Pass

3 out of 3 indicators were rated as PASS.

All three indicators must pass for the bay to be rated as PASS.

Learn more about how this report is created

Summary:

The overall health in Sarasota Bay has remained high. Water quality metrics remained relatively constant, with chlorophyll a decreasing slightly and nitrogen and phosphorus edging upward.

Water Quality: All three water quality indicators (chlorophyll a, nitrogen, and phosphorus) were rated as excellent (below their respective targets). The mean for chlorophyll a was calculated as an arithmetic mean and the means for nitrogen and phosphorus were calculated as geometric means (per the Numeric Nutrient Criteria outlined in the Florida Administrative Code, section 62-302.532). Mean chlorophyll a concentration was 0.0045 mg/l, below the target value of 0.0052 mg/l. The mean concentration of total nitrogen increased slightly to 0.3901 mg/l, still below its target value of 0.490 mg/l calculated in 2010*. Mean phosphorus concentration increased very slightly as well, but at 0.0588 mg/l, was well below its target value of 0.150 mg/l.

Biotic Indicator: A survey of the biotic indicator, seagrass, was performed in 2014 by the Southwest Florida Water Management District. In 2014, the total area of seagrass in the lower portion of Sarasota Bay (the area within Sarasota County) was estimated to be 3,397 acres. The total for the whole of Sarasota Bay was estimated to be 10,261 acres, well above the target threshold of 7,269 acres.

*A new target value for nitrogen has not been defined for Sarasota Bay because insufficient color data exist to perform the necessary calculation.

Sarasota Bay

Sarasota Bay

Water Chemistry Ratings

Total nitrogen, total phosphorus, and chlorophyll a levels are monitored carefully by water resource managers and used by regulatory authorities to determine whether a bay meets the water quality standards mandated by the Clean Water Act. The trend graphs for these indicators are shown below, along with their target and threshold values. A target value is a desirable goal to be attained, while a threshold is an undesirable level which is to be avoided. An individual indicator receives an "Excellent" rating if its mean value is below the target, a "Good" rating if its mean value is above the target but does not exceed the threshold, and a "Caution" rating if the mean value exceeds the threshold. Learn More about these ratings and how they are calculated »

The Five-year Trend Graphs below illustrate the general trend of water quality parameters. They show a six-month running average, which moderates high and low values in the data.

Chart Legend
  • Trend Line
  • Annual Mean
  • Target
  • Threshold
Excellent

Chlorophyll a

Score: Excellent How was this determined?
Units: mg/l Year
2014
Historical
period of record
High 0.023 0.049
Mean 0.004 0.005 0.0041065 0.0052000000
Low 0.001 0.000
No. of Samples 245 3963

Five-year Trend Graph

  • Annual Mean
Excellent

Nitrogen, Total

Score: Excellent How was this determined?
Units: mg/l Year
2014
Historical
period of record
High 0.900 1.870
Mean 0.390 0.19182627 0.5100000000
Low 0.040 0.030
No. of Samples 244 3772

Five-year Trend Graph

  • Annual Mean
Targets and thresholds shown on this graph are advisory approximations computed by Sarasota County using recent data. Regulatory thresholds have not been established. Learn more about Sarasota Bay Nitrogen targets/thresholds »
Excellent

Phosphorus, Total

Score: Excellent How was this determined?
Units: mg/l Year
2014
Historical
period of record
High 0.140 4.400
Mean 0.058 0.087 0.13328858 0.1500000000
Low 0.050 0.002
No. of Samples 306 4508

Five-year Trend Graph

  • Annual Mean

Dissolved Oxygen

Units: mg/l Year
2014
Historical
period of record
High 103.60 103.60
Mean 7.14 6.71 1.59669
Low 3.80 1.48
No. of Samples 234 15045

Five-year Trend Graph

  • Annual Mean

Apparent Color

Units: PCU Year
2014
Historical
period of record
High 25.00 98.00
Mean 9.25 13.28 9.58946
Low 4.00 0.00
No. of Samples 254 4484

Five-year Trend Graph

  • Annual Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2014
Historical
period of record
High 3.40 9.20
Mean 0.92 1.17 0.76416
Low 0.50 0.50
No. of Samples 254 3124

Five-year Trend Graph

  • Annual Mean

Dissolved oxygen saturation

Units: percent (%) Year
2014
Historical
period of record
High 138.00 214.71
Mean 97.22 97.71 19.23792
Low 63.00 21.92
No. of Samples 296 15351

Five-year Trend Graph

  • Annual Mean

Karenia brevis ("red tide")

Units: #/l Year
2014
Historical
period of record
High 2000.00 6380000.00
Mean 1003.95 55269.94 377167.85228
Low 1000.00 1000.00
No. of Samples 253 2345

Five-year Trend Graph

  • Annual Mean

Light Attenuation

Units: K(1/m) Year
2014
Historical
period of record
High 5.68 5.68
Mean 0.68 0.69 0.32095
Low 0.20 0.05
No. of Samples 222 2920

Five-year Trend Graph

  • Annual Mean

Nitrogen, Ammonia + Ammonium as N

Units: ug/l Year
2014
Historical
period of record
High 39.00 159.00
Mean 8.91 11.40 10.8775
Low 5.00 5.00
No. of Samples 254 3639

Five-year Trend Graph

  • Annual Mean

Nitrogen, Kjeldahl

Units: ug/l Year
2014
Historical
period of record
High 870.00 1850.00
Mean 413.03 370.73 187.22505
Low 0.01 0.01
No. of Samples 310 4617

Five-year Trend Graph

  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: ug/l Year
2014
Historical
period of record
High 30.00 210.00
Mean 9.30 8.66 10.15535
Low 5.00 1.00
No. of Samples 306 5476

Five-year Trend Graph

  • Annual Mean

pH

Units: None Year
2014
Historical
period of record
High 8.50 9.62
Mean 8.10 8.07 0.33763
Low 7.60 3.90
No. of Samples 356 13039

Five-year Trend Graph

  • Annual Mean

Rainfall

Units: inches/yr Year
2014
Historical
period of record
High 42.3 56.0
Mean 35.9 15.1375999308565
Low 8.1
No. of Samples 354 5377

Five-year Trend Graph

  • Annual Mean

Salinity

Units: PSS Year
2014
Historical
period of record
High 36.40 42.30
Mean 33.80 33.19 2.37364
Low 28.70 3.60
No. of Samples 235 16576

Five-year Trend Graph

  • Annual Mean

Specific conductance

Units: umho Year
2014
Historical
period of record
High 54780.00 62750.00
Mean 51335.82 51782.52 3600.41565
Low 44500.00 31.20
No. of Samples 297 4836

Five-year Trend Graph

  • Annual Mean

Temperature, water

Units: deg F Year
2014
Historical
period of record
High 88.52 100.40
Mean 76.16 76.99 9.12479
Low 62.96 35.24
No. of Samples 408 17511

Five-year Trend Graph

  • Annual Mean

Turbidity

Units: NTU Year
2014
Historical
period of record
High 21.00 39.00
Mean 2.69 2.64 2.4846
Low 0.30 0.03
No. of Samples 246 13524

Five-year Trend Graph

  • Annual Mean

Other Measures of Bay Health

In addition to nutrient levels and chlorophyll concentration, dissolved oxygen levels, and water clarity are also objective indicators of bay health. These have complex interactive cycles which are affected by rainfall, temperature, and tidal action, as well as other factors. High nutrient levels (nitrogen and phosphorus) can stimulate excessive growth of marine algae (indicated by chlorophyll a level), resulting in reduced water clarity (and increased light attenuation) and depleted oxygen levels. Both plants and animals in a bay need oxygen to survive, and the seagrasses which provide food and cover for bay creatures need light for photosynthesis.

Bay Contour Maps (2014)

Contour mapping is one of the best ways to visualize spatial differences in coastal water quality. The interactive map shown below presents monthly data for one selected water quality indicator atop an aerial view of the bay. Choose a different water quality parameter from the list at the top to change the map. Learn More about Water Quality Contour Mapping »

Showing 2014 Monthly Contour Maps for: January
Loading interactive contour map viewer...
Contour Visibility:

Visit the Water Quality Contour Mapping Tool to view and compare monthly water quality contour maps for ten different water quality indicators. In addition, you can generate your own custom maps.

Contour Legend:

  • Less than 1 mg/l
  • 1.0 - 5.9 mg/l
  • 6.0 - 10.9 mg/l
  • 11.0 - 17.9 mg/l
  • Greater than 18 mg/l

Seagrasses

Among the most important habitats in Florida's estuarine environments, seagrass beds are indispensable for the role they play in cycling nutrients, supplying food for wildlife, stabilizing sediments, and providing habitat for juvenile and adult finfish and shellfish. Use the interactive map below to observe the size, density and location of seagrass beds from year to year. The graph shows how the total amount of seagrass in the bay has changed over time.
Learn More about Seagrasses »

Showing Seagrass Coverage for :
Loading interactive seagrass coverage viewer...
Loading interactive chart...
  • Target 2,022 acres

Visit our Seagrass page to discover the beauty and importance of seagrass habitats, and sign up to help monitor their health.

Impervious Features

Sarasota Bay is located within the Sarasota Bay Watershed. View details about the Sarasota Bay Watershed »

Rain that falls on land that is in a natural state is absorbed and filtered by soils and vegetation as it makes it way into underground aquifers. However, in developed areas, "impervious surfaces" impede this process and contribute to polluted urban runoff entering surface waters. These surfaces include human infrastructure like roads, sidewalks, driveways and parking lots that are covered by impenetrable materials such as asphalt, concrete, brick and stone, as well as buildings and other permanent structures. Soils that have been disturbed and compacted by urban development are often impervious as well. Learn more about Impervious Features »

The Sarasota County Stormwater Environmental Utility (SEU) mapped impervious surfaces in the County in 2014. A map showing impervious surfaces can be viewed using the interactive Sarasota NPDES Viewer.

19% of the land area within the Sarasota Bay Watershed is covered by impervious surfaces

Impervious Surface Coverage by Type

Land Use / Land Cover

Land use within a bay's watershed has a major effect on its water quality. In general, less development means better water quality. Land Cover/Land Use classifications categorize land in terms of its observed physical surface characteristics (upland or wetland, e.g.), and also reflect the types of activity that are taking place on it (agriculture, urban/built-up, utilities, etc.). Florida uses as its standard a set of statewide classifications which were developed by the Florida Department of Transportation. Learn More about Land Use and Land Cover »

Sarasota Bay is located within the Sarasota Bay Watershed. The chart below shows the land use / land cover characteristics for Sarasota Bay Watershed within the boundary of this Water Atlas. View details about the Sarasota Bay Watershed »

Acreage and Percentage within each Land Use / Land Cover Category for Sarasota Bay Watershed
Land Use Classification 1990 2005 2014 Trend
Urban & Built-up 32,90853.3% 37,84461.3% 37,98761.6%
Agriculture 6,33810.3% 2,4974% 2,3093.7%
Rangeland 5470.9% 1990.3% 4300.7%
Upland Forests 3,5885.8% 2,1093.4% 1,9233.1%
Water 13,35021.6% 14,22723.1% 14,13122.9%
Wetlands 2,8704.7% 2,2273.6% 2,3723.8%
Barren Land 290% 90% 1090.2%
Transportation and Utilities 1,8453% 2,6024.2% 2,4534%
Land Use Chart

Data Sources

The data sources listed below provided water quality data used to create the report on this page. Not all data sources provided data for every bay, and not every Bay Conditions Report used data from all listed data sources. While some data sources have no data for the scored year, they provided period-of-record (historical high, mean, low) data. Click on a data source name to review its metadata.