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VIDEO: Mahogany Tides Hit Mid-Bay Rivers, Fish Kills Follow

It’s an effect of Chesapeake Bay nutrient pollution that we just can’t ignore: those mahogany tides that turns the water a muddy reddish-brown and the fish kills that result from them.

The middle of the Bay is experiencing these impacts in intense, widespread fashion. The Maryland Department of the Environment (MDE) reports fish kills in the tens of thousands in the Severn and Magothy Riversheds.

A high-density algae bloom (Prorocentrum minimum) hit the mid-Chesapeake hard this May, causing the rust-colored water commonly known as a mahogany tide. It’s likely to be found in the Bay and in every system from Back River down to the Potomac River. It usually arrives in April, according to MDE, and dies off in early-to-mid-May as water temperatures rise, but the cool spring delayed that timeline.

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Instead, the bloom is just now dying off, which causes oxygen depletion as the algae decomposes. Beginning Friday, MDE got reports of “unpleasant odors, orange/red/brown stained water, extreme buildups of foam, and fish kills (two) in several parts of the Magothy and Severn Rivers.”

“Fish kills now are being reported in many of the creek areas in the Magothy! The river water now stinks and the smell has been nauseating,” the Magothy River Association posted on Facebook Monday.

On Spa Creek in Annapolis there were 4,400 dead fish totaling nine species along an 80-foot stretch of shoreline at Amos Garrett Park. More dead fish were reported at Truxton Park across the creek. Up the Severn River inside Valentine Creek, the Severn River Association reports finding more dead fish. On Dividing Creek in the Magothy, about 6,000 fish have died, mostly small Atlantic menhaden and Norfolk spot.

As of Sunday, there were additional fish kills under investigation in the mainstem of the upper Magothy Rier, Cockey, Old Man, and Cattail creeks. Kim Gurski Myers, who lives near the top of Old Man Creek, captured video of bottom-dwelling fish appearing to come up to the surface for air.

“It was one of the most heartbreaking things I’ve ever seen and I have lived on the water my entire life. I’ve never seen anything like it,” Myers tells Bay Bulletin. Watch her video below:

Video: Kim Gurski Myers

In the downstream spots, MDE says the dead fish are mostly juvenile menhaden, but as you move upstream the kill becomes dominated by pumpkinseed sunfish. Several other species are involved in smaller numbers.

MDE tells Bay Bulletin. “The total number of dead fish is easily in the tens of thousands.” Investigators found all of the complaints to be direct results of the algae die-off.

“This is very sad. Let’s take this moment to recommit to improving water quality… Mahogany tides are caused by excess nutrients so please cut back on fertilizers, plant native plants, help us push back on the progressive paving of our watershed. We are seeing a death by 1000 cuts!” pleads the Magothy River Association.

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Algae blooms like Prorocentrum minimum are fueled by nutrient pollution that lands in the Bay through runoff. This video helps explain how it happens: https://www.chesapeakebay.net/discover/bay-101/bay_101_algae_blooms

MDE asks anyone who sees a fish kill to call its Bay environmental hotline at 877-224-7229 so that scientists can investigate.

Hotline update: MDE tells us the hotline has been having some technical issues, and if you can’t get through, call 866-MDE-GOTO (866-633-4686).

-Meg Walburn Viviano

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