Damariscotta River: Research Through Time

Coastal Rivers Conservation Trust works to preserve and monitor land around the Damariscotta River, including Great Salt Bay Farm, and also the river itself. The land trust leads a citizen science program focused on horseshoe crabs, and the Darling Marine Center has contributed to some of this work. Maine is at the crabs’ northern range limit and the Damariscotta River estuary is one of the northernmost places to find them in the state.

Coastal Rivers Conservation Trust and the Darling Marine Center also work together to monitor water quality in Great Salt Bay and other Maine coastal waters. They are part of the  Maine Coastal Observing Alliance (MCOA) , a group that coordinates water quality monitoring on the Maine coast from Casco Bay to Belfast. Kathleen Thornton, a Research Associate at the Darling Marine Center, provides technical support for the program. Kathleen has worked at the DMC for more than 25 years and advises the volunteer monitoring program, along with Sarah Gladu of CRCT. Collaborations among CRCT and enhance the knowledge and capacity for community-led stewardship of the Damariscotta and other coastal waters in Maine, supporting a healthy river, both now and in the future. 

Between the Damariscotta-Newcastle Bridge and Great Salt Bay lies a narrow stretch of the Damariscotta River less than a mile long. Within this are located the remains of two very large prehistoric shell heaps, or middens. These were formed when early Indigenous Peoples harvested shellfish like oysters or clams and left the shells in large piles. These piles can be found across New England and the United States.

Two notable middens are located in this stretch of the Damariscotta River: the Glidden and Whaleback Middens. The Whaleback Midden was mined for chicken feed in the 1800s and little is left today, although the remains are preserved as a State Historic Site. The Glidden Midden is located across the river from the Whaleback midden and is the largest midden on the Atlantic coast north of Georgia. Both middens are protected and can be visited  via trails  maintained by Coastal Rivers Conservation Trust. Coastal Rivers and the  Maine Midden Minders , a citizen-science group, work together to monitor the Glidden and Whaleback middens, as well as other smaller middens in the Damariscotta River region, all of which are threatened by sea level rise and erosion due to climate change.

Total number of documents involving the middens: 11

 Shell Midden research documents can be found here .

Several people have devoted many years to studying the middens and ancient sea level rise in coastal Maine. These include Dr. Alice Kelley, a Research Associate Professor at UMaine, and collaborators, including Dr. Daniel Belknap and Dr. David Sanger. Dr. Kelley studies how past humans dealt with changing environments in Maine, Peru, and Europe. She organized efforts to identify and  document Maine’s ancient shell middens  – not just the large ones on the Damariscotta River – that are threatened by rising sea levels. The middens provide a window into past environments and human activities, and are valuable tools for researchers. Dr. Belknap and Dr. Sanger studied the formation of the Whaleback and Glidden middens and described how ancient sea level rise led to their creation and eventual abandonment by ancient Indigenous Peoples. 

Early European visitors were intrigued by the middens, in part because they were primarily constructed from oyster shells but there were almost no wild oysters in the Damariscotta River. Considerable research was done to determine the age of the middens and whether historical artifacts were buried within them. This research helped increase understanding of prehistoric cultures after the end of the last ice age. Another research area that arose from the middens was an opportunity to describe how the oysters that formed the middens grew in the river and then vanished. This story is closely linked to environmental change and sea level rise after the last ice age.

Studying the middens has also informed understanding of long-term environmental change and sea level rise in coastal Maine after the last ice age. When the last ice age ended, over 10,500 years ago, ancient sea levels were almost 200 feet lower than they are today and the Damariscotta River was a completely freshwater river. The sea level did not remain low, however, and gradually started rising. As this happened, salt water started intruding into the Damariscotta River, turning it into an estuary. Oysters prefer brackish, or moderately salty water, and the newly salty Damariscotta River was ideal habitat. Initially, only the lowermost parts of the river were salty, but as the sea level continued to rise, the middle and upper stretches of the river became salty as well. Oysters followed the salty water up the river and eventually established large populations in the upper river and Great Salt Bay at least 3,000 years ago. Sea levels continued to rise, making the river saltier and allowing oyster predators to live in the river. Humans also started harvesting the oysters and created the middens. The combination of predators and human harvesting caused the oyster populations to decline and the middens were abandoned about 1,000 years ago.

The Head Segment in the upper Damariscotta River Estuary is the epicenter of Maine’s oyster aquaculture industry. Most of the farms, some of them among the oldest in the state, are located here. 

This area has also been the site of aquaculture research related to blue mussels (Mytilus edulis) and American oysters (Crassostrea virginica). Research has played an important part in supporting the growth of the industry. Many early oyster researchers worked at the Darling Marine Center; several early oyster farmers conducted graduate research on aquaculture-related topics at the DMC. Collaboration among farmers and researchers at the DMC, Bigelow Lab, and UMaine remains strong to this day. 

Total number of documents involving the Head Segment: 55

 Head Segment research documents can be found here .

Aquaculture leases are common in the Head Segment of the Damariscotta River Estuary. This map shows the number of standard aquaculture leases (yellow) and Limited Purpose Aquaculture Licenses, or LPAs (brown circles) in the Head Segment. LPAs allow farmers to use 400 square feet of water for one year. They are renewable and are designed to help farmers experiment with gear, species, and farm locations. Standard leases are intended for established farms. They are granted for up to 20 years and are capped at 100 acres - substantially larger than the size of most oyster farms, which are often less than 10 acres.

The aquaculture industry in the Head Segment of the Damariscotta River Estuary contributes to scientific, educational, and employment opportunities for many community members, including. Aquaculture science in the Damariscotta is about more than shellfish biology. It also includes a focus on the interactions among organisms and their environment; predator-prey interactions related to farmed and wild shellfish populations; integration of environmental and economic information to inform siting of new farms; and social science research on the interactions among aquaculture and other human uses in coastal ecosystems, and their perceptions and beliefs about those interactions. 

(Note: DMR aquaculture data downloaded on July 16, 2021.  For most recent data, visit the DMR Open Data Portal )

One person associated with aquaculture in the Damariscotta River is Chris Davis. Chris is a founding member of Pemaquid Oyster Company and is the Executive Director of  Maine Aquaculture Innovation Center (MAIC) . MAIC supports research and development projects for sustainable aquaculture throughout Maine. MAIC also runs  business incubators  at the Darling Marine Center and the Center for Cooperative Aquaculture Research in coordination with UMaine; these spaces provide space and business development support for new aquaculture companies. Chris teaches aquaculture training classes at the DMC and statewide.

Chris first came to the DMC to study shellfish in the mid-1980s. His interest in the estuary was sparked through a course with Prof. Bernie McAlice, and ultimately led to Chris’ UMaine PhD project, which he defended in 2000. Chris investigated oyster growth rates and found that oysters with faster growth rates were better able to avoid dying from Juvenile Oyster Disease (now called Roseovarius Oyster Disease), a disease that killed many juvenile oysters in the Damariscotta River in the 1990s. Chris’ current research focuses on sea scallops (Placopecten magellanicus), and includes a collaborative study with scientific and industry partners at the DMC’s experimental aquaculture farm in Lowes Cove and at other sites statewide. 

The Darling Marine Center is located on Wentworth and McGuire Points, on the east side of the Damariscotta River in the village of Walpole, Maine. It is home to more than 40 full-time faculty, staff, and graduate student researchers from the University of Maine. Visiting scientists and students, from UMaine and other institutions, use the DMC as a base for research and education throughout the year. While applied research has been part of DMC researchers’ activities from its founding in 1965, researchers also engage in a wide array of fundamental marine and environmental research topics. These include deep sea and nearshore marine biodiversity, studies of the biology, chemistry, and physics of ocean environments from the coast to the deep sea, and integrated studies of human-environment interactions in coastal areas worldwide. The vast majority of research at the DMC and about the Damariscotta River is related to environmental science and few studies have focused on social science topics. This has changed recently with studies focused on climate change and human-environment interactions (e.g. Pellowe and Leslie, 2019), but additional social science is needed on the river to understand changing human uses of the river.  More information on DMC facilities and researchers is available here . (Note: lab-based studies and undergraduate projects are not fully represented)

Total number of documents involving the Darling Marine Center: 99

 Darling Marine Center research documents can be found here .           

Here we highlight the work of Dr. Meg Estapa. Meg is an Assistant Professor of Oceanography at UMaine and is based at the DMC. Meg recieved her Ph.D. from UMaine in 2011 and started as an assistant professor at UMaine in 2020. She studies the movement of particles in the ocean – for example the sinking of small, carbon-rich particles to the bottom of the ocean. Learning how organic matter behaves in the deep ocean impacts our understanding of how the oceans will respond to climate change, which impacts not only the open ocean where Meg does her work, but also coastal ecosystems like those in the Damariscotta River. Meg recently participated in a scientific research cruise in the North Atlantic Ocean to study these particles. While she does not currently study the area directly adjacent to the DMC, she uses the DMC as her base to conduct lab experiments and test field equipment on the river. For example, Meg tested a sediment trap – a device that collects falling particles in the ocean – in the Damariscotta River to prepare for her most recent research cruise. 

Meg’s research highlights the value of the DMC to connect people to the ocean, both locally and globally. The DMC is a popular comparison site for studies that take place elsewhere in the river. Oceanographers also work out of Bigelow Laboratory for Ocean Sciences, which is located in Boothbay at the mouth of the Damariscotta River. These two marine stations play an important role in research and education by enabling scientists and their students to access the diverse ecosystems of the Maine coast and nearshore oceans to document how it is changing both locally and globally, particularly in the face of climate change. 

(Image: DMC staff deploy and test a sediment trap from the DMC dock to prepare for Meg's research cruise)

Adjacent to the Darling Marine Center is a small intertidal mudflat called Lowes Cove, which is incredibly well-studied. The DMC also has an experimental aquaculture lease from the Maine Department of Marine Resources in the cove.  

Total documents involving Lowes Cove: 58

 Lowes Cove research documents can be found here .

Research in Lowes Cove includes topics as diverse as mudflat geology, sediment dynamics, and the biology of microbes, algae, and invertebrates that live in the mud. The cove has changed in recent years – a mussel bar previously in the lower cove is now gone, and many other changes have resulted from its loss. Lowes Cove is an important research site and its proximity to the DMC makes it an accessible place for research and teaching. Like many other mudflats in the River, the cove is an important place for commercial harvesting: worm harvesters are active on the flats year-round and historically, the softshell clam harvest has been an important activity in the area. 

One person who has studied Lowes Cove extensively is Dr. Larry Mayer. He has had a 40+ year research and teaching career at the DMC and currently is an Emeritus Professor of Oceanography at UMaine. He studies the amount of food present in the mud for animals to eat, the structure, formation, and maintenance of the mudflat, and how organic material is used or preserved in sediments. He has supervised many graduate and undergraduate students who studied the mudflat and animals that live within it. Of the 99 DMC studies, 58 involved Lowes Cove and Larry contributed to at least 17 of them. Larry has also taught many classes at the DMC, both to UMaine students and local community members. He has taken lessons learned in Lowes Cove and applied them throughout the Damariscotta River and around the world.  

The middle section of the Damariscotta River, where the DMC is located, is heavily studied. Studies in this area have often focused on plankton movement and species composition, as well as environmental conditions. Studies in this section of the river have often included comparisons among multiple locations along the length of the estuary.

In addition to studying plankton, researchers have studied nutrients (primarily nitrogen and phosphorus) in this and other locations in the river to evaluate what conditions best support plankton growth. Plankton fuel estuarine food webs, including the growth of farmed shellfish, and so understanding these dynamics is important. 

Total number of documents involving the Basin Segment: 26

 Basin Segment research documents can be found here .

One person who extensively studied plankton in the Damariscotta River was Bernie McAlice. He conducted several river-wide studies in the 1970s and 1990s that described patterns of the ecology, geology, and physics of the estuary. These studies provide baseline information for nearly all other studies that have been conducted since. Dr. McAlice started a long-term water temperature and plankton monitoring program from the DMC dock that continues today. This long-term monitoring program has helped researchers and their community and industry partners understand how the estuarine ecosystems have changed over the last 50 years. McAlice passed away in 2013 but his legacy of research still supports scientists, students, and the local community to this day. 

The ocean segment is the part of the Damariscotta River Estuary between Fort Island Narrows and the mouth of the estuary. This area hasn’t been studied as extensively as some of the other areas, but it still has been an important research site. The water in the lower estuary is nearly as salty as the open Gulf of Maine and the species composition resembles nearby open ocean habitats. Research in the lower estuary is diverse and includes a focus on commercially important species like scallops and lobster, as well as farmed shellfish species and the plankton they consume. Many researchers have studied the behavior of specific animals in the lower river, like crabs eating mussels or sea urchin reproduction, and compared their results with information from locations at the DMC or the upper estuary. 

Total number of documents involving the Ocean Segment: 16

 Ocean Segment research documents can be accessed here .

One person with a long history of research in the lower river is Dr. Bob Steneck. Bob is a Professor in UMaine’s School of Marine Sciences and has been based at the Darling Marine Center since 1982. and also got his Masters degree at UMaine in 1978. Bob’s research includes studies of both temperate and tropical reef environments around the world. He has been studying the bottom-dwelling (aka benthic) species and benthic habitats of the Gulf of Maine for more than 40 years. Thanks to his close and long-term observations, Bob and his students have documented how the biology of the American lobster has responded to both changing ocean conditions and human activities.

Much of Bob’s research has been conducted in close collaboration with fishermen. He has investigated how lobster fit into the larger Gulf of Maine ecosystem and ways that overfishing and climate change impact them and the people who rely on these indefatigable invertebrates. He also studied the ecology of the green sea urchin, which was a very valuable commercial fishery in the 1980s and 1990s, but then was overfished and has largely disappeared from Maine. These population-level changes in urchins caused cascading ecosystem changes because urchins eat large amounts of algae and influence the types of habitats that are available to other species in the Gulf of Maine. 

Pemaquid Point is located near the mouth of the Damariscotta River. The rocky intertidal zone and the adjacent cove at the point have been popular ecological study sites for decades. Researchers at Pemaquid Point have studied how interactions among intertidal organisms – including alage, barnacles, mussels, and snails – shape the way that the biological community looks and functions.

The exposed, rocky shore at Pemaquid Point makes it very different from the habitats found in the inner Damariscotta River and it is sometimes used as a comparison site for that reason. Pemaquid Point has also been used as an important comparative site for studies that encompass larger geographic regions, from southern New England to the Canadian Maritime region. The research captured here is an incomplete list, but is meant to highlight the diversity and significance of studies at Pemaquid Point. 

Total number of documents involving Pemaquid Point: 24

 Pemaquid Point research documents can be accessed here .

Jane Lubchenco and Bruce Menge are two of the researchers who have used Pemaquid Point to conduct comparative ecological studies. Lubchenco is Deputy Director for Climate and Environment at the White House Office of Science and Technology Policy and a Distinguished Professor at Oregon State University. Menge is the Wayne and Gladys Valley Professor of Marine Biology and a Distinguished Professor of Integrative Biology, also at Oregon State University.