Caution

1 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:

Water quality indicators for Upper Lemon Bay improved in 2017, but only very slightly and its ratings remained unchanged. While phosphorus concentration remained well below the desired target, chlorophylll and nitrogen levels are still above their regulatory thresholds; mean values for all three water quality measures were slightly lower than the previous year, but overall water quality remains a concern.

Water Quality: Chlorophyll a mean concentration in 2017 was 0.0130 mg/l, exceeding the threshold of 0.0089 mg/l. Mean nitrogen concentration decreased to 0.6031 mg/l, remaining above the threshold of 0.560 mg/l. At 0.1261 mg/l, mean phosophorus concentration is well below the target and is again rated as “Excellent”. 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).

Biotic Indicator: Measurement of the biotic indicator, seagrass, was performed in 2016 by the Southwest Florida Water Management District. Between 2014 to 2016, seagrass coverage in Lemon Bay (including both the Upper and Lower segments) remained at 3,913 acres, exceeding the combined target value of 3,890 acres. Lower Lemon Bay was not surveyed separately, but has a target level of 1,010 acres.

Upper Lemon Bay

Upper Lemon 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 Rolling Average 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
Caution

Chlorophyll a

Score: Caution How was this determined?
Units: mg/l Year
2017
Historical
period of record
High 0.070 0.085
Mean 0.015 0.010 0.0094724 0.0067000000
Low 0.000 0.000
No. of Samples 94 2435

Five-year Rolling Average

  • Annual Mean
Caution

Nitrogen, Total

Score: Caution How was this determined?
Units: mg/l Year
2017
Historical
period of record
High 1.465 1.465
Mean 0.585 0.533 0.20276834 0.5200000000
Low 0.315 0.055
No. of Samples 92 1374

Five-year Rolling Average

  • Annual Mean
Excellent

Phosphorus, Total

Score: Excellent How was this determined?
Units: mg/l Year
2017
Historical
period of record
High 0.300 0.880
Mean 0.136 0.167 0.09197569 0.2200000000
Low 0.050 0.050
No. of Samples 97 1391

Five-year Rolling Average

  • Annual Mean

Dissolved Oxygen

Units: mg/l Year
2017
Historical
period of record
High 9.80 12.00
Mean 6.57 6.24 1.49091 0.0000000000
Low 2.60 0.20
No. of Samples 88 2947

Five-year Rolling Average

  • Annual Mean

Apparent Color

Units: PCU Year
2017
Historical
period of record
High 160.00 280.00
Mean 33.27 31.97 28.60119
Low 4.00 4.00
No. of Samples 85 1378

Five-year Rolling Average

  • Annual Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2017
Historical
period of record
High 5.20 7.60
Mean 2.16 1.79 1.12196
Low 0.50 0.50
No. of Samples 85 1236

Five-year Rolling Average

  • Annual Mean

Dissolved oxygen saturation

Units: percent (%) Year
2017
Historical
period of record
High 128.00 180.07
Mean 93.40 89.50 19.29861
Low 50.00 21.60
No. of Samples 80 2804

Five-year Rolling Average

  • Annual Mean

Karenia brevis ("red tide")

Units: #/l Year
2017
Historical
period of record
High 434000.00 4480000.00
Mean 10557.38 28690.15 242084.66692
Low 0.00 0.00
No. of Samples 61 802

Five-year Rolling Average

  • Annual Mean

Light Attenuation

Units: K(1/m) Year
2017
Historical
period of record
High 3.11 3.85
Mean 1.20 1.13 0.55551 0.0000000000
Low 0.14 0.14
No. of Samples 60 1188

Five-year Rolling Average

  • Annual Mean

Nitrogen, Ammonia + Ammonium as N

Units: ug/l Year
2017
Historical
period of record
High 99.00 359.00
Mean 10.87 25.16 35.21643
Low 5.00 5.00
No. of Samples 85 1380

Five-year Rolling Average

  • Annual Mean

Nitrogen, Kjeldahl

Units: ug/l Year
2017
Historical
period of record
High 900.00 900.00
Mean 701.43 701.43 175.44501
Low 370.00 370.00
No. of Samples 7 7

Five-year Rolling Average

  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: ug/l Year
2017
Historical
period of record
High 54.00 130.00
Mean 6.35 8.99 11.16864
Low 4.00 4.00
No. of Samples 97 1822

Five-year Rolling Average

  • Annual Mean

pH

Units: None Year
2017
Historical
period of record
High 8.50 8.90
Mean 7.96 7.97 0.32143
Low 7.49 4.80
No. of Samples 86 2507

Five-year Rolling Average

  • Annual Mean

Salinity

Units: PSS Year
2017
Historical
period of record
High 37.60 40.60
Mean 28.71 29.75 5.14435
Low 10.70 2.80
No. of Samples 114 3260

Five-year Rolling Average

  • Annual Mean

Specific conductance

Units: umho Year
2017
Historical
period of record
High 55300.00 60590.00
Mean 33850.41 45128.92 9627.59404
Low 35.30 35.30
No. of Samples 80 1383

Five-year Rolling Average

  • Annual Mean

Temperature, water

Units: deg F Year
2017
Historical
period of record
High 92.30 107.60
Mean 79.08 77.89 8.8252
Low 61.70 46.76
No. of Samples 88 3222

Five-year Rolling Average

  • Annual Mean

Turbidity

Units: NTU Year
2017
Historical
period of record
High 6.90 22.00
Mean 3.04 2.97 1.7097
Low 0.86 0.21
No. of Samples 92 2613

Five-year Rolling Average

  • 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 (2017)

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 2017 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 1,010 acres

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

Impervious Features

Upper Lemon Bay is located within the Lemon Bay Watershed. View details about the Lemon 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.

10% of the land area within the Lemon 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 »

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

Acreage and Percentage within each Land Use / Land Cover Category for Lemon Bay Watershed
Land Use Classification 1990 2005 2014 Trend
Urban & Built-up 11,33133.6% 12,87238.2% 13,58940.4%
Agriculture 2,5157.5% 2,3256.9% 2,2556.7%
Rangeland 2,2096.6% 4,47913.3% 4,11512.2%
Upland Forests 9,36027.8% 5,63716.7% 5,10915.2%
Water 3,1049.2% 3,43710.2% 3,50110.4%
Wetlands 4,68913.9% 4,26512.7% 4,37513%
Barren Land 290.1% 00% 00%
Transportation and Utilities 4431.3% 6551.9% 7262.2%
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.