Undergraduate Research

Is coastline seaweed in danger?

Each summer, the University of Rhode Island Graduate School of Oceanography (GSO) hosts undergraduate students from all over the country to participate in oceanographic research. These Summer Undergraduate Research Fellows (SURFOs) have not only been working with GSO scientists, but they also have spent part of their time learning how to communicate this science to the public.

Lizzy Soranno is a fifth-year student at Northeastern University in Boston, MA. She is majoring in marine biology and minoring in environmental science with a concentration in conservation biology. Lizzy spent the past summer working with Dr. Cathy Johnson to develop a study that assessed the diversity and abundance of intertidal seaweed along the rocky coastlines of Acadia National Park.

A Love (or Hate) of Seaweed

Seaweed grows all along the shorelines of the world in both freshwater and saltwater. To many of us, the most familiar forms are found when we take a dip in a lake and jump when it brushes up against our legs unexpectedly!

One type of seaweed is called macroalgae, which is visible to the human eye. While you may not enjoy seeing it grow in abundance while swimming, seaweed is vital to marine organisms along oceanic coastlines. In particular, seaweed that grows within the rocky intertidal zones of the United States supports entire ecosystems – even ours!

Surviving the Rocky Intertidal Zone

Seaweed and marine organisms typically found within the rocky intertidal zone of New England. Image source

The intertidal zone, which is where the land and the ocean meet, is subjected to tides every single day. The most common tidal cycle on the east coast is a semidiurnal tide, which means two high tides and two low tides every 24 hours. Whatever lives on that part of the coast must deal with the area being covered by water for half a day.

Along the rocky coastlines of New England, it is an important area for researchers who try to understand how organisms tolerate a half-submerged lifestyle. 

Seaweed Community Health 

In the first scientific studies of the intertidal zone, it became very clear that marine organisms, such as barnacles, snails, mussels, and crabs, relied heavily on seaweed to protect them from drying out in the sun during low tides. These studies led to more in-depth surveys of the seaweed species found in the intertidal zones. 

A very detailed study by Duncan Johnson and Alexander Skutch in 1928 on Mt. Desert Island in Acadia National Park in Maine created the first baseline of identifiable algal species in this national park located in coastal Maine. Unfortunately, only a few studies have returned to Johnson & Skutch’s site to look at the seaweed communities that they had originally published. Even fewer studies have since been conducted in Acadia to determine seaweed species diversity and abundance in the park. 

This gap in the knowledge of seaweed community health in Acadia led to the creation of my study with Dr. Cathy Johnson. I conducted this project while working at the Graduate School of Oceanography at the University of Rhode Island. We found a few historical studies, similar to Johnson and Skutch (1928), that assessed the abundance and diversity of seaweed in a few key sites in Acadia. Seeing as these sites had not been revisited in more than ten years, I decided to return to each site and mimic each study’s methodology so that I could see what new or different species of seaweed had appeared since then.

Fieldwork in Acadia

Early morning fieldwork at Johnson and Skutch’s (1928) site, Otter Point. (Image source: Lizzy Soranno)

I ventured onto Acadia’s rocky coastline to reach seaweed beds in the intertidal zone. Once there, I laid a transect tape, which is a very long measuring tape covered in markings, from the splash zone (rocks only splashed by the water) to the low zone (rocks almost always covered by water). I then determined which species of algae were most abundant in each of the tidal zones.

After completing the transects, I performed an algal survey to assess species diversity by taking pictures of every species of seaweed I could find within a certain time and distance. At the end of the day, I sorted through the photos and determined the species name of each specimen of seaweed.

The Future of Intertidal Ecosystems

I found noticeable shifts in seaweed community composition. Not only was species diversity much lower in the study sites, but new species were replacing the original ones that were first documented in the earliest historical studies. While these results are preliminary, they can tell us about the future of the health of the intertidal zone. 

Warming ocean temperature and a rising sea level continue to threaten this fragile ecosystem. We hope to use the results of this study to influence management decisions regarding the recreational, commercial, and ecological uses of the rocky intertidal zone of Acadia National Park. 


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