Buffers: Wetlands are major buffers filtering out large quantities of sediment, pollutants and nutrients before they reach streams, rivers and bays. Maryland marsh photo by Sandy Rodgers.

Contents

The State of the Bay

The Language of Resilience

Towards Adaptive Management

Identifying Thresholds

A Meeting of Minds

More About Resilience

A new Bay for the Oyster?

Forests and wetlands trap sediments and help slow the flow of pollutants into the Bay. Their loss, coupled with the decline of grasses and oysters in the 1970s and 1980s, caused the Bay to lose much of its resilience.

The plankton net abruptly breaks the water's surface and dangles precariously from the winch, a long porous stocking trailing behind a 2-foot-square metal frame, dripping brackish water. From the deck of the research boat bobbing in the Rhode River this summer morning, two scientists and the captain lean out and swing it aboard, soaking their shirts as they lower the net onto the deck. The lead scientist, Denise Breitburg, kneels and carefully unscrews the large cylinder at the base of the net — the so-called cod-end that traps whatever is floating in the water. She pours some of the gelatinous contents into a giant measuring cup, pausing to record the volume. Then she empties the cupful into a large, circular metal sieve.

Blop, blop, splat. Like raw eggs hitting cookie batter, gelatinous animals fall by the hundreds onto the sieve. Breitburg swiftly sorts through the organisms, which range in size from fingernail to nearly whole hand, surveying the catch. Standing quickly, she flings the contents of the sieve overboard — gelatinous animals flying through the air before hitting the water. As the boat cruises ahead to the next station, she turns back to the cylinder and pours another sample into the measuring cup.

"Only comb jellies again," Breitburg says, shaking her head. "We haven't seen a single sea nettle in the area this season."

All summer, Breitburg's group had been using a small 16-foot skiff to sample the Rhode for sea nettles, the stinging jellyfish well known to anyone who has swum in the Chesapeake, and comb jellies, their non-stinging cousins. Each week yielded the same result...no nettles. Today, Breitburg, an estuarine ecologist at the Smithsonian Environmental Research Center (SERC) in Edgewater, Maryland, along with her graduate student and post-doctoral fellow, is aboard SERC's 42-foot R/V Saxatilis, sampling for nettles and comb jellies again, using a bigger net. Breitburg wants to verify that the smaller net pulled by the skiff was not simply missing the larger nettles. But the 12-foot-long Neuston net pulled by the bigger boat filters huge volumes of water over and over again, with the same result...no nettles.

Absent nettles in the Rhode might not be so unusual, Breitburg explains, especially since the river's salinity is low and these animals gravitate toward saltier waters. She has only just begun sampling this river for gelatinous creatures so it is hard to tell if the missing nettles, Chrysaora quinquecirrha, and bountiful comb jellies or ctenophores (pronounced teen-o-fors), Mnemiopsis leidyi, in the Rhode are part of a more ominous story that has been steadily unfolding two tributaries to the south.

In the saltier Patuxent River, located roughly 40 miles south of the Rhode, the decline in sea nettles has been unmistakable. Breitburg has sampled the Patuxent since 1992, creating a data set that complements a long-term inventory started in the 1960s by the late fisheries biologist Dave Cargo, of the University of Maryland Center for Environmental Science (UMCES) Chesapeake Biological Laboratory in Solomons, Maryland. Breitburg and Cargo independently documented a strong downward trajectory in the jellyfish population that has steadily gained momentum since 1985.

Of course, to most, the absence of nettles in the summer is cause for celebration — allowing carefree swims in the Bay. So demonized are these "stinger nettles" that, in 1966, the U.S. Congress passed a "Jellyfish Control Act," for the purpose of "promoting and safeguarding water-based recreation for present and future generations...by controlling and eliminating jellyfish...and other pests." The federal government authorized up to $1,000,000 per year for studies of innovative extermination techniques and control programs.

Despite their historical unpopularity with swimmers and boaters, the Bay's long-tentacled jellyfish are powerfully influential in the food web. Voracious predators, they spread across the Bay and its rivers during the summer months, eating comb jellies and other zooplankton as they go. Without sea nettles to keep their numbers in check, the seemingly benign comb jellies prey heavily upon young (larval) bay anchovies and on oyster larvae, says Breitburg. They also compete directly with adult bay anchovy for food. In the world of eat or be eaten, bay anchovies are a major food for top fish-eating predators — such as striped bass — who may go hungry as anchovies and other forage fish decline.

"I've always been fascinated by jellyfish," Breitburg says. "They are such simple animals, yet they are so dominant in the ecosystem."

Forty years ago, it would have been impossible to imagine the downside of a diminishing sea nettle population. But today, nettles are dwindling in number in the Patuxent and possibly beyond — not through any force of Congressional action — and Breitburg, for one, takes it as a troubling sign.

Declining in concert, sea nettles and oysters followed the same downward path in the Patuxent River from 1985-1995 (left, no data for 1989). Denise Breitburg (below) pours the contents of a catch —only comb jellies —into a tray for sorting. Graph adapted from Breitburg (unpublished).

This page was last modified September 15, 2018