Sarasota County Water Atlas

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Roberts Bay Sarasota

Roberts Bay Sarasota

Roberts Bay Sarasota


located within the following watersheds: Little Sarasota Bay Watershed, Sarasota Bay Watershed

General Information


Explore general as well as scientific information about the movement, chemistry and biology of area surface water environments.

Latest Information

Click the links below for more details:

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Map Legend

Water Quality sampling site
Hydrology sampling site
Closest Rainfall site
Rainfall sampling site
Multi-type sampling site
Other sampling site

Beach Water Quality from the Florida Healthy Beaches Program

Coastal beach water samples collected every two weeks by the county health departments are analyzed for enterococci and fecal coliform bacteria. High concentrations of these bacteria may indicate the presence of microorganisms that could cause diseases, infections, or rashes. County health departments will issue health advisories or warnings when these conditions are confirmed. Learn more about the Florida Healthy Beaches Program »

Note: We are currently unable to provide you with the most recent samples and alerts on this page. Please click on the county/beach links below to find beach status and alerts.

Source: Florida Healthy Beaches Program
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    Red Tide

    The gulf and bays of southwest Florida experience a "red tide" that is caused by recurring high concentrations of an alga that discolors the water and releases toxic chemicals. In Florida, under suitable conditions, the microscopic organism (Karenia brevis) successfully reproduces to more than a million cells per liter. The toxins kill fish, manatees, birds, and other wildlife, make shellfish inedible, and make beachgoers uncomfortable. The economic losses to the recreation industry can exceed tens of millions of dollars. Public outcry about persistent red tides has stimulated an increased resolve among researchers to understand the complex bloom mechanisms and to develop methods to alleviate the troublesome effects.
    Learn more about Red Tide >>

    Waterbody Characteristics
    Parameter Latest Value Historic Range Additional Information
    Red Tide Counts
    (Karenia brevis)
    0 cells/l
    7/11/2018 1:50:00 PM
    0 - 912,000 cells/l
    9/13/2005 - 7/11/2018
    1,465 samples
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      Overall Trophic State Index

      "Trophic" means "relating to nutrition." The Trophic State Index (TSI) takes into account chlorophyll, nitrogen, and phosphorus, which are nutrients required by plant life. The Florida Department of Environmental Protection (FDEP) uses this information to determine a rating for the waterbody. Learn more about the Trophic State Index »

      Water Quality Index
      Latest Value Limiting Nutrient Historic Range Additional Information
      40 (Good)
      Source: Sarasota County Coastal Creeks
      Water Quality Trophic State Index Trophic State Classification
      GOOD0 - 49Oligotrophic through Mid-Eutrophic
      FAIR50 - 59Mid-Eutrophic through Eutrophic
      POOR60 - 100Hypereutrophic
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        Nutrient Chemistry

        Although present in all surface waters, nutrients are among the leading causes of degradation of Florida water resources. Learn more about nutrient chemistry »

        Nutrient Chemistry
        Parameter Latest Value Historic Range Additional Information
        Total Nitrogen (TN) 448.0 ug/l
        Source: Sarasota County Environmental Services Department Sampling Data
        65.0 - 2,216.0 ug/L
        7/8/1982 - 9/5/2018
        4,264 samples
        Total Phosphorus (TP) 80.0 ug/L
        Source: Sarasota County Coastal Creeks
        6.0 - 1,120.0 ug/L
        3/20/1975 - 9/5/2018
        4,387 samples
        Chlorophyll a,
        uncorrected for
        pheophytin help icon
        9.6 ug/L
        7/11/2018 1:50:00 PM
        Source: Sarasota County Coastal Creeks
        0.1 - 57.7 ug/L
        8/8/1990 - 9/5/2018
        2,467 samples
        Chlorophyll a,
        corrected for
        pheophytin help icon
        12.2 ug/L
        Source: Sarasota County Coastal Creeks
        0.3 - 48.4 ug/L
        2/25/1998 - 8/3/2016
        2,737 samples
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          Water Clarity

          Water clarity or turbidity measures the degree to which light is blocked because the water is cloudy or contains suspended particles, such as algae. Water clarity is one indicator of a waterbody's ability to sustain plants and wildlife. Learn more about water clarity »

          Water Clarity
          Parameter Latest Value Historic Range Additional Information
          Secchi Depth 4.3 ft
          Source: Sarasota County Environmental Services Department Sampling Data
          0.3 ft - 15.1 ft
          9/11/1980 - 9/5/2018
          2,722 samples
          Turbidity 3.4 NTU
          7/11/2018 1:50:00 PM
          Source: Sarasota County Coastal Creeks
          0.2 NTU - 24.0 NTU
          10/25/1979 - 9/5/2018
          4,660 samples
          Light Attenuation 0.88 Alpha/M
          Source: Sarasota County Coastal Creeks
          0.20 NTU - 4.17 Alpha/M
          8/8/1990 - 5/10/1994
          90 samples
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            The currently used bacterial indicators for recreational waters include total coliform, fecal coliform and enterococcus. Indicator organisms themselves are not necessarily pathogenic but their presence "indicates" or suggests recent contamination by human sewage or other waste which may result in human illness. Sources of contamination include storm water runoff, sewage overflows and feces from wild and domestic animals. Learn more about marine indicator bacteria »

            Parameter Latest Value Historic Range Additional Information
            Fecal Coliform 110 CFU/100ml
            Source: Sarasota County Historic Data from Legacy STORET
            3 - 1,800 CFU/100ml
            6/14/1979 - 9/28/1992
            354 samples
            Total Coliform 1,000 CFU/100ml
            Source: Sarasota County Historic Data from Legacy STORET
            0 - 19,000 CFU/100ml
            1/11/1971 - 9/28/1992
            541 samples
            Enterococcus NO DATA NO DATA NO DATA
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              Dissolved Oxygen

              Dissolved Oxygen (DO) is one of the most important indicators of water quality. It is essential for the survival of fish and other aquatic organisms. Learn more about dissolved oxygen »

              Additional Parameters
              Parameter Latest Value Historic Range Additional Information
              Dissolved Oxygen 6.1 mg/l
              Source: Sarasota County Environmental Services Department Sampling Data
              0.1 - 12.7 mg/l
              4/17/1973 - 9/5/2018
              14,459 samples
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                Salinity measures the amount of salts dissolved in water. An estuary can exhibit a change in salinity throughout its length as fresh water entering from the tributaries mixes with seawater from the ocean. Learn more about salinity »
                Parameter Latest Value Historic Range Additional Information
                Salinity 29.8 ppt
                Source: IMAP Water Quality Data
                0.2 - 36.4 ppt
                11/25/1981 - 9/5/2018
                1,313 samples
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                Bathymetric Maps and Depth Information

                These are the latest available contour maps of the bay's bottom. These maps can be used to determine where "holes" (deep spots) exist on the bay bottom. Such areas are often productive for fishing. Learn more about bathymetric maps »

                Bathymetric Map
                View Map Details Method River Elevation
                No Data Available No Data Available No Data Available No Data Available
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                Water Quality Contour Maps

                Example Contour Map

                Contour mapping is one of the best ways to visualize spatial differences in coastal water quality, but the software and technical expertise needed to create them is unavailable to the general public and is out of reach even to many environmental resource managers and scientists. With original funding from an Environmental Protection Commission of Hillsborough County's Pollution Recovery Fund grant, the Water Atlas Program developed online tools to allow rapid map creation and comparison. Using these tools, anyone can view, download and print predefined maps that are automatically generated from selected data on a periodic basis. Optionally, users can create their own custom contour maps to display any data that is stored on the Water Atlas, by choosing a water quality parameter and date range that interests them.

                Available water quality parameters include:

                Chlorophyll a, Color, Dissolved Oxygen (Bottom), Dissolved Oxygen (Surface), Salinity (Bottom), Salinity (Surface), Secchi Depth, Total Nitrogen, Total Phosphorus, Turbidity

                Create Custom Water Quality Contour Maps

                Access the Water Quality Contour Mapping System to generate your own custom water quality contour maps.


                View Generated Water Quality Contour Maps

                Monthly generated contour maps for all the parameters below are available.

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                  Impaired Waters

                  The Impaired Waters Data is the most recent available data from FDEP, but it may not reflect the current FDEP impaired list. These data are updated when and as soon as they are made available from FDEP.


                  This waterbody is impaired according to the State of Florida's Impaired Waters Rule (IWR) Chapter 62-303 F.A.C. that governs the Total Maximum Daily Loads (TMDL) Program or according to the U.S. Environmental Protection Agency (EPA). Identification of Impaired Surface Waters (IWR) is a new scientific approach for guiding Florida Department of Environmental Protection process for identifying and prioritizing impaired surface waters in Florida. The rule evaluates whether waters meet their designated uses for a particular analyte, which include aquatic life use support, primary contact and recreation use support, fish and shellfish consumption use support, and drinking water use support. All water resources in this county are designated as Class III waters. Class III waters are considered recreational use waters, which means that the water should be fishable and swimmable. Class II waters are for shellfish propagation and harvesting. Class I waters are considered potable (drinkable) water supplies. As part of the terms of a court order related to the 1998 303(d) list of impaired waters, some waters are listed as impaired by EPA but not listed by the State of Florida. Learn more about impaired waters »


                  This waterbody has been associated with the following WBIDs deemed impaired by the Environmental Protection Agency's 303(d) list:

                  WBID Basin Impairment(s) EPA Details
                  1968D ROBERTS BAY MERCURY IN FISH TISSUE View additional EPA information »

                  Source(s): US Environmental Protection Agency

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                  Advanced Data Features

                  Files Graphs

                  Data Download and Advanced Graphing Tool
                  Download and/or graph water quality, hydrology, and rainfall trends using the data presented on the Atlas for use in your own analyses and reports.

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