Little Sarasota Bay Condition Report for 2011

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 of Little Sarasota Bay has improved since 2010 with all water quality parameters below the threshold levels, the caution alert for chlorophyll a has been removed. Additionally, the mean acreage of seagrass has continued to increase. 

Water quality: All three water quality indicators (chlorophyll a, nitrogen, and phosphorus) were rated as pass (below the threshold). The mean for chlorophyll a was calculated as an arithmetic mean and the means for nitrogen and phosphorus were calculated as geometric means (Numeric Nutrient Criteria Recommendations). The mean chlorophyll a level in Little Sarasota Bay has improved since 2010 (0.0091 mg/l) and was scored as “Good” (scored as caution in 2010), below the threshold (0.0104 mg/l). The mean nitrogen level (0.4993 mg/l) has slightly decreased and remains below the threshold (0.600 mg/l) and target level (0.520 mg/l). Therefore, the mean nitrogen level was scored as “Excellent”. The mean phosphorus level (0.0824 mg/l) has remained constant and was scored as “Excellent”, below the target (0.180 mg/l) and threshold (0.210 mg/l) levels.

Biotic Indicator:  The biotic indicator, seagrass, was determined to be in good condition with a continued increase in acreage since 1988. In 2010, the total acreage of seagrass increased 49% to 1,000 acres.

Little Sarasota Bay

Little Sarasota Bay
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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 charts 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
  • Six-month Moving Average
  • Annual Mean
  • Target
  • Threshold
Excellent

Chlorophyll a

Score: Excellent How was this determined?
Units: ug/l Year
2011		 Historical
period of record
High 21.55 43.45
Mean 8.09 7.53 6.7362 8.2000000000
Low 1.63 0.06
No. of Samples 72 1072
  • Six-month
    Moving Average
  • Annual
    Mean
Excellent

Nitrogen, Total

Score: Excellent How was this determined?
Units: mg/L Year
2011		 Historical
period of record
High 0.865 1.175
Mean 0.503 0.16948795 0.5200000000
Low 0.215 0.055
No. of Samples 72 1056
  • Six-month
    Moving Average
  • Annual
    Mean
Excellent

Phosphorus, Total

Score: Excellent How was this determined?
Units: mg/L Year
2011		 Historical
period of record
High 0.699 0.699
Mean 0.095 0.148 0.07540532 0.1800000000
Low 0.050 0.050
No. of Samples 84 1100
  • Six-month
    Moving Average
  • Annual
    Mean

Dissolved Oxygen

Units: mg/l Year
2011		 Historical
period of record
High 9.40 11.60
Mean 6.69 6.57 1.19016
Low 4.60 2.80
No. of Samples 72 1209
  • Six-month
    Moving Average
  • Annual
    Mean

Apparent Color

Units: PCU Year
2011		 Historical
period of record
High 90.00 140.00
Mean 28.10 25.08 19.09335
Low 5.00 4.00
No. of Samples 84 1100
  • Six-month
    Moving Average
  • Annual
    Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2011		 Historical
period of record
High 3.70 6.50
Mean 1.49 1.75 0.95287
Low 0.50 0.50
No. of Samples 84 955
  • Six-month
    Moving Average
  • Annual
    Mean

Dissolved oxygen saturation

Units: percent (%) Year
2011		 Historical
period of record
High 124.00 167.00
Mean 95.99 95.02 15.17492
Low 75.00 45.00
No. of Samples 72 1218
  • Six-month
    Moving Average
  • Annual
    Mean

Karenia brevis ("red tide")

Units: #/l Year
2011		 Historical
period of record
High 1000.00 2603000.00
Mean 1000.00 20547.88 160500.88465
Low 1000.00 1000.00
No. of Samples 72 449
  • Six-month
    Moving Average
  • Annual
    Mean

Light Attenuation

Units: K(1/m) Year
2011		 Historical
period of record
High 1.87 2.85
Mean 0.95 1.00 0.43907
Low 0.08 0.08
No. of Samples 72 981
  • Six-month
    Moving Average
  • Annual
    Mean

Nitrogen, Ammonia + Ammonium as N

Units: ug/l Year
2011		 Historical
period of record
High 88.00 203.00
Mean 16.42 16.92 20.17372
Low 5.00 5.00
No. of Samples 72 1076
  • Six-month
    Moving Average
  • Annual
    Mean

Nitrogen, Kjeldahl

Units: mg/L Year
2011		 Historical
period of record
High 1.240 1.240
Mean 0.569 0.489 0.17932956
Low 0.210 0.000
No. of Samples 84 1100
  • Six-month
    Moving Average
  • Annual
    Mean

Nitrogen, Nitrite + Nitrate as N

Units: mg/L Year
2011		 Historical
period of record
High 0.461 0.536
Mean 0.028 0.009 0.02818719
Low 0.005 0.005
No. of Samples 84 1657
  • Six-month
    Moving Average
  • Annual
    Mean

pH

Units: None Year
2011		 Historical
period of record
High 8.50 8.50
Mean 8.04 7.95 0.18763
Low 7.70 6.20
No. of Samples 72 1218
  • Six-month
    Moving Average
  • Annual
    Mean

Salinity

Units: PSS Year
2011		 Historical
period of record
High 35.50 39.50
Mean 30.77 30.83 4.89838
Low 21.10 7.30
No. of Samples 72 1185
  • Six-month
    Moving Average
  • Annual
    Mean

Specific conductance

Units: umho Year
2011		 Historical
period of record
High 53970.00 59030.00
Mean 47174.86 47253.83 6815.43696
Low 33650.00 12670.00
No. of Samples 72 1218
  • Six-month
    Moving Average
  • Annual
    Mean

Temperature, water

Units: deg F Year
2011		 Historical
period of record
High 88.70 92.12
Mean 76.59 76.91 9.17886
Low 62.42 47.48
No. of Samples 72 1217
  • Six-month
    Moving Average
  • Annual
    Mean

Turbidity

Units: NTU Year
2011		 Historical
period of record
High 11.00 15.00
Mean 4.26 3.88 1.94808
Low 1.00 0.60
No. of Samples 72 1063
  • Six-month
    Moving Average
  • Annual
    Mean

Annual Averages

Indicator Units 2007 2008 2009 2010 2011 Trend
Dissolved Oxygen mg/l 7.19 6.69
Dissolved oxygen saturation percent (%) 98.64 95.99
Light Attenuation K(1/m) 1.12 0.95
Salinity PSS 29.96 30.77
Turbidity NTU 4.39 4.26

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 (2011)

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 2011 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 ug/l
  • 1.0 - 5.9 ug/l
  • 6.0 - 10.9 ug/l
  • 11.0 - 17.9 ug/l
  • Greater than 18 ug/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. Seagrass calculations are aggregates of patchy and continuous seagrass measurements only. Recordings of attached algae are not included in these summaries.
Learn More about Seagrasses »

Showing Seagrass Coverage for :
Loading interactive seagrass coverage viewer...
Loading interactive chart...
  • Target 702 acres

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

Impervious Features

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

14% of the land area within the Little 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 »

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

Acreage and Percentage within each Land Use / Land Cover Category for Little Sarasota Bay Watershed
Land Use Classification 1990 2005 2011 2014 2017 2020 Trend
Urban & Built-up 8,94331.9% 11,83442.2% 12,10243.1% 12,16243.3% 12,77745.5% 13,34347.5%
Agriculture 3,55012.6% 3,22811.5% 3,25811.6% 4,22315% 3,12411.1% 2,83710.1%
Rangeland 8252.9% 1,8226.5% 1,4745.3% 5792.1% 1,2334.4% 8773.1%
Upland Forests 7,09825.3% 3,06610.9% 2,98110.6% 2,7259.7% 2,6879.6% 2,6039.3%
Water 3,42912.2% 4,12314.7% 4,14714.8% 4,17514.9% 4,22715.1% 4,33715.5%
Wetlands 3,49012.4% 3,13311.2% 3,19111.4% 3,22711.5% 3,12111.1% 3,12011.1%
Barren Land 620.2% 180.1% 190.1% 200.1% 60% 60%
Transportation and Utilities 6752.4% 8413% 8923.2% 9523.4% 8983.2% 9483.4%
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.