October 2024 Water Quality Update

Published: October 15, 2024

Late season salinity surge … but problems persist 

by Tom Guay

The big news in the Severn River is that our water quality monitoring teams are tracking a sharp rise in salinity. Our teams of volunteers, led by SRA Program Officer Tom Guay, are tracking salinity levels in excess of 10 parts per thousand (ppt).

At some stations, we’re recording salinity over 13 ppt. For example, at our mid-river station offshore from Epping Forest, Tom and SRA board member Richard Turman found salinity ranging between 13.43 ppt at 8 meters depth to 10.43 ppt at the surface.  

At our Peach Orchard oyster reef (see image above), Tom and new volunteer, Juliet, recorded salinity at 12.42 ppt on the bottom (3.5 meters) where our oysters live. Additionally, the bivalves are also enjoying pretty good, dissolved oxygen (DO) levels, 4.7 mg/L. We find the boost in Severn River salinity levels exciting because oysters can reproduce when salinity exceeds 10 ppt. Alas, this boost arrived too late in the season to spur our oysters to reproduce now. Hopefully next year will see higher levels of salinity throughout the year for new baby oysters to be born.

Meanwhile, there are still pockets of not so good news.  We are still recording areas with low oxygen levels (areas with less than 2 mg/L Dissolved Oxygen (D.O.)), especially in the headwater areas of many creeks and in the upper river. D.O. was well below the 2 mg/L mark at our WQ stations at Mill Creek, Indian Landing, Narrows, Forked Creek, Valentine Creek, and Round Bay North. 

At Round Bay North, the layers of low oxygen (in the 0.24 to 1.45 mg/L range) covered more than 50% of the water column. By contrast, D.O. at our Eaglenest station in the Round Bay community was excellent – 5.43 mg/L at 2.5 meter depth. Oysters will certainly thrive here if we  open a restoration reef at this location in the future. 

The other bit of bad news is that we are seeing excessive algae activity inside some creeks-Meredith, Whitehall, Mill, Cove of Cork. This is discouraging news as these masses of algae will create new waves of low-oxygen layers in the lower water column. 

Looking ahead, we should soon be able to witness a sharp increase in clarity as the water cools. If you’d like to help track this good news, please join our volunteer team of water quality monitors on Wednesday, Thursday, and Friday mornings through the end of October. Contact Tom Guay at taguay@severnriver.org