Winter Algae Bloom Muck’s Up The Severn

ANNAPOLIS, Dec. 29, 2019 — The muddy orange color mucking up the Severn Riveris a rare (hopefully) winter algae bloom.

Reports of the algae bloom started over a week ago. Our first call came in from a north branch of Chase Creek.

At left is what the algae did to the once-clear waters of Chase Creek on Dec. 22.

This algae species has been identified by Maryland Department of Environment biologist Chris Luckett as Prorocentrum minimum (see pic at right).

He told Capital reporter Rachael Pacella that this algae is generally non-toxic to the touch and should not harm our underwater grasses, which are dormant over the winter.

Reported toxicity is from ingesting shellfish from waters with active algae blooms.

But that shouldn’t be a problem in the Severn River because shellfish harvesting has been banned for many years due to poor water quality caused by septic and stormwater pollution.

Some good news: As the cold winter returns, we should be able to avoid the scenario in the 1958 movie, The Blob, which relates the story of an amoeboidal entity that ingests entire communities.

However, this real life blob has been persistent.

It started popping up just before Christmas. Our first report was from a northern branch of Chase Creek.

Then within hours, the orange mess covered most of the river (see pic to left of the bloom in Little Round Bay).

Then it started fading away only to bounce back again … three times as of Jan. 6, 2020.

More bad news long term

Just like any algae bloom, as these blooms run through their life cycle, they end up absorbing all the oxygen around them.

This depletes oxygen levels and helps create dead zone conditions during the hot summer months. In 2019, the Severn River had a dead zone that was the size of Denton Maryland. For details, click here.

Hopefully, the great clarity we were enjoying on the Severn River in 2019 will return this spring and usher in a bountiful crop of underwater grasses.

Why Now, Not Summer?

SRA member, John Page Williams, noted writer, naturalist, educator and fisherman, explains that the unusual winter bloom could be due to the recent cold snap that iced in many of our creeks.

This cold spell was then followed by the sudden influx of warmer, mild weather.

As the ice melted, that cold, icy water sank to the bottom, which in turn pushed the nitrogen and phosphorous pollutants up from the bottom to the surface where they combined with sunlight and warmer temperatures to fuel the algae bloom.

The ultimate source of this algae bloom is the same that causes dead zones in the summer time – uncontrolled stormwater runoff that overloads our waterways with nitrogen and phosphorus.

Even after a sustained drought, these pollutants remain on the river and creek bottoms where they lie in wait to cause more troubles.

Photos: Eric Madsen, Ted Delaplaine, Chris Luckett.