Fiddler crabs are migrating north to cooler waters

This video became supported by funding from the Howard Hughes Medical Institute.

TRANSCRIPT

David Johnson: So in 2014, we were on a muddy bank within the marsh up here in Massachusetts, and I saw this small crab scuttle across the mud bank and pa right into a hole. And so I dug out the crab, and it became a fiddler crab. I became stunned. I had worked a decade for the duration of this marsh and had never seen a fiddler crab up here.

And I assumed, what's this crab doing here? It’s now not supposed to be north of Cape Cod, Massachusetts. And I had an concept that I wasn’t just holding, you realize, a crab. What I became taking a glance at became climate change.

My name is David Johnson, and I study marine invertebrates and coastal ecosystems and examine the effect of climate change on those marine invertebrates. The Great Marsh — it’s this living laboratory I get to work in, and after I’m up here, I get to assert, ‘oh, it truly is my day on the place of business.’ Even in my twenty second season, I’m still finding things.

And that gets me excited to be out here.

Anne Giblin: The Great Marsh is the name for a complex of marshes that in point of fact goes into New Hampshire and down into Essex. And it’s the largest remaining swamp marsh left in New England. It’s important since it truly is the sort of large marsh, and it has so many services and products that it provides.

Johnson: A salt marsh is a grassland, so imagine a prairie that you just may in finding in Kansas, but it surely undoubtedly’s flooded twice a day by the ocean.

Giblin: They’re nursery grounds for fish, so an top quality deal of the commercial fish, equivalent to striped bass, start their life here. It’s also very good for shell fishing and to head birding to experience the just the wonder of the place. Water is warming faster within the Gulf of Maine within the ocean than almost anywhere else within the area. So as water’s warm, we’re going to see an enlarge in warm water species.

Johnson: And the next stage within the research is to check out their impacts within the Great Marsh as they move in.

So after we found out that we had a new crab, I started doing surveys and sure enough, I found them as a chronic way north as central Maine.

As I found more crabs, I started monitoring them to in sorting out, is this population growing? It’s easy to in finding them in the market within the marsh since the males have this giant claw, which is generally the largest weapon proportional to its body within the animal kingdom. So when the tide goes out, you are in a position to in finding them seeking to attract a female with that claw next to it.

So generally you exit and you place out quadrants in quite an top quality deal of places every year. So it’s an annual census. So the primary four years we saw the population became rising. We also were finding females with eggs. That became telling us that they're here to remain. So the next question is do they've a distinct ecology, do they've a distinct biology than the crabs south of Cape Cod?

Johnson: They thought for the for the past 0.5 century is that after they create these burrows, they liberate nutrients and they assist the flowers grow. But the population of grass that’s here within the Great Marsh has never seen fiddler crabs sooner than. And there are no other burrowing crabs for the duration of this salt marsh, until now. So we wanted to check this concept.

And what we found became that once fiddler crabs were present, they reduced the volume of grass by forty percent. So the alternative of what we stumble on south of Cape Cod. So a tremendous question is why do we see a difference here? We think flowers south of Cape Cod have in some way adapted to the presence of these crabs digging around their roots and compensated for that.

But size may also be a factor also influencing while you measure the crabs up here versus down there. There are 25 percent bigger, and an even bigger crab may impact them by having mechanical damage resulting from burrowing. But there may also be absolutely a instantaneously relationship between the volume of cord grass and a marsh’s ability to keep up up with sea level rise. Because the tide comes in, those stems slow down the water so that mud can settle out, and that mud layer stacks up over time.

So when you've gotten got less biomass to trap that mud, which may impact its ability to increase and keep up with sea level rise. The choice way is by adding roots.

Giblin: So it’s producing as an top quality deal material within the sediments as it truly is above ground. A choice of that material decomposes that builds the marsh up.

Johnson: Along with as the flowers that we just study, we examine out what's the impact of these fiddler crabs on the pliability for the marsh to store carbon?

Giblin: Salt marshes store more carbon than almost yet another ecosystems on Earth.

Johnson: So as you start punching holes into the marsh, you introduce oxygen. And that carbon that became stored within the marsh then goes back into the atmosphere.

Giblin: If this marsh were to be degraded and every and every of the carbon that’s been stored is lost, which may represent a real enlarge in carbon to the atmosphere.

Johnson: So that’s a study that we can do.

When we see a new species arrive in our ecosystem. All of us have a knee jerk reaction to be worried. And there are with out a doubt going to be winners and losers on the rapid rate of climate migrations that we see.

Giblin: So yet another species that appears to be moving in is the blue crab. We’re seeing them more on a regular basis but their numbers are very, very low.

Johnson: The crab that I’m fascinated about showing up is on the complete also referred to as the purple marsh crab. So it eats the grass and the roots.

Giblin: That may additionally be a crab that as well south, it’s grow to be quite destructive to salt marshes.

Johnson:  I’ve been keeping a watch on them. I haven’t seen them north of Cape Cod yet, but fiddler crabs and this species of plant have figured out a technique to co-exist for millennia.

They’ve done it south of Cape Cod. And so I don’t predict total devastation that you just may also see with an top quality deal of your invasive species, despite the proven fact that their population is rising at this point, are the impacts enough to guide the local economy and their local ecology? The answer just is never any. Around the globe the future, we don’t know.

Giblin: The system is being subjected to an top quality deal of different changes, so I feel the jury’s still out on the fiddler crab.

Johnson: That’s why it’s critical to continue monitoring the impacts of these fiddler crabs, or yet another climate migrants to happen to move in.