Where Have All The Redheads Gone???

Published: September 9, 2021

Susan prepares SAV samples.

The famous SAV Navy is a group of dedicated volunteer scientists who survey, map and identify the types of submerged aquatic vegetation (SAV) in the Severn River each summer.

Susan Benac and Jackie Agnew are working through their 3rd year monitoring SAV beds at the Narrows, where they sample underwater grasses at 31 locations!

In the previous two years, they found SAV in 19 locations and reported that our grass beds were “pretty dense,” creating habitat for river species and protecting shorelines from wave action.

This year, however, they found SAV in only 9 locations, and it was very sparse.

The grasses present this year included Horned Pondweed, Sago Pondweed, and Widgeon: three species typical in our river.

Redhead Grasses Disappearing

The now-elusive Redhead grass.

The big surprise in 2021: Redhead grass, another native species, was largely missing from the Severn River, even in areas where it was thriving in past years.

SRA is working with the Maryland Department of Natural Resources, which analyses data from our SAV Navy.

We’re trying to understand what’s happening to the Redhead grass and explain why the once prodigious SAV is now hard to find in areas where it used to thrive.

Susan and Jackie’s data help confirm that SAV acreage has plummeted in the Severn River during 2020-2021.

The most likely culprit was the intense Harmful Algae Bloom, a full-blown Mahogany Tide, that blanketed the Severn during May-June of 2020.

– Emi McGeady, SRA Field Investigator

Photos: Jackie and Susan