Back when we met Douglas McMullin at Maine Coast Heritage Trust’s headquarters in Somesville, he pointed out a measuring station in Babson Creek that was designed to track marsh migration. I was intrigued and followed up with the organization that installed the gadget, and eventually, on May 23, 2018, I met Jim Lynch of the National Park Service Northeast Coastal and Barrier Network at the Bass Harbor Marsh to find out more about the program. It was a gorgeous day, sunny with a light breeze, and when we started out at 10:45 am it was 64ºF. We hauled Jim’s gear out to the marsh and I started pelting him with questions.
Jenn: So you come up twice a year?
Jim: Right. I work for the Inventory and Monitoring Division of the Park Service, and I work in coastal wetlands in the northeast US, from Virginia to Maine.
Jenn: About how many marshes are you monitoring?
Jim: Well, I monitor four sites here at Acadia. I also work at parks in Boston Harbor, Cape Cod National Seashore, Fire Island National Seashore, and Gateway National Recreation Area, which is New York City, right by JFK airport. I also work in Maryland, at Assateague Island National Seashore, and in Virginia on Jamestown Island, which is in Colonial National Historical Park. All these parks have tidal wetlands and the work that I do is related to sea level rise and monitoring elevation change in these systems. I have a piece of equipment in this case called an SET. It stands for “Surface Elevation Table” and it is used to measure really small changes in elevation.
Jenn: Of the marsh bottom?
Jim: Of whatever you’re measuring, yeah. The sea level has been rising since the last Ice Age, and as the sea levels rises these wetlands also rise up in elevation. If they don’t, they end up getting flooded out and disappearing. Soil and other materials in the water can get deposited or trapped on the marsh surface when the marsh floods. These deposits and other processes like root growth help the marsh to build up vertically, too. But it’s at a really small rate, like millimeters per year.
Jenn: So it’s kind of a race between the marsh and the sea level.
Jim: Yes. The marsh is sort of reacting, I guess, to the sea rising. That’s driving the whole thing. The ocean’s rising slowly but surely; I think three millimeters a year is the global average. It sounds like a small number, but it’s increasing from what it was.
Jenn: Adds up.
Jim: I’ve got three of these SETs here at Bass Harbor which are used to monitor elevation. I was just at Babson Creek at Maine Coast Heritage Trust. There are three there. There are three at Schoodic. There are three in the marsh on Thompson Island, right when you drive onto Mount Desert Island. … Most federal properties now, like Fish and Wildlife Refuges or National Parks, that have a substantial amount of wetlands in them will have these SETs installed to help monitor what that marsh is doing.
Jenn: And is this research for its own sake or is there sort of a plan?
Jim: It’s actually monitoring, it’s not really research. We’re basically characterizing what the wetlands are doing, and how that compares to what the body of water next to the marsh is doing. … The SET system is a custom-made piece of equipment that attaches to this stable benchmark post that stays out here all the time; it goes down 50 or 60 feet.
Jim: The post is made of metal bars, about four feet long. You drive one into the ground, then you screw another one on and you drive it down, you screw another one on, … You keep going until you hit bedrock or significant resistance. We didn’t actually hit bedrock here in Bass Harbor, which was surprising with all the bedrock in Acadia. … It’s a very simple technique. We attach the SET to this benchmark post and we lower pins down until they touch the marsh surface. Then I measure how far the pins stick up above this horizontal bar. I’m doing what’s called a repeated measure. I’m coming back to this same piece of marsh year after year after year and taking a repeated measure over and over again of the same piece of marsh. The SET moves in fixed positions around the center post … This technique is actually measuring what the surface of the marsh is doing over time. Is it going up or is it going down? At what rate? Is it going up at five millimeters per year? Is it going down at two millimeters per year? It gives you a rate of change of the marsh surface. The analogous information in the waters around Acadia comes from a tide gauge. It measures water levels continuously over time and they can calculate the rate of change of the water surface from this data. That’s how they calculate sea level rise. So the SET is sort of analogous to what a tide gauge does, in terms of measuring the rate of change of the sea. I think at the NOAA Bar Harbor tide gauge [Ed. Note: the nearest sea level rise tide gauge], sea level is rising about 2.2 millimeters per year. Really small numbers. You look out at a marsh and it looks healthy, but how do you actually measure anything? The SET is a technique used to help quantify some of the processes going on in the marsh, which occur with such small values we had to develop something customized to measure it.
Jenn: Who invented this?
Jim: A Dutch graduate student used it in Louisiana in the early 1980’s; a PhD student at LSU. This technique originated in Holland. I think they were monitoring some of the low areas of Holland. The student at LSU did his PhD on a different version of this, but I was involved soon after that and we modified the design.
Jenn: It’s a wicked clever concept. I mean, once you see it, you’re like, ‘well of course. That makes perfect sense.’
Jim: See what I’m doing here? I’ve got the horizontal bar level. I take readings in four directions, every 90 degrees. And I have a stake here that marks what I call my ‘A’ direction, the starting direction. … I lower these pins down just until they touch the marsh surface.
Jenn: And by that you mean the top of the soil?
Jim: Yeah, the top of the soil. Now, I have to make a decision about what I’m calling the top of the soil. Up here at Acadia it’s pretty easy. The marshes we’re standing on, they’re really firm. It’s a pretty easy determination. … Some places where I work it’s sloppy and muddy. Then you have to make a subjective call about what you’re calling the surface. So, I lower these pins down, just until they touch the marsh surface. I can usually see it or feel it. Then I measure how far this pin sticks up above this bar in millimeters. … So I’m the reader. … I’ll give you nine numbers, straight down one per box. Nine numbers straight down that column.
Jenn: You got it.
[We proceeded to take and record the measurements.]
Jim: The assumption is that every time I come back this bar is in the same position it was last time I was here, and the pin is falling on the same piece of marsh. This bar is in the same position, we’re on the same piece of marsh, and I lower the pin and it sticks up some distance that I record. So that pin going up or that pin going down is due to the marsh going down or the marsh going up, not due to the SET benchmark moving. That’s why it’s so deep in the ground. The assumption is that if this thing is deep enough, it’s not going be moving around a lot.
Jenn: So how long have you been working at Bass Harbor? At this marsh?
Jim: All four of these sites were installed in 2011. Not that old. These are actually some of the newer ones I work on. … I’ve been working for the Federal Government since the early ‘90s doing this kind of stuff. I lived in Louisiana for 15 years, working wetlands in Louisiana and the Gulf of Mexico when I worked for the US Geological Survey. I’ve traveled all over the country doing this.
So, these pins go up and they go down and I’ll track each one … This is Pin One for this direction. I’ll track that one individual pin over that entire time period and you can run a line through the data and get a rate of change. This pin probably has been creeping up slowly. It might go down one season, but in general, they’re all creeping up slightly higher each time. There’s a lot of variation. It takes a lot of years of measurements to show some change, because the change is so small. It varies all over the country. … The rates up here are generally very low. This is a stable bedrock. There’s no sinking or subsidence issues here. You always hear about Louisiana sinking. … The ground is naturally sinking down there, but on top of that the water’s also rising, so they get a double whammy. Here you’ve only got the water rising. The land isn’t moving too much.
Jenn: Do you also have changes there from greater sedimentation or erosion?
Jim: Yeah, the rates of change are usually much higher in those areas. As you go south, the rates of sea level rise generally increase – Up here, I think sea level rise is about two millimeters a year. Down in Maryland, it’s four or five millimeters per year. And places like Louisiana it might be ten millimeters a year. That number includes the sinking of the land, too. So, there are other issues as well. … This is a long-term monitoring program. I have to take about five years of measurements before I start actually having enough data to sort of get a track of what’s going on.
Jenn: And is the data available to the public?
Jim: Yes. It has to go through a QA/QC process to get it verified. [Ed.note: Quality Assurance/Quality Control] … Then we publish it and make it available. All the data that we collect eventually becomes public.
[Ed.note: In this next section we are talking about Marker Horizons which are used to quantify how much material is deposited on the marsh surface over time. At each sampling station Jim measures “elevation change” with the SET and “surface deposition” with the Marker Horizons. You can see them in the graphic near the beginning of this post, too.]
We started taking these measurements seven or eight years ago. I’m looking for these white stakes. There are four of them here. We put a layer of white powdered clay, called feldspar clay, down on the marsh surface, … the clay gets wet and forms a layer. But the layer is buried now under sediment. You can’t see anything. We have it marked with these stakes so I know where it was. I’ll take a core in here and I’ll show you. I’m just cutting a little square of marsh out with my knife. It might be deep. … Here we go.
Jenn: Oh, cool.
Jim: We have a white layer here and there’s a certain amount of material on top of that white layer. I know the date when we put that out, so we can actually calculate the amount of change. I take some numbers and record them on the data sheet there. These are called Marker Horizons.
Jim: There’s another one over here. … We try not to make them too visible. And sometimes the ice pulls them up or they get stepped on. Here’s one. Looks like a pie slice.
Jenn: Yeah, I was thinking chocolate torte.
Jim: And there’s a third one over here. These are measuring deposition on the surface. It’s a similar process to what the SET is measuring. They’re complementary, just different techniques.
Jenn: And this one’s a little more specific about soil deposition?
Jim: The Marker Horizon is only looking at surface deposition, whereas [the SET] measures everything from the bottom of the benchmark post to the marsh surface. It’s integrating everything that’s going on in the marsh. The Marker Horizon is mainly looking at stuff going on at the very top of the marsh. We put that white layer down and I go, ‘Well I measured an inch of material on top of that white layer, so the marsh must be an inch higher than last year.’ But that’s not always the case, because the marsh could be sinking or there could other stuff going on below the white layer. That’s why this technique with the SET is a little different. It’s measuring elevation change from a benchmark, whereas that white layer could be moving up or moving down. It’s still measuring stuff on top of it, but the layer itself might be moving.
A really good example in Louisiana is sinking. You put these white layers out and after five years, we go, ‘Oh, there’s three inches of stuff on that white layer. Wow, this marsh must be three inches higher.’ But, when we look at the SET measurements over the same time period, the elevation did not change. The elevation stayed the same, so the marsh was actually sinking and stuff was coming in and being deposited. The SET is a newer technique. The Marker Horizons have been around a long time.
Jenn: That actually answers the question I asked earlier about how sedimentation affects the measurements you’re getting from this. You’re measuring both.
Jim: Yes. This is measuring everything that’s going on.
Jenn: That’s very cool.
Jenn: How did you end up doing this?
Jim: Well I got my Master’s degree down in Louisiana doing work in mangroves in south Florida and Mexico, looking at sediment and doing that kind of work. I got lucky and got hired by the federal government – back then it was the US Fish and Wildlife service – to do wetland work at a center they were building in the town we lived in.
Jenn: That’s handy.
Jim: At the USFWS we really expanded the use of the SET technique and we promoted it to different groups of people … Initially only academics, university students doing a specific project or addressing some research question. Then the federal government starting using it to do research. But that’s how I got started doing it. So I’ve always done wetland work and I’ve always worked in the coastal plain, like the Gulf of Mexico or the east coast.
Jenn: How did you even find out about it? I mean, when I was in high school, I didn’t know that this kind of work existed.
Jim: Me too. I never had any grand plan. I just sort of went with the flow. I went to the Coast Guard Academy and was miserable. I quit after my freshman year. I switched to the University of Delaware and I ended up getting a double major in chemistry and biology. I got a summer job at a marine lab on the Chesapeake Bay doing chemistry-related wetland work with a post-doc who needed an assistant. He had just gotten his PhD and was working at the University of Maryland on a project. While I was working there, he got a job in Louisiana and I followed him down to Louisiana as a grad student.
Jim: I just got lucky.
Jim: Alright. Yeah, look at this. A big ice floe deposited this-
Jim: Maybe at low tide, that area floods and then it freezes and then a big tide comes in. It picks up the ice and the mud that’s frozen to it, floats it onto the marsh and drops it.
Jim: Yeah, it’s pretty neat.
Jim: People are now using GPS to take measurements, but GPS doesn’t have the precision to do something in the millimeter range. It’s very good, but … in general, if the water’s going up at a slow rate, the marshes go up at a slow rate. The big issue is that the rate of sea level rise is changing. The rate of change may double. At a rate of three millimeters a year, sea level rises about one foot per century. That’s sort of a ballpark figure. Maybe down by me in Maryland, the water level comes up about a foot every hundred years. And the marshes typically grow vertically about a foot … They grow along with it. So the trick is, if you’re talking about sea level rise doubling, maybe to two feet per hundred years, instead of one foot … Maybe even tripling, you know? You’re talking big numbers, but no one knows for sure yet if the marshes can keep up. They’re doing fine with the somewhat consistent rate that’s been going on for thousands of years, but we don’t know how the increase will affect them.
We plugged away and got all Jim’s numbers recorded for the three stations, and by the time we finished around 1pm the temperature had soared to 75 degrees, which for May in Maine is officially Pretty Damn Hot. Can’t speak for Jim but I know I was glad to head for the shade.
Many thanks to Jim for letting me tag along and ask so many questions!
Transcription of this interview was funded by a grant from the Frenchman Bay Partners Environmental Stewardship Award.