The Wrack

The Wrack is the Wells Reserve blog, our collective logbook on the web.

Science: Building Upon the Work of Others

Posted by | September 5, 2012

Dr. Jennifer Dijkstra measures a snail with calipers.Jennifer Dijkstra was always going to be a scientist. As a child summering on Grand Manan, she clambered over the island’s rocky shoreline grabbing fistfuls of seaweed and peering into shallow waters to spy on crabs and snails. This summer she’s been doing the same thing, but with three degrees of separation (BS, MS, and PhD), she now calls her objects of interest Ascophyllum, Carcinus, and Littorina.

For many budding biologists, the journey from tide pool playground to salt marsh research transect stops short. For Dr. Dijkstra, research scientist at the Wells Reserve, the dream came true.

Jenn’s route was academically direct while covering half the western hemisphere. She started at the University of New Brunswick, where her passion for biology really took hold. From there, she was off with her husband to the Alfred Wegener Institute for Polar and Marine Research in Germany. After volunteering at the institute for a while, she decided to get her master’s there.

That pursuit required learning German, the language of her courses and exams, and featured a three-month voyage aboard an icebreaker in Antarctica. On the Weddell Sea, she used a remotely operated vehicle to map underwater habitats and examine “how icebergs scour the sea floor and how that affects the community of hydroids, glass sponges, and bryozoans.”

After her three-year stint overseas, Jenn migrated to the University of New Hampshire. It was there, studying the otherworldly filter feeders called sea squirts, that she scaled a new scientific plateau.

In a master’s everything is new. With that I think every student is a little bit nervous about how they’re doing—‘Is it a good project? Am I analyzing this correctly? Do I need to do something else?’ Whereas working on my Ph.D., I really felt like all the ideas were completely mine—‘I thought it up. I’ve done the work. I’ve analyzed the data. I’m publishing papers.’ It was me. I really enjoyed that. That was when I said, ‘Okay, now I’m a scientist. I’m confident that I can come up with my own research program.’

After earning her doctorate in 2007, Jenn spent a year teaching and continuing her studies, but the post-doctoral question “Now where?” was ever on her mind.

Connecting to the Wells Reserve

During her doctoral quest at UNH, Jenn had shared a lab with Megan Tyrrell who, after obtaining her own degree, had worked at the Wells Reserve with support from Laudholm Trust’s George and Eleanor Ford Post-Doctoral Research Fellowship. Later, as Megan was wrapping up her fellowship, Jenn saw an opportunity.

Honestly, I didn’t know much about the reserve. I knew about Michele [Dionne]. Megan had said very good things about Wells and about Michele, so I thought this would be a really great place to work. Michele and I were both interested in ecological theory, so we found some common ground.

Moving from a background in subtidal ecology to the intertidal zone was a huge switch. But that’s what a post-doc should be: Exploring a new environment or a new technique, so you’re always developing and moving forward.

As she began investigating the salt marsh system, Jenn quickly discovered a helpful foundation; her predecessor had done an experiment comparing plots where algae was removed to others where algae was left in place, demonstrating the importance of seaweed to other forms of life on the salt marsh.

Megan’s experiment was elegant because it was so simple. I wanted to build from that. That’s what science is, building on the work of others.

The salt marsh wouldn’t exist without grasses. Spartina traps sediment. But the grass does not support a diverse biological community. The secondary habitat formed by algae surpasses the primary habitat in terms of species richness and interaction.

Much of the seaweed in the salt marsh comes from somewhere else. Storms and ice rafts break off seaweed growing on rocky shorelines and some of it eventually drifts onto salt marshes.

Once there, the algae is exposed to a new environmental regime—fresh water runoff alternating with salt water inundation—that researchers believe causes a dramatic change in form. Any holdfast threads remaining from the algae’s rock-gripping days disappear, as do the air bladders that helped fronds float on an incoming tide. The algae loses its sense of direction, too, so rather than simply growing upward it extends fronds in any direction.

This free-living form of the algae, called an ecad, may take several years to reach the most advanced stages of change. Over this time, the ecad gradually loses much of the resemblance to its original form.

Jenn wondered how the roles of two dominant ecads in the salt marsh, Ascophyllum and Fucus, differ from each other and from their original forms in the rocky intertidal zone. She designed a series of experiments aimed at uncovering how the animals that inhabit the salt marsh use each distinctive seaweed habitat for food, shelter from predators, and protection from the sun.

Those “animals that inhabit the salt marsh” reconnect Jenn to the crabs and snails that fascinated the nascent scientist on Grand Manan. This summer, she and her assistants have been counting snails, measuring their growth, and testing their vulnerability to green crab predation, all against a backdrop of four unique forms of algae. While today’s research has components of curiosity and wonder, it also has real-world implications.

Seaweed is a harvestable crop used for packing and fertilizer, as well as animal feed and cosmetics. Maine’s 2010 rockweed harvest was 12.7 million pounds, with some harvesters using machines capable of hauling in 100,000 pounds per day. The capacity for harvest has increased dramatically without a full understanding of potential ecological effects.

While proper harvesting leaves holdfasts in place so algae can regrow, it can take up to a decade for a cut stand to recover. And with the salt marsh ecosystem largely dependent upon immigration of algae from rocky intertidal areas, the removal of a significant amount of seaweed from the coastal system could be detrimental to organisms at the salt marsh surface that gain protection or sustenance from the algae.

Megan’s and my studies have shown that if you remove seaweed from the salt marsh, the ecosystem is significantly altered. As we follow up on these findings, the reserve will be laying a scientific foundation for the management of seaweed resources.

From Watermark 29(1), Summer 2012

← View all Blog Posts