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Chesapeake Bay News

Jul
16
2009

Looking for fish habitat on the Magothy with a 4-year-old

On Friday, July 3, I did my usual twice-monthly volunteer water quality sampling at four sites on the Magothy River near where I live. I started doing this in 1991 through a program run by Anne Arundel County to get a better understanding of Bay water quality, and I’ve kept doing it ever since. The county program was discontinued, but I’ve continued sampling with the Magothy River Association, which has other volunteers who also do water monitoring. 

This monitoring trip was different from recent ones because my four-year-old granddaughter came with me. This was only the second time she'd seen any part of the Chesapeake up close (she lives in Vermont and usually visits us at Christmas).  Thus, I was thinking about how she was reacting to it.  It’s been a long time since my own kids helped me with monitoring (my youngest child is 26).

We started our sampling at the end of the Bayberry pier, on the south shore on the lower part of the river’s mainstem, where all seemed to be well. Several people were catching juvenile spot (Leiostomus xanthurus) pretty regularly, and my granddaughter was fascinated by watching them. The reason they were able to catch these bottom-dwelling fish at that location was apparent when we measured the dissolved oxygen (DO): it was over 8 mg/l on both the surface and bottom, plenty of oxygen for fish.  The bottom DO here has not fallen below 5 mg/l (the EPA and state standard for fish habitat) since I started sampling at Bayberry in April.

The fish & DO story was different at the three other Magothy sites I sample, and the news was not good.

At the first two these sites, Ulmstead in the mouth of Forked Creek and in my own neighborhood (Stewarts Landing) on Old Man Creek, the bottom DO was less than 1 mg/l at both sites, but that’s fairly common in the summer.  There were no weird colors or smells, and people were fishing or crabbing in shallow water nearby, although not in water as deep as where I sample.

However, in upper Cattail Creek in Berrywood, the water was a weird milky green and there was a musky smell, so I knew before I lowered the meter that the DO would be bad.  The color and the smell are both signs of an algae bloom that died and is decomposing.  The surface DO was only 0.7 mg/l, the second lowest surface DO reading I've ever made, and the bottom DO was definitely anoxic with 0.00 mg/l, the lowest DO meter reading I’ve ever seen.  My granddaughter can't quite read numbers yet, but she knows zero when she sees it. It made me sad to show her how dead the creek was.  Amazingly there were no signs of any dead fish; I think the fish usually avoid the whole upper creek when it's such a dead zone.  I’ve never seen anyone fishing or crabbing nearby.  A week after I sampled there, Cattail Creek had a health advisory against swimming posted by the county health department for high bacteria levels, so that creek has multiple problems.

The water quality in these creeks was not always this dismal. Both Cattail and Old Man creeks were much healthier in 2004 and 2005, when dark false mussels covered almost all of the hard surfaces over a variety of depths in both creeks. By pure luck, when I chose my sampling sites in 1991 I picked two sites that would have some of the densest mussels 13 years later, so I have been able to document the water quality improvements that followed their filtration. Water clarity (measured by Secchi depth) and bottom dissolved oxygen showed dramatic improvements in both creeks in those years, and underwater bay grass (SAV) acreage in the Magothy went up in both 2004 and 2005.  Volunteer divers and kayakers organized by Dick Carey of the Magothy River Association estimated the number of mussels and the volume of the creek. From that research they estimated that, in 2004, the mussels could filter the water in Cattail Creek every two days, while it took them 15 days in 2005. (Watch an eight-minute video about the mussels and the 2004 surveys.) Imagine how healthy the Bay would be if oysters were filtering its water every two days, or even every 15 days. 

People who remember the mussels from 2004 keep asking me how we can get them back, along with improved water quality.  I don’t have an easy answer.  Memories of the mussels do give me hope that improvement is possible.  I just wish the mussels and the good water quality were still here to show my granddaughter, instead of zeroes on the DO meter.

About Peter Bergstrom - Peter Bergstrom is a biologist with the National Oceanic and Atmospheric Administration (NOAA) Chesapeake Bay Office.


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