Chesapeake Bay Strangely Clean

The Chesapeake Bay is looking strangely clear. But why?

But, thankfully, the watermen of Tangier have found a happier topic of conversation. Lately and without a ready explanation, the bay around them looked unusually clear.

At times, it’s been the clearest some folks like Mayor James “Ooker” Eskridge can remember in years.

“It’s been the talk of the town some days,” the mayor said last week. “Lots of folks noticed it. … I was commenting to some of the other crabbers: We’ve got water like you’d see in the Caribbean.”

The mayor, a waterman himself, remembers first noticing the greater clarity toward the end of September. It’s typical for bay waters to sparkle more at that time as temperatures drop and algae growth slows. But this fall, even some old-timers have been struck by just far down into the water they could peer some days.

Another thing that contributes to the clarity in fall that the article didn't mention is that the community of organisms that filter algae, oysters, clams and mussels, and a host of attached animals like sea squirts, grows up over the summer, so that they are able to filter the water faster in fall. That, combined with the reduced algae growth due to less light and lower temperatures results in much lower amounts of algae in the water. Combine that with a good stretch of favorable (not rainy) weather, and you can get remarkable water clarity.

I've seen very clear water in Fall before; sometimes we have been able to see almost 10 feet down, but it seems better and more widespread this year. The last time I was out in the eastern shore islands with Pete, it was very clear, and we could see more of the foundation of the old house on Holland Island than ever before, even on a pretty high tide.

Now, scientists have become intrigued. Is it a one-time event or a sign of more to come?
Chris Moore, senior scientist in Virginia for the Chesapeake Bay Foundation, is hoping it’s the latter.

Clearer water is good for the bay’s health, Moore said. It allows more sunlight to reach the bottom of shallow areas. That helps restore underwater grasses, which provide food and habitat for crabs, fish and other creatures.

What’s not so clear is why Tangiermen and other folks who venture out on the Chesapeake began seeing the bottom for the first time – or at least the first time in a long while – in many places.

Moore’s theory for this is rooted in the weather. During long periods of dry weather in the late summer and fall across the mid-Atlantic, less water flowed into the bay from rivers, creeks and streams. Moore looked up a U.S. Geological Survey website that shows discharge rates in Harrisburg, Pa., for the Susquehanna River. During some stretches in September and October, the river was flowing at two-thirds the rate or less of its 125-year average. There were many more days of below-average than above-average readings.