Merrymeeting Bay and the lower Kennebec estuary in Midcoast Maine suffered catastrophic environmental collapse with human presence. This freshwater tidal ecosystem, a confluence of 6 rivers (Kennebec, Androscoggin, Abagadasset, Eastern, Cathance, and Muddy), drains roughly 1/3 of the land area of the state of Maine. Primarily in the second half of the 20th century, human activities, from overfishing and land clearance to massive input of industrial pollutants, led to a collapse in this ecosystem in which historically plentiful populations of ducks and anadromous fish thrived. After the Clean Water Act legislation of the 1970’s, marked improvements have been noted in the water quality. However, biotic components respond slowly to such improvements and further steps must be taken to restore submerged aquatic vegetation, fish, and macroinvertebrates. Each of these biotic components is part of a complex web of interactions that ranges from the headwaters of each river to the ocean. Similarly, humans are an intricate part of this web of dependencies as the anadromous fish that spawn in this enormous freshwater ecosystem may form an important food base for cod and other economically valuable offshore groundfish species.
This summer was the beginning of a long-term study of the watershed and its current health. Specifically, our team of 6 students began to map submerged aquatic vegetation (SAV) such as freshwater tape grass (Vallisneria americana) and saltwater eelgrass (Zostera marina). Our studies also included plot comparisons of benthic macroinvertebrate populations and assessments of juvenile andromous fish runs (Alewife, American Shad, and Blueback Herring) using 5-hoop fyke nets and beach seine nets both inside and outside of SAV beds.
While our primary work was done as a team, my individual interests included freshwater mussels (Unionoidea). These complex, yet imperiled, freshwater macroinvertebrates are sessile suspension feeders, filtering detritus and other floating particulate matter from the water column for food. They are relatively sedentary, but they may form large beds that are capable of greatly influencing the water clarity and chemistry. Their life cycle also ties them closely to the anadromous fish populations by including a parasitic life stage where they attach quite specifically to the gills of fish and redistribute themselves, later dropping off as developing juvenile mussels. Curiously, Merrymeeting Bay supports a relatively small population of freshwater mussels. While our attempts to explore this further during the summer yielded no results, their presence raises many questions concerning their connection to the anadromous fish populations in the Bay, water quality, and potential habitat as well as their historic distribution within the watershed.
Ultimately, this summer showed that there are certainly advancements to be made in both the status and the assessment methods in Merrymeeting Bay and the lower Kennebec estuary. It is important to note, however, that there is growing recognition of the need for not only continued surveys of the biotic and abiotic components of the Bay, but also the increased public awareness and participation of local communities.
Faculty Mentor: Professor John Lichter
Funded by the Sustainable Solutions Partners