Algae Bloom Returns To Upper River
Published: October 14, 2020
Terrible news to report for the upper Severn River yesterday – the giant algae bloom is back.
The river from Severn Run headwaters and outside Bear Branch at Ben Oaks is infested with the algae that creates the Mahogany Blooms.
Our Water Quality Monitoring teams have tracked the emergence of this bloom on their weekly rounds since at least early September.
You can see this in the first picture at right. SRA’s Field Investigator, Emi McGeady, holds a white disk at the surface to reveal the discoloration in the river.
The river has a rusty red-brown color to it. It’s as if Moses has dipped his staff into the waters along the shores of the Pointfield Landing, Ben Oaks and Indian Landing communities.
The rusty color, which is caused by an explosion of algae known as prorocentrum minimum (see left) was obvious all the way down stream, through The Narrows, inside Forked, Valentine and Plum Creeks and off the coast of Lindstead.
Algae blooms occur when stormwater runoff brings an overload of nutrients (nitrogen and phosphorous) mixed with warm water and lots of sunlight.
Note: The rusty-red color of the active algae is much more intense than this pictures represents. Compare this to the same disk Emi used at Eaglenest Point where the river water color was the normal green for this time of year.
As the algae return to the river, so does the dead zone because as the algae go through their life cycle, their decomposition depletes oxygen content in the water as they fall to the bottom.
When oxygen levels are less than 2 mg/L in the water, it is considered a dead zone where fish and crabs suffocate if they can’t swim to better water.
After recording improvements late this summer, the dead zone is back in the Upper River, from The Narrows to Indian Landing and Ben Oaks portions of the river.
The dead zone at The Narrows was at least two meters tall. On the bottom at 5 meters, oxygen was horrible, 0.04 mg/L. At 3 meters depth, it was still horrible, 0.08 mg/L. Oxygen does recover at the surface. We measured oxygen at 6.65 mg/L
We also spotted sea nettles everywhere and a brown snake dropped by to see what our WQ Crew was up to.
This giant, spread-out nettle popped up just as our one of our WQ Crew was ready to deploy the Secchi Disk for a clarity reading. Ouch!
If you see the river turning red or some non-green color, join our Algae Watchers team and send us a note – and a picture – so we can track duration and extend of these algae blooms.
Send reports to: Info@severnriver.org. Put Algae in the message box.