Learning to Love Benthic Algae

I am the type of person that attributes songs to the work that I do. And after my first day sampling for benthic algae last summer, I already had the chorus of the Beatles’ Twist and Shout running through my head.


My field partners Haley and Megan helping me take benthic algal cores in the mudflat and tall Spartina alterniflora zones.

That may seem an odd choice of song, but I assure you that there is no better musical masterpiece to describe the complete process of benthic algae sampling and running. In the field, with our four-centimeter diameter corers, we cut back the cordgrass Spartina patens in the high marsh to reveal the sediment beneath. The dense Spartina patens roots woven through the soil, however, force us to twist the corer to break up those roots, eventually releasing our sediment core sample. There we have the lyrics “Twist and shout,” shouting in joy (or frustration) optional.

The next week, I travel with my samples back to the lab at the Woods Hole Research Center, where I extract the cores in acetone before running them on a UV Spectrophotometer, to measure chlorophyll a absorbance at different wavelengths of UV light (which, in turn, tells us benthic algae abundance). With running the samples, though, comes a lot of tube shaking, after adding acetone and again before being spun down in the centrifuge to run on the Spectrophotometer. Hence, “Shake it up, baby, now.” Shake those samples!


Running benthic algae samples using the UV Spectrophotometer with my mentor Hillary.

If you couldn’t already tell, I’m quite passionate about benthic algae, the topic of my independent research. However, it took a little while for this interest to grow on me.

The first time I heard the words benthic and algae together was last summer, when it was proposed by the Lead Principal Investigator Linda Deegan that I be in charge of field sampling, organizing the past fifteen years of data, and eventually finding the story behind the microalgae response to nitrogen fertilization. I did my best to act knowledgeable about the topic, but in my two years of undergraduate study, I had only come across macroalgae, and never algae described as benthic. Cue the background research!


Demonstrating the “twist and shout!” portion of the sampling process–trying to separate sediment cores from plant roots!

What we refer to as benthic algae is microalgae, such as cyanobacteria and diatoms, found in the first few centimeters of marsh sediment. Benthic algae is important for the uptake of nitrogen and carbon, and serves as a source of energy for grazers, among a myriad other things. This algae is also resilient to many environmental factors like extended darkness and hypoxic or anoxic environments, which means that it could play a role in salt marsh recovery from nitrogen loading; but should benthic algae be negatively affected by that nitrogen addition, there could be potential consequences for the salt marsh ecosystem.

Through research, I began to see benthic algae as a link between marsh invertebrate ecology, a topic I was familiar with and loved, and biogeochemistry, an area new to me when I began with TIDE. Armed with my corers in the field, a UV Spectrophotometer in the lab, and fifteen years of historic data in the office, I hope to unlock the full, fifteen-year story of how benthic microalgae responds to nutrient loading and marsh recovery this upcoming year.


Written by Kate Armstrong

Strangers in a Strange Land: Bioinvasions in the Gulf of Maine

2101Imagine for a moment that you are a crab larva. Floating in the middle of an urban estuary (say, the Port of Rotterdam in the Netherlands), you just hatched, and are one of millions of little baby crabs hoping to survive long enough to make it to adulthood. Then suddenly, inexplicably, you are sucked up into a strong current that you don’t understand. The sun disappears, and you are surrounded by thousands of your brothers and sisters, but also many other larvae that you don’t recognize. Time seems to stand still, and you do what you can to make the best of a bad situation. Then suddenly, the same current again pulls you, but now in the opposite direction, back the way you came. Hooray, you are free! But wait, this new water feels different; this is not at all what you remembered of your home. By this time, you are a little older, a little larger, and a little bit more aware of your surroundings. You recognize you must be in a different place entirely, but you again make the best of a bad situation, and settle along the marshy shores of your new locale (not knowing you just entered Boston Harbor). You grow into an adult, and you discover to your relief that your home is not so bad after all. Predators don’t recognize you as prey, and parasites don’t infect you. So you yourself then reproduce, your offspring survive in massive numbers, and your species excels in this new home; a truly crabby paradise.

2103Congratulations! You just experienced what it was like to be an invasive (i.e. non-native, non-indigenous, etc.) species transported from the Europe to the Eastern United States by ballast water from a commercial vessel. In order to maintain buoyancy and pitch while at sea, ships take on various kinds of ballast including rocks and water. Rock ballast was more commonly used in early shipping in New England in the 17th, 18th, and 19th centuries. In fact, the first arrival of the European green crab Carcinus maenas to New England was through British and American merchants unloading rocks (which also contained crabs) at ports along the Gulf of Maine. A second wave of green crabs was introduced to the eastern seaboard more recently in the 1980s through water ballast (much like your own crab experience). Although seemingly beneficial for the crab, bioinvasions rapidly became a problem by the mid to late 1980s not only for native organisms, but also for people. In 1988, the zebra mussel was introduced accidentally to the Great Lakes in North America from Bulgaria in Europe. A fouling species of mussel that grows on practically any surface it touches, intake pipes from Lake Michigan to Chicago were clogged for weeks until utility companies were able to replace the critical infrastructure. The result: zebra mussels cost taxpayers millions to remediate the problem. Therefore, it is incredibly important to continue to understand global effects of bioinvasions on a variety of ecosystems including the Plum Island Estuary, and how to prevent their spread; no matter how much those crabs need a change of scenery!

Written by Michael Roy

Ode to Flux Week

By Sophie Drew

Adapted from Lewis Carroll’s “Jabberwocky”


Sophie (that’s me!) and Bridget in the zone mid-flux

‘Twas brilliant, when the golden sun
Did show its face upon the marsh
All set were we to work as one
The heat arising, greenheads harsh

Behold the power of plants, my friend!
CO2 in, oxygen out!
I’ll tell you before poem’s end
What my research is about

We have a chamber, logger, tubing,
Across the marsh these things we heave
We set it up, we get it grooving
And watch, in real time, marsh grass breathe

Full sun, then shade, then darkness too
That’s three light levels for ya
To see how our dear friend responds,
Spartina alterniflora


My project partner Bridget modeling proper gear-carrying technique and flux week style

And why do this? What can we learn?
Seems an odd summer vacation
It’s to find out if these plants just might
Recover from eutrophication

When nitrate’s added in excess
To a system so fine tuned
The carbon cycle becomes a mess
If we’re not careful, it’s all doomed

‘Twas brilliant, when the golden sun
Did set across the shining creeks
Carbon fluxes, July, done!
Until again, in four short weeks



A high marsh flux in action


New England’s salt marshes were some of the first ecosystems I was immersed in (literally) as I began my jaunt into marine science. For many people, the draw is their tranquility, as looking out onto a cordgrass meadow gently rippling in the breeze can be quite relaxing. Something that fascinated me then, and still does now, is how these peaceful feelings can be evoked by such a harsh environment. Large, strong tides, cold, salty water, and hot, unrelenting sun all represent real hazards for animals residing in these coastal margins. Yet salt marsh critters don’t run from these dangers: in fact, food webs in these areas are designed to meet stressors head on, taking life-threatening risks in order to reap the energetic rewards that pushing these boundaries can provide.


I am here studying Plum Island’s food webs. One of the major cogs in the always-churning ecosystem machine is the mummichog, a small minnow that easily dominates the other marsh critters in terms of sheer numbers of individuals residing in the creeks. You can catch these baitfish by the hundreds in all sorts of traps and nets, and though they can eat a plant-based diet, in order for them to truly grow big and strong, they need some protein! Big fish can eat the shrimp and invertebrates found in the creeks, but how can a mummichog get to that size in the first place? The answer is by risking life and fin and riding the tide up to the dangerous high marsh, to snack on unsuspecting insects and spiders. Seems crazy, but the risk of getting stranded up there, or eaten by a bird or other predator, is definitely worth it for the potential energetic boost they can get. In this way, mummichog function as an incredibly important link between these two (high marsh and creek) distinct habitats, gathering energy in the form of food produced in the high marsh (insects and spiders) and making it available to the consumers we all love, like striped bass and flounder in the creek. Not bad for such a little guy!

One of the most interesting effects of increased nutrient load on these coastal systems is IMG_3934the sloughing and disintegration of the low marsh area of the creeks, which normally act as a ramp for these mighty minnows to make their daring climb. How does the loss of that ramp affect the mummichog’s ability to bridge the two ecosystems, and what does a change in the strength of that link mean for the creek’s other residents? How does the ecosystem respond to this decoupling of the creek and high marsh? These are the questions I’m hoping to answer this summer. As we head out to West Creek with our trusty seine net to collect fish, shrimp, and other marine critters for our analyses, we come across a dead American eel on the path, stranded as the tide receded and desiccated by the strong summer sun. Clearly, the high marsh bounty is worth risking everything for, and I hope to understand how that link, and its loss, drives the function and long-term stability of these “peaceful” ecosystems.



Fiddlers on the Marsh

The day begins early, tide dependent of course. My team assembles. We are a small group consisting of PhD candidate Michael Roy, Jarrett Byrnes’ undergraduate lab assistant IMG_2978Richard Wong, and I, Byrnes lab undergraduate field tech. We gather our gear; our scientific instruments, our boots and buckets. We set out for a glorious day of experimental set up in the salt marsh. I am so excited to be here as this is my first time working in the field. This is the reason I went to college for Biology, to have a career in which I am spending copious amounts of time in nature.

So far I have gotten to be very close to nature, sometimes waist deep in it when catching the fiddler crabs for our particular experiment. I feel beyond honored to have been selected to be a field tech this summer. Michael reminds me that I earned my place helping him at the field station with my hard work and enthusiasm in my marine ecology this past school year. Michaels’ experiment is on comparing the affects the marsh fiddler crab at various densities have on the marsh sediment in there native region South of Cape Cod verses the Gulf of Maine were they have recently expanded their range to include because of the changing climate. It just so happens to be a question I find myself very interested in as well.

We are headed to the marsh today to catch the crabs that will be occupying the cages we built for them in the marsh. We have taken our initial measurements of the sediment strength, buried a log of peat in mesh to examine root growth, and buried small mesh bags of grass to assess how decomposition may increase as the crabs burrow into the sediment.

I can’t help but think that our cages look beautiful when they are up and running, with their steel flashing affixed around the tops which ensures no crabs crawl out or in. I am really enjoying my job as I am standing in the cool creek on a beautiful sunny summer day, poking crabs out of their holes in the mud. We will leave them over the rest of the summer and measure how they have changed the marsh in their cage after some time has passed. I truly can’t wait to evaluate the results and find out!



Written by Linnea Sturdy 

Eutrophication makes marsh microbes hibernate

A study recently published in Nature Communications from the TIDE Project reveals that eutrophication can cause some marsh microbes to go dormant, affecting the overall health of the ecosystem. Below is a copy of the original press release put out by the National Science Foundation, a major funder of the TIDE Project.

Researcher Patrick Kearns fills tubes of mud to look at microbes' responses to nutrients.

Patrick Kearns, lead author, samples mud microbes. (c) John Angell



Could the future of a salt marsh be hidden in the health of its microbes? Scientists say yes.

Salt marshes play key roles in reducing the effects of urbanization and climate change. Marshes absorb carbon dioxide from the atmosphere, and their microbes break down carbon.

That’s why researchers are working to find out how these vital ecosystems tick.

Jennifer Bowen of Northeastern University and colleagues have studied microbes in the sediments of salt marshes in the National Science Foundation (NSF) Plum Island Ecosystems Long-Term Ecological Research (LTER) site in northeastern Massachusetts.

They’re working to discover how the marsh — and the microbes in it — change over time when outside influences, such as nitrogen, are introduced to the ecosystem.

“A lot of the ecological services salt marshes provide are facilitated by microbes,” Bowen said. “They’re involved in the carbon cycle and the nitrogen cycle, and they remove nutrient pollution through their metabolic processes.”

Dormant microbes

In a new paper published in the journal Nature Communications, Bowen and her Northeastern colleague Patrick Kearns, who is first author of the paper, along with researchers at the Marine Biological Laboratory and Woods Hole Oceanographic Institution, set out to discover what would happen to microbes in salt marshes if specific nutrients were added to the environment — through urbanization and climate change, for example.

Adding nutrients like nitrogen produced no change in the types of bacteria present in the salt marsh — at least, temporarily. But over time, a large number of the microbes became dormant.

“It’s kind of like a bear going into hibernation,” Bowen said. “These dormant bacteria are in a low metabolic state. They just bide their time until environmental conditions return that are suitable for them.”

When the microbes go dormant, they don’t contribute to the critical ecosystem services that make salt marshes important.

Human-salt marsh interactions

“This study shows that human activities are affecting bacteria essential to salt marshes in ways we never suspected,” said Matt Kane, program director in the NSF Division of Environmental Biology, which co-funded the research with NSF’s Division of Ocean Sciences. “Coastal salt marshes provide many benefits — supporting diverse wildlife, helping to reduce pollution, and protecting us from flooding.”

What happens to salt marshes and their bacteria, Kane explained, ripples into human lives.

The study’s results help explain why salt marshes contain so much microbial diversity. One group of microbes is specialized for a specific set of conditions, while another is linked with others. As the environment changes, different bacteria take advantage of the conditions that are most suitable to them.

“These investigators have made an important discovery about the resilience of microbial communities in salt marsh ecosystems,” said David Garrison, program officer in NSF’s Ocean Sciences Division.

A salt marsh, the researchers say, is a constant balancing act.

“If we see an increase in the abundance of bacteria that are able to decompose the marsh, we also see an increase in bacteria that can help fix carbon,” Bowen said. “If a marsh is failing, there is no way to restore the microbes. But what can be created is an environment that will help these microbes thrive.”

To save the marshes, she said, save their microbes.