Category Archives: Salt marsh

Ghost Forests of the Chesapeake

Chesapeake Bay, Virginia

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Skeletal trees tower over the salt marsh, their bare arms outstretched like scarecrows. The salty sea wind polishes their chalky bones. The skeletons loiter like teenagers in the middle of the marsh – bored, out of place and suspicious. Trees, whether dead or alive, are not supposed to be in the grassy plains of the salt marsh unless elevated on a hill. Dead trees that appear in the middle of nowhere like fairy rings or Stonehenge hint at the supernatural; but these ghost forests are impeccably natural.

Throughout the Chesapeake ghost forests line the edge of salt marshes or sometimes rise up like specters in the middle of a marsh half a kilometer from the nearest forest. These are corpse-filled forests created by the sea where dead trees mean new life for the salt marsh.

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Salt marshes chose real estate at the edge of the sea. And like any real estate at the ocean’s edge, it has to deal with not only flooding, but also a rising sea. A salt marsh has the same options as a house to deal with a rising sea: build vertically or move to higher ground. But the higher ground is often occupied by forests. A salt marsh wants to invade the forest and take over its land, but the tree is greedy and grabs sunlight by the armloads, leaving little energy for the forest floor. The salt marsh’s advantage is its ability to tolerate salty land and so it stays in the lowlands. In a rapidly rising sea, however, the salt marsh is caught between a woody devil and a not-so-deep-or-blue sea. One key to the marsh’s survival is patience and opportunity.

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The skeletal remains of trees on a muddy beach on the Goodwin Islands, Virginia. Here the sea not only rose to kill the trees, but also eroded the marsh edge exposing trunk and roots alike.
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The same muddy beach, which serves as a tree graveyard.

The sea has no politics. It does not care about borders and territory and competition between bickering ecosystems. As it rises, it slips past the forest boundary to bathe trunks and roots in brine. In time, trees will die, shedding their light-grubbing leaves, bathing the ground in solar energy. Awash in sunlight and without competition with tree roots, the salt marsh grasses march in and encircle woody trunks as bark flecks and falls away. Trees have always been stubborn and don’t easily give in to gravity or mortality and will stand tall over the marsh long after their phloem no longer flows, continuing to stake their claim even in the afterlife.

The movement of marshes into higher ground, especially into forests, is called marsh migration and is an important mechanism for salt marshes to escape a rising sea. Where a forest sees death, a marsh sees life. A salt marsh does not fear a ghost forest; it fears a hill, a seawall, a Food Lion parking lot, and a road – anything that prevents its escape against a rising sea.

Post Script:

Ghost forests can be found anywhere in the world where there are salt marshes, not just in the Chesapeake. There is a great post on saltmarsh migration by Joe Smith from New Jersey. There are also two great scientific publications on saltmarsh migration. One by  Joe Smith and the other by Matt Kirwan at the Virginia Institute of Marine Science.

 

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The vanity of fish and snails like underwater ants

A wonderful video taken in a salt marsh ditch in Newbury, Mass. The fish is who wants to make sure the camera gets his good side is the mummichog, Fundulus heteroclitus. For scale, the snails are the size of a BB from a BB gun. In all my time in the salt marsh, I’ve never seen so many! I guess I’ve got to stick my head underwater more often. Thanks to DeRosa Environmental for bringing the video to my attention.

 

Need a new yoga pose? Try the stretch spider!

The still brown grass crunches under my feet as I walk the salt marshes of the Goodwin Islands at the mouth of York River. I stop when when I see a blade of grass scramble across the other grass blades like a panicked airplane passenger who climbs over other passengers trying to get to the evacuation slide first. I snatch the panicked grass blade in my hand and it sprouts eight legs and repels from my hand down a silken thread, dangling for a moment like Christmas ornament before transmogrifying back into a grass blade. My grass blade is a spider in the tetragnatidae family. Tetra means ‘four’ and gnathid means ‘jaw’; it looks like it has four jaws but she doesn’t. See, science isn’t so hard once you crack the code. Tetragnathid (the ‘g’ is silent) spiders are also called ‘stretch’ spiders because they stretch their bodies in their own yoga pose: four legs forward and two to hold on and two legs back (some spiders try other combinations). Make yourself as thin as possible. And try to look like that grass blade or leaf or cattail.

I am amazed by this spider that looks like dead grass. I assume the yoga pose and combined with the drab-colored yoga outfit is to blend in to avoid detection by 1) potential prey and 2) potential predators. If she had not have scrambled, I would have never seen her. Even when I found her and made her pose for me on a blade of grass I still had trouble figuring out where the grass ended and she started. Look at that pose. Incredible strength and limberness. Stretch spiders can be found in your house, your backyard or your garden. So if you’re looking for a new twist for your boring yoga routine, run to the closet tree you can find, stretch out and see if anyone can find you.

This spider reminds me of another cryptic yoga pose: the toothpick grasshopper.

Namaste.

The savory swimmer swims north?

A blue crab (Callinectes sapidus) found north of Cape Cod in 2012. Plum Island Estuary, Massachusetts
A blue crab (Callinectes sapidus) found north of Cape Cod in 2012. Plum Island Estuary, Massachusetts

In the summer of 2012 I was having dinner with colleagues when one offhandedly said that he’d seen a blue crab, Calinectes sapidus in the marsh (the Great Marsh in northeast Mass.). Incredulous, I said a more colorful version of, “Equine feces.” He was claiming that a blue crab was in the Great Marsh, far north of its northern limit of Cape Cod.

Then other sightings of blue crabs in the Great Marsh were reported.

I grabbed a long-handled net and walked the tidal creek bottoms. I saw many green crabs scuttle but then, in a deep pool, I saw a crab swim sideways and instantly knew it was a blue crab (blue crabs are in the family Portunidae which are swimming crabs with flattened back legs). I found three more that summer.

Finding a blue crab in the the Great Marsh was surprising because the marsh lies in the Gulf of Maine which extends from Cape Cod to Canada and is kept cold by cold water currents from Canada. Water too cold for blue crabs.

Using the list-servs, Twitter and colleagues I crowd-sourced information about observations of blue crabs throughout the Gulf of Maine and from 2012 – 2014 these often-called ‘Maryland’ crabs were found as far north as Maine and Nova Scotia. The reason? I hypothesize warming oceans. Water temperatures in 2012 and 2013 were much warmer than the average of the previous decade which may have lowered the temperature barrier. Earlier I reported on a similar range extension for the fiddler crab.

Solid line: historic blue crab distribution. Dashed line: potential new range extension.
Solid line: historic blue crab distribution. Dashed line: potential new range extension. Arrows indicate sightings of crabs from 2012-2014.

It may be a logical fallacy to talk about climate change and warming seas when Boston is undergoing record snows (record-breaking snows are consistent with climate-change theory as warmer air holds more moisture prior to storm events), but we cannot deny that the climate is changing. One prediction of climate change is that as the climate and oceans warm species will start shifting where they are found. We’ve seen this already in many commercial species such as hake, flounder, and lobsters in the northeast where the concentration of their biomass has shifted north. The Connecticut lobster fishery (CT the southern end of the lobster’s distribution) is severely depleted, possibly in part to lobsters moving north.

What makes my observations of blue crabs north of Cape Cod unique is that this is the first time a commercially important species has been reported to potentially expand into the Gulf of Maine. It should be noted that in the past 150 years there have been four other reports of blue crabs in the Gulf of Maine, but none of those populations were permanent. It’s still to be seen if the 2012 blue crab population is a permanent extension of their range. If so, then it means that crab cakes are expanding north thanks to climate change.

The blog’s title? Callinectes sapidus means ‘savory swimmer’.

The article can be found here: The savory swimmer swims north: a northern range extension of the blue crab Callinectes sapidus?

A unicorn in the marsh

A fiddler crab, tee hee
A rare species of fiddler crab

In the Great Marsh, he should be a myth, like a unicorn. But there he is. Like a nervous cuckoo clock in the mud, he pops out two or three times before he completely shows himself. A male fiddler crab (Uca pugnax), with a blue burnish to his shell and the characteristic obscenely large claw. I am astonished to see him. Astonished because I am probably the first person to see a fiddler crab pop out of the Great Marsh mud.

The Great Marsh stretches like a verdant yawn in the Gulf of Maine, which is the whole of the ocean from Nova Scotia to Cape Cod. Here the salty waters are chilled by the Labrador Current, a river of sub-arctic seawater that is born between Canada and Greenland and plunges south like a fist. The warmer waters from the south are deflected off the flexed arm of Cape Cod and kept out of the Gulf of Maine by the colder waters of the Labrador Current. As my New Englander friends like to brag, particularly when the snow is deep and the wind biting, this is a place only for the hardiest of souls.

Ovigerous (egg-bearing) fiddler crab, Uca pugnax, caught in a Rowley, Massachusetts, salt marsh
Ovigerous (egg-bearing) fiddler crab, Uca pugnax, caught in a Rowley, Massachusetts, salt marsh. Credit: Ashley Bulseco-McKim

Fiddler crabs are a warm-water species preferring the temperate waters south of Cape Cod. I am of the same opinion. I can snorkel in swim trunks in Buzzards Bay in July, which is on the south side of Cape Cod, but when I try to do the same on Cape Anne and its rocky shores, it’s like an ice cream headache for my entire body. I, too, am a warm-water species.

I search the mudbanks for other crabs, but find only him. Maybe he is a unicorn. An accident of currents and luck. Then I search other tidal creeks. Jericho, West, Clubhead, Nelson. Though their numbers are low, I find more fiddlers. Their burrows, only as wide as my thumbnail, perforate high in the mudbanks near the hairline of the Spartina grass. Many burrows are abandoned. Active burrows are identified by what look like chocolate ice-cream sprinkles – what we locally call ‘jimmies’ – scattered around the burrow entrance. These are fecal pellets from a recently fed crab. A quick probe with my finger (a very scientific technique, I assure you) confirms the fiddler’s residency.

I search beyond the Rowley marshes and find more fiddlers. Directly behind J.T. Farnhams’ in Essex. Off Atlantic Avenue in Gloucester. Chubb’s Point in Manchester-by-the-Sea. Next to the Endicott Square Shopping Plaza in Danvers. Massachusetts indeed has a new resident. So does New Hampshire as the fiddlers have journeyed as far north as Hampton.

Salt marsh fiddler crab, Uca pugnax, Manchester-by-the-Sea, Massachusetts
Salt marsh fiddler crab, Uca pugnax, Manchester-by-the-Sea, Massachusetts. Credit: Jon Whitcomb

How can a warm-water crab invade the province of the cold, a place where it has never before been able to survive? The answer lies in the fact that the province of the cold is becoming warmer. As the climate warms, so too does the ocean as the overburdened atmosphere gives some of its heat to the ocean to hold, an arrangement as old as the Earth. In the summers of 2012 and 2013 the Gulf of Maine waters warmed to 68 degrees Fahrenheit from the typical and chillier 63 degrees of years prior.

Those five degrees may not mean much to those of us who can adjust thermostats, but those five degrees are significant to an animal that uses the environment to regulate its temperature. For fiddler crabs, those five degrees are the difference between scuttling across the marsh and an arctic death.

Fiddler crabs did not arrive in the Great Marsh in the form that we recognize them, with their snapping claws and rounded bodies. They instead arrived as larvae carried by the currents and tides. The larvae are mostly heads, translucent triangles with Pinocchio noses and topped with a single spine, with legs and tails dangling. For fiddler-crab larvae, 64 is the key that unlocks the Gulf of Maine. Below that number in degrees Fahrenheit and these drifting triangles do not metamorphose into the crabs that make thumbnail sized burrows in the marsh. But give that number a degree or five, and those once-thought unicorns of the Great Marsh become a reality.

And so, borne on the currents of climate change, the fiddlers have made a surreptitious arrival to the Gulf of Maine and the Great Marsh.

The consequences of this incipient colony are unknown. As burrowers, fiddler crabs are engineers that re-work the soil and the marsh chemistry. If the effect is positive or negative is not yet known. I can only give you the answer that is common given by scientists that can be utterly frustrating:

It depends.

Too many crabs and the marsh grass cannot establish, which may ultimately lead to marsh loss. Only a few crabs and the marsh grass grows better. What I can tell you for certain is that with the arrival of these new colonists, just as when we arrived in the 1600’s, the Gulf of Maine and the Great Marsh will be changed forever.

Already we have seen marine species such as lobster, flounder and hake shift northward as a result of climate change. Some, however, still consider climate change a myth, like the unicorn. But sometimes seeing is believing. Like a fiddler crab in the Great Marsh.

The science is here: Fiddler on the Roof: A northern range extension for the marsh fiddler crab Uca pugnax

Pantyhose ingenuity

How would you catch this dragonfly?
How would you catch this dragonfly?

In the fall of 2012, I was to teach entomology at Sewanee: University of the South, whose campus is 13,000 acres of largely undeveloped forested land on the Cumberland Plateau. All about Lake Cheston dragonflies maneuvered like jet fighters. I didn’t know how to catch these lightning-fast aerialists. Field guides offered no suggestions, but the scientific literature did: shotguns.
From a 1972 paper by T.M. Neal and W.H. Whitcomb in the Florida Entomologist, “High flying…dragonflies were shot down with a 20 gauge shotgun; the shot in the shell replaced with fine sand.”

I immediately asked my colleagues what they thought about letting my students use shotguns on Sewanee’s 13,000 acre campus to collect dragonflies. My colleagues were, I’ll say, intrigued by the idea, but said I’d have to get approval from the administration for my ‘shotgun pedagogy.’

Could I really get the University to not only buy shotguns as an entomological supply, but also let the students blast bugs out of the air?

I don’t know what the answer because I never asked the administration. I thought twice about arming my students with shotguns and instead armed them with nets and traps and cameras. The dragonflies, and likely the faculty, are probably better for it.

But I really liked the ‘shotgun ingenuity’ of Neal and Whitcomb’s approach. I imagine them sitting around beers saying, “How are we going to catch these things?” And then Whitcomb suggests, half as a joke and half serious, “What if we blasted them with a shotgun?” They both laugh and sip their beers. Then they both get quiet for a moment. Then Neal says, “You know, if we pepper them with a smaller shot, it might just work.”

Field biology and ecology requires a large number of tools, but the most important one is ingenuity. Often there is not a ready-made, manufactured piece of equipment for your particular needs. A field scientist must be able to think on his feet or engage in what I call, ‘shoot-from-the-hip-ecology.’

One of my own moments of ‘shotgun ingenuity’ came in 2007 when I was conducting an experiment where I needed to keep grasshoppers in cages in a salt marsh to determine how many grasshoppers it took to severely damage plants. But first I had to catch hundreds of grasshoppers. The problem is, how do you put 100 grasshoppers into a bucket without some escaping every time you open the lid to put one in?

Let’s go to that moment:

Prarie grasshopper (Melanoplus sp.) in the saltmarsh. Plum Island Estuary, Massachusetts
The quarry: a prairie grasshopper (Melanoplus sp.) in the saltmarsh. Rowley, Massachusetts

July 2007
The Great Marsh
Rowley, Massachusetts

The grasshoppers thumped like popcorn in the five-gallon bucket. I had 10 but needed hundreds more. Every time I opened the lid to put one in, two jumped out. I needed to be able to add grasshoppers to the bucket without opening the top.

I wandered around the local Kmart and found the answer in hosiery. Pantyhose.

I stared at the pantyhose size chart which was some sort of cryptogram that correlated letters to weight. I tried to figure out how much I would weigh if my legs were the size of five-gallon buckets. Would I be a B or a Queen Petite or a Queen 2? It depended on how tall I was.

Not able to crack the code I asked a sales associate.

“Excuse me. I’m trying to put pantyhose on a five-gallon bucket. Can you help me figure out what size I need?”
She asked immediately, “On a bucket?”
“It’s for grasshoppers,” I said as if that explained it all.
“Grasshoppers?” she asked.
“I’m a scientist,” I added.

Possibly not wanting to hear anymore cryptic answers she consulted with me about sizes. She also taught me about control tops and the different colors (nude, taupe, black!). She told me the difference between pantyhose (which go to the waist), stockings (which go to the thigh like long socks), and leggings (long socks with no feet). So many grasshopper options!

After some experimentation, I found that the best fit for a five-gallon bucket was a queen size control top. Stretching the waist over the bucket top and cutting off one of the legs let me plunge my closed fist holding a grasshopper into the bucket, release it and pull my hand out without the grasshoppers escaping. It also allowed for sufficient airflow and temperature regulation, which minimized mortality during collection.

The scientific term is:  orthopteran retention vessel. Or a bucket with pantyhose on its head.
The scientific term is: orthopteran retention vessel. Or a bucket with pantyhose on its head.

The significance of the result of my ‘pantyhose ingenuity’ can be found here. The data on the difference between ‘taupe’ and ‘nude’, however, remain inconclusive.

Have you used ‘pantyhose ingenuity’ in your own work?