Summary:

Because target values for chlorophyll a and nutrients have not yet been established for Lower Lemon Bay, it is not being assigned an overall score. The water quality measures used here to assess bay conditions all creeped upward in 2017, with the annual mean concentration of chlorophyll a exceeding the regulatory threshold. The mean concentration of nitrogen is high, with some individuals exceeding the threshold, but the mean is still below it. Phosphorus continues to be very low compared to the threshold, and its annual mean did not change appreciably from 2016.

Water Quality: The mean concentration of nitrogen in 2017 increased to 0.6053 mg/l, with some samples exceeding the regulatory threshold of 0.62 mg/l. The mean concentration of phosphorus in 2017 also increased, to 0.0551 mg/l, still well below the regulatory limit. The mean concentration of chlorophyll increased  to 0.0069 mg/l, pushing it above the regulatory mean of 0.0061 mg/l. The means for chlorophyll a, nitrogen and phosphorus were calculated as arithmetic 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 unchanged 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 2,880 acres.

Lower Lemon Bay

Lower 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
Unavailable

Chlorophyll a

Units: mg/l Year
2017
Historical
period of record
High 0.052 0.119
Mean 0.007 0.006 0.00696789
Low 0.001 0.001
No. of Samples 21 1025

Five-year Rolling Average

  • Annual Mean
Unavailable

Nitrogen, Total

Units: mg/l Year
2017
Historical
period of record
High 1.404 2.660
Mean 0.605 0.534 0.31443109 0.0000000000
Low 0.384 0.000
No. of Samples 21 1047

Five-year Rolling Average

  • Annual Mean
Unavailable

Phosphorus, Total

Units: mg/l Year
2017
Historical
period of record
High 0.150 1.300
Mean 0.075 0.081 0.15103709 0.0000000000
Low 0.039 0.010
No. of Samples 7 438

Five-year Rolling Average

  • Annual Mean

Dissolved Oxygen

Units: mg/l Year
2017
Historical
period of record
High 7.20 13.60
Mean 5.34 5.93 1.61481 0.0000000000
Low 2.30 1.30
No. of Samples 19 6414

Five-year Rolling Average

  • Annual Mean

Apparent Color

Note: The latest available sample for this parameter is from December 2009
Units: PCU Year
2017
Historical
period of record
High 210.00
Mean 17.35 23.71509
Low 1.00
No. of Samples 0 440

Five-year Rolling Average

  • Annual Mean

Dissolved oxygen saturation

Note: The latest available sample for this parameter is from March 2013
Units: percent (%) Year
2017
Historical
period of record
High 210.45
Mean 88.51 22.69681
Low 22.34
No. of Samples 0 2153

Five-year Rolling Average

  • Annual Mean

Nitrogen, Kjeldahl

Units: ug/l Year
2017
Historical
period of record
High 1400.00 2240.00
Mean 714.29 615.20 359.41833
Low 390.00 21.30
No. of Samples 7 451

Five-year Rolling Average

  • Annual Mean

Nitrogen, Nitrite + Nitrate as N

Units: ug/l Year
2017
Historical
period of record
High 11.00 269.00
Mean 5.00 29.50 29.86955
Low 4.00 4.00
No. of Samples 7 163

Five-year Rolling Average

  • Annual Mean

pH

Units: None Year
2017
Historical
period of record
High 8.40 9.76
Mean 7.41 7.98 0.39801
Low 3.20 3.20
No. of Samples 8 4817

Five-year Rolling Average

  • Annual Mean

Salinity

Units: PSS Year
2017
Historical
period of record
High 37.10 63.10
Mean 31.49 33.32 3.159
Low 17.10 3.70
No. of Samples 24 7369

Five-year Rolling Average

  • Annual Mean

Specific conductance

Note: The latest available sample for this parameter is from December 2009
Units: umho Year
2017
Historical
period of record
High 58890.00
Mean 51949.64 4495.0873
Low 11990.00
No. of Samples 0 1033

Five-year Rolling Average

  • Annual Mean

Temperature, water

Units: deg F Year
2017
Historical
period of record
High 86.72 99.50
Mean 74.55 77.89 8.91603
Low 62.42 34.16
No. of Samples 10 7034

Five-year Rolling Average

  • Annual Mean

Turbidity

Units: NTU Year
2017
Historical
period of record
High 4.30 40.00
Mean 2.30 3.27 2.49413
Low 1.00 0.15
No. of Samples 21 5141

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 2,880 acres

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

Impervious Features

Lower 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 »

Lower 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.