August: Bay Marshes at Summer's End

Chesapeake Almanac Podcast Episode and Transcript

Episode 23
Copyright © John Page Williams Jr. All rights reserved.

This is John Page Williams with another reading from Chesapeake Almanac. The month is August and the title of this chapter is "A Nice Gestalt: Bay Marshes at Summer's End."

Gene Silverhorn stood knee-deep in a marsh at the head waters of Upper Machodoc Creek, a Potomac tributary near Dalhgren, Virginia. Smoke from his almost-ever-present pipe curled around his head as he examined the smartweed plant that he had carefully dug from the black mucky soil. "A marsh like this has a really nice gestalt," he said with a grin. I had to admit to not knowing what gestalt meant, so I went straight for the dictionary as soon as i got home. The term developed in a school of psychology that originated in Germany in the early twentieth century. The Oxford Reference Dictionary defines it as "a perceived whole that is more than the sum of its parts." Trust the Germans to pack many layers of meaning into a single word. In my mind, I translated Gene's gestalt into the word "presence."

It helped to know that, for Gene, marshes do indeed have many layers of presence. He was head of the wetlands section at the Virginia Institute of Marine Science from the early 1970s until he retired around the turn of the century, so he viewed the Bay's marshes with the fascination of a professional botanist and the curiosity of a research program director. VIMS also performed some state agency functions, and Gene's group had always provided advisory services on tidal wetland permit applications, so Gene and his colleagues had always had a bureaucratic point of view as well. Finally, Gene's an avid fisherman and general naturalist, so he always appreciated the contributions that marshes make to food and habitat in the Chesapeake system. A good marsh has a rich gestalt indeed for him and for many of the rest of us.

Since that day, I've found gestalt to be a useful term for thinking about the Chesapeake's marshes. Especially now, at the end of the summer, the growth of marsh plants is lush, thick with ripe seeds and colorful flowers. Plants in the seed category include smartweed, wild rice, millet, and others in the upriver freshwater marshes, and saltmarsh cord grass and big cord grass in the downriver salt marshes. Flower colors range from brilliant red cardinal flower and blue pickerel weed upriver to crimson-centered white hibiscus and pink and midsalinities, and sea lavender down the Bay. A host of animals from juvenile menhaden and crabs to snapping turtles, river otters, eagles, and ducks depend on them. There are many layers for us to appreciate.

One layer of presence that particularly intrigues me derives from the fact that marsh plants flourish under difficult growing conditions. They do so well in part because their soils are very fertile; but those same soils have some hostile features as well.

The fertility comes in part from the fact that rich river-borne sediments collect in the marshes. The marshes are, in fact by definition, natural sediment traps. They also function as perpetual compost piles for the plant materials that collect in them.

But the tides that bring in rich sediments also cover the marsh and waterlog the soil. And, if the marsh is downriver, the water is salty, creating conditions that kill most plants very quickly. The Bay's marsh plants have made adaptations to deal with these problems.

Waterlogged soil creates an oxygen problem for all marsh plants. Because of the water, there is only a little oxygen in the surface layer of the soil, and none below. But plant root cells need oxygen just as much as above ground cells do. In addition,the plant's roots need a combination of nutrients, like phosphorus and nitrogen, which they can absorb best in oxidized (or oxygen containing) forms. Some of these nutrients are by-products of the metabolism of aerobic (or oxygen-using) bacteria. The interplay between plant and bacteria can be very important, and yet the bacteria cannot live in totally waterlogged soils--some natural plant toxins build up in anaerobic (or oxygen-lacking) wet soils. A good example is hydrogen sulfide gas, whose rotten egg odor is familiar to anyone who has ever slogged through a deep marsh on foot.

The solution for most marsh plants is a system of passageways in the stems which allow oxygen to diffuse to the roots. A few floating-leaved plants that grow on the water's edge of the marsh, like lily pads (yellow pond lily), even have pressurized systems that pump oxygen down to their roots. All of these systems work well enough to allow some excess oxygen to diffuse out of the roots, creating a thin layer of aerobic soil around them. If you carefully cut out a section of marsh soil with a shovel, you can see this oxygen-containing zone as a very thin gray or tan layer next to the roots, surrounded by black, sulfurous material. The aerobic zone may be splotched with a red iron sulfate which forms when hydrogen sulfide is oxidized, effectively preventing it from harming the plant. A similar process occurs with the conversion of nitrogen's ammonium compounds to the oxidized nitrate forms, allowing the plant to use them as nutrients.

Salt marsh plants have to deal with a double whammy: waterlogged soil and salt. Salt can destroy the water balance within a plant''s cells. You may remember in school soaking a carrot in a strong brown solution and having it go as limp as cooked spaghetti. The number of plants that can deal with salt is quite small, so salt marshes are much less diverse--they have far fewer species--than fresh marshes.

What saltmarsh plants like the cord grasses can do is extract the salt that diffuses into the cells and pump it out through pores in their leaves. Run your thumb carefully down a leaf of a cord grass plant at this time of year and then lick it. You'll taste the excreted salt and maybe even feel the grains on your tongue. The plant must use energy to pump out salt, but the soil is so rich, and the plant gets so much sunlight out on the open marsh, that it more than makes up for the loss. The opportunity for growth on the marsh soil is the reward for plants with the adaptations to deal with the problems it brings.

Places like Upper Machodoc Creek are backwaters not normally frequented by Bay boaters. For that reason, they're worth exploring if you have a suitable craft. That could be a canoe, a kayak, a stand-up paddleboard, a skiff. But in almost any boat, the gestalts of the Bay's marshes are obvious at this time of year. At late summer, from Eastern Neck Island on the Chester River to the creeks on the Severn; from Knapps Narrows at Tilghman Island to the coves on the St. Mary's at the mouth of the Potomac; from the Corrotoman on the Rappahannock to Occahannock Creek on Virginia's Eastern Shore; or from the Big Salt Marsh at Poquoson to the rice marshes on the Chickahominy River. Here's hoping these ideas add to your enjoyment of those marshes.

Next, read our blog, "Late Summer Glory in Tidal Fresh Marshes."

For more happenings around the Bay in August see our other Chesapeake Almanac podcasts.

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