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 showed deterioration in 2016. After an improvement in chlorophyll a concentration in 2014, this water quality measure continued the worsening trend observed in 2015 with further increases in 2016. The mean concentration of both total nitrogen and total phosphorus also showed an increasing trend. The higher chlorophyll a and nitrogen levels continued the rating for those water quality measures as “Caution”, causing the overall rating for Upper Lemon Bay also to remain as “Caution”.

Water Quality: Chlorophyll a mean concentration in 2016 was of 0.0136 mg/l, exceeding the threshold of 0.0089 mg/l. Mean nitrogen concentration increased to 0.6362 mg/l, exceeding the threshold of 0.560 mg/l. Mean phosophorus concentration  also elevated, and at 0.138 mg/l is “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
2016
Historical
period of record
High 0.060 0.088
Mean 0.014 0.009 0.00907866 0.0067000000
Low 0.002 0.000
No. of Samples 82 1636

Five-year Rolling Average

  • Annual Mean
Caution

Nitrogen, Total

Score: Caution How was this determined?
Units: mg/l Year
2016
Historical
period of record
High 1.266 2.800
Mean 0.636 0.575 0.27002126 0.5200000000
Low 0.385 0.000
No. of Samples 82 1635

Five-year Rolling Average

  • Annual Mean
Excellent

Phosphorus, Total

Score: Excellent How was this determined?
Units: mg/l Year
2016
Historical
period of record
High 0.260 0.880
Mean 0.136 0.169 0.09345218 0.2200000000
Low 0.050 0.050
No. of Samples 74 1294

Five-year Rolling Average

  • Annual Mean

Dissolved Oxygen

Units: mg/l Year
2016
Historical
period of record
High 10.10 12.00
Mean 6.33 6.04 1.57472 0.0000000000
Low 1.60 1.20
No. of Samples 78 3121

Five-year Rolling Average

  • Annual Mean

Apparent Color

Units: PCU Year
2016
Historical
period of record
High 140.00 280.00
Mean 40.89 31.88 28.47028
Low 10.00 5.00
No. of Samples 74 1293

Five-year Rolling Average

  • Annual Mean

BOD, Biochemical oxygen demand

Units: mg/l Year
2016
Historical
period of record
High 4.70 7.60
Mean 1.69 1.76 1.11619
Low 0.50 0.50
No. of Samples 74 1151

Five-year Rolling Average

  • Annual Mean

Dissolved oxygen saturation

Units: percent (%) Year
2016
Historical
period of record
High 128.00 180.07
Mean 90.90 89.39 19.44517
Low 62.00 21.60
No. of Samples 60 2724

Five-year Rolling Average

  • Annual Mean

Karenia brevis ("red tide")

Units: #/l Year
2016
Historical
period of record
High 1480000.00 4480000.00
Mean 59500.00 30182.86 251279.6721
Low 1000.00 1000.00
No. of Samples 41 741

Five-year Rolling Average

  • Annual Mean

Light Attenuation

Units: K(1/m) Year
2016
Historical
period of record
High 3.79 3.85
Mean 1.39 1.12 0.53707 0.0000000000
Low 0.53 0.16
No. of Samples 54 1100

Five-year Rolling Average

  • Annual Mean

Nitrogen, Ammonia + Ammonium as N

Units: ug/l Year
2016
Historical
period of record
High 177.00 359.00
Mean 28.62 26.09 35.98492
Low 5.00 5.00
No. of Samples 74 1295

Five-year Rolling Average

  • Annual Mean

Nitrogen, Kjeldahl

Units: ug/l Year
2016
Historical
period of record
High 990.00 1330.00
Mean 635.81 555.16 201.31905
Low 380.00 0.05
No. of Samples 74 1294

Five-year Rolling Average

  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: ug/l Year
2016
Historical
period of record
High 58.00 130.00
Mean 11.22 9.14 11.36637
Low 5.00 5.00
No. of Samples 74 1725

Five-year Rolling Average

  • Annual Mean

pH

Units: None Year
2016
Historical
period of record
High 8.60 8.90
Mean 7.99 7.97 0.32513
Low 7.30 4.80
No. of Samples 90 2421

Five-year Rolling Average

  • Annual Mean

Rainfall

Units: inches/yr Year
2016
Historical
period of record
High 57.0 68.9
Mean 40.0 20.1825227610425
Low 9.4
No. of Samples 366 5332

Five-year Rolling Average

  • Annual Mean

Salinity

Units: PSS Year
2016
Historical
period of record
High 35.80 41.50
Mean 28.01 29.86 5.23981
Low 9.60 2.80
No. of Samples 81 3444

Five-year Rolling Average

  • Annual Mean

Specific conductance

Units: umho Year
2016
Historical
period of record
High 52910.00 60590.00
Mean 42021.50 45821.39 7966.08788
Low 18500.00 5800.00
No. of Samples 60 1303

Five-year Rolling Average

  • Annual Mean

Temperature, water

Units: deg F Year
2016
Historical
period of record
High 90.50 107.60
Mean 79.52 77.86 8.86621
Low 64.22 46.76
No. of Samples 68 3134

Five-year Rolling Average

  • Annual Mean

Turbidity

Units: NTU Year
2016
Historical
period of record
High 7.60 66.00
Mean 3.27 2.97 2.05226
Low 0.92 0.21
No. of Samples 82 2881

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 (2016)

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 2016 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.