 1 0 Suspect data
SWMP 2 1 Reserved for future use
SWMP 3 1 Calculated data: non-vented depth/level sensorcorrection for changes in barometric pressure
SWMP 4 1 Historical: Pre-auto QA/QC
SWMP 5 1 Corrected data

Water Column

The water column habitat extends from the water’s surface to the bottom sediments, and it’s where fish, dolphins, crabs and people swim! So much life makes its home in the water column that the health of marine and coastal ecosystems, as well as human economies, depend on the condition of this vulnerable habitat. Local patterns of rainfall, temperature, winds and currents can rapidly change the condition of the water column, while global influences such as El Niño/La Niña, large-scale fluctuation in sea temperatures and climate change can have long-term effects. Inputs from the prosperity of our day-to-day lives including farming, mining and forestry, and emissions from power generation, automobiles and water treatment can also alter the health of the water column. Acting alone or together, each input can have complex and lasting effects on habitats and ecosystems.


SEACAR evaluates water column health with several essential parameters. These include nutrient surveys of nitrogen and phosphorus, and water quality assessments of salinity, dissolved oxygen, pH, and water temperature. Water clarity is evaluated with Secchi depth, turbidity, levels of chlorophyll a, total suspended solids, and colored dissolved organic matter. Additionally, the richness of nekton is indicated by the abundance of free-swimming fishes and macroinvertebrates like crabs and shrimps.

Seasonal Kendall-Tau Analysis

Indicators must have a minimum of five to ten years, depending on the habitat, of data within the geographic range of the analysis to be included in the analysis. Ten years of data are required for discrete parameters, and five years of data are required for continuous parameters. If there are insufficient years of data, the number of years of data available will be noted and labeled as “insufficient data to conduct analysis”. Further, for the preferred Seasonal Kendall-Tau test, there must be data from at least two months in common across at least two consecutive years within the RCP managed area being analyzed. Values that pass both of these tests will be included in the analysis and be labeled as Use_In_Analysis = TRUE. Any that fail either test will be excluded from the analyses and labeled as Use_In_Analysis = FALSE. The points for all Water Column plots displayed in this section are monthly averages. Trend significance will be denoted as “Significant Trend” (when p < 0.05), or “Non-significant Trend” (when p >= 0.05). Any parameters with insufficient data to perform Seasonal Kendall-Tau test will have their monthly averages plotted without a corresponding trend line.

Water Quality - Discrete

The following files were used in the discrete analysis:

  • Combined_WQ_WC_NUT_Chlorophyll_a_corrected_for_pheophytin-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Chlorophyll_a_uncorrected_for_pheophytin-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Colored_dissolved_organic_matter_CDOM-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Dissolved_Oxygen-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Dissolved_Oxygen_Saturation-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_pH-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Salinity-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Secchi_Depth-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Total_Nitrogen-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Total_Phosphorus-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Total_Suspended_Solids_TSS-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Turbidity-2025-Sep-04.txt

  • Combined_WQ_WC_NUT_Water_Temperature-2025-Sep-04.txt

Chlorophyll a, Corrected for Pheophytin - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average levels of chlorophyll a, corrected for pheophytin, over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only laboratory-analyzed chlorophyll a (triangles) is included in the plot.
Scatter plot of monthly average levels of chlorophyll a, corrected for pheophytin, over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only laboratory-analyzed chlorophyll a (triangles) is included in the plot.
Seasonal Kendall-Tau Trend Analysis for Chlorophyll a, Corrected for Pheophytin
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Lab Significantly increasing trend 699 19 2001 - 2025 5.7 0.1302 4.1393 0.1061 0.0473

Monthly average chlorophyll a, corrected for pheophytin, increased by 0.11 µg/L per year, indicating a decrease in water clarity.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Chlorophyll a, Corrected for Pheophytin
ProgramID N_Data YearMin YearMax
5002 638 2001 2025
5016 81 2019 2025

Program names:

5002 - Florida STORET / WIN1
5016 - NEAP Monthly Water Quality Monitoring2

Chlorophyll a, Uncorrected for Pheophytin - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average levels of chlorophyll a, uncorrected for pheophytin, over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only laboratory-analyzed chlorophyll a (triangles) is included in the plot.
Scatter plot of monthly average levels of chlorophyll a, uncorrected for pheophytin, over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only laboratory-analyzed chlorophyll a (triangles) is included in the plot.
Seasonal Kendall-Tau Trend Analysis for Chlorophyll a, Uncorrected for Pheophytin
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Lab No significant trend 379 14 2004 - 2025 6.8 -0.1007 9.1688 -0.0546 0.6

Chlorophyll a, uncorrected for pheophytin, showed no detectable trend between 2004 and 2025.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Chlorophyll a, Uncorrected for Pheophytin
ProgramID N_Data YearMin YearMax
5002 293 2010 2025
5016 82 2019 2025
103 6 2004 2015
118 3 2005 2010

Program names:

103 - EPA STOrage and RETrieval Data Warehouse (STORET)/WQX3
118 - National Aquatic Resource Surveys, National Coastal Condition Assessment4
5002 - Florida STORET / WIN1
5016 - NEAP Monthly Water Quality Monitoring2

Dissolved Oxygen - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average dissolved oxygen over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only dissolved oxygen values measured in the field (circles) are included in the plot.
Scatter plot of monthly average dissolved oxygen over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only dissolved oxygen values measured in the field (circles) are included in the plot.
Seasonal Kendall-Tau Trend Analysis for Dissolved Oxygen
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Field Significantly decreasing trend 22657 30 1995 - 2025 6.8 -0.2692 7.3169 -0.0369 0

Monthly average dissolved oxygen decreased by 0.04 mg/L per year.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Dissolved Oxygen
ProgramID N_Data YearMin YearMax
69 19767 2001 2024
5002 2689 1997 2025
95 189 2013 2018
5016 81 2019 2025
118 12 2005 2021
115 4 1995 1995
103 3 2015 2015

Program names:

69 - Fisheries-Independent Monitoring (FIM) Program5
95 - Harmful Algal Bloom Marine Observation Network6
103 - EPA STOrage and RETrieval Data Warehouse (STORET)/WQX3
115 - Environmental Monitoring Assessment Program7
118 - National Aquatic Resource Surveys, National Coastal Condition Assessment4
5002 - Florida STORET / WIN1
5016 - NEAP Monthly Water Quality Monitoring2

Dissolved Oxygen Saturation - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average dissolved oxygen saturation over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only dissolved oxygen saturation values measured in the field (circles) are included in the plot.
Scatter plot of monthly average dissolved oxygen saturation over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only dissolved oxygen saturation values measured in the field (circles) are included in the plot.
Seasonal Kendall-Tau Trend Analysis for Dissolved Oxygen Saturation
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Field No significant trend 1431 20 2000 - 2025 88 -0.075 87.9841 -0.0808 0.1877

Dissolved oxygen saturation showed no detectable trend between 2000 and 2025.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Dissolved Oxygen Saturation
ProgramID N_Data YearMin YearMax
5002 1449 2000 2025

Program names:

5002 - Florida STORET / WIN1

pH - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average pH over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only pH values measured in the field (circles) are included in the plot.
Scatter plot of monthly average pH over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only pH values measured in the field (circles) are included in the plot.
Seasonal Kendall-Tau Trend Analysis for pH
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Field Significantly decreasing trend 22580 30 1995 - 2025 7.6 -0.1486 7.7407 -0.0052 0.0002

Monthly average pH decreased by 0.01 pH units per year.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for pH
ProgramID N_Data YearMin YearMax
69 19771 2001 2024
5002 2576 1997 2025
95 192 2013 2018
5016 81 2019 2025
103 7 2015 2015
115 3 1995 1995

Program names:

69 - Fisheries-Independent Monitoring (FIM) Program5
95 - Harmful Algal Bloom Marine Observation Network6
103 - EPA STOrage and RETrieval Data Warehouse (STORET)/WQX3
115 - Environmental Monitoring Assessment Program7
5002 - Florida STORET / WIN1
5016 - NEAP Monthly Water Quality Monitoring2

Salinity - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average salinity over time. If the time series included ten or more years of discrete observations, significant (blue) or non-significant (magenta) trend lines are also shown. Discrete salinity values derived from grab samples analyzed in the field (circles) or the laboratory (triangles) are both included in the plot.
Scatter plot of monthly average salinity over time. If the time series included ten or more years of discrete observations, significant (blue) or non-significant (magenta) trend lines are also shown. Discrete salinity values derived from grab samples analyzed in the field (circles) or the laboratory (triangles) are both included in the plot.
Seasonal Kendall-Tau Trend Analysis for Salinity
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
All No significant trend 22769 30 1980 - 2025 30.5 -0.0506 29.8116 -0.0481 0.1992

Salinity showed no detectable trend between 1980 and 2025.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Salinity
ProgramID N_Data YearMin YearMax
69 19830 2001 2024
5002 2678 1997 2025
95 212 1980 2018
5016 52 2019 2024
118 13 2015 2021
115 4 1995 1995

Program names:

69 - Fisheries-Independent Monitoring (FIM) Program5
95 - Harmful Algal Bloom Marine Observation Network6
115 - Environmental Monitoring Assessment Program7
118 - National Aquatic Resource Surveys, National Coastal Condition Assessment4
5002 - Florida STORET / WIN1
5016 - NEAP Monthly Water Quality Monitoring2

Secchi Depth - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average Secchi depth over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Secchi depth is only measured in the field (circles).
Scatter plot of monthly average Secchi depth over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Secchi depth is only measured in the field (circles).
Seasonal Kendall-Tau Trend Analysis for Secchi Depth
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Field Significantly increasing trend 20402 26 2000 - 2025 -0.7 0.1122 -0.7929 0.0032 0.0085

Monthly average Secchi depth became shallower by less than 0.01 m per year, indicating a decrease in water clarity.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Secchi Depth
ProgramID N_Data YearMin YearMax
69 19754 2001 2024
5002 648 2000 2025
103 2 2003 2015

Program names:

69 - Fisheries-Independent Monitoring (FIM) Program5
103 - EPA STOrage and RETrieval Data Warehouse (STORET)/WQX3
5002 - Florida STORET / WIN1

Total Nitrogen - Discrete

Total Nitrogen Calculation:

The logic for calculated Total Nitrogen was provided by Kevin O’Donnell and colleagues at FDEP (with the help of Jay Silvanima, Watershed Monitoring Section). The following logic is used, in this order, based on the availability of specific nitrogen components.

  1. TN = TKN + NO3O2;
  2. TN = TKN + NO3 + NO2;
  3. TN = ORGN + NH4 + NO3O2;
  4. TN = ORGN + NH4 + NO2 + NO3;
  5. TN = TKN + NO3;
  6. TN = ORGN + NH4 + NO3;

Additional Information:

  • Rules for use of sample fraction:
    • Florida Department of Environmental Protection (FDEP) report that if both “Total” and “Dissolved” components are reported, only “Total” is used. If the total is not reported, then the dissolved components are used as a best available replacement.
    • Total nitrogen calculations are done using nitrogen components with the same sample fraction, nitrogen components with mixed total/dissolved sample fractions are not used. In other words, total nitrogen can be calculated when TKN and NO3O2 are both total sample fractions, or when both are dissolved sample fractions. Future calculations of total nitrogen values may be based on components with mixed sample fractions.
  • Values inserted into data:
    • ParameterName = “Total Nitrogen”
    • SEACAR_QAQCFlagCode = “1Q”
    • SEACAR_QAQC_Description = “SEACAR Calculated”

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average total nitrogen over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only nitrogen values obtained from laboratory analyses (triangles) are included in the plot.
Scatter plot of monthly average total nitrogen over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only nitrogen values obtained from laboratory analyses (triangles) are included in the plot.
Seasonal Kendall-Tau Trend Analysis for Total Nitrogen
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Lab No significant trend 1022 27 1997 - 2025 0.4 0.0254 0.3678 0.0012 0.6032

Total nitrogen showed no detectable trend between 1997 and 2025.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Total Nitrogen
ProgramID N_Data YearMin YearMax
5002 932 1997 2025
5016 78 2019 2025
103 12 2004 2006

Program names:

103 - EPA STOrage and RETrieval Data Warehouse (STORET)/WQX3
5002 - Florida STORET / WIN1
5016 - NEAP Monthly Water Quality Monitoring2

Total Phosphorus - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average total phosphorus over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only phosphorus values obtained from laboratory analyses (triangles) are included in the plot.
Scatter plot of monthly average total phosphorus over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only phosphorus values obtained from laboratory analyses (triangles) are included in the plot.
Seasonal Kendall-Tau Trend Analysis for Total Phosphorus
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Lab No significant trend 1560 27 1997 - 2025 0.067 0.0226 0.0589 0.0002 0.5539

Total phosphorus showed no detectable trend between 1997 and 2025.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Total Phosphorus
ProgramID N_Data YearMin YearMax
5002 1490 1997 2025
5016 81 2019 2025
103 12 2004 2015

Program names:

103 - EPA STOrage and RETrieval Data Warehouse (STORET)/WQX3
5002 - Florida STORET / WIN1
5016 - NEAP Monthly Water Quality Monitoring2

Total Suspended Solids - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average total suspended solids (TSS) over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only TSS values obtained from laboratory analyses (triangles) are included in the plot.
Scatter plot of monthly average total suspended solids (TSS) over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only TSS values obtained from laboratory analyses (triangles) are included in the plot.
Seasonal Kendall-Tau Trend Analysis for Total Suspended Solids
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Lab No significant trend 880 26 1997 - 2025 18 0.0623 17.3657 0.149 0.1986

Total suspended solids showed no detectable trend between 1997 and 2025.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Total Suspended Solids
ProgramID N_Data YearMin YearMax
5002 931 1997 2025

Program names:

5002 - Florida STORET / WIN1

Turbidity - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average turbidity over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only turbidity values measured in the laboratory (triangles) are included in the plot.
Scatter plot of monthly average turbidity over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only turbidity values measured in the laboratory (triangles) are included in the plot.
Seasonal Kendall-Tau Trend Analysis for Turbidity
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Lab Significantly increasing trend 1042 27 1997 - 2025 7.1 0.1774 4.038 0.136 0.0001

Monthly average turbidity increased by 0.14 NTU per year, indicating a decrease in water clarity.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Turbidity
ProgramID N_Data YearMin YearMax
5002 983 1997 2025
5016 82 2019 2025
103 4 2005 2006

Program names:

103 - EPA STOrage and RETrieval Data Warehouse (STORET)/WQX3
5002 - Florida STORET / WIN1
5016 - NEAP Monthly Water Quality Monitoring2

Water Temperature - Discrete

Seasonal Kendall-Tau Trend Analysis

Scatter plot of monthly average water temperature over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only water temperature measurements taken in the field (circles) are included in the plot.
Scatter plot of monthly average water temperature over time. If the time series included ten or more years of discrete observations, a significant (blue) or non-significant (magenta) trend line is also shown. Only water temperature measurements taken in the field (circles) are included in the plot.
Seasonal Kendall-Tau Trend Analysis for Water Temperature
Activity Type Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
Field Significantly increasing trend 22815 30 1995 - 2025 23 0.1299 22.1092 0.0348 0.0013

Monthly average water temperature increased by 0.03°C per year.

Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of discrete water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Programs contributing data for Water Temperature
ProgramID N_Data YearMin YearMax
69 19834 2001 2024
5002 2692 1997 2025
95 212 2007 2018
5016 81 2019 2025
115 4 1995 1995

Program names:

69 - Fisheries-Independent Monitoring (FIM) Program5
95 - Harmful Algal Bloom Marine Observation Network6
115 - Environmental Monitoring Assessment Program7
5002 - Florida STORET / WIN1
5016 - NEAP Monthly Water Quality Monitoring2

Water Quality - Continuous

The following files were used in the continuous analysis:

  • Combined_WQ_WC_NUT_cont_Dissolved_Oxygen_NE-2025-Sep-19.txt

  • Combined_WQ_WC_NUT_cont_Dissolved_Oxygen_Saturation_NE-2025-Sep-19.txt

  • Combined_WQ_WC_NUT_cont_pH_NE-2025-Sep-19.txt

  • Combined_WQ_WC_NUT_cont_Salinity_NE-2025-Sep-19.txt

  • Combined_WQ_WC_NUT_cont_Turbidity_NE-2025-Sep-19.txt

  • Combined_WQ_WC_NUT_cont_Water_Temperature_NE-2025-Sep-19.txt

Continuous monitoring locations in Nassau River-St. Johns River Marshes Aquatic Preserve

Station overview for Continuous parameters by Program
ProgramID ProgramLocationID Years of Data Use in Analysis Parameters
7 02231291 3 FALSE DO , TempW
5006 NECI 3 FALSE DO , DOS , pH , Sal , Turb , TempW
5006 NEHM 4 FALSE DO , DOS , pH , Sal , Turb , TempW
5006 NEKD 8 TRUE DO , DOS , pH , Sal , Turb , TempW
5006 NELC 7 TRUE DO , DOS , pH , Sal , Turb , TempW
5006 NENR 3 FALSE DO , DOS , pH , Sal , Turb , TempW
5061 NCB19020038 5 TRUE DO , DOS , pH , Sal , Turb , TempW
5061 NCBARD16 2 FALSE DO , DOS , pH , Sal , Turb , TempW
5061 NCBNRCM 5 TRUE DO , DOS , pH , Sal , Turb , TempW

Program names:

7 - National Water Information System8
5006 - Northeast Aquatic Preserves Continuous Water Quality Monitoring9
5061 - St. Johns River Water Management District Continuous Water Quality Programs10

Map showing continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. Sites marked as Use In Analysis (green) are featured in this report.
Map showing continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. Sites marked as Use In Analysis (green) are featured in this report.

Dissolved Oxygen - Continuous

Scatter plot of monthly average dissolved oxygen over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Scatter plot of monthly average dissolved oxygen over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Seasonal Kendall-Tau Results for Dissolved Oxygen - All Stations
Station Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
02231291 Insufficient data to calculate trend 689 3 2014 - 2016 5.70 - - - -
NECI Insufficient data to calculate trend 54461 3 2023 - 2025 6.20 - - - -
NEHM Insufficient data to calculate trend 85227 4 2022 - 2025 5.90 - - - -
NEKD No significant trend 110958 8 2004 - 2011 6.40 -0.04 6.59 -0.02 0.56
NCBNRCM No significant trend 35477 5 2015 - 2019 5.79 0.05 5.78 0.01 0.8
NENR Insufficient data to calculate trend 31438 3 2009 - 2011 5.80 - - - -
NELC Significantly decreasing trend 95860 7 2005 - 2011 5.60 -0.34 5.93 -0.11 0
NCB19020038 No significant trend 34476 5 2015 - 2019 6.16 -0.03 6.23 -0.03 0.61
NCBARD16 Insufficient data to calculate trend 7417 2 2015 - 2016 5.08 - - - -

At one program location, monthly average dissolved oxygen decreased by 0.11 mg/L per year. No detectable change in monthly average dissolved oxygen was observed at three locations. There was insufficient data to fit a model for five locations.

Map showing location of dissolved oxygen continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of dissolved oxygen continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.

Dissolved Oxygen Saturation - Continuous

Scatter plot of monthly average dissolved oxygen saturation over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Scatter plot of monthly average dissolved oxygen saturation over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Seasonal Kendall-Tau Results for Dissolved Oxygen Saturation - All Stations
Station Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
NEHM Insufficient data to calculate trend 85226 4 2022 - 2025 74.60 - - - -
NECI Insufficient data to calculate trend 54808 3 2023 - 2025 82.40 - - - -
NEKD No significant trend 110983 8 2004 - 2011 89.10 0 87.49 -0.04 0.93
NENR Insufficient data to calculate trend 31438 3 2009 - 2011 73.20 - - - -
NELC Significantly decreasing trend 95868 7 2005 - 2011 77.90 -0.27 78.93 -1.6 0.01
NCBNRCM No significant trend 35240 5 2015 - 2019 82.06 -0.05 81.1 -0.14 0.8
NCB19020038 No significant trend 34438 5 2015 - 2019 87.06 -0.16 86.02 -0.6 0.13
NCBARD16 Insufficient data to calculate trend 7417 2 2015 - 2016 74.44 - - - -

At one program location, monthly average dissolved oxygen saturation decreased by 1.60% per year. No detectable change in monthly average dissolved oxygen saturation was observed at three locations. There was insufficient data to fit a model for four locations.

Map showing location of dissolved oxygen saturation continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of dissolved oxygen saturation continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.

pH - Continuous

Scatter plot of monthly average pH over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Scatter plot of monthly average pH over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Seasonal Kendall-Tau Results for pH - All Stations
Station Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
NECI Insufficient data to calculate trend 52513 3 2023 - 2025 7.70 - - - -
NEHM Insufficient data to calculate trend 87193 4 2022 - 2025 7.10 - - - -
NEKD Significantly increasing trend 113471 8 2004 - 2011 7.90 0.19 7.87 0.01 0.05
NENR Insufficient data to calculate trend 31438 3 2009 - 2011 7.10 - - - -
NCB19020038 No significant trend 34405 5 2015 - 2019 7.88 -0.01 7.85 0 1
NELC No significant trend 96488 7 2005 - 2011 7.50 0.02 7.51 0 0.91
NCBNRCM No significant trend 35819 5 2015 - 2019 7.72 -0.01 7.69 0 0.93
NCBARD16 Insufficient data to calculate trend 6952 2 2015 - 2016 7.66 - - - -

At one program location, monthly average pH increased by 0.01 pH units per year. No detectable change in monthly average pH was observed at three locations. There was insufficient data to fit a model for four locations.

Map showing location of ph continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of ph continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.

Salinity - Continuous

Scatter plot of monthly average salinity over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Scatter plot of monthly average salinity over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Seasonal Kendall-Tau Results for Salinity - All Stations
Station Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
NEHM Insufficient data to calculate trend 88721 4 2022 - 2025 14.40 - - - -
NEKD Significantly increasing trend 118328 8 2004 - 2011 33.20 0.31 30.29 0.52 0
NECI Insufficient data to calculate trend 54462 3 2023 - 2025 29.60 - - - -
NCB19020038 No significant trend 34438 5 2015 - 2019 31.75 -0.06 31.07 -0.11 1
NCBNRCM No significant trend 35411 5 2015 - 2019 30.29 -0.12 30.26 -0.39 0.55
NENR Insufficient data to calculate trend 31438 3 2009 - 2011 12.40 - - - -
NELC No significant trend 100339 7 2005 - 2011 27.90 0.09 25.3 0.53 0.44
NCBARD16 Insufficient data to calculate trend 7418 2 2015 - 2016 30.07 - - - -

At one program location, monthly average salinity increased by 0.52 ppt per year. No detectable change in monthly average salinity was observed at three locations. There was insufficient data to fit a model for four locations.

Map showing location of salinity continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of salinity continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.

Turbidity - Continuous

Scatter plot of monthly average turbidity over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Scatter plot of monthly average turbidity over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Seasonal Kendall-Tau Results for Turbidity - All Stations
Station Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
NEHM Insufficient data to calculate trend 83369 4 2022 - 2025 12.00 - - - -
NECI Insufficient data to calculate trend 53689 3 2023 - 2025 14.00 - - - -
NEKD No significant trend 114181 8 2004 - 2011 4.00 0.02 6.06 0.05 0.87
NCBNRCM No significant trend 34696 5 2015 - 2019 8.64 -0.1 10.09 -0.14 0.6
NCB19020038 No significant trend 31407 5 2015 - 2019 5.77 -0.01 6.79 0.12 0.79
NENR Insufficient data to calculate trend 31087 3 2009 - 2011 21.00 - - - -
NELC No significant trend 96153 7 2005 - 2011 15.00 0.16 15.18 0.64 0.15
NCBARD16 Insufficient data to calculate trend 7385 2 2015 - 2016 12.89 - - - -

No detectable change in monthly average turbidity was observed at four locations. There was insufficient data to fit a model for four locations.

Map showing location of turbidity continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of turbidity continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.

Water Temperature - Continuous

Scatter plot of monthly average water temperature over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Scatter plot of monthly average water temperature over time at continuously monitored program locations. Each location is analyzed separately, with significant (blue) or non-significant (magenta) trend lines shown for time series that included five or more years of observations.
Seasonal Kendall-Tau Results for Water Temperature - All Stations
Station Statistical Trend Sample Count Years with Data Period of Record Median tau Sen Intercept Sen Slope p
02231291 Insufficient data to calculate trend 710 3 2014 - 2016 23.50 - - - -
NEKD No significant trend 118328 8 2004 - 2011 22.10 -0.04 21.88 -0.01 0.81
NECI Insufficient data to calculate trend 54825 3 2023 - 2025 21.00 - - - -
NEHM Insufficient data to calculate trend 89130 4 2022 - 2025 22.80 - - - -
NCB19020038 No significant trend 34483 5 2015 - 2019 24.78 -0.03 23.32 -0.01 1
NENR Insufficient data to calculate trend 31438 3 2009 - 2011 22.00 - - - -
NELC No significant trend 100343 7 2005 - 2011 22.70 0.05 22.26 0.04 0.74
NCBNRCM No significant trend 35817 5 2015 - 2019 24.03 0.07 23.26 0.05 0.67
NCBARD16 Insufficient data to calculate trend 7419 2 2015 - 2016 25.08 - - - -

No detectable change in monthly average water temperature was observed at four locations. There was insufficient data to fit a model for five locations.

Map showing location of water temperature continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.
Map showing location of water temperature continuous water quality sampling locations within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve. The bubble size on the maps above reflect the amount of data available at each sampling site.

References

1.
Florida Department of Environmental Protection (DEP). Florida STORET / WIN. (2024).
2.
Florida Department of Environmental Protection (DEP); Office of Resilience and Coastal Protection (RCP); Northeast Florida Aquatic Preserves; Division of Environmental Assessment and Restoration. NEAP Monthly Water Quality Monitoring . (2024).
3.
U.S. Environmental Protection Agency (EPA). EPA STOrage and RETrieval Data Warehouse (STORET)/WQX. (2023).
4.
U.S. Environmental Protection Agency (EPA); Office of Water; National Oceanic and Atmospheric Administration (NOAA); U.S. Geological Survey (USGS); U.S. Fish and Wildlife Service (USFWS); National Estuary Program (NEP); coastal states. National Aquatic Resource Surveys, National Coastal Condition Assessment. (2021).
5.
Florida Fish and Wildlife Conservation Commission (FWC). Fisheries-Independent Monitoring (FIM) Program. (2022).
6.
Florida Fish and Wildlife Conservation Commission (FWC); Florida Fish and Wildlife Research Institute (FWRI). Harmful Algal Bloom Marine Observation Network. (2018).
7.
U.S. Environmental Protection Agency (EPA); Office of Research and Development. Environmental Monitoring Assessment Program. (2004).
8.
U.S. Geological Survey (USGS). National Water Information System. (2024).
9.
Florida Department of Environmental Protection (DEP); Office of Resilience and Coastal Protection (RCP); Northeast Florida Aquatic Preserves. Northeast Aquatic Preserves Continuous Water Quality Monitoring. (2024).
10.
St. Johns River Water Management District (SJRWMD). St. Johns River Water Management District Continuous Water Quality Programs. (2024).