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Roberts Bay Condition Report for 2010

View 2011 Report

Caution

2 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 Roberts Bay has decreased due to an alert level of chlorophyll a and below the target level of seagrass.  The other two water quality indicators, (nitrogen and phosphorus) were rated as pass.

Water quality: Only two water quality indicators (nitrogen and phosphorus) were rated as pass (below the threshold) and remained in "Excellent" condition. Nitrogen levels have remained constant and below the threshold (0.540 mg/l) but slightly above the target level of 0.450 mg/l. Phosphorus levels have decreased with the average below the target level (0.190 mg/l).  Chlorophyll a levels have greatly increased since 2009 and are now scored as alert because levels exceed the threshold of 0.011 mg/l.

Biotic Indicator:  The total acreage of seagrass has remained relatively constant since 1988 but in 2010 the average level of seagrass (283 acres) was still below the target of 348 acres.

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. 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.

Caution

Chlorophyll a

Score: Caution How was this determined?
Units: mg/l Year
2010
Historical
period of record
High 0.0389 0.0484
Mean 0.0138 0.0079 0.0078407 0.0082000000
Low 0.001 0.0003
No. of Samples 385 4,835

Five-year Trend Graph

     
1/1/20062.4350.0024300mg/l
2/1/20061.0350.0017300mg/l
3/1/20062.2250.0018900mg/l
4/1/20062.0850.0019400mg/l
5/1/20061.1350.0017800mg/l
6/1/20063.9950.0021500mg/l
7/1/20069.0050.0032400mg/l
8/1/20067.9950.0044000mg/l
9/1/200618.0050.0070300mg/l
10/1/20066.0760.0077000mg/l
11/1/20063.6950.0081200mg/l
12/1/20061.9260.0077800mg/l
1/1/20071.7050.0065600mg/l
2/1/20070.5450.0053200mg/l
3/1/20071.1550.0025100mg/l
4/1/20074.8050.0023000mg/l
5/1/20072.9550.0021800mg/l
6/1/20072.4850.0022700mg/l
7/1/20075.4560.0029000mg/l
8/1/20075.9160.0037900mg/l
9/1/20074.3060.0043200mg/l
10/1/20078.3860.0049100mg/l
11/1/20072.4060.0048200mg/l
12/1/20072.9460.0049000mg/l
1/1/20083.8860.0046400mg/l
2/1/20083.0860.0041600mg/l
3/1/20082.6560.0038900mg/l
4/1/20086.2060.0035300mg/l
5/1/20088.1960.0044900mg/l
6/1/20085.6960.0049500mg/l
7/1/20086.9260.0054600mg/l
8/1/200813.9460.0072700mg/l
9/1/200816.6650.0096000mg/l
10/1/200814.6460.0110100mg/l
11/1/20084.4460.0103800mg/l
12/1/20081.6060.0097000mg/l
1/1/20095.9450.0095400mg/l
2/1/20091.4850.0074600mg/l
3/1/20091.9550.0050100mg/l
4/1/20093.9150.0032200mg/l
5/1/200911.9250.0044700mg/l
6/1/20096.3950.0052700mg/l
7/1/200910.0150.0059400mg/l
8/1/20099.1650.0072200mg/l
9/1/200912.8350.0090400mg/l
10/1/200926.1350.0127400mg/l
11/1/20098.7250.0122100mg/l
12/1/20097.2450.0123500mg/l
1/1/20101.2950.0109000mg/l
2/1/20103.0250.0098700mg/l
3/1/20101.1860.0079300mg/l
4/1/20108.3250.0049600mg/l
5/1/201012.4950.0055900mg/l
6/1/201016.7660.0071800mg/l
7/1/201015.3560.0095200mg/l
8/1/201030.6650.0141300mg/l
9/1/201033.6650.0195400mg/l
10/1/201013.9550.0204800mg/l
11/1/201010.4550.0201400mg/l
12/1/20103.1650.0178700mg/l
Loading Chart...
Target
0.0082 mg/l
Threshold
0.011 mg/l
Excellent

Nitrogen, Total

Score: Excellent How was this determined?
Units: mg/l Year
2010
Historical
period of record
High 0.846 1.376
Mean 0.4494 0.17737254 0.4500000000
Low 0.215 0.065
No. of Samples 60 768

Five-year Trend Graph

     
1/1/2006350.4050.3504000mg/l
2/1/2006275.8050.3131000mg/l
3/1/2006379.0050.3350700mg/l
4/1/2006383.8050.3472500mg/l
5/1/2006310.8050.3399600mg/l
6/1/2006372.2050.3453300mg/l
7/1/2006564.6730.3810500mg/l
8/1/2006625.6050.4393500mg/l
9/1/2006650.2050.4845500mg/l
10/1/2006467.8360.4985500mg/l
11/1/2006384.0050.5107500mg/l
12/1/2006433.8360.5210200mg/l
1/1/2007435.0050.4994100mg/l
2/1/2007208.6050.4299100mg/l
3/1/2007325.0050.3757100mg/l
4/1/2007207.0050.3322400mg/l
5/1/2007347.0050.3260700mg/l
6/1/2007330.2050.3088000mg/l
7/1/2007436.6760.3090800mg/l
8/1/2007358.3360.3340300mg/l
9/1/2007450.3360.3549200mg/l
10/1/2007461.6760.3973700mg/l
11/1/2007427.6760.4108100mg/l
12/1/2007412.8360.4245800mg/l
1/1/2008382.6760.4155800mg/l
2/1/2008334.6760.4116400mg/l
3/1/2008313.1760.3887800mg/l
4/1/2008414.6050.3809400mg/l
5/1/2008398.3360.3760500mg/l
6/1/2008418.6760.3770200mg/l
7/1/2008503.3360.3971300mg/l
8/1/2008581.5060.4382700mg/l
9/1/2008568.3360.4807900mg/l
10/1/2008473.0050.4905300mg/l
11/1/2008426.1760.4951700mg/l
12/1/2008521.1760.5122500mg/l
1/1/2009418.8050.4981600mg/l
2/1/2009319.0050.4544100mg/l
3/1/2009371.0050.4215200mg/l
4/1/2009361.0050.4028600mg/l
5/1/2009521.0050.4186600mg/l
6/1/2009445.0050.4059700mg/l
7/1/2009411.0050.4046700mg/l
8/1/2009329.0050.4063300mg/l
9/1/2009449.6050.4194300mg/l
10/1/2009505.0050.4434300mg/l
11/1/2009413.6050.4255300mg/l
12/1/2009506.0050.4357000mg/l
1/1/2010275.0050.4130300mg/l
2/1/2010399.6050.4248000mg/l
3/1/2010240.0060.3898700mg/l
4/1/2010627.8050.4103300mg/l
5/1/2010499.0050.4245700mg/l
6/1/2010547.0060.4314000mg/l
7/1/2010426.8360.4567100mg/l
8/1/2010517.0050.4762700mg/l
9/1/2010643.2050.5434700mg/l
10/1/2010409.0050.5070100mg/l
11/1/2010751.6050.5491100mg/l
12/1/2010386.4050.5223400mg/l
Loading Chart...
Target
0.45 mg/l
Threshold
0.54 mg/l
Excellent

Phosphorus, Total

Score: Excellent How was this determined?
Units: mg/l Year
2010
Historical
period of record
High 0.19 0.48
Mean 0.0838 0.06846986 0.1900000000
Low 0.05 0.05
No. of Samples 377 4,836

Five-year Trend Graph

     
1/1/2006146.0050.1460000mg/l
2/1/2006136.0050.1410000mg/l
3/1/2006192.0050.1580000mg/l
4/1/2006172.0050.1615000mg/l
5/1/2006152.0050.1596000mg/l
6/1/2006162.0050.1600000mg/l
7/1/2006188.0050.1670000mg/l
8/1/2006202.0050.1780000mg/l
9/1/2006268.0050.1906700mg/l
10/1/2006190.0060.1936700mg/l
11/1/2006178.0050.1980000mg/l
12/1/2006178.3360.2007200mg/l
1/1/2007144.0050.1933900mg/l
2/1/2007112.0050.1783900mg/l
3/1/2007134.0050.1560600mg/l
4/1/2007100.0050.1410600mg/l
5/1/2007144.0050.1353900mg/l
6/1/2007132.0050.1276700mg/l
7/1/2007152.0050.1290000mg/l
8/1/2007170.0060.1386700mg/l
9/1/2007196.0050.1490000mg/l
10/1/2007150.0050.1573300mg/l
11/1/2007133.3360.1555600mg/l
12/1/2007134.0050.1558900mg/l
1/1/2008166.6760.1583300mg/l
2/1/2008115.0060.1491700mg/l
3/1/2008140.0050.1398300mg/l
4/1/2008168.0050.1428300mg/l
5/1/2008203.3360.1545000mg/l
6/1/2008168.0050.1601700mg/l
7/1/2008153.3360.1579400mg/l
8/1/2008225.0060.1762800mg/l
9/1/2008130.0060.1746100mg/l
10/1/2008100.0060.1632800mg/l
11/1/200875.0060.1418900mg/l
12/1/200891.6760.1291700mg/l
1/1/200998.0050.1199500mg/l
2/1/200966.0050.0934500mg/l
3/1/200968.0050.0831100mg/l
4/1/200982.0050.0801100mg/l
5/1/2009108.0050.0856100mg/l
6/1/200992.0050.0856700mg/l
7/1/2009100.0050.0860000mg/l
8/1/200990.0050.0900000mg/l
9/1/2009108.0050.0966700mg/l
10/1/2009144.0050.1070000mg/l
11/1/200966.0050.1000000mg/l
12/1/200972.0050.0966700mg/l
1/1/201050.0050.0883300mg/l
2/1/201054.0050.0823300mg/l
3/1/201054.0050.0733300mg/l
4/1/201090.0050.0643300mg/l
5/1/2010152.0050.0786700mg/l
6/1/2010135.0060.0891700mg/l
7/1/201052.0050.0895000mg/l
8/1/201074.0050.0928300mg/l
9/1/2010168.0050.1118300mg/l
10/1/2010102.0050.1138300mg/l
11/1/2010164.0050.1158300mg/l
12/1/201064.0050.1040000mg/l
Loading Chart...
Target
0.19 mg/l
Threshold
0.23 mg/l

Dissolved Oxygen

Units: mg/l Year
2010
Historical
period of record
High 9.80 11.40
Mean 7.03 6.47 1.20793
Low 4.90 3.60
No. of Samples 60 961

Five-year Trend Graph

     
1/1/20067.2657.2600000mg/l
2/1/20068.2257.7400000mg/l
3/1/20067.3457.6100000mg/l
4/1/20065.6257.1100000mg/l
5/1/20064.5656.6000000mg/l
6/1/20065.8656.4800000mg/l
7/1/20066.4256.3400000mg/l
8/1/20067.1656.1600000mg/l
9/1/20066.7856.0700000mg/l
10/1/20067.2456.3400000mg/l
12/1/20066.5656.8300000mg/l
1/1/20078.0257.1500000mg/l
2/1/20078.4257.4000000mg/l
3/1/20077.8457.6200000mg/l
4/1/20077.5657.6800000mg/l
5/1/20076.2657.4400000mg/l
6/1/20075.5057.2700000mg/l
7/1/20075.2456.8000000mg/l
8/1/20075.4856.3100000mg/l
9/1/20074.8655.8200000mg/l
10/1/20076.5655.6500000mg/l
11/1/20076.6055.7100000mg/l
12/1/20076.5255.8800000mg/l
1/1/20087.1856.2000000mg/l
2/1/20087.3056.5000000mg/l
3/1/20087.0656.8700000mg/l
4/1/20086.2456.8200000mg/l
5/1/20086.3656.7800000mg/l
6/1/20085.2856.5700000mg/l
7/1/20085.9256.3600000mg/l
8/1/20085.5856.0700000mg/l
9/1/20086.5055.9800000mg/l
10/1/20085.6055.8700000mg/l
11/1/20086.8055.9500000mg/l
12/1/20087.1656.2600000mg/l
1/1/20096.2456.3100000mg/l
2/1/20098.0056.7200000mg/l
3/1/20096.8056.7700000mg/l
4/1/20097.3057.0500000mg/l
5/1/20097.5057.1700000mg/l
6/1/20096.3257.0300000mg/l
7/1/20095.8856.9700000mg/l
8/1/20095.9456.6200000mg/l
9/1/20094.6656.2700000mg/l
10/1/20095.6856.0000000mg/l
11/1/20095.8055.7100000mg/l
12/1/20099.0656.1700000mg/l
1/1/20109.5656.7800000mg/l
2/1/20107.7057.0800000mg/l
3/1/20107.7257.5900000mg/l
4/1/20107.4857.8900000mg/l
5/1/20106.5258.0100000mg/l
6/1/20105.6257.4300000mg/l
7/1/20106.1256.8600000mg/l
8/1/20106.9056.7300000mg/l
9/1/20105.5256.3600000mg/l
10/1/20106.4056.1800000mg/l
11/1/20107.6056.3600000mg/l
12/1/20107.2256.6300000mg/l
Loading Chart...
Target
mg/l
Threshold
0.00 mg/l

Light Attenuation

Units: K(1/m) Year
2010
Historical
period of record
High 1.72 3.56
Mean 1.15 1.01 0.44878
Low 0.31 0.19
No. of Samples 60 767

Five-year Trend Graph

     
1/1/20060.8850.8800000K(1/m)
2/1/20060.6750.7800000K(1/m)
3/1/20060.8550.8000000K(1/m)
4/1/20060.6250.7600000K(1/m)
5/1/20060.6250.7300000K(1/m)
6/1/20060.7850.7400000K(1/m)
7/1/20061.0750.7700000K(1/m)
8/1/20061.1350.8500000K(1/m)
9/1/20062.7551.1600000K(1/m)
10/1/20061.6851.3400000K(1/m)
11/1/20061.1351.4200000K(1/m)
12/1/20061.0251.4600000K(1/m)
1/1/20070.9851.4500000K(1/m)
2/1/20070.5651.3500000K(1/m)
3/1/20070.7451.0200000K(1/m)
4/1/20070.9850.9000000K(1/m)
5/1/20070.7150.8300000K(1/m)
6/1/20070.9050.8100000K(1/m)
7/1/20070.7050.7700000K(1/m)
8/1/20070.8850.8200000K(1/m)
9/1/20070.6650.8100000K(1/m)
10/1/20071.1750.8400000K(1/m)
11/1/20071.3350.9400000K(1/m)
12/1/20071.3551.0200000K(1/m)
1/1/20081.2351.1000000K(1/m)
2/1/20080.5451.0500000K(1/m)
3/1/20080.7851.0700000K(1/m)
4/1/20080.8451.0100000K(1/m)
5/1/20080.8250.9300000K(1/m)
6/1/20080.5750.8000000K(1/m)
7/1/20080.9050.7400000K(1/m)
8/1/20081.0650.8300000K(1/m)
9/1/20081.4650.9400000K(1/m)
10/1/20081.2451.0100000K(1/m)
11/1/20080.8551.0100000K(1/m)
12/1/20080.7651.0500000K(1/m)
1/1/20091.0951.0800000K(1/m)
2/1/20090.7451.0200000K(1/m)
3/1/20090.5950.8800000K(1/m)
4/1/20090.8050.8100000K(1/m)
5/1/20091.4250.9000000K(1/m)
6/1/20090.7450.9000000K(1/m)
7/1/20091.1650.9100000K(1/m)
8/1/20090.8650.9300000K(1/m)
9/1/20091.1851.0300000K(1/m)
10/1/20091.5851.1600000K(1/m)
11/1/20091.1851.1200000K(1/m)
12/1/20091.1351.1800000K(1/m)
1/1/20100.6951.1000000K(1/m)
2/1/20100.7351.0800000K(1/m)
3/1/20100.6250.9900000K(1/m)
4/1/20101.2750.9400000K(1/m)
5/1/20101.3450.9600000K(1/m)
6/1/20101.2650.9900000K(1/m)
7/1/20101.1451.0600000K(1/m)
8/1/20101.2751.1500000K(1/m)
9/1/20101.5751.3100000K(1/m)
10/1/20101.5251.3500000K(1/m)
11/1/20101.5251.3800000K(1/m)
12/1/20100.8751.3200000K(1/m)
Loading Chart...
Target
K(1/m)
Threshold
0.00 K(1/m)

Rainfall

Units: inches/yr Year
2010
Historical
period of record
High 43.15 54.47
Mean 36.95 11.4111515969788
Low 14.17
No. of Samples 365 4,834

Five-year Trend Graph

     
1/1/20060.90310.9000000inches
2/1/20061.15281.1500000inches
3/1/20060.26310.2600000inches
4/1/20060.13300.1300000inches
5/1/20060.83290.8300000inches
6/1/20061.91301.9100000inches
7/1/20062.07312.0700000inches
8/1/20061.90311.9000000inches
9/1/20062.19302.1900000inches
10/1/20060.03310.0300000inches
11/1/20061.05301.0500000inches
12/1/20061.75311.7500000inches
1/1/20072.79312.7900000inches
2/1/20071.76281.7600000inches
3/1/20070.31310.3100000inches
4/1/20072.56292.5600000inches
5/1/20070.96310.9600000inches
6/1/20073.18303.1800000inches
7/1/20078.28318.2800000inches
8/1/20074.65314.6500000inches
9/1/20075.15305.1500000inches
10/1/20075.48315.4800000inches
11/1/20070.22300.2200000inches
12/1/20070.89310.8900000inches
1/1/20081.89311.8900000inches
2/1/20082.16292.1600000inches
3/1/20083.02313.0200000inches
4/1/20082.62302.6200000inches
5/1/20081.86311.8600000inches
6/1/20083.91303.9100000inches
7/1/20086.83316.8300000inches
8/1/20086.03316.0300000inches
9/1/20084.26304.2600000inches
10/1/20081.63311.6300000inches
11/1/20080.69300.6900000inches
12/1/20081.43301.4300000inches
1/1/20091.56321.5600000inches
2/1/20090.56280.5600000inches
3/1/20091.22311.2200000inches
4/1/20091.64301.6400000inches
5/1/20094.54314.5400000inches
6/1/20094.21304.2100000inches
7/1/20095.75315.7500000inches
8/1/20094.99314.9900000inches
9/1/20098.83308.8300000inches
10/1/20091.00311.0000000inches
11/1/20091.53301.5300000inches
12/1/20093.03313.0300000inches
1/1/20103.95313.9500000inches
2/1/20102.11282.1100000inches
3/1/20105.09315.0900000inches
4/1/20101.38301.3800000inches
5/1/20100.87310.8700000inches
6/1/20106.31306.3100000inches
7/1/20105.45315.4500000inches
8/1/201012.113112.1100000inches
9/1/20102.24302.2400000inches
10/1/20100.01310.0100000inches
11/1/20102.77302.7700000inches
12/1/20100.86310.8600000inches
Loading Chart...
Target
inches/yr
Threshold
inches/yr

Salinity

Units: PSS Year
2010
Historical
period of record
High 34.30 38.80
Mean 30.48 30.67 5.18029
Low 24.70 1.80
No. of Samples 60 963

Five-year Trend Graph

     
1/1/200631.06531.0600000PSS
2/1/200632.48531.7700000PSS
3/1/200633.92532.4900000PSS
4/1/200635.60533.2700000PSS
5/1/200637.62534.1400000PSS
6/1/200635.78534.4100000PSS
7/1/200625.68533.5100000PSS
8/1/200626.24532.4700000PSS
9/1/200622.36530.5500000PSS
10/1/200631.00529.7800000PSS
12/1/200629.80527.0200000PSS
1/1/200731.74528.2300000PSS
2/1/200731.82529.3400000PSS
3/1/200733.74531.6200000PSS
4/1/200734.58532.3400000PSS
5/1/200734.60532.7100000PSS
6/1/200736.96533.9100000PSS
7/1/200734.52534.3700000PSS
8/1/200735.00534.9000000PSS
9/1/200736.54535.3700000PSS
10/1/200733.94535.2600000PSS
11/1/200731.62534.7600000PSS
12/1/200733.26534.1500000PSS
1/1/200834.66534.1700000PSS
2/1/200834.52534.0900000PSS
3/1/200834.80533.8000000PSS
4/1/200831.50533.3900000PSS
5/1/200835.92534.1100000PSS
6/1/200835.84534.5400000PSS
7/1/200831.28533.9800000PSS
8/1/200827.00532.7200000PSS
9/1/200828.60531.6900000PSS
10/1/200831.22531.6400000PSS
11/1/200834.68531.4400000PSS
12/1/200832.76530.9200000PSS
1/1/200932.18531.0700000PSS
2/1/200934.76532.3700000PSS
3/1/200934.90533.4200000PSS
4/1/200935.34534.1000000PSS
5/1/200936.18534.3500000PSS
6/1/200934.02534.5600000PSS
7/1/200931.22534.4000000PSS
8/1/200933.40534.1800000PSS
9/1/200930.38533.4200000PSS
10/1/200930.90532.6800000PSS
11/1/200932.94532.1400000PSS
12/1/200927.42531.0400000PSS
1/1/201030.04530.8500000PSS
2/1/201027.16529.8100000PSS
3/1/201031.14529.9300000PSS
4/1/201027.82529.4200000PSS
5/1/201031.38529.1600000PSS
6/1/201033.16530.1200000PSS
7/1/201031.68530.3900000PSS
8/1/201028.92530.6800000PSS
9/1/201026.68529.9400000PSS
10/1/201031.50530.5500000PSS
11/1/201032.84530.8000000PSS
12/1/201033.48530.8500000PSS
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Turbidity

Units: NTU Year
2010
Historical
period of record
High 11.00 24.00
Mean 5.23 4.1 1.90257
Low 0.95 0.95
No. of Samples 385 4,848

Five-year Trend Graph

     
1/1/20061.5251.5200000NTU
2/1/20062.1851.8500000NTU
3/1/20064.3452.6800000NTU
4/1/20062.9452.7500000NTU
5/1/20062.1452.6200000NTU
6/1/20062.9852.6800000NTU
7/1/20064.6853.2100000NTU
8/1/20064.3253.5700000NTU
9/1/20065.8653.8200000NTU
10/1/20063.6063.9300000NTU
11/1/20062.3453.9600000NTU
12/1/20065.8364.4400000NTU
1/1/20072.0654.0000000NTU
2/1/20071.9253.6000000NTU
3/1/20072.4253.0300000NTU
4/1/20074.2653.1400000NTU
5/1/20072.6453.1900000NTU
6/1/20072.1852.5800000NTU
7/1/20072.7362.6900000NTU
8/1/20073.2362.9100000NTU
9/1/20072.3262.8900000NTU
10/1/20073.9562.8400000NTU
11/1/20072.7262.8600000NTU
12/1/20072.3862.8900000NTU
1/1/20082.3262.8200000NTU
2/1/20081.6362.5500000NTU
3/1/20082.1562.5300000NTU
4/1/20083.1262.3900000NTU
5/1/20083.4262.5000000NTU
6/1/20082.4452.5100000NTU
7/1/20082.9362.6200000NTU
8/1/20084.1053.0300000NTU
9/1/20085.3563.5600000NTU
10/1/20085.8864.0200000NTU
11/1/20083.3864.0100000NTU
12/1/20081.9763.9400000NTU
1/1/20093.2253.9800000NTU
2/1/20093.6653.9100000NTU
3/1/20093.1653.5500000NTU
4/1/20095.4053.4700000NTU
5/1/20096.3253.9600000NTU
6/1/20094.2054.3300000NTU
7/1/20094.3854.5200000NTU
8/1/20094.7454.7000000NTU
9/1/20094.5054.9200000NTU
10/1/20096.4055.0900000NTU
11/1/20095.0854.8800000NTU
12/1/20093.4854.7600000NTU
1/1/20101.1054.2200000NTU
2/1/20102.9453.9200000NTU
3/1/20103.2563.7100000NTU
4/1/20107.0453.8200000NTU
5/1/20106.8854.1200000NTU
6/1/20107.0064.7000000NTU
7/1/20105.4065.4200000NTU
8/1/20107.6056.2000000NTU
9/1/20104.4856.4000000NTU
10/1/20105.4856.1400000NTU
11/1/20107.3856.2200000NTU
12/1/20103.2855.6000000NTU
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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 (2010)

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 »

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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 »

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Target
348 acres

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 »

Roberts 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 »

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