Andy Bell ’11 (Biology and Environmental Studies). Bowdoin College. SSP Fellowship. John Lichter and Phil Camill, advisors.
Ecological and Economic recovery of the Kennebec and Androscoggin Rivers, Estuary and Nearshore Marine Environment
Benthic Macroinvertebrates in Merrymeeting Bay Andy Bell, Class of 2011
Project Summary:
Merrymeeting Bay is a large freshwater tidal bay that drains over a third of the area of Maine. Historically, the bay was a thriving and productive ecosystem known for supporting abundant populations of migratory waterfowl and anadromous fish. By the middle of the 20th century, three centuries of environmental stress led to the collapse of Merrymeeting Bay and its fish populations (Lichter et al. 2006). Human impacts have drastically altered the ecosystem including a shift from a benthic food web to a planktonic dominated food web. The decline of submerged aquatic vegetation coincided with the switch in the food web. Growth and productivity of submerged aquatic vegetation is conducive to increased richness of invertebrates, which makes the vegetation patches a prime forging ground for fish (Yazzo and Smith, 1998).
Benthic macroinvertebrates are animals without backbones that live at the bottom of aquatic ecosystems. These invertebrates, which include insects, crustaceans and worms, are found living near or in the sediment. By providing a link between vegetation and predators, benthic macroinvertebrates are an important component in the food chain of aquatic ecosystems. In Merrymeeting Bay, benthic invertebrates link submerged aquatic vegetation with numerous species of fish and waterfowl. Understanding the role of benthic macroinvertebrates in the Merrymeeting Bay ecosystem is important in developing and understanding the path for ecological recovery.
For the past two summers, I have looked at role of benthic macroinvertebrates in the food web of the freshwater system. Previous studies had looked at the invertebrates in the water column but found little difference between the areas with vegetation and without vegetation. The macroinvertebrates living in the sediment of the bay were largely ignored in previous surveys. These macroinvertebrates are an important part of the food web because they are included in the diet of many species of fish. In 2009, I was able to sample the benthic macroinvertebrates in the sediment by using an Ekman grab (a handheld dredge) and an aquatic sweep net. On average, I found that there were four times as many macroinvertebrates in the vegetation than the unvegetated areas. This summer, I expanded the extent of the research project by involving several different factors to further explore the relationship between vegetation and benthic macroinvertebrates. We collected samples of sediment from beds of vegetation of different sizes, density and species composition. The results from the project could have important implications for future efforts to replant vegetation in Merrymeeting Bay by determining ideal patch size and density. Understanding the interaction between submerged aquatic vegetation and benthic macroinvertebrates is an absolutely crucial for the long-term health and recovery of the ecosystem becaust invertebrates provide a link between vegetation and the higher trophic levels in the ecosystem.
Faculty Mentor: John Lichter Funded by Sustainability Solutions Partners References
Lichter, John, Heather Caron, Timothy S Pasakarnis, Sarah L Rodgers, Thomas S Squires, Jr., and Charles S Todd. 2006. The ecological collapse and partial recovery of a freshwater tidal system. Northeastern Naturalist. 13 (2): 153-178.
Yazzo, David J., and David E. Smith. 1998. Composition and abundance of resident marsh-surface Nekton: comparison between tidal freshwater and salt marches in Virginia, USA. Hydrobiologia. 362: 9-19.