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: 2026-06-10

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
Chlorophyll a, Uncorrected for Pheophytin ug/L - -
Dissolved Oxygen mg/L -0.000001 50
Dissolved Oxygen Saturation % -0.000001 500
Fluorescent Dissolved Organic Matter QSE - -
Salinity ppt -0.000001 70
Specific Conductivity mS/cm -0.000001 200
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 (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, inorganic 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 Ammonia (N) mg/L - -
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-2026-May-18.txt

  • Combined_WQ_WC_NUT_Chlorophyll_a_uncorrected_for_pheophytin-2026-May-18.txt

  • Combined_WQ_WC_NUT_Colored_dissolved_organic_matter_CDOM-2026-May-18.txt

  • Combined_WQ_WC_NUT_Dissolved_Oxygen-2026-May-18.txt

  • Combined_WQ_WC_NUT_Dissolved_Oxygen_Saturation-2026-May-18.txt

  • Combined_WQ_WC_NUT_pH-2026-May-18.txt

  • Combined_WQ_WC_NUT_Salinity-2026-May-18.txt

  • Combined_WQ_WC_NUT_Secchi_Depth-2026-May-18.txt

  • Combined_WQ_WC_NUT_Total_Nitrogen-2026-May-18.txt

  • Combined_WQ_WC_NUT_Total_Phosphorus-2026-May-18.txt

  • Combined_WQ_WC_NUT_Total_Suspended_Solids_TSS-2026-May-18.txt

  • Combined_WQ_WC_NUT_Turbidity-2026-May-18.txt

  • Combined_WQ_WC_NUT_Water_Temperature-2026-May-18.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 No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
Lab No detectable trend 722 19 2001 - 2025 5.7 0.1056 4.5326 0.0783 0.1155

Chlorophyll a, corrected for pheophytin, showed no detectable trend between 2001 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, Corrected for Pheophytin
ProgramID N_Data YearMin YearMax
5002 658 2001 2025
5016 84 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 No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
Lab No detectable trend 382 14 2004 - 2025 6.8 -0.1033 9.1688 -0.0523 0.6373

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 84 2019 2025
103 6 2004 2015
118 3 2005 2010

Program names:

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

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 No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
Field Decreasing trend 22688 30 1995 - 2025 6.8 -0.2727 7.3252 -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 19765 2001 2024
5002 2719 1997 2025
95 189 2013 2018
5016 84 2019 2025
118 12 2005 2021
115 4 1995 1995
103 3 2015 2015

Program names:

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

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 No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
Field No detectable trend 1461 20 2000 - 2025 88 -0.0858 88.7588 -0.0885 0.1199

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 1479 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 No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
Field Decreasing trend 22611 30 1995 - 2025 7.6 -0.14 7.7414 -0.0049 0.0005

Monthly average pH decreased by less than 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 19769 2001 2024
5002 2606 1997 2025
95 192 2013 2018
5016 84 2019 2025
103 7 2015 2015
115 3 1995 1995

Program names:

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

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 No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
All No detectable trend 22784 30 1980 - 2025 30.5 -0.0641 30.3694 -0.0574 0.0985

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 19828 2001 2024
5002 2708 1997 2025
95 212 1980 2018
5016 52 2019 2024
115 4 1995 1995

Program names:

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

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 No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
Lab No detectable trend 1079 27 1997 - 2025 0.419 0.0333 0.3646 0.0016 0.5048

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 985 1997 2025
5016 81 2019 2025
103 13 2004 2015

Program names:

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

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 No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
Lab No detectable trend 1615 27 1997 - 2025 0.067 0.0164 0.0627 0.0001 0.6538

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 1543 1997 2025
5016 84 2019 2025
103 12 2004 2015

Program names:

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

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 No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
Lab Increasing trend 1098 27 1997 - 2025 7.1075 0.1819 4.204 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 1040 1997 2025
5016 85 2019 2025
103 4 2005 2006

Program names:

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

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 No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
Field Increasing trend 22846 30 1995 - 2025 23 0.1165 22.1719 0.0322 0.0041

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 19832 2001 2024
5002 2722 1997 2025
95 212 2007 2018
5016 84 2019 2025
115 4 1995 1995

Program names:

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

Water Quality - Continuous

The following files were used in the continuous analysis:

  • Combined_WQ_WC_NUT_cont_Chlorophyll_a_Uncorrected_for_Pheophytin-2026-Mar-06.txt

  • Combined_WQ_WC_NUT_cont_Dissolved_Oxygen-2026-Mar-06.txt

  • Combined_WQ_WC_NUT_cont_Dissolved_Oxygen_Saturation-2026-Mar-06.txt

  • Combined_WQ_WC_NUT_cont_Fluorescent_Dissolved_Organic_Matter-2026-Mar-06.txt

  • Combined_WQ_WC_NUT_cont_pH-2026-Mar-06.txt

  • Combined_WQ_WC_NUT_cont_Salinity-2026-Mar-06.txt

  • Combined_WQ_WC_NUT_cont_Specific_Conductivity-2026-Mar-06.txt

  • Combined_WQ_WC_NUT_cont_Turbidity-2026-Mar-06.txt

  • Combined_WQ_WC_NUT_cont_Water_Temperature-2026-Mar-06.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 Dissolved Oxygen , Water Temperature , Specific Conductivity
5006 NECI 3 FALSE pH , Dissolved Oxygen Saturation, Dissolved Oxygen , Turbidity , Water Temperature , Salinity , Specific Conductivity
5006 NEHM 4 FALSE pH , Dissolved Oxygen Saturation, Dissolved Oxygen , Turbidity , Water Temperature , Salinity , Specific Conductivity
5006 NEKD 8 TRUE pH , Dissolved Oxygen Saturation, Dissolved Oxygen , Turbidity , Water Temperature , Salinity , Specific Conductivity
5006 NELC 7 TRUE pH , Dissolved Oxygen Saturation, Dissolved Oxygen , Turbidity , Water Temperature , Salinity , Specific Conductivity
5006 NENR 3 FALSE pH , Dissolved Oxygen Saturation, Dissolved Oxygen , Turbidity , Water Temperature , Salinity , Specific Conductivity
5061 NCB19020038 5 TRUE pH , Dissolved Oxygen Saturation, Dissolved Oxygen , Turbidity , Water Temperature , Salinity , Specific Conductivity
5061 NCBARD16 2 FALSE pH , Dissolved Oxygen Saturation, Dissolved Oxygen , Turbidity , Water Temperature , Salinity , Specific Conductivity
5061 NCBNRCM 5 TRUE pH , Dissolved Oxygen Saturation, Dissolved Oxygen , Turbidity , Water Temperature , Salinity , Specific Conductivity

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.

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
Program Location Statistical Trend No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
NECI Insufficient data to calculate trend 60282 3 2023 - 2025 7.70 - - - -
NEHM Insufficient data to calculate trend 116425 4 2022 - 2025 7.10 - - - -
NEKD Significantly increasing trend 113471 8 2004 - 2011 7.90 0.19 7.87 0.01 0.05
NELC No significant trend 96488 7 2005 - 2011 7.50 0.02 7.51 0 0.91
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
NCBARD16 Insufficient data to calculate trend 6952 2 2015 - 2016 7.66 - - - -
NCBNRCM No significant trend 35819 5 2015 - 2019 7.72 -0.01 7.69 0 0.93

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.

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
Program Location Statistical Trend No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
NECI Insufficient data to calculate trend 62577 3 2023 - 2025 80.50 - - - -
NEHM Insufficient data to calculate trend 114458 4 2022 - 2025 71.50 - - - -
NEKD No significant trend 110983 8 2004 - 2011 89.10 0 87.49 -0.04 0.93
NELC Significantly decreasing trend 95868 7 2005 - 2011 77.90 -0.27 78.93 -1.6 0.01
NENR Insufficient data to calculate trend 31438 3 2009 - 2011 73.20 - - - -
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 - - - -
NCBNRCM No significant trend 35240 5 2015 - 2019 82.06 -0.05 81.1 -0.14 0.8

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.

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
Program Location Statistical Trend No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
02231291 Insufficient data to calculate trend 689 3 2014 - 2016 5.70 - - - -
NECI Insufficient data to calculate trend 62230 3 2023 - 2025 5.80 - - - -
NEHM Insufficient data to calculate trend 111776 4 2022 - 2025 5.50 - - - -
NEKD No significant trend 110958 8 2004 - 2011 6.40 -0.04 6.59 -0.02 0.56
NELC Significantly decreasing trend 95860 7 2005 - 2011 5.60 -0.34 5.93 -0.11 0
NENR Insufficient data to calculate trend 31438 3 2009 - 2011 5.80 - - - -
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 - - - -
NCBNRCM No significant trend 35477 5 2015 - 2019 5.79 0.05 5.78 0.01 0.8

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.

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
Program Location Statistical Trend No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
NECI Insufficient data to calculate trend 60677 3 2023 - 2025 15.00 - - - -
NEHM Insufficient data to calculate trend 108736 4 2022 - 2025 12.00 - - - -
NEKD No significant trend 114181 8 2004 - 2011 4.00 0.02 6.06 0.05 0.87
NELC No significant trend 96153 7 2005 - 2011 15.00 0.16 15.18 0.64 0.15
NENR Insufficient data to calculate trend 31087 3 2009 - 2011 21.00 - - - -
NCB19020038 No significant trend 31407 5 2015 - 2019 5.77 -0.01 6.79 0.12 0.79
NCBARD16 Insufficient data to calculate trend 7385 2 2015 - 2016 12.89 - - - -
NCBNRCM No significant trend 34696 5 2015 - 2019 8.64 -0.1 10.09 -0.14 0.6

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

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
Program Location Statistical Trend No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
02231291 Insufficient data to calculate trend 710 3 2014 - 2016 23.50 - - - -
NECI Insufficient data to calculate trend 62594 3 2023 - 2025 23.10 - - - -
NEHM Insufficient data to calculate trend 118362 4 2022 - 2025 24.60 - - - -
NEKD No significant trend 118328 8 2004 - 2011 22.10 -0.04 21.88 -0.01 0.81
NELC No significant trend 100343 7 2005 - 2011 22.70 0.05 22.26 0.04 0.74
NENR Insufficient data to calculate trend 31438 3 2009 - 2011 22.00 - - - -
NCB19020038 No significant trend 34483 5 2015 - 2019 24.78 -0.03 23.32 -0.01 1
NCBARD16 Insufficient data to calculate trend 7419 2 2015 - 2016 25.08 - - - -
NCBNRCM No significant trend 35817 5 2015 - 2019 24.03 0.07 23.26 0.05 0.67

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

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
Program Location Statistical Trend No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
NECI Insufficient data to calculate trend 62231 3 2023 - 2025 29.80 - - - -
NEHM Insufficient data to calculate trend 113173 4 2022 - 2025 14.40 - - - -
NEKD Significantly increasing trend 118328 8 2004 - 2011 33.20 0.31 30.29 0.52 0
NELC No significant trend 100339 7 2005 - 2011 27.90 0.09 25.3 0.53 0.44
NENR Insufficient data to calculate trend 31438 3 2009 - 2011 12.40 - - - -
NCB19020038 No significant trend 34438 5 2015 - 2019 31.75 -0.06 31.07 -0.11 1
NCBARD16 Insufficient data to calculate trend 7418 2 2015 - 2016 30.07 - - - -
NCBNRCM No significant trend 35411 5 2015 - 2019 30.29 -0.12 30.26 -0.39 0.55

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.

Specific Conductivity - Continuous

Scatter plot of monthly average specific conductivity 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 specific conductivity 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 Specific Conductivity - All Stations
Program Location Statistical Trend No. of Samples No. Years with Data Period of Record Median Result Value Tau Sen Intercept Sen Slope P
02231291 Insufficient data to calculate trend 682 3 2014 - 2016 30.40 - - - -
NECI Insufficient data to calculate trend 62231 3 2023 - 2025 45.94 - - - -
NEHM Insufficient data to calculate trend 111827 4 2022 - 2025 23.57 - - - -
NEKD Significantly increasing trend 118327 8 2004 - 2011 50.62 0.31 46.46 0.71 0
NELC No significant trend 100339 7 2005 - 2011 43.33 0.08 39.43 0.77 0.51
NENR Insufficient data to calculate trend 31438 3 2009 - 2011 20.04 - - - -
NCB19020038 No significant trend 34438 5 2015 - 2019 48.67 -0.06 47.75 -0.15 1
NCBARD16 Insufficient data to calculate trend 7418 2 2015 - 2016 46.32 - - - -
NCBNRCM No significant trend 35411 5 2015 - 2019 46.65 -0.12 46.58 -0.54 0.55

At one program location, monthly average specific conductivity increased by 0.71 mS/cm per year. No detectable change in monthly average specific conductivity was observed at three locations. There was insufficient data to fit a model for five locations.

Oyster

The data file used is: All_OYSTER_Parameters-2026-Jun-04.txt

Maps showing the temporal scope of oyster sampling sites within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve by program name.
Maps showing the temporal scope of oyster sampling sites within the boundaries of Nassau River-St. Johns River Marshes Aquatic Preserve by program name.

Click here to view spatio-temporal plots on GitHub.

Density

For natural reefs, there was insufficient data to calculate a trend for density.

Natural

Scatter plot of oyster density over time. If the time series included five or more years with observations, an estimated trend (blue line) and a 95% credible interval (purple band) may also be plotted. Data points are jittered horizontally to reduce overlap.
Scatter plot of oyster density over time. If the time series included five or more years with observations, an estimated trend (blue line) and a 95% credible interval (purple band) may also be plotted. Data points are jittered horizontally to reduce overlap.
Model results for Oyster Density - Natural
Habitat Type Shell Type Statistical Trend Period of Record Estimate Standard Error Credible Interval
Natural Live Oysters Insufficient data 2016 - 2016 - - -
Map showing location of oyster density 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 oyster density 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.

Percent Live

For natural reefs, there was insufficient data to calculate a trend for percent live cover.

Natural

Scatter plot of percent live oysters over time. If the time series included five or more years with observations, an estimated trend (blue line) and a 95% credible interval (purple band) may also be plotted. Estimation method is represented as percent (circles), point-intercept (triangle), or estimated percent (square), with data points jittered horizontally to reduce overlap.
Scatter plot of percent live oysters over time. If the time series included five or more years with observations, an estimated trend (blue line) and a 95% credible interval (purple band) may also be plotted. Estimation method is represented as percent (circles), point-intercept (triangle), or estimated percent (square), with data points jittered horizontally to reduce overlap.
Model results for Oyster Percent Live - Natural
Habitat Type Shell Type Statistical Trend Period of Record Estimate Standard Error Credible Interval
Natural Live Oysters Insufficient data 2016 - 2016 - - -
Map showing location of oyster percent live 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 oyster percent live 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.

Shell Height

For natural reefs, there was insufficient data to calculate a trend for live oysters in either the 25-75mm or the ≥75mm size class.

Natural

Model results for Oyster Shell Height - Natural
Habitat Type Shell Type SizeClass Statistical Trend Period of Record No. of Samples Estimate Standard Error Credible Interval
Natural Live Oysters >75mm Insufficient data 2016 - 2016 144 - - -
Natural Live Oysters 25-75mm Insufficient data 2016 - 2016 1100 - - -
Map showing location of oyster shell height 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 oyster shell height 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).