An ecosystem can be defined as
a community of organisms interacting with their inanimate environment;
or a system resulting from the integration of all living and non-living factors in the environment (Van Dyne 1969).
This study has identified the following ecosystems for Merrymeeting Bay:
Ponds
Marshes, Wet Meadows, Swamps, Bogs and Heaths
Recently Harvested Forests/ Disturbed Forests
Reverting Fields
Suburban Areas
Areas of Man-Induced Stress (gravel pits, dumps)
The most important ecosystems in the Merrymeeting Bay area include the Bay itself and its tributaries, wetlands (tidal flats, marshes, bogs, wet meadows, and swamps) and forests. Farmland, reverting fields, suburban areas, and areas of man-induced stress have important effects on the Bay but are not considered of importance in the maintenance of the Bay's vital natural functions.
The following discussion will describe in detail the significance of each of the above ecosystems.
Several ecological studies have been conducted in the Merrymeeting Bay region. H. E. Spencer (1957, 1959, 1960, 1963, 1966, 1967) did an extensive ecological investigation of the Bay for the Maine Department of Inland Fisheries and Game. Other reports have documented the value of Merrymeeting Bay as a wildlife habitat (Anderson and Powell 1961; DeGarmo 1962), and the fishery potential of the watershed (DeRoche 1967; Foye, et al. 1969; Dow and Flagg, 1970, Flagg 1972).
Overall the Bay is an excellent habitat for waterfowl and is well populated during spring and fall migration with black duck, green winged teal, blue-winged teal, mallards, goldeneye, Canada geese, and other species. Merrymeeting Bay has the state's largest spring concentration of geese.
The Bay and its tributaries also provide habitat for a substantial smelt, alewife, and striped bass fishery which provide good sport and commercial fishing. The Kennebec River drainage contributes 58% of the total winter anadromous smelt fishery in Maine (Flagg 1972; see also Chapter 5.0). Also, the lower Kennebec-Sheepscot River complex supports the only known populations of shortnose sturgeon in Maine. The shortnose sturgeon is a rare and endangered species (LaBastille 1973).
In addition, the Kennebec, the dominant system in the Merrymeeting area, once supported very large runs of anadromous fish (Foye et al. 1969). Historically, development of dams and pollution of the river have restricted fish movements and destroyed most spawning grounds for salmon. Consequently, natural anadromous fish runs have been greatly reduced and much of the Kennebec's anadromous fishery no longer exists, although remnant runs of salmon, alewives, shad, and striped bass still take place up the Kennebec as far as Augusta.
The extensive spawning and nursery areas which exist in Merrymeeting Bay are of limited value to anadromous fishery resources because of heavy industrial pollution from up-river sources. There is great potential for an expanded fishery for migrating anadromous fish, however. Good fishery management in the Kennebec would be most beneficial for the anadromous fishery of Merrymeeting Bay and the lower Kennebec. Excellent potential does exist in the upper part of the drainage. The existing potential for Atlantic Salmon has been estimated at 296 to 2,584 adult fish annually with a potential salmon nursery area totaling 13,722,550 square yards (Foye et al. 1969). Dow and Flagg (1970) estimate that fish passage in the main river and all tributaries below Wyman Dam in Bingham could produce 16 million pounds per year of alewives. Potential srnelt fishery for the Kennebec below Waterville would be about 500,000 to 1,000,000 pounds per year if the Augusta dam were removed (Flagg, personal communication).
Expansion of the Kennebec anadromous fishery is dependent on a much hiqher water quality in the river. An estimated 500,000-pound commercial fishery for shad is possible in the Merrymeeting Bay area alone if water quality can be upgraded to the pre-World War I level (Philip Goggins, Department of Marine Resources, written communication, June 1975). To restore the Kennebec drainage to its full potential for anadromous fish would also require an extensive and extremely costly fishway construction program according to Fred Hurley (Department of Inland Eisheries and Game, personal communication, June 1975).
In consideration of extending the anadromous fishery in the Kennebec drainage, European carp are an important factor. Carp in Maine are currently restricted to the lower Kennebec area. The distribution of this hearty nuisance species has been limited thus far by the absence of fishways in the Kennebec drainage.
One scheme which would have allowed anadromous fish access to the upper reaches of the Kennebec was suggested by Flagg (personal communication 1973). He had proposed that the Augusta dam be removed to allow fish free access upstream to Waterville. This would have provided maximum development of the smelt fishery in the 20-mile stretch from Augusta to Waterville. Other anadromous fish would have benefited also. A spawning population of striped bass could have been reestablished in the lower Kennebec River and extension of spawning areas could have been realized for shad, smelt, and sturgeon. Salmon angling areas would have become established and, with a man-operated fishway at Waterville, alewives and shad could have been selectively allowed upstream further. This was felt feasible as alewives and shad usually have a four to six week run. As to the carp, pond outlet streams that enter the stretch between Augusta and Waterville are obstructed by dams so the problem of carp spreading to new areas would have been minimized.
Unfortunately, the recent reconstruction of the Augusta dam has precluded this option for the immediate future. The potential for restoring the Kennebec to its original status as one of the most productive fish rivers of the East remains, however, for future times when the dams have outlived their utility and extensive upgrading of water quality is realized. Back to Ecosystems
Of the total of 9,600 acres found in the Bay itself, 4,300 acres lie in the intertidal zone according to Spencer (1966). Of these tidal flats, 3,300 acres or 78% are covered with aquatic vegetation. These are called littoral mud flats. The remainder is described as bare silt flats or barren sands.
Littoral mudflats are typically black, mucky sediments over silty, sandy, or clayey soil material (U.S.D.A. Soil Conservation Service 1970). These soils were formed mainly by sedimentation of silt and sludge from upstream. They support a very dense vegetation complex and are extremely productive areas. This is evident in the diversity and density of the vegetation. It is probably that this high productivity and diversity is caused in part by the tidal draining of the Bay which allows aerobic decomposition of the vegetable matter. Nutrient accumulation from Kennebec and Androscoggin pollution sources also helps explain the rich nature of Merrymeeting Bay sediments.
Littoral vegetation of the Bay is characterized by a two-story development. Generally wild rice (Zizania aquatica), three-square bullrush (Scripus americanus), and soft stem bullrush (S. validus) form a canopy over submerged bushy pond weed (Najas flexilis), muskgrass Chara,spp.), bladderwort (Utricularis spp.), and pondweed (Potamogeton spp.). Sweetflag (Acorus calamus) and river bullrush (Scirpus fluvlatii occasionally form pure, single species stands (Spencer 1959).
Distinct aquatic vegetation associations were identified by Spencer (1959) for each of several sub-areas. Associations are analyzed according to species and their densities. The association types are basically different concentrations of dominant species; wild rice, three-square bullrush, softstem bullrush, submerged aquatics, and yellow waterlily. Each association type is represented by different percentage compositions of the many species at different localities (sub-areas). Associations and their relative compositions are listed in the Appendix. Salinity was found not to be a limiting factor of the vegetation of Merrymeeting Bay above the Chops (Spencer 1960). Salt content ranged from 2.0 to 3.5 ppth (10% that of seawater). Back to Ecosystems
Marshes and wet meadows are wetlands in which the dominant vegetation is emergent non-woody plants. Marshes are a successional stage in the chronological transition from lakes and rivers to forests; these transitions are called ecotones.
Because water provides them a fairly stable environment without eliminating light, marshes are very productive. The productivity of marshes benefits adjacent water bodies especially. The marshes of Merrymeeting Bay are subject to tidal fluctuation and are thus highly productive. Normally, anaerobic sediments limit the availability of nutrients and, hence, productivity; but here, sediments are aerated during low tide increasing nutrient availability. There are few other important stresses acting upon them.
The freshwater marshes are most significant to this study because of their cover value for waterfowl nesting and rearing. Most of the important marsh acreage is located in the Muddy and Cathance Rivers. The major limiting factors in marshes are moisture and substrate. The wetter areas generally support sedges (Carex spp.), burreed (Sparganium sp.), manna grass (Glyceria sp.), and some cattail (Typha latifolia) (DeGarmo 1962). In the drier areas, many grasses, especially Bluejoint (Calamagrostis canadensis) with associated Spiraea and blackberry (Rubus spp.) are characteristic.
Swamps are wetlands dominated by woody vegetation and generally represent the last stage in the succession from lake to forest. Three types of swamp are found in the Merrymeeting Bay area...coniferous, deciduous, and mixed. Alder swamps (mixed) occur only along the rivers; they are prevented from succeeding to forests by high water each spring.
Transition zones between marsh and upland ecosystems are common. These generally support dense arboreal growths of alder (Alnus rugosa), willow (Salix spp.), red maple (Acer rubrum), or ash (Fraxinus). There are some swampy stands of spruce, fir, and tamarack present in the Merrymeeting Bay area.
As already mentioned, a great number of different waterfowl species inhabit the Bay at different times of the year. Quantities of excellent forage are available for migrating waterfowl in both sprinq and fall.
In addition to forage, the surrounding wetlands provide good breeding cover. Several species (black ducks, ring-necked ducks, blue- and green-winged teal, mergansers) nest on dry elevated areas either in the marsh or adjacent upland, usually within 75 yards of the water (Spencer 1963). In addition, other water bird species are known to nest in these areas, for example, common snipe, green and great blue heron, American bittern, pied-billed grebe, greater and lesser yellow legs, herring gull, and great black-backed gull (DeGarmo 1962). A list of most of the birds observed in the area and their status is included in the Appendix.
Recently, the Inland Fisheries and Game Department has conducted a survey of inland wetlands in Maine and evaluated them as waterfowl habitat. Table 3-5 details the wetlands ranked as high to moderate according to this system in Merrymeeting Bay. Map No. 7 shows the locations of these and the areas of potential value (such areas lack standing water presently).
In addition to providing habitat for waterfowl, the variety of vegetative associations in marshes and swamps also provide excellent habitat for beaver, otter, muskrat, and other animal species.
Aside from their wildlife values, these wetlands perform a variety of other functions which help maintain the Bay. These include:
1. Provision of an absorptive capacity for storm water runoff which minimizes erosion and flood water damage. One acre of marsh is capable of absorbing 300,000 gallons of excess water.
2. Filtering and settling out of silt and organic debris from storm waters, thus helping to prevent the rapid siltation of the Bay.
3. The chemical and biological oxidation of organics and pollutants.
4. Provision of recreational and educational opportunities.
Some interesting attempts have been made to attach monetary values to these functions. Three researchers at the University of Georgia, Gosselink, Pope, and Odum (no date), value tidal marshes at $4,000 per acre. Another researcher at Georgia State University, Charles Wharton (1970) calculated that a river swamp is worth: $1,750/acre/year for education
(1,000/acre/year for silt deposition on agricultural lands, 450/acre/year for water quality and erosion control, 250/acre/year for hardwood production, 100/acre/year for water supply)
giving a total of $3,550/acre/year. This estimate does not include values attributable to wetlands for wildlife habitat (hunting, wildlife observation, etc.). Although these figures were derived in areas outside of Maine, they illustrate generally how valuable these wetlands are and why it is so important to protect them. Back to Ecosystems
Forested land in Merrymeeting Bay is divided into deciduous, coniferous, and mixed forest types, and further into those which have been recently harvested.
Recently harvested forests are defined as those in which the main crown canopy is less than half closed or in which the main crown canopy is less than 15 feet above the ground. Many of these forests, those which have not been severely damaged, are quite productive. Their open canopy makes them somewhat inefficient but the vigor of young growth and the development of undergrowth partially compensates for it. Disturbed forests often resemble early successional stages and, like these are not very fragile.
Deciduous forests are those in which hardwoods comprise over two thirds of the main crown canopy. An exception may be tamarack, a deciduous conifer. The height and stratification of forests make them very efficient users of their environment and deciduous forests are usually even more productive (net primary productivity) than coniferous forests (Ovington 1965). This productivity does not apply to commercial exploitation. Beech and aspen do provide useable wood but they are marginal species (economically) compared to most conifers. White Birch is a valuable resource which in some areas of the state is being overcut due to its desirability (Fred Holt, sureau of Forestry, written communication, June 1975).
Because they are a climax or subclimax ecosystem, forests are more complex than other ecosystems. This complexity provides some stability but because the ecosystem is so highly evolved, it takes much longer to recover from a serious disturbance.
Coniferous forests are those in which softwoods or evergreens comprise over two-thirds of the main crown canopy. These forests are presently more valuable than deciduous forests from a commercial standpoint because they arein greater economic demand. However, there is a growing demand for hardwood for veneer, boat stock, lobster trap stock, etc. (see Chapter 4, section 4.4.2, for a discussion of their economic significance in Merrymeeting Bay). The density of most coniferous canopies limits the growth of herbs and shrubs and the relative unpalatability of conifers limits animal production. Like deciduous forests, coniferous forests are slow to recover from serious disturbance due to their highly complex nature.
Mixed forests are those in which neither conifers or deciduous trees comprise more than two-thirds of the main crown canopy. It is difficult to generalize about the productivity of mixed forests as compared to other forest ecosystems. In some cases, the greater diversity of mixed forests might lead to increased efficiency of site utilization. The diversity of mixed forests make them less susceptible to serious damage by insects or diseases.
Forested areas are most significant in this study for their ability to slow surface water runoff and hence reduce erosion. One study conducted in the Potomac River Basin (Wark and Keller 1963) showed that as forest cover declined from ~30 percent to 20 percent, sediment yield increased from 50 to 400 tons per square mile per year, an eightfold increase. Maintaining forest buffer strips adjacent to bodies of water or on steep slopes is thus critical for the protection of the Bay's environs. This will be particularly important as development increases (see Chapter 7.0, section 7.1, for a discussion of shoreland zoning as a means of accomplishing this).
Furthermore, proper forest management becomes important, not only for the overall stability of the forest systems, but also for its relationship to sediment control. Significantly, in the last ten years (1962-1972) all but a few areas in Merrymeeting Bay have been commercially cut (from aerial photo interpretation). Many logging operations in the bay area are small scale and are without regard to long term forest management practices. Erosion and damage to the future productivity of the forest are the results. In the Lincoln, Sagadahoc, and Cumberland County area, over 50 percent of the existing forests are composed of the seedling to sapling size class. This class of stand reflects the abandonment of agricultural fields, overcutting, and a lack of planning and will require an accelerated program of forest management (SCS 1974). This is as important to sediment control as it is to improving the quality of the forest stock. Chapter 4.0, section 4.4 elaborates on this problem.
Finally, forests are a significant wildlife habitat in the bay for many species including deer, moose, squirrels, mink, weasel, fisher, raccoon, porcupine, red fox, and skunk. Ruffed grouse and woodcock are also found. Some of these also inhabit reverting fields and certain wetlands. The Department of Inland Fisheries and Game is presently undertaking an assessment of habitat and management needs for many of these species as well as others as part of a five-year program for wildlife and fisheries management. They may be contacted for further information. Back to Ecosystems
Farmland consists of any cultivated cropland, orchards, or pasture land. It is usually quite productive because it receives an energy subsidy from fossil fuels (fertilizers). The monoculture nature of most farmlands makes it a fragile ecosystem susceptible to disease and insects. Farmland is of interest as an ecosystem in this study for two reasons: (1) for its potential adverse effects on the Bay in terms of pesticide and sediment runoff; and (2) for its significance to wildlife. Chapter 4.0, section 4.4 deals with the economic aspects of farming.
The negative effects of certain pesticides, particularly DDT, on plant and animal life, are well known (Elson 1967; Elson et al 1973; Dimond, Getchell and Blease 1971). Recently, the eagle population has been declining in the area due to the problems caused by DDT residues. Research on the effects of other pesticides, such as Guthion, Malathion, Dieldrin, and Zectran seems to indicate a relatively inoxous effect on aquatic organisms (Dimond 1976; Dimond et al. 1972; Gibson and Chapman 1972). However, there is some speculation that Guthion and DDT interact, possibly synergistically--that is, the combined effect is greater than the sum of the individual effects (Locke and Havey 1972) while Zectran and DDT are known to have additive effects (Kennedy 1969). Because of the value of the Bay to wildlife, and be cause there is still little known on the effects of various pesticides, either singley or in combination, we recommend that extremely conservative measures ought to be taken in the use of any pesticides in the Bay area and that attempts be made by the Friends of Merrymeeting Bay and others to keep abreast of the most recent developments in pesticide research.
As to sedimentation, there is a direct correlation between the amount of land in cultivation and the degree of sedimentation. The Potomac River Basin Study mentioned above found that as land in crops increased from 10 to 50 percent sediment yield increased from 70 to 300 tons per square mile per year. We recognize that this can be a problem and, therefore, are recommending that farmers in the area consider such conservation practices as the planting of a winter wheat crop in the fall to hold the soil over the winter.
Finally, cropland and pastureland are utilized by migrating waterfowl (primarily geese) and deer throughout the Bay. Cereals are very important in their diet and grain and cornfields are maintained both by the state and by individuals to maintain geese in the Bay area. This year the state Inland Fisheries and Game Department will maintain 70 acres of winter rye grass on Swan Island and 10 acres in Bowdoinham. The state's activities are, in part, an effort to avoid crop damage to farms around the Bay.
For the purposes of this study, ecological characteristics and functions are significant for the following reasons:
1. The Bay is nationally significant as a stopover ground for migrating waterfowl, due to its size, relatively undeveloped character, and unusual productivity. A shallow fresh water Bay with tidal influence, the Bay contains 3,300 acres of vegetated mudflats and a sizeable acreage in wetlands along its perimeter and adjacent to its tributaries. Maintaining the value of the Bay for its waterfowl habitat represents a primary objective of this study and underlines many of its recommendations.
2. The Bay is also significant as a fishery habitat which is utilized extensively by sports fishermen. At one time, the Bay was also highly significant for commercial fisheries including salmon, alewives, and sturgeon. Pollution has diminished the fishery resource and dams have obstructed the migration of anadromous fish, however. Alleviating these problems, particularly the pollution, should be a majorconcern for the state. Preventing the future aggravation of these problems should be a concern of each town located in the Bay surrounds.
3. Wetlands, including marshes, swamps, bogs, and tidal flats, have important hydrological and pollution control functions which are intimately related to the maintenance of the Bay and of water supplies. These should be maintained in their natural state.
4. Forest systems are especially significant to sediment control, and should be used extensively for this through the maintenance of forested buffer strips along all bodies of water. They also provide significant habitat for wildlife.
5. Farming activities could potentially have adverse effects on the Bay, particularly through sediment, pesticide, and fertilizer runoff. Strict land conservation measures should be followed, such as the planting of a winter crop to hold the soil ove winter. Where possible, a hedge row of trees should be maintained between the Bay or its tributaries and cultivated land.