Severn River Hypoxia 2012: The Mainstem

Severn Riverkeeper Summer Water Quality Monitoring Program

2012 Weekly Dissolved Oxygen Results—Mainstem Stations

Pierre Henkart, PhD

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.

Our oxygen depth profiles show habitat stress

Dissolved We show our water quality data as depth profile bar graphs. You can
oxygen, think of yourself as a scuba diver entering the water from our monitoring
0 mg/liter boat and then heading straight for the bottom. As you go down oxygen
levels will change. We’ve plotted the depth in a downward direction, so
>5 the longer the bar, the deeper the water. The water quality is color
1 coded, and our graphs show oxygen levels since that has been our
principal focus. The colors represent oxygen concentrations needed by
2 3-5 different marine organisms. The Severn’s large active fish need at least 5
Depth, meters

mg/liter oxygen, and levels greater than that are colored green. Since
most oxygen in the water comes from the air, the top of the water
3 column has higher oxygen. In most cases, water near the surface has
1-3 more than 5 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
4 water with less than three mg/liter dissolved oxygen. They will utilize
.2-1 both the green and yellow portions of the water column. Benthic
organisms that live in or on the bottom (oysters, worms, etc) are adapted
5 to yet lower oxygen levels down to 1 mg/liter, and they will tolerate
bottom water in the orange 1-3 mg/liter oxygen range. Oxygen levels
<.2 below 1 mg/liter (red) are stressful to tough benthic organisms, even for
6 short durations. Truly anoxic conditions exist below 0.2 mg/liter
oxygen, where only anaerobic bacteria can live. This anoxic water will
suffocate even the toughest multicellular organisms quickly.

Severn River Dissolved Oxygen, May 23, 2012
D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4

6
Depth, meters

8

10

12 Dissolved Oxygen, mg/liter
14 <.2 .2-1 1-3 3-5 >5
16

Mainstem stations

Severn River Dissolved Oxygen, May 30, 2012
D

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

Mainstem stations

Severn River Dissolved Oxygen, June 6, 2012
D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0
Depth, meters

2

4
Depth, meters

6

8

10
12
<.2 .2-1 1-3 3-5 >5

14

Mainstem stations

D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8
10
<.2 .2-1 1-3 3-5 >5
12

Mainstem stations

D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8

10
12
<.2 .2-1 1-3 3-5 >5
14

Mainstem stations

D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8

10
12 <.2 .2-1 1-3 3-5 >5
14

Mainstem stations

Severn River Dissolved Oxygen, July 4, 2012
D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8

10

14 <.2 .2-1 1-3 3-5 >5

16

Mainstem stations

D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8

10
12 <.2 .2-1 1-3 3-5 >5

14

Mainstem stations

Severn River Dissolved Oxygen, August 1, 2012
D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8
10
<.2 .2-1 1-3 3-5 >5
12

Mainstem stations

D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8

10
12 <.2 .2-1 1-3 3-5 >5

14

Mainstem stations

D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8

12 <.2 .2-1 1-3 3-5 >5

14

Mainstem stations

D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8

10
12 <.2 .2-1 1-3 3-5 >5

14

Mainstem stations

Severn River Dissolved Oxygen, September 13, 2012
D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8

12 <.2 .2-1 1-3 3-5 >5

14

Mainstem stations

Severn River Dissolved Oxygen, September 20, 2012
D

N
WT7.1

Annapolis

1 2 3 4 5 6 7 8 9
0

2

4
Depth, meters

6

8
10
<.2 .2-1 1-3 3-5 >5

12

Mainstem stations

Severn River Hypoxia 2012: The Mainstem

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