CT DEEP sampled 42 stations during the WQSEP18 survey that was conducted 27 August through 29 August 2018. The lowest dissolved oxygen recorded during this survey was at Station A4 with a concentration of 2.34 mg/L. Four other stations sampled during this survey had concentrations below 3 mg/L, 14 stations were less than 3.5 mg/L and 14 additional stations were below 4.8 mg/L. Data are available in an Excel spreadsheet format. The DO at Station A4 during WQSEP surveys from 1998-2018 (n=20) ranged from 0.93 mg/L (WQSEP04) to 6.08 mg/L (WQSEP00). The average DO at A4 during the WQSEP surveys is 3.29 mg/L (+/- 1.51mg/L) and the median is 2.92mg/L. There were 133.6 km2 of bottom water that had dissolved oxygen concentrations less than 3.0 mg/L during the WQSEP18 survey and an additional 1278.2 km2 of bottom water with concentrations less than 4.8 mg/L. These values are much higher from the HYAUG18 survey when 909.1 km2 were below 4.8mg/L (19.7 km2 of those were below 3.0 mg/L). The estimated average area of bottom waters having concentrations below 3.0 mg/L during WQSEP surveys from 1998-2018 is 128.6 km2. Between 1998 and 2018, minimum dissolved oxygen levels in the bottom waters of Long Island Sound were less than 1.0 mg/L on two occasions and were above 3.0 mg/L on five occasions (Table 1).

0200400600800

1000120014001600

Are

a (k

m²)

Hypoxic Areal Estimates from WQSEP Cruises 1998-2018

Area less than 3 mg/L (km²) Area less than 4.8 mg/L (km²)

[Volume 2, Issue 7]

Long Island Sound Water Quality Monitoring

Program

www.ct.gov/deep/lis

79 Elm Street Hartford, CT 06106 (860) 424-3176 Katie.obrien-clayton@ct.gov

5 Stations with Dissolved Oxygen Concentrations Below 3 mg/L

September 2018

WQSEP18 Summary

WQSEP18 Survey

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7

6

5

4

3

2

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0

Station (West to East)

Dis

solv

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Oxyg

en

(m

g/L

)Dissolved Oxygen Concentrations of Bottom Waters in Long Island Sound

WQSEP 1998-2018

2018 Data

Table 1. Minimum Dissolved Oxygen Cocnentrations and Areal Estimates for WQSEP Cruises Conducted from 1998-2018 by CT DEEP.

Cruise Minimum DO

Observed (mg/L)

Station with Minimum DO

Area under 4.8 mg/L (km2)

Area under 3 mg/L (km2)

WQSEP98 1.19 B3 1457.8 435.3

WQSEP99 3.75 H6 169.3 0

WQSEP00 3.39 15 455 0

WQSEP01 1.02 02 1216.7 292.4

WQSEP02 4.58 B3 107.5 0

WQSEP03 2.23 E1 1241.1 33.5

WQSEP04 0.93 A4 1396.7 296.1

WQSEP05 0.99 A4 1031.8 223.8

WQSEP06 2.89 F3 593.9 0

WQSEP07 2.88 A4 886 41.6

WQSEP08 2.17 02 1562.5 340.5

WQSEP09 1.84 E1 1234.1 332.1

WQSEP10 3.66 A4 213.7 0

WQSEP11 4.32 A4 75 0

WQSEP12 2.55 02 1643 131.7

WQSEP13 2.33 B3 1207.3 100.1

WQSEP14 2.74 A4 856.7 34.3

WQSEP15 2.52 A4 892.4 56.3

WQSEP16 1.87 A4 1170.1 139

WQSEP17 2.46 A4 565.9 109.8

WQSEP18 2.34 A4 1411.8 133.6

Dissolved Oxygen

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WQSEP18

The WQSEP18 survey had hot humid weather with substantial amounts of fog and haze manifesting on August 27 and 29. Over the course of the three day survey, Bridgeport temperatures averaged in the mid 80’s with average winds southwest at 8 mph and gusts up to 20mph on August 28. Precipitation totals for the Northeast were generally above 100% of the normal amounts for the month of August, only 7 of the 35 NRCC climate sites received less than 100% of their normal precipitation. Connecticut follows this deviation because while Hartford received 232% of its normal precipitation, Bridgeport only received 74% for the month. The Northeast US drought monitor displayed only a few portions of Southern Maine and Upper State New York developing some abnormally dry areas as we enter September.

The NOAA Climate Prediction Center outlook for September indicates that the New England has equal chances to be above, below, or at normal precipitation levels for the month of September. The Northeast has a 60-70% likelihood of having above-normal temperatures through September.

The NOAA Atlantic hurricane season outlook update from August 9 indicates that there is a 60% chance of a below-normal hurricane season. Therefore, less activity is predicted to occur for the latter half of the Atlantic hurricane season. The El Niño Southern Oscillation (ENSO) alert system status has an El Niño watch for the remaining hurricane season (September-November). With El Niño events, upper level westerly winds and high wind shears develop across the Caribbean into the tropical Atlantic. These potential winds can tear apart developing tropical storms that would eventually evolve into hurricanes. Sea surface temperatures (SST) remained at near-average levels across the central and equatorial pacific for the first half of the hurricane season. This lack of temperature anomalies could lead to a greater chance for El Niño to develop ENSO-negative conditions and therefore would indicate a less active end to the hurricane season as well.

More Detailed weather information can be viewed on the Northeast Regional Climate Center’s website.

Weather

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8.6

8.4

8.2

8.0

7.8

7.6

7.4

7.2

7.0

pH

Surface and Bottom Water pH Across Long Island Sound WQSEP Cruises

2011-2018

Bottom pH

Surface pH2018 Bottom Values

2018 Surface Values

No 2018 Data Available for K2 Stations (West to East)

WQDEC

WQN

OV

WQOCT

HYSEP

WQSE

P

HYAUG

WQAUG

HYJUL

WQJU

L

HYJUN

WQJU

N

WQM

AY

WQAPR

WQM

AR

WQFE

B

WQJA

N

8.6

8.4

8.2

8.0

7.8

7.6

7.4

7.2

pH

(S

U)

Average Bottom pH of Long Island Sound

December 2010 - September2018

2018 Data

No pH recordings for WQJAN17 or WQFEB17

WQDEC

WQN

OV

WQOCT

HYSEP

WQSE

P

HYAUG

WQAUG

HYJUL

WQJU

L

HYJUN

WQJU

N

WQM

AY

WQAPR

WQM

AR

WQFE

B

WQJA

N

8.75

8.50

8.25

8.00

7.75

7.50

pH

Average Surface pH of Long Island SoundDecember 2010 - September2018

2018 Data

No pH recordings for WQJAN17 or WQFEB17

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pH

During this survey the surface pH averaged 7.63 and the bottom averaged 7.47, about 0.23 to 0.21 SU below the mean value for WQSEP surveys (2011-2018). These values are also slightly lower than the WQSEP17 survey (7.69 and 7.56 surface and bottom respectively). Both surface and bottom water average temperatures were warmer by 1.15°C and 0.24°C respectively during this survey compared to the WQSEP11-18 averaged temperatures. These temperature increases may have increased dissolution of H2CO3, therefore decreasing pH in the bottom waters.

The average surface and bottom pH only include the 17 year-round water quality stations.

https://sfmsi.wordpress.com/tag/ocean-acidification/

Temperature

Table 2. Average temperatures from all stations for the September water quality surveys.

WQSEP 1998-2018 WQSEP18

Surface 22.8°C 24.4°C

Bottom 22.0°C 22.7°C

Surface waters have continued to warm throughout the Sound as this summer comes to an end. This year surface waters were significantly above the 11 year average. The sea surface satellite image taken during the WQSEP18 survey appears to have warm eddies evolving off the Gulf Stream which may also be influencing the coastal waters of New England. The warmest bottom temperature recorded was 23.91°C at station 25 and the warmest surface temperature recorded was 26.13°C at station H6. Delta T’s ranged from 0.22°C at station J2 to 4.05°C at station H6. The 1998-2018 average surface and bottom temperature graphs reflect only data from the 17 year-round water quality stations.

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Left: Sea surface temperature three day composite the week of the WQSEP18 survey. Right: Sea surface temperature three day composite the week of the WQSEP17 survey.

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5

10

15

20

25

30Te

mp

era

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(ºC

)Average Monthly Temperature of Long Island Sound

Average Surface (2 m) Temperature (ºC)

Average Bottom (5 m above bottom)Temperature (ºC)

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Temperature cont.

Surface waters deviated ±.0.89 and bottom waters deviated ±0.63 from their average values for the WQSEP surveys. Both surface waters were warmer than last year (WQSEP17) at this time when they average 22.04°C and

21.8°C, respectively.

WQSEP

HYA

UG

WQAU

G

HYJUL

WQJU

L

HYJ

UN

WQJU

N

WQM

AY

WQAPR

WQM

AR

WQFEB

WQJA

N

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1

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Secch

i D

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th (

m)

A4

B3

D3

F3

H4

I2

M3

Station

Secchi Depths Across Long Island Sound2018 Cruises

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Station (West to East)

Secch

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m)

Secchi Depths Across Long Island SoundWQSEP Cruises

1998-2018

2018 Data

Secchi Disk Depths

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Suspended solids, organic matter, phytoplankton and zooplankton can all reduce water clarity. The Long Island Sound Report Card has established four threshold levels for grading water clarity in Long Island Sound. Secchi depths less than 0.7 m are considered poor/failing. Secchi depths between 0.7 and 1.1 m are marginal and depths between 1.1 and 2.4 are fair. Secchi depths greater than 2.4 m are considered excellent/passing.

Secchi disk transparency depths, which reflect water clarity, during this survey ranged from 1.2 meters at 02 to 5.6 meters at E1. Depths averaged around 2.9 meters with 26 of the 40 stations sampled having readings greater than 2.4 meters. For this survey Secchi depth generally increased West to East.

Next Survey The next survey is scheduled for 10-11 September (HYSEP18) aboard the R/V Patricia Lynn. The schedule for the

remainder of 2018 is available on our website.

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