Severn River Hypoxia 2012: The Mainstem

Severn Riverkeeper Summer Water Quality Monitoring Program

2012 Weekly Dissolved Oxygen Results—Mainstem Stations

Pierre Henkart, PhD

Annapolis

N

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.

SR1 – Our “USNA” station in mid-channel opposite College Creek, with a 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 monthly MD DNR monitoring data (their station WT7.1) on the “Eyes on the Bay” website.

SR3 – Our “Joyce” station in a deep hole south of Joyce Point, at a depth of 12-13 meters (~40 feet). There are a few other deep spots like this in the Severn.

RBS – Our “Round Bay South” station, which is interesting because the bottom sometimes gets anoxic in the summer. It has a typical Severn depth of ~ 7 meters.

SR5 – Our mid Round Bay station with a depth of 7 meters. Bottom anoxia usually sets in by early July, and in the absence of storms, persists until September.

RBN – Our “Round Bay North” station, with a typical Severn depth of ~ 7 meters. This is the heart of the Severn summer dead zone.

SR6 – Our Severn Narrows station with a depth of 5 meters. We generally notice fresher water near the surface, the influence of the fresh Severn Run entering to the northeast. Summer bottom anoxia is pronounced here.

SR7 – Our shallow (~1.5m) upper station with fresher water from nearby Severn Run, especially after rains. Turbidity is high.

Severn mainstem monitoring stations

The distancefrom SR0 to SR7:18 km = 11 miles

Our oxygen depth profiles show habitat stress

Dissolvedoxygen,mg/liter

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 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 the longer the bar, the deeper the water. The water quality is color coded, and our graphs show oxygen levels since that has been our principal focus. The colors represent oxygen concentrations needed by different marine organisms. The Severn’s large active fish need at least 5 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 column has higher oxygen. In most cases, water near the surface has 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 water with less than three mg/liter dissolved oxygen. They will utilize both the 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 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 (red) are stressful to tough benthic organisms, even for 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.

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Severn River Dissolved Oxygen, May 23, 2012

Annapolis

N

Mainstem stations

Dissolved Oxygen, mg/liter

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

WT7.1

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

Severn River Dissolved Oxygen, May 30, 2012

N

Annapolis

Mainstem stations

WT7.1

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Severn River Dissolved Oxygen, June 6, 2012

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Annapolis

1 2 3 4 5 6 7 8 90

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Annapolis

1 2 3 4 5 6 7 8 90

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Mainstem stations

WT7.1

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Annapolis

Mainstem stations

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WT7.1

DSevern River Dissolved Oxygen, July 4, 2012

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Annapolis

Mainstem stations

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Annapolis

Mainstem stations


WT7.1

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Annapolis

Mainstem stations


WT7.1

1 2 3 4 5 6 7 80

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Annapolis

Mainstem stations


WT7.1

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DSevern River Dissolved Oxygen, August 1, 2012

N

Annapolis

Mainstem stations


WT7.1

1 2 3 4 5 6 7 80

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Annapolis

Mainstem stations


WT7.1

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Annapolis

Mainstem stations


WT7.1

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Annapolis

Mainstem stations


WT7.1

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Annapolis

Mainstem stations


WT7.1

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DSevern River Dissolved Oxygen, September 13, 2012

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Annapolis

Mainstem stations


WT7.1

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DSevern River Dissolved Oxygen, September 20, 2012

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Annapolis

Mainstem stations


WT7.1

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Severn River Hypoxia 2012: The Mainstem

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