Low Water, High Temps, Nutrients = Algae!

We received almost an inch of rain yesterday in addition to the localized storms that have been rumbling through the Valley this entire week.

It certainly has been an interesting season as river levels have stayed at or above normal most of the spring and summer. Last week, river levels finally dropped to normal summer pool conditions and as soon as that happened we started seeing algae up and down the river. 

The free floating algae we’ve seen in the water column, called planktonic, is what gives the water its peagreen color.

We’ve observed algae growing on rocks on the bottom and on plants growing in the water. The algae that clings to the bottom like a spongy, gooey mess is sometimes called rock snot. The algae growing out into the water column but attached to the river bottom comprise the larger filamentous algae looks like seaweed or long mermaid hair.

But we have also noticed this season, that we have more of the good grasses, the subaquatic vegetation, growing in the Shenandoah River. The last few years we have not seen as much of the good grasses so this is good news indeed.

Subaquatic vegetation contributes to the biodiversity of the river and makes for a healthier ecosystem. It gives small fish a place to hide, filters out the sediment floating in the river and allows sunlight to penetrate to the river bottom and allows the grasses to outcompete the algae.

In years past, we observed more star grass than other grasses. Star grass can be identified by its little yellow starlike flower at the very top of the plant. This year, we are seeing far more wild celery than star grass but star grass is definitely still around in addition to common waterweed and coontail.

Lower water levels and high temps are two ingredients the algae loves. The third item needed in the algae recipe is high levels of nutrients that come in the form of runoff, primarily, but not exclusively from agricultural fields. Those three things – low water, high temps and high level of nutrients give you the algae trifecta.

We have been trying for the past several years to get the Shenandoah River placed on Virginia’s Impaired Water List for excessive algae or exceedingly high levels of nutrients. Having the state list the river as impaired by the algae blooms and nutrient pollution would force the state to eventually develop regional pollution limits for the Shenandoah. Virginia’s Department of Environmental Quality has turned a deaf ear toward us, saying that there are no nutrient standards for flowing water and that trying to assess narrative statements, in the form of complaint letters from anglers, paddlers, swimmers, birders, hikers, landowners, and anybody else who enjoys using the river, is too difficult of a job for them to assess.

This year, they have nonetheless brought on staff two technicians evaluating the expanse of the algae in the river. While it is a start, algae blooms on the river have been going on far too long for the Commonwealth to turn a blind eye and do nothing about it.

To keep up to date on river conditions and our efforts to eliminate algae, listen to me, Shenandoah Riverkeeper Mark Frondorf, every Monday and Friday morning at 8:40am on The River 95.3FM. And follow me on Facebook.

‘We’ve primed the system': Why disgusting toxic blue-green algae blooms seem increasingly common, The Washington Post, July 25, 2016