Introduction

General nature of The study

Lakes are valuable natural resources. The lake and its surrounding watershed provide important habitats for numerous aquatic and terrestrial wildlife. In addition, lakes encourage the influx of both people and businesses because of the recreational opportunities they provide. Human activity has the potential to drastically alter the natural processes within a lake.

Lakes age through the natural process of eutrophication (Chapman 1996). A young, nutrient poor lake matures as nutrients are added from decaying organic matter as well as other sources. This increase in nutrients in turn promotes plant growth. Eutrophication is accelerated by human activities that increase the nutrients entering the lake. Phosphorus levels influence lake productivity because of their effect on plant growth. When nutrient levels become very high, algae populations bloom and cause the lake to become green and murky. Not only are algal blooms aesthetically unappealing, but they are also ecologically detrimental. Lower levels of dissolved oxygen as a result of algal blooms causes fishkills and decreased biodiversity (Chapman 1996).

The Lake Wesserunsett watershed was chosen as our study site. It is a characteristic New England lake located in Madison, Maine. Lake Wesserunsett is a popular site for recreation and development, and is home to many species of flora and fauna. This lake is at an intermediate stage of its life cycle. Although algal blooms have not yet occurred, human activities continue to contribute a substantial nutrient load. If the amount of nutrient input to the lake is carefully monitored and controlled, Lake Wesserunsett will remain healthy and productive.

The purpose of this study was to evaluate the impact of land use and development on the water quality of Lake Wesserunsett. The physical and chemical parameters of the lake were evaluated in order to determine the present water quality and trends over time. The current land use patterns were also examined and categorized with respect to their effect on water quality. Development within the watershed was evaluated through the assessment of residences, septic systems and roads. The water budget and flushing rate were also calculated. These test results were used to construct a phosphorus model, a tool used to predict present and future phosphorus loading. A

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Geographic Information System (GIS) was used to construct models of land use and soil characteristics in the Lake Wesserunsett watershed. These models were used to predict future impacts of activities in the watershed on lake water quality. The results obtained from the lake and watershed analysis can be used to make recommendations concerning the health of Lake Wesserunsett. Water quality and land use assessment in this study was conducted by the Colby Environmental Assessment Team (CEAT) during the spring, summer and fall of 2000.

Background

Lake Characteristics

Differences Between a Lake and a Pond

Lakes and ponds are inland bodies of standing water created either naturally, through geological processes or artificially, through human intervention (Smith and Smith 2001). Lakes and ponds differ in their in size and depth profiles. Lakes most often have greater surface area and are deeper than ponds (Smith and Smith 2001). Lakes generally develop both vertical and horizontal stratification while ponds do not. Horizontal stratification in a lake divides the lake into zones based on sunlight penetration and the growth of vegetation. The littoral zone is the shallow-water zone in which sunlight can penetrate to the bottom allowing vegetation to grow from the substrate. The limnetic and profundal zones make up the deep-water area where sunlight cannot reach the bottom and rooted plants are not able to grow. A pond, on the other hand, does not have this zonation, as it is shallow enough that vegetation is rooted throughout (Smith and Smith 2001).

The vertical zonation found in a lake is dependent on density and water temperature. Deep lakes will stratify with the most dense water on the bottom and layers of less dense water toward the surface. Ponds and shallow lakes do not stratify because disturbance of wind and waves cause constant mixing and temperature distribution. Although Lake Wesserunsett does not stratify, it is considered a lake due to the lack of rooted vegetation throughout the lake basin.

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General Characteristics of Maine Lakes

Lakes are a vital natural resource in Maine (Davis et al. 1978). They provide fresh water for swimming, fishing, drinking, livestock, and agriculture. Maine's beautiful lakes draw many tourists throughout the year and also serve as important habitats for wildlife.

The majority of Maine lakes were formed during the Wisconsonian glaciation of the Pleistocene period, which occurred about 10,000 years ago (Davis et al. 1978). As a result of glacial activity in Maine, glacial till, bedrock, and glaciomarine clay-silt dominate most lake basin substrates. Generally, these deposits and the underlying granitic bedrock, are of an infertile nature. As a result, most of Maine's lakes are relatively nutrient poor. The movement of glaciers in Maine was predominantly southeasterly, carving out Maine lakes in a northwest to southeast direction (Davis et al. 1978). This unique orientation, along with lake surface area and shape, play a fundamental role in the effect of wind on the water body. Wind is an important factor in lake turnover or the mixing of thermal layers.

Most lakes in Maine are located in lowland areas among hills (Davis et al. 1978). Many lake watersheds within the state are forested. These stands are potentially threatened by logging from timber companies. Residential development of watersheds and increased construction of lake recreation facilities may also pose a significant threat to the water quality in many lakes and ponds in Maine. In watersheds where agricultural practices are less significant, both residential development and forestry may be the most acute sources of anthropogenic, or human caused, nutrient loading (Davis et al 1978).

In Maine, many factors influence lake water quality. These include proximity to the ocean, location within the state, residence time of water within the soil, wetland influences, and bedrock chemistry (Davis et al. 1978). Terrestrial and aquatic vegetation as well as the presence of unique habitat types may also affect the water quality. Depth and surface area can affect temperature and turnover in the lake.

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Annual Lake Cycles

Stratification is a vital component in lake ecosystem function, created by the different densities due to variations in temperature with depth. Water has the unique physical property of being most dense at 4° C (Smith and Smith 2001). Water decreases in density at temperatures above and below 4° C, allowing ice to float on the surface of lakes and ponds because it is less dense than the warmer water below it.

In the summer, direct radiation warms the upper levels of the water column forming the epilimnion, which hosts the most abundant floral communities (Davis et al. 1978). The photosynthetic capacities of the plants create an oxygen rich stratum. However, available nutrients in the epilimnion can be depleted by algal populations growing in the water column and may remain depleted until the turnover of early fall (Smith and Smith 2001). The process of lake cycling is summarized in Figure 1.

Below the epilimnion is a layer of sharp temperature decline, known as the metalimnion (Smith and Smith 2001). Within this stratum is the greatest temperature gradient in the lake, called the thermocline (Smith and Smith 2001). This thermocline separates the epilimnion from the hypolimnion, the lowest stratum of a lake. The hypolimnion, only found in the deepest lakes, is beyond the depth to which sufficient light can penetrate in order to facilitate effective photosynthesis (Figure 1). It is in the substrate of the hypolimnion, where most decomposition of organic material takes place through both aerobic and anaerobic biological processes. While aerobic (requiring oxygen) bacteria break down organic matter quicker than anaerobic bacteria, they also significantly deplete the oxygen at these depths (Davis et al. 1978).

As the months become colder, water temperature decreases and wind facilitates thermal mixing until the vertical profile of the water column is uniform in temperature. This event, known as turnover, reoxygenates the lower depths and mixes nutrients throughout the strata. The cold water near the surface can hold increased levels of oxygen, which is redistributed with turnover. Through this process, organisms at depth receive oxygenated water. A similar turnover event also occurs in the spring (Smith and Smith 2001).

In winter, lakes in Maine are covered with ice for 4-5 months. The stratification is reversed as

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the coldest water (ice) is on the surface and the warmer water (4 C) is at depth. Significant snow cover on the ice may affect the photosynthetic processes during the winter months under the ice by blocking some of the incoming solar radiation. This situation can deplete oxygen levels enough to cause significant fishkills (Smith and Smith 2001).

In the spring solar radiation warms the upper stratum of the lake and the ice melts. Once the temperature in the water column is uniform, oxygen and nutrients are again mixed throughout the water column. As late spring approaches, solar radiation increases, stratification becomes evident and temperature profiles return to that of summer (Smith and Smith 2001).

Trophic Status of Lakes

One biological classification of lakes is based on nutrient levels (Maitland 1990). Lakes are divided into four major categories: oligotrophic, mesotrophic, eutrophic, and dystrophic (Table 1). The mesotrophic characterization is not included in Table 1, because it is referred to as a transitional stage between oligotrophic and eutrophic states (Chapman 1996). Young or oligotrophic lakes are lacking in nutrients, while eutrophic lakes are nutrient rich (Niering 1985). Oligotrophic lakes tend to be deep and oxygen rich with steep-sided basins creating a low surface to volume ratio. Although they may be high in nitrate levels, oligotrophic lakes are primarily deficient in phosphorus, the limiting nutrient for plant productivity in most freshwater ecosystems. The shape of a lake can also influence its productivity. Steep-sided oligotrophic lakes are not conducive to extensive growth of rooted vegetation because there is no shallow margin for attachment.

Eutrophic lakes are nutrient rich (Chapman 1996) and have a relatively high surface to volume ratio (Maitland 1990). These lakes have a large phytoplankton population that is supported by the increased availability of dissolved nutrients (Table 1). Low dissolved oxygen levels at the bottom of a eutrophic lake are a result of high decomposition activity. This activity leads to the release of phosphorus and other nutrients from the bottom sediments, resulting in their eventual recycling through the water column (Chapman 1996). This nutrient release stimulates even further growth of phytoplankton populations such as algae (Smith and Smith 2001). Due to sediment loading over the

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years, eutrophic lakes tend to be shallow and bowl shaped, which allows for the establishment of rooted plants.

Dystrophic lakes receive large amounts of organic matter from the surrounding land, particularly in the form of humic (dead organic) materials (Smith and Smith 2001). The large quantity of humic materials stains the water brown. Dystrophic lakes have highly productive littoral zones, high oxygen levels, high macrophyte productivity, and low phytoplankton numbers (Table 1). Eventually, the invasion of rooted aquatic macrophytes chokes the habitat with plant growth. The lake basin is filled in, resulting in the development of a terrestrial ecosystem (Goldman and Home 1983).

The natural aging process of a lake begins as oligotrophic and progresses through eutrophication, eventually to become a terrestrial landscape (Niering 1985). This process can be greatly accelerated by anthropogenic activities, which increase nutrient loading. The United States Environmental Protection Agency (USEPA) characterizes the process of eutrophication by the following criteria:

1) Decreasing hypolimnetic dissolved oxygen concentrations

2) Increasing nutrient concentrations in the water column

3) Increasing suspended solids, especially organic material

4) Progression from a diatom population to a population dominated by

cyanobacteria and/or green algae

5) Decreasing light penetration (e.g., increasing turbidity)

6) Increasing phosphorus concentrations in the sediments (Henderson-Sellers and Markland 1987)

As a lake ages, it fills with dead organic matter and sediment from various inputs that settle to the bottom. Lakes may receive mineral nutrients from streams, groundwater, and runoff as well as precipitation. The increase in nutrient availability promotes primary productivity. Increased productivity leads to more dead organic material that accumulates as sediment in lentic ecosystems (standing bodies of water such as lakes and ponds). Over time, lakes will fill in, decrease in size, and are eventually replaced by a terrestrial community (Chiras 1994).

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Phosphorus and Nitrogen

In freshwater lakes, phosphorus and nitrogen are the two major nutrients required for the growth of algae and macrophytes (Smith and Smith 2001). Each nutrient has its own complex chemical cycle within the lake (Overcash and Davidson 1980). It is necessary to understand these cycles in order to devise better techniques to control high nutrient levels.

Phosphorus is considered the most important nutrient in lakes because it is the limiting nutrient for plant growth in freshwater systems (Maitland 1990). Phosphorus naturally occurs in lakes in minute quantities measured in parts per billion (ppb). However, this concentration is sufficient for plant growth, due to the high efficiency with which plants can assimilate phosphorus (Maitland 1990). There are multiple external sources of phosphorus (Williams 1992), but a large supply is also found in the lake sediments (Henderson-Sellers and Markland 1987). The cycle of phosphorus in a lake is complex, with some models including up to seven different forms of phosphorus (Frey 1963). For the purposes of this study it is necessary to understand two broad categories of phosphorus in a lake: dissolved phosphorus (DP), and particulate phosphorus (PP). The phosphorus cycle in a stratified lake is summarized in Figure 2. DP is an inorganic form of phosphorus, which is readily available for plant use in primary production. It is this form of phosphorus that is limiting to plant growth. PP is a form of phosphorus, which is incorporated into organic matter such as plant and animal tissues. DP is converted to PP through the process of primary production. PP then gradually settles into the hypolimnion in the form of dead organic matter. PP can be converted to DP through aerobic and anaerobic processes. In the presence of oxygen, PP will be converted to DP through decomposition by aerobic bacteria. In anoxic conditions, less efficient anaerobic decomposition occurs (Lerman 1978).

An important reaction occurs in oxygenated water, which involves DP and the oxidized form of iron, Fe(III) (Chapman 1996). This form of iron can bind with DP to form an insoluble complex, ferric phosphate, which can effectively tie up large amounts of phosphorus as it settles into the bottom sediments. Fe(III) is reduced to Fe(II) in the presence of decreased oxygen levels at the sediment water interface, resulting in the release of DP. The ferric phosphate complex, combined with the anaerobic bacterial conversion of PP to DP, can lead to a significant build-up of DP in

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anoxic sediments. The sediments of a lake can have phosphorus concentrations of 50-500 times the concentration of phosphorus in the water (Henderson-Sellers and Markland 1987). Sediments can be an even larger source of phosphorus than external inputs. Because nutrients are inhibited from mixing into the epilimnion during the summer by stratification, DP concentrations build up in the lower hypolimnion until fall turnover.

The fall turnover results in a large flux of nutrients creating the potential for algal blooms. Algal blooms can occur when phosphorus levels are rise above12 to 15 ppb. If an algal bloom does occur, DP will be converted to PP in the form of algal tissues. The algae will die as winter approaches and the dead organic matter will settle to the bottom where PP will be converted back to DP and build up again, allowing for another large nutrient input to surface waters during spring overturn (Chapman 1996).

Nitrogen, the other major plant nutrient, is not usually the limiting factor for plant growth in a lake (Chapman 1996). However, it is still important to understand its cycle because high concentra

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tions can lead to algal blooms in the presence of phosphorus.

Available nitrogen exists in lakes in three major chemical forms: nitrates (NO₃^-), nitrites (NO₂^-), and ammonia (NH₃). The nitrogen cycle is summarized in Figure 3. The majority of free nitrogen in a lake exists in the form of nitrates (Maitland 1990). This form of nitrogen is directly available for assimilation by algae and macrophytes. In eutrophic lakes, there may be so much algae and macrophyte growth that most of the nitrates in the lake are incorporated into plant tissues (Maitland 1990). Nitrites, however, cannot be used by plants. Nitrate-forming bacteria in aerobic conditions convert nitrites to nitrates. Ammonia enters the lake ecosystem as a product of the decomposition of plant and animal tissues and their waste products. It can follow one of three paths. First, many macrophytes can assimilate ammonia directly into their tissues. In aerated conditions, aerobic bacteria will convert the ammonia directly to nitrates, the more usable form of nitrogen. In anaerobic decomposition, which commonly occurs in the sediments of stratified lakes, nitrates can be reduced to nitrites. If these anaerobic conditions persist, the nitrites can be broken down to

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elemental nitrogen (N₂). This form is not available to any plants without the aid of nitrogen-fixing bacteria. Plants depend on these bacteria to convert nitrogen to nitrates through the process of nitrogen fixation (Overcash and Davidson 1980).

The underlying pattern evident from this cycle is that all foms of nitrogen added to the lake will eventually become available for plant use. The various forms of nitrogen as well as the oxygen concentrations (aerobic and anaerobic conditions) of the water must be considered in order to understand the availability of this nutrient for plant growth.

Several in-lake mitigation techniques exist to deal with the problem of excessive nutrients once they are present in the lake (Henderson-Sellers and Markland 1987). None of these techniques are without disadvantages, but for lakes with serious algal growth problems they may be necessary (Henderson-Sellers and Markland 1987).

One technique used to eliminate excessive nutrients is to rapidly decrease the water level of the lake (Henderson-Sellers and Markland 1987). A lake controlled by a dam can quickly be flushed by releasing a large volume of water. The result may be the rapid export of many nutrients from the epilimnion of the lake. However, in cases where the lake drains into another lake or significant water body, the problem may not be eliminated, but simply shifted to another site. Additionally this may only be a temporary solution because if the nutrient source is not eliminated it will continue to supply nutrients to lake.

Another approach to nutrient reduction involves removing the nutrient rich hypolimnetic water. By inserting a large pipe into the hypolimnion and pumping the water out in such a way that it would not go directly back into the lake, the nutrient levels in the water would be reduced (Henderson-Sellers and Markland 1987).

Chemical precipitation is a relatively simple technique. It is based on the natural affinity of iron to complex with phosphorus. Adding salt to the water will complex the DP to form an insoluble compound that will immobilize the P (Henderson-Sellers and Markland 1987). This is an effective technique but, due to the cost, is not practical for very large lakes. Furthermore, the P will eventually be released from this complex, requiring reapplication after several years.

Aeration of the hypolimnion is a process that requires expensive machinery to perform. It

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operates on the principle that an increase in the oxygen levels in the lower strata of the hypolimnion will reduce the amount of DP released from the sediments. If there is oxygen present where the sediment and water interface, there will be no conversion of iron to its reduced form, and therefore, no DP will be released from the ferric phosphate complex (Henderson-Sellers and Markland 1987).

Another approach in lakes with large macrophyte production is to harvest the plants. This method can be expensive due to the cost of equipment used and the frequency with which the harvesting must be performed. This procedure removes all the nutrients tied up in the plants at the time of harvest, preventing them from re-entering the lake cycle. It is important that harvested plants are not left along the shore, allowing nutrients from decomposing plants to leach into the lake. There is some debate over the effectiveness of this method because macrophytes also act as a sink for nutrients. At the time of removal, the nutrients that would normally have been taken up by the macrophytes will be available to algae, perhaps resulting in an algal bloom (Chapman 1996). On the other hand, if only the foliage of the plants is harvested, then the plants will still be able to take up nutrients via the roots.

One final management option is dredging. This process extracts the nutrients from the sediments by removing the sediments themselves. Although dredging is effective, it is extremely expensive due to the large amount of labor and equipment cost needed (Henderson-Sellers and Markland 1987). There are additional questions as to the ecological disruption that these actions may have on the lake ecosystem.

It is evident from these techniques that eliminating nutrients once they have built up in a lake is a challenging task. The ideal method for controlling nutrients in a lake is to regulate and monitor the input sources. This allows the natural processes of nutrient cycling and uptake by flora and fauna to compensate for nutrient inputs without accelerated eutrophication of the lake.

Freshwater Wetlands

Wetlands are important transitional areas between lake and terrestrial ecosystems. They support a wide range of biotic species (MLURC 1976). Table 2 gives descriptions of freshwater inland

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wetlands. Wetlands also help to maintain lower nutrient levels in an aquatic ecosystem because of the efficiency in nutrient uptake by their vegetation (Smith and Smith 2001). Wetlands have the potential to absorb heavy metals and nutrients from various sources including mine drainage, sewage, and industrial wastes (Chiras 1994). Agricultural runoff adds excess nitrogen and phosphorus to the lake. Wetlands are able to improve the overall water quality by the absorption and storage of nutrients through their assimilation into organic plant tissues (Niering 1985).

Wetlands usually have a water table at or above the level of the land. Wetland soil is periodically or perpetually saturated and contains non-mineral substrates such as peat. Wetlands also contain hydrophytic vegetation that is adapted for life in saturated and anaerobic soils (Chiras 1994).

Watershed Land Use

Land Use Types

A watershed is the total land area that contributes a flow of water to a particular basin. The boundary of a watershed is defined by the highest points of land that surround a lake or pond and its tributaries. Any water introduced to a watershed will be absorbed, evaporate (including transpiration by plants), or flow into the basin of the watershed.

Nutrients bind to soil particles. If eroded, nutrient-rich soil will add to the nutrient load of a lake, hastening the eutrophication process and leading to algal blooms (USEPA 1990). Due to influence on erosion and runoff, different types of land use have distinct effects on nutrient loading in lakes. Assessment of land use within a watershed is therefore essential in the determination of factors that affect lake water quality.

A land area cleared for agricultural, residential, or commercial use contributes more to nutrient loading than a naturally vegetated area such as forested land (Dennis 1986). The combination of vegetation removal and soil compaction involved in the clearing of land results in a significant increase in surface runoff. This amplifies the erosion of sediments carrying nutrients and pollutants of human origin.

Naturally vegetated areas offer protection against soil erosion and surface runoff (Firmage,

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pers. comm). The forest canopy reduces erosion by diminishing the direct physical impact of rain on soil. The root systems of trees and shrubs reduce soil erosion by decreasing the rate of runoff, allowing water to percolate into the soil. Roots decrease the nutrient load in runoff through direct absorption of nutrients for use in plant structure and function. Due to these features, a forested area acts as a buffering system by decreasing surface runoff and absorbing nutrients before they enter water bodies.

Residential areas are a significant threat to lake water quality for a number of reasons. These areas generally contain lawns, driveways, parking spaces, roof-tops and other impervious surfaces that reduce percolation and thereby increase surface runoff. Due to their proximity to lakes, shoreline residences are often direct sources of nutrients to the water body.

Because forests cover much of Maine, the development or expansion of residential area often necessitates the clearing of wooded land. New development dramatically increases the amount of surface runoff because natural ground cover is replaced with impervious surfaces (Dennis 1986). Evidence of increased surface runoff due to development and consequent effects on nutrient transport is presented in a study concerning phosphorus loading in Augusta, Maine (Figure 4). The study revealed that surface runoff from a residential area contained ten times more phosphorus than runoff from an adjacent forested area. The study concluded that the surface-runoff flow rate of residential area can be in excess of four times the rate recorded for forested land.

The use of chemicals in and around the home is potentially harmful to water quality. Products associated with cleared and residential land include fertilizers, pesticides, herbicides, and detergents that often contain nitrogen, phosphorous, other plant nutrients and miscellaneous chemicals (MDEP 1992a). These products can enter a lake by leaching directly into ground water or traveling with eroded sediments. Heavy precipitation aids the transport of these high nutrient products due to increased surface runoff near residences (Dennis 1986). Upon entering a lake, these wastes have adverse effects on water quality.

Septic systems associated with residential and commercial land are significant sources of nutrients when improperly designed, maintained, or used (USEPA 1980). Proper treatment and disposal of nutrient rich human waste is essential in maintaining high lake water quality.

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Commercial uses of forested land can have detrimental effects on lake water quality. Activities that remove the cover of the canopy and expose the soil to direct rainfall increase erosion. Two

Commercial uses of forested land can have detrimental effects on lake water quality. Activities that remove the cover of the canopy and expose the soil to direct rainfall increase erosion. Two

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studies by the Land Use Regulation Commission on tree harvesting sites noted that erosion and sedimentation problems occurred in 50 percent of active and 20 percent of inactive logging sites selected (MDC 1983). Skidder trails may pose a problem when they run adjacent to or through streams (Hahnel, pers. comm.). Shoreline zoning ordinances have established that a 75 ft strip of vegetation must be maintained between a skidder trail and the normal high water line of a body of water or upland edge of a wetland to alleviate the potential impact of harvesting on the water body (MDEP 1990).

Roads are a source of excessive surface runoff if they are poorly designed or maintained (Michaud 1992). Different road types have varying levels of nutrient loading potential. In general, roughly 80% of the nutrient loading problems are caused by only 20% of the culverts or crossings. Furthermore, roads and driveways leading to shoreline areas or tributaries can cause runoff to flow directly into a lake.

As land use conversion occurs, it is critical that factors influencing nutrient loading are considered. Public education and state and local regulations that moderate nutrient loading are essential in maintaining lake water quality. Understanding the effects of changing land use practices is critical in evaluating the ecological health of a watershed ecosystem and making predictions about its future.

Buffer Strips

Buffer strips play an important role in absorbing runoff, thereby helping to control the amount of nutrients entering a lake (MDEP 1990). Excess amounts of nutrients such as phosphorus and nitrogen can promote algal growth and increase the eutrophication rate of a lake (MDEP 1990). According to the Shoreline Zoning Ordinance for the Municipality of Madison, "within a strip of land extending 100 ft horizontal distance inland from the normal high water line of Lake Wesserunsett, and 75 ft horizontal distance from any other water body, tributary stream, or the upland edge of a wetland, a buffer strip of vegetation should be observed" (Madison 1995).

A good buffer should have several vegetation layers and a variety of plants and trees to

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maximize the benefit of each layer (MDEP 1990). Naturally occurring vegetation forms the most effective buffer. Trees and their canopy layer provide the first defense against erosion by lessening the impact of rain and wind on the soil. Their deep root systems absorb water and nutrients while maintaining the topographical structure of the land. The shallow root systems of the shrub layer also aid in absorbing water and nutrients, and help to hold the soil in place. The groundcover layer, including vines, ornamental grasses, and flowers slows down surface water flow, and traps sediment and organic debris. The duff layer, consisting of accumulated leaves, needles, and other plant matter on the forest floor, acts like a sponge to absorb water and trap sediment. Duff also provides a habitat for many microorganisms that break down plant material and recycle nutrients (MDEP 1990).

An example of an ideally buffered home is shown in Figure 5. This home has a winding path down to the shoreline. Runoff is diverted into the woods where it can be absorbed in the forest litter. The house itself is set back from the shoreline 100 ft, and has a dense buffer strip between it and the water. The buffer is composed of a combination of canopy trees, understory shrubs and

groundcover. In addition, the driveway is curved. This allows for runoff that is accumulating on these surfaces to be deposited into a number of diversions along its path down the slope of the land. As opposed to a steep, straight, and paved path that leads directly into the water, a curved driveway

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can be a very effective deterrent to runoff. Slopes within a buffer strip that are less than two percent are most effective at slowing down the surface flow and increasing absorption of runoff (MDEP 1998). Steep slopes are susceptible to heavy erosion and will render buffer strips ineffective.

In addition to buffer strips, riprap can be an effective method of preventing shoreline erosion by protecting the shoreline and adjacent shoreline property against heavy wave action (MDEP 1990). Riprap consists of three primary components: the stone layer, the filter layer, and the toe protection. The stone layer consists of rough, large, angular rock. The filter layer is composed of a special filter cloth that allows groundwater drainage and prevents the soil beneath the riprap from washing through the stone layer. The toe protection prevents settlement or removal of the lower edge of the riprap. Riprap depends on the soil beneath it for support, and should therefore be built only on stable shores or bank slopes (MDEP 1990).

Nutrient Loading

Nutrient loading into a lake can be affected by natural and anthropogenic processes (Hem 1970). Human activity usually accelerates the loading of nutrients and sediments into a lake. In this way, the water quality can be adversely affected in a short period of time. Clearing away forests to construct roads and buildings with impervious surfaces increases runoff, carrying nutrients from agricultural, residential, and industrial products (such as detergent, fertilizer, and sewage) into the lake. Since phosphorus and nitrogen are the limiting nutrients to algal growth, and algal growth affects the trophic state of a lake, increases of phosphorus and nitrogen from these sources can lead to a decrease in lake water quality and eventual eutrophication.

Total phosphorus loading to a lake can be determined using a phosphorus loading model. This model takes into account the various aspects upon which the phosphorus concentration in the lake basin is dependent, such as lake size, volume, flushing rate, and land use patterns within the watershed (Cooke et al. 1986). The model allows for the projection of the impact that various factors may have on phosphorus loading and generates predictions of lake responses to changes in land use. The accuracy of the predictions is determined by the accuracy of the assumptions (USEPA 1990).

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Soil Types

Nutrient loading in a lake ecosystem is partially a function of the soil types and their respective characteristics. Both the physical characteristics of soil, such as permeability, depth, particle size, organic content, and the presence of an impermeable layer (fragipan), as well as the environmental features (slope, average depth to the water table, and depth to the bedrock) which influence them, are important to consider in determining the nutrient loading functions (USDA 1978). These factors can determine appropriate land uses such as forestry, agriculture, and residential or commercial development. The soils most capable of accommodating such disturbances, by preventing extreme erosion and runoff of both dissolved and particulate nutrients, are those which have medium permeability, moderate slopes, deep water tables, low rockiness and organic matter, and no impermeable layer (USDA 1992). Soils that do not meet these criteria should be considered carefully before implementing a development, forestry, or agricultural plan.

Zoning and Development

The purpose of shoreline zoning and development ordinances is to control water pollution, protect wildlife and freshwater wetlands, monitor development and land use, conserve wilderness, and anticipate the impacts of development (Madison 1995). Shorelinezoning ordinancesregulate development along the shoreline in a manner that reduces the chances for adverse impacts on lake water quality. Uncontrolled development along the shoreline can result in a severe decline in water quality that is difficult to correct. In general, these regulations have become more stringent as increased development has caused water quality to decline in many watersheds (MDEP 1992b). If no comprehensive plan or town ordinances have been enacted, the state regulations are used by default.

Shoreline Residential Areas

Shoreline residential areas are of critical importance to water quality due to their proximity to

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the lake. This study considered houses less than 200 feet from the shoreline to be shoreline residences. Any nutrient additives from residences (such as fertilizers) have only a short distance to travel to reach the lake. Buffer strips along the shore are essential in acting as a sponge for the nutrients flowing from residential areas to the lake (Woodard 1989). These buffer strips consist of an area of natural vegetation growing between a building and the body of water in question. Town ordinances in Madison regulate buffer strip widths, which help to control phosphorus loading in the lake.

Residences that have lawns leading directly down to the shore have no obstacles to slow runoff, allowing phosphorus to pass easily into the lake. Buffer strips, when used in conjunction with appropriate setback laws for house construction, can dramatically reduce the proximity effects of shoreline residences (MDEP 1992b).

Seasonal residences, especially older ones located on or near the shoreline in a cluster, can contribute disproportionately to phosphorus loading into the lake ecosystem. Such clusters of camps usually exist because they have been grandfathered, and do not follow shoreline zoning laws. Although seasonal, they may involve large numbers of people. Therefore, phosphorus export from these areas is likely to increase during periods of heavy use. The location and condition of septic systems also effects the nutrient loading from these plots (see: Sewage disposal systems).

Non-Shoreline Residential Areas

Nonshoreline residential areas (greater than 200 feet from the shoreline) can also have an impact on nutrient loading, but generally less than that of shoreline residential areas. Runoff, carrying fertilizers and possibly phosphorus containing soaps and detergents, usually filters through buffer strips consisting of forested areas several acres wide, rather than a few feet wide (as with shoreline buffers). In these cases, phosphorus has the opportunity to be absorbed into the soils and vegetation. The majority will not reach the lake directly, but will simply enter the forest's nutrient cycle.

However, residences located up to one half mile away from the lake can potentially supply the lake with phosphorus almost directly when poorly constructed roads persist. Runoff collected on

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roofs and driveways may travel unhindered down roads or other runoff channels to the lake. Although nonshoreline homes are not as threatening as shoreline residences, watersheds having large residential areas with improper drainage can have a significant effect on phosphorus loading.

Tributaries can make nonbuffered, nonshoreline residences every bit as much of a nutrient loading hazard as a shoreline residence with a large lawn. Phosphorus washed from residential lawns without buffer strips can enter into a stream and eventually into the lake. Therefore, similar restrictions and regulations as those for shoreline residences apply to nonshoreline homes that are located along many streams.

Sewage Disposal Systems

Subsurface wastewater disposal systems are defined in the State of Maine Subsurface Wastewater Disposal Rules as: "a collection of treatment tank(s), disposal area(s), holding tank(s), alternative toilet(s), or other devices and associated piping designed to function as a unit for the purpose of disposing of wastewater in the soil" (MDHS 1988). These systems are generally found in areas with no municipal disposal systems such as sewers. Examples of these subsurface disposal systems include pit privies and septic systems.

Pit Privy

Pit privies are also known as outhouses. Most privies are found in areas with low water pressure systems. They are simple disposal systems consisting of a small, shallow pit or trench. Human excrement and paper are the only wastes that can be decomposed and treated. Little water is used with pit privies therefore chances of ground water contamination are reduced. Contamination due to infiltration of waste into the upper soil levels may occur if the privy is located too close to a body of water

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Holding Tank

Holding tanks are watertight, airtight chambers, usually with an alarm, which hold waste for periods of time. The tanks are durable and made of either concrete or fiberglass (MDHS 1988). The minimum capacity for a holding tank is 1500 gallons. These must be pumped or else they could back up into the structure or leak into the ground, causing contamination. According to Paul Lussier (pers. comm.), the plumbing inspector for Waterville, holding tanks are "the system of last resort". Although purchasing a holding tank is inexpensive, the owner is then required to pay to have the holding tank pumped on a regular basis.

Septic System

Septic systems are the most widely used subsurface disposal system. The system includes a building sewer, treatment tank, effluent line, disposal area, distribution box, and often a pump. The pump enables the effluent to be moved to a more suitable leach field location if the location of the treatment tank is unsuitable for a leaching field (MDHS 1983). Figure 6 shows the basic layout of the components of a typical septic system. Septic systems are an efficient and economical alternative to a sewer system, provided they are properly installed, located, and maintained. Unfortunately, many septic systems that are not installed or located properly may lead to nutrient loading and groundwater contamination. The location of the systems and the soil characteristics determine the effectiveness of the system.

The distance between a septic system and a body of water should be sufficient to prevent contamination of the water by untreated septic waste. The shoreline regulations in Madison state that septic systems need to be at least 100 ft away from a lake and 50 ft away from streams. Unfortunately, many parcels of land are grandfathered, which means their septic systems were installed before the passage of current regulations. Those systems may be closer to the shore than is currently permitted. However, any replacement systems in these grandfathered areas must reflect the new regulations. Replacement systems can either be completely relocated, or an effluent pump installed on the outside of the existing treatment tank can be used to move the sewage uphill to an alternative

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disposal area further from the water body (MDHS 1983).

Human waste and gray water are transferred from a residence through the building sewer to the treatment tank. There are two kinds of treatment tanks, aerobic and septic, both of which are tight,

disposal area further from the water body (MDHS 1983).

Human waste and gray water are transferred from a residence through the building sewer to the treatment tank. There are two kinds of treatment tanks, aerobic and septic, both of which are tight,

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durable, and usually made of concrete or fiberglass (MDHS 1983). The aerobic tanks rely on aerobic bacteria, which are more active than anaerobic bacteria. Unfortunately, aerobic bacteria are also more susceptible to condition changes. These tanks also require more maintenance, energy to pump in fresh air, and are more expensive. For these reasons, septic tanks are preferable. Septic tanks rely on anaerobic bacteria. Solids are held until they are sufficiently decomposed and suitable for discharge (MDHS 1983).

As the physical, chemical, and biological breakdowns occur, scum and sludge are separated from the effluent. Figure 7 shows the cross section of a typical treatment tank. Scum is the layer of grease, fats, and other particles that are lighter than water and move to the top of the treatment tank. Scum is caught by the baffles so that it cannot escape into the disposal area. Sludge is composed of

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the solids that sink to the bottom of the tank. Over time, much of the scum and sludge is broken down by anaerobic digestion. The effluent then travels through the effluent line to the disposal area.

The purpose of a disposal area is to provide additional treatment of the wastewater. The disposal area can be one of three types: bed, trench, or chamber (MDHS 1983). Beds are wider than trenches, and usually require more than one distribution line; typically, beds need a distribution box. Chambers are made of pre-cast concrete. The size of the disposal area depends on the volume of water and soil characteristics. The soils in the disposal area serve to distribute and absorb effluent, provide microorganisms and oxygen for treatment of bacteria, and remove nutrients from the wastewater through chemical and cation exchange reactions (MDHS 1983). Effluent contains anaerobic bacteria as it leaves the treatment tank. Treatment is considered complete when aerobic action in the disposal field has killed the anaerobic bacteria. If the effluent is not treated completely, it can be a danger to a water body and the organisms within it, as well as to human health. Incomplete treatment of the effluent is also a threat to groundwater. Three threats to lakes include organic particulates, nutrient loading, and water contamination through the addition of viruses and bacteria (MDHS 1983). Organic particulates also increase the biological oxygen demand (BOD).

BOD is the oxygen demanded by decomposers to break down organic waste in water. Organic matter will increase if there is contamination from human and animal wastes. As the amount of organic material increases, BOD increases. If the BOD depletes dissolved oxygen, species within a lake may begin to die. If a lake's flushing rate is low, reduced dissolved oxygen levels and increasing organic matter could become problematic.

The three major types of wastes that travel into the septic system are garbage disposal wastes, black water, and gray water. Garbage disposal wastes can easily back up the septic system and therefore should not be discharged to a septic system. Black water and gray water are significant contributors of phosphorus. Black water also contributes nitrogen, toilet wastes, and microorganisms. Gray water brings in chemicals and nutrients. Once a system is clogged or a leak develops, humans are exposed to potential bacterial and viral contamination (MDHS 1983).

Reducing the chances of clogging will allow septic systems to be most efficient. Year-round residents should have their septic tanks pumped every two to three years, or when the sludge level

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fills half the tank (Williams 1992). Seasonal residents should pump their septic tanks every five to six years to prevent clogging from occurring in the disposal field. Garbage disposals place an extra burden on a septic system (Williams 1992). Cigarette butts, sanitary napkins, and paper towels should never be disposed of in septic systems as they are not easily broken down by the microorganisms and fill the septic tank too quickly. The disposal of chemicals, such as pouring bleach or paint down the drain, may also affect septic systems by killing microorganisms. Water conservation slows the flow through the septic system and allows more time for bacteria to treat the water. By decreasing the amount of water passing through the disposal field, the septic system can work more effectively and recover after heavy use (Williams 1992). Odors, extra green grass over the disposal field, and slow drainage are symptoms of a septic system that has been subject to heavy use and not functioning properly

When constructing a septic system, it is important to consider soil characteristics and topography when determining the best location. An area with a gradual slope (10 to 20 percent) that allows for gravitational pull is necessary for proper sewage treatment (MDHS 1988). Too gradual of a slope causes stagnation, while too steep a slope drains the soil too quickly. Treatment time is cut short and water is not treated properly. Adding or removing soils to decrease or increase the slope is one solution to this problem.

Soil containing loam, sand, and gravel allows the proper amount of time for runoff and purification (MDHS 1983). Soils cannot be too porous; otherwise water runs through too quickly and is not sufficiently treated. Depth of bedrock is another important consideration. If the bedrock is too shallow, waste will remain near the soil surface. Fine soils such as clay do not allow for water penetration, again causing wastewater to run along the soil surface untreated. Adding loam and sand to clay-like soils would help alleviate this problem. In the opposite case, if a soil drains too quickly, loam and clay can be added to slow down the filtration of wastewater.

Federal, state, and local laws are in place to protect land and water quality. The federal government sets minimum standards for subsurface waste disposal systems. States can then choose to make their rules stricter but not more lenient than federal guidlines.. Maine's Comprehensive Land Use Plan sets standard regulations that each city and town must follow. Individual municipalities

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have the ability to establish their own comprehensive land use plan in accordance with the state regulations. However, many towns develop local ordinances that consider specific issues such as shoreline zoning. The Maine Department of Environmental Protection (MDEP), Maine Department of Conservation (MDC), and local Code Enforcement Officers are responsible for overseeing the enforcement of these laws.

Since 1974, state mandates have prevented septic systems from being installed without a site evaluation or within 100 ft from the high water mark. Other regulations state that there must be no less than 300 ft between a septic system disposal field and a well that uses more than 2000 gallons per day (MDHS 1988). Also, 20 percent is the maximum slope of the original land that can support a septic system. These regulations are in place for the safety of people living in the Lake Wesserunsett watershed as well as for the aquatic ecosystem.

Roads

Roads can significantly contribute to the deterioration of water quality by adding phosphorus to runoff and creating a route to the lake for the runoff to travel down. They may allow easy access for runoff of other nutrients and organic pollutants into the lake via improperly constructed culverts and ditches. Improper road construction and maintenance can increase the nutrient load entering the lake.

Proper drainage of roads is very important when trying to control phosphorus loading within a watershed. Construction materials, such as pavement, dirt, or gravel, may influence the amount and rate of runoff (Woodard 1989). The inevitable erosion of these building materials due to road traffic causes deterioration of the road surface. Storms increase road deterioration by dislodging particles from the road surface. Nutrients attached to these particles are transported to the lake by runoff from the roads (Michaud 1992).

Road construction should try to achieve the following long-term goals: minimize the surface area covered by the road, minimize runoff and erosion with proper drainage and the placement of catch basins (as well as culverts and ditches), and maximize the lifetime and durability of the road

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(MDEP 1990). A well constructed road should divert road surface waters into a vegetated area to prevent excessive amounts of surface runoff, phosphorus, and other nutrients from entering the lake. Items which should be considered before construction begins include: road location, road area, road surface material, road cross section, road drainage (ditches, diversions, and culverts), and road maintenance (MDEP 1992a).

Although the State of Maine has set guidelines to control the building of roads, road location is typically determined by the area in which homes are built (MDEP 1990). All roads must be set back at least 100 ft from the shoreline of a lake if they are for residential use, and 200 ft for industrial, commercial, or other non-residential uses involving one or more buildings (MDEP 1991).

Designing a road with future use in mind is very important. For instance, a road should be constructed no longer than is absolutely necessary. A particular road should not be extended past the last structure that is to be serviced by that road. The width of a road, which is often based upon the maintenance capabilities of the area, must also be considered (Cashat 1984). Proper planning for maintenance is a more effective, practical, and economical way to develop the road area (Woodard 1989).

Road surface material is another important factor to consider in road construction. Studies have shown that phosphorus washes off paved surfaces at a higher rate than from sand and gravel surfaces (Lea, Landry, and Fortier 1990). On the other hand, sand and gravel roads erode more quickly and have the potential for emptying more sediment and nutrients, into a body of water. Consequently, pavement is chosen for roads with a high volume of traffic, while sand and gravel roads are typically used for low traffic areas or seasonal use areas. Both types of roads need proper maintenance and gravel road surfaces should be periodically replaced and properly graded so that a stable base may be maintained and road surface erosion minimized.

The road cross section is another important factor to consider when planning road construction. A crowned road cross section allows for proper drainage and helps in preventing deterioration of the road surface (MDOT 1986). This means that if the road is pictured in cross section, it will slope downward from the middle, towards the outer edges. The crown should have a slope of 1/8 to 1/4 inches per foot of width for asphalt and 1/2 in to 3/4 in per foot of width for gravel roads (Michaud

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1992). This slope allows the surface water to run off down either side of the road as opposed to running along its whole length. Road shoulders should also have a slightly steeper cross slope than the road itself so that runoff can flow into a ditch or buffer zone (Michaud 1992).

The drainage of a road and the land that surrounds it must also be considered during construction or maintenance projects. Both ditches and culverts are used to help drain roads into buffer zones where nutrients added by the road can be absorbed by vegetation. These measures are also used in situations for handling runoff that may be blocked by road construction. Ditches are necessary along wide or steep stretches of road to divert water flow off the road and away from a body of water. They are ideally parabolic in shape with a rounded bottom, are of a sufficient depth, and do not exceed a depth to width ratio of 2:1. The ditch should be free of debris and covered with abundant vegetation to reduce erosion (Michaud 1992). Ditches must also be constructed of a proper soil that will not be easily eroded by the water flowing through them.

Culverts are hollow pipes that are installed beneath roads to channel water in proper drainage patterns. The most important factor to consider when installing a culvert is its size. It must be large enough to handle the expected amount of water that will pass through it during the peak flow periods of the year. If this is not the case, water will tend to flow over and around the culvert and wash out the road. This may increase the sediment load entering the lake. The culvert must be set in the ground at a 30° angle down slope with a pitch of 2 percent to 4 percent (Michaud 1992). A proper crown above the culvert is necessary to avoid creating a low center point in the culvert. The standard criteria for covering a culvert is one inch of crown for every 10 ft of culvert length (Michaud 1992). The spacing of culverts is based upon the road grade.

Diversions allow water to be channeled away from the road surface into wooded or grassy areas. These are important along sloped roads, especially those leading towards a lake. By diverting runoff into wooded or grassy areas, natural buffers are used to filter sediment and decrease the volume of water through infiltration before the it reaches the lake (Michaud 1992). Efficient installation and spacing of diversions can also reduce the use of culverts (Michaud 1992).

Maintenance is very important to keep a road in good working condition as well as to prevent it from causing problems for a lake. Over time, roads deteriorate. Problems will only become worse if

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ignored and will cost more money in the long run to repair. Roads should be periodically graded, and ditches and culverts cleaned and regularly inspected to assess any problems that may develop. Furthermore, any buildup of sediment on the sides of the road (especially berms), which prevents water from running off into the adjacent ditches, must be removed. These practices will help to preserve the water quality of a lake and improve its aesthetic value.

Agriculture and Livestock

Agriculture within a watershed can contribute to nutrient loading in a lake. Plowed fields and livestock grazing areas are potential sources of erosion, which can carry sediments and nutrients to a lake (Williams 1992). Animal wastes are also sources of excess nutrients. To minimize these problems there are ordinances that prohibit new tilling of soil and new grazing areas within 100 ft of a lake or river. However, problems can still exist in areas that were utilized for agriculture prior to the enactment of these ordinances by the State of Maine in 1990. According to the Shoreline Zoning Act, these areas can be maintained as they presently exist and therefore may result in relatively high levels of erosion and decreased water quality (MDEP 1990). Some methods to reduce erosion are to plow with the contour lines (across as opposed to up and down a slope), and to strip crop. Both solutions will reduce soil erosion and sediment deposition in the lake.

Another potential agricultural impact on water quality comes from livestock manure. Improper storage of manure may result in excess nutrient loading. Manure also becomes a problem when it is spread as a fertilizer, a common agricultural practice. Manure spreading can lead to nutrient loading, especially in winter when the ground is frozen and nutrients do not have a chance to filter into the soil. These problems become worse with the tendency to over fertilize. To help prevent these problems the state has passed zoning ordinances, which prohibit the storage of manure within 100 ft of a lake or river (MDEP 1990). Another solution is to avoid spreading manure in the winter Town may provide subsidies as an incentive if the problem is large enough. These solutions, though, do not address the problem of livestock that defecate close to water bodies. One solution for this may be to put up fences to keep the cattle away from the water.

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Runoff containing fertilizers and pesticides may also add nutrients and other pollutants to a lake. This problem can be minimized by fertilizing only during the growing season and not before storms. Pesticides can also have negative impacts on water quality. Alternative methods of pest control may be appropriate, including biological controls such as integrated pest management and inter-cropping, which is planting alternating rows of different crops in the same field.

Forestry

Forestry is another type of development that can contribute to nutrient loading through erosion and runoff. The creation of logging roads and skidder trails may direct runoff into a lake. The combination of erosion, runoff, and pathways can have a large impact on the water quality of a lake (Williams 1992). Again, there are state and municipal shoreline zoning ordinances in place to tackle these specific problems. For example, timber harvesting equipment such as skidders, cannot use streams as travel routes unless the streams are frozen and traveling on them causes no ground disturbance (MDEP 1990). Also, there is a ordinance that prohibits clear-cutting within 75 ft of the shoreline of a lake or a river running to the lake. At distances greater than 75 ft, harvest operations cannot create clear-cut openings greater than 10,000 ft² in the forest canopy, and if they exceed 500 ft², they have to be at least 100 ft apart. These regulations are intended to minimize erosion (MDEP 1990). In order for these laws to be effective they have to be enforced. This may be a difficult task for most towns since they do not have the budgets necessary to regulate these areas. Illegal forestry practices may occur and negatively impact lake water quality.

Cleared Land

Cleared land also presents potential problems of erosion and nutrient runoff especially when large areas are cleared of trees and vegetation that once acted as natural filters. Sediments from these cleared areas could create a problem if they carry large amounts of nitrogen, phosphorus, other plant nutrients, and chemicals to a lake. Without vegetation acting as a buffer, problems are made

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even worse. Since pasture land is created by the replacement of natural vegetation with forage crops, it is included in this category. Also included in this category are large grassy areas, such as lawns and parks.

The MDEP (1990) has established specific guidelines for cleared land. There can be no cleared openings greater than 250 ft² in the forest canopy within 100 ft of a lake or river. Where there are cleared lands, some solutions to minimize erosion are construction of terraces and plowing parallel to the contour lines. Both techniques decrease the flow of storm water down a slope, allowing the nutrients to settle out before they get to the lake. These two solutions also may prevent erosion by breaking up large areas of tilled soil.

Transitional Land

Before any form of development occurred in the Lake Wesserunsett watershed, the entire area was covered primarily by forest. As population increased, much of the forest surrounding the lake was cleared for agricultural, residential, industrial and recreational use. In recent years, land use has changed as some agricultural area has been allowed to revert back to forested land.

Succession is the replacement of one vegetative community by another that results in a mature and stable community referred to as a climax community (Smith and Smith 2001). An open field ecosystem moves through various successional stages before it develops into a mature forest. The earliest stages of open field succession involve the establishment of smaller trees and shrubs throughout a field (reverting land). Intermediate and later successional stages involve the growth of larger, more mature tree species. The canopy of this forest is more developed, resulting in less light reaching the forest floor. This land use type, in which a forest is nearing maturity and contains over 50 percent mature trees, is referred to as regenerating land.

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Wetlands

There are different types of wetlands that may be found in a watershed. A bog, which is dominated by sphagnum moss, sedges and spruce, has a high water table (Nebel 1987). Fens are open wetland systems that are nutrient rich and may include such species as sedges, sphagnum moss, and bladderwort. Marshes have variable water levels and may include cattails and arrowheads (Nebel 1987). Swamps are characterized by waterlogged soils and can either be of woody or shrub types, depending on the vegetation. In Maine, shrub swamps consist of alder, willow, and dogwoods while woody swamps are dominated by hemlock, red maple, and eastern white cedar (Nebel 1987). Wetlands are important because they contain a variety of animals, such as waterfowl and invertebrates (Nebel 1987).

The type of wetland and its location in a watershed are important factors when determining whether the wetland is a nutrient sink or source, either preventing nutrients from going into a lake or contributing nutrients to a lake. It is also important to note that one wetland may be both a source and a sink for different nutrients. This characteristic may vary with the season, depending on the amount of input to the wetland. Vegetation type within a wetland is important because different flora absorb different nutrients. For example, willow and birch assimilate more nitrogen and phosphorus than sedges and leatherleaf (Nebel 1987). This indicates that shrub swamps are better nutrient sinks than many other types of wetlands. When nutrient sink wetlands are located closer to the lake, the buffering capacity is greater than those located further back from the water body. Wetlands that filter out nutrients are important in controlling the water quality of a lake. These wetlands also help moderate the impact of erosion near the lake.

Although there are regulations controlling wetland use, a lack of enforcement leads to development and destruction of wetlands. These areas should be protected by the Resource Protection Districts and other means, which limit development to 250 ft away from the wetland. Due to the nature of their location, wetlands along the shoreline may be more prone to development (Nebel 1987). Therefore, the decrease of wetlands caused by development will most likely have negative effects on the water quality of a lake due to runoff, erosion, and a decrease of natural buffering.

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