This document summarizes water quality monitoring results from stations along the Severn River from May to June 2012. Oxygen levels decreased with depth at all stations, showing hypoxic conditions near the bottom. The deepest stations experienced bottom anoxia by early July. Salinity was highest near the surface and decreased with depth. Oxygen levels below 1 mg/L stressed bottom-dwelling organisms.

1. Severn Riverkeeper Summer Water Quality Monitoring Program
2012 Weekly Dissolved Oxygen Results—Mainstem Stations
Pierre Henkart, PhD

2. Severn mainstem monitoring stations
SR7 – Our shallow
N SR6 – Our Severn Narrows station with a depth of 5 meters. We
generally notice fresher water near the surface, the influence of the
(~1.5m) upper
fresh Severn Run entering to the northeast. Summer bottom anoxia
station with
is pronounced here.
fresher water from
nearby Severn
Run, especially SR5 – Our mid Round Bay station with a depth of 7
after rains. meters. Bottom anoxia usually sets in by early July, and
Turbidity is high. in the absence of storms, persists until September.
RBN – Our “Round Bay North” SR3 – Our “Joyce” station in a deep hole
station, with a typical Severn depth south of Joyce Point, at a depth of 12-13
of ~ 7 meters. This is the heart of meters (~40 feet). There are a few other
the Severn summer dead zone. deep spots like this in the Severn.
RBS – Our “Round Bay South” SR1 – Our “USNA” station in
station, which is interesting because the mid-channel opposite College
bottom sometimes gets anoxic in the Creek, with a depth of 7 meters
summer. It has a typical Severn depth of ~
7 meters.
SR2 – Our “Rte 50 bridge” station with a depth of 7
meters. We get to watch the peregrine falcons that nest
on the bridge. We also get to compare our data with the The distance
monthly MD DNR monitoring data (their station WT7.1) Annapolis from SR0 to SR7:
on the “Eyes on the Bay” website.
18 km = 11 miles
SR0 – Our “near Chesapeake” station south of Greenbury
Point, in the channel, with a depth of 6 meters (a bit less than
20 ft). SR0 is near the NOAA “Annapolis” buoy providing
great continuous on-line water quality data at 1 meter depth.

3. Oxygen depth profiles show habitat stress and “hypoxic squeeze”
We show our water quality data as depth profile bar graphs. You can
think of yourself as a scuba diver entering the water from our monitoring
Dissolved boat and then heading straight for the bottom. As you go down oxygen
oxygen, levels will change. We’ve plotted the depth in a downward direction, so
0 mg/liter the longer the bar, the deeper the water. The oxygen levels are color
coded according to the oxygen concentrations needed by different
>5 marine organisms. The Severn’s large active fish need at least 5 mg/liter
1 oxygen, and levels greater than that are colored green. Since most
oxygen in the water comes from the air, the top of the water column has
3-5 higher oxygen. In most cases, water near the surface has more than 5
2
Depth, meters
mg/liter, so the tops of most bars are green. Smaller fish like white perch
are adapted to live with lower oxygen levels, but will avoid water with
3 less than three mg/liter dissolved oxygen. They will utilize both the
1-3 green and yellow portions of the water column. Benthic organisms that
live in or on the bottom (oysters, worms, etc) are adapted to yet lower
4 oxygen levels down to 1 mg/liter, and they will tolerate bottom water in
the orange 1-3 mg/liter oxygen range. Oxygen levels below 1 mg/liter
.2-1 (red) are stressful to tough benthic organisms, even for short durations.
5 Truly anoxic conditions exist below 0.2 mg/liter oxygen, where only
anaerobic bacteria can live. This anoxic water will suffocate even the
<.2 toughest multicellular organisms quickly.
6
The lower oxygen levels in deeper water will “squeeze” fish habitat
toward the surface. The extent of squeeze will depend on the oxygen
preference of the fish involved, but few fish will be found in waters with
less than 1 mg/liter dissolved oxygen.

4. D
Severn River Salinity and Dissolved Oxygen, May 23, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Dissolved Oxygen, mg/liter
12
<.2 .2-1 1-3 3-5 >5
14
16 1 2 3 4 5 6 7 8 9
0
2
4
Depth, meters
6
8
10
Salinity, psu
12
9-10 8-9 7-8 6-7 5-6
14
16

5. D
Severn River Salinity and Dissolved Oxygen, May 30, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10 Dissolved Oxygen, mg/liter
12 <.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Salinity, psu
12 9-10 8-9 7-8 6-7
14

6. D
Severn River Salinity and Dissolved Oxygen, June 6, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
Depth, meters
0
2
Depth, meters
4
6
8
Dissolved Oxygen, mg/liter
10
12 <.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10 Salinity, psu
12 11-12 10-11 9-10 8-9 7-8 6-7
14

7. D
Severn River Salinity and Dissolved Oxygen, June 13, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10 Dissolved Oxygen, mg/liter
<.2 .2-1 1-3 3-5 >5
12
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
Salinity, psu
10 9-10 8-9 7-8 6-7
12

8. D
Severn River Salinity and Dissolved Oxygen, June 20, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Dissolved Oxygen, mg/liter
12 <.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Salinity, psu
12
8-9 7-8 6-7 5-6 4-5
14

9. D
Severn River Salinity and Dissolved Oxygen, June 27, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10 Dissolved Oxygen, mg/liter
12
<.2 .2-1 1-3 3-5 >5
14 1 2 3 4 5 6 7 8 9
0
2
4
Depth, meters
6
8
10 Salinity, psu
12-13 11-12 10-11 9-10 8-9 7-8 6-7
12
14

10. D
Severn River Salinity and Dissolved Oxygen, July 4, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10 Dissolved Oxygen, mg/liter
12 <.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
4
Depth, meters
6
8
10 Salinity, psu
12 10-11 9-10 8-9
14

11. D
Severn River Salinity and Dissolved Oxygen, July 11, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10 Dissolved Oxygen, mg/liter
12 <.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Salinity, psu
12
11-12 10-11 9-10 8-9 7-8
14

12. Severn River Salinity, D 11, 2012
July
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Salinity, psu
12
11-12 10-11 9-10 8-9 7-8
14

13. D
Severn River Salinity and Dissolved Oxygen, July 18, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10 Dissolved Oxygen, mg/liter
12 <.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10 Salinity, psu
12 12-13 11-12 10-11 9-10 8-9
14

14. D
Severn River Salinity and Dissolved Oxygen, July 25, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Dissolved Oxygen, mg/liter
12
<.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
4
Depth, meters
6
8
10 Salinity, psu
12 12-13 11-12 10-11 9-10 8-9 7-8
14

15. D
Severn River Salinity and Dissolved Oxygen, August 1, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
Dissolved Oxygen, mg/liter
10
<.2 .2-1 1-3 3-5 >5
12
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
Salinity, psu
10 13-14 12-13 11-12 10-11 9-10 8-9
12

16. D
Severn River Salinity and Dissolved Oxygen, August 8, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Dissolved Oxygen, mg/liter
12 <.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
4
Depth, meters
6
8
10
Salinity, psu
12
14
11-12 10-11 9-10 8-9
16

17. D
Severn River Salinity and Dissolved Oxygen, August 15, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Dissolved Oxygen, mg/liter
12 <.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Salinity, psu
12
12-13 11-12 10-11 9-10
14

18. D
Severn River Salinity and Dissolved Oxygen, August 22, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
4
Depth, meters
6
8
10 Dissolved Oxygen, mg/liter
12 <.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
Depth, meters
4
6
8
10
Salinity, psu
12 12-13 11-12 10-11 9-10
14

19. D
Severn River Salinity and Dissolved Oxygen, August 29, 2012
N
WT7.1
Annapolis
1 2 3 4 5 6 7 8 9
0
2
4
Depth, meters
6
8
10
Dissolved Oxygen, mg/liter
12
<.2 .2-1 1-3 3-5 >5
14
1 2 3 4 5 6 7 8 9
0
2
4
Depth, meters
6
8
10 Salinity, psu
12 13-14 12-13 11-12 10-11 9-10 8-9
14