In a natural process through which a lake fills in erosional substances carried by tributary streams to the lake, it would require increased productivity to help sustain life within it. The process through which the lake productivity increases as it ages is referred to eutrophication (Report on Swan Lake 4). Factors such as human influence accelerate the process, and when eutrophication becomes influenced in this manner, it is called cultural eutrophication. As a result of the human influence, the biological production of the lake finds positive impetus. However, the lake increased productivity can lead to a high rate of lake filling (Giblett 8). Despite this fact, lake aging eutrophication does not mean lake aging. In essence, eutrophication increases nutrients inputs in the lake and thus certain activities cause eutrophication. For example, lands use changes that may result in significant nutrients inputs.

According to the studies conducted by the New Hampshire, phosphorus export from agricultural land occurs five times greater than from the forested lands (Report on Swan Lake 4). In urban areas, the occurrence effect might become even greater in effect of up to ten times faster (Giblett 8). Storm-water runoff coming from developed land areas creates a major source of nutrients for lakes. Lawn and garden fertilizers, faulty septic system, washing soap, erosion, dumping and many other related activities also work to accelerate eutrophication. Eutrophication has become a global problem as aggravated by the on-going universal contamination of the lakes around the world. As a consequence, the world has seen a consistent deteriorating water body due to the stress caused by eutrophication.

Swan Lake

Swan Lake has surface area of over three thousand acres and a depth of over one hundred feet. The lake drains the Swan River watershed which delivers the mainstream flow to the lake. The lake normally empties about five times per year and contains excellent water quality and a good level of nutrients. Around the lake, several activities take place with harvest of forest and woodland products being the major land uses. The activities that undergo around the lake make it susceptible to eutrophication.

Therefore, the study seeks to determine whether Swan lake has eutrophication or not.

Like any other lake, Swan Lake watershed experiences a number of land pressures due to the above-mentioned activities around its basin. According to sedimentation analyzes conducted on the lake, the lowest mean ever recorded came between the years 1874 to 1899. The preceding years have seen sedimentation increasing consistently throughout the 90s. However, around 1930 the sedimentation effect decreased due to the low level of timber harvest during that time. In the run up to the Swan Highway construction and the renewed interest on timber harvest the sedimentation rate shot up. The increase in population and the doubled harvest on timber harvest increased the rate of sedimentation to its highest level from 1970s throughout to 1990.

According to the research by the department of environment debris and residues elements, were found within the feeder streams making the lake more susceptible to the collateral pollution (Last, Smol, & Birks 32). Accordingly, the effects have affected aquatic life within the lake. According to the report, the major source of the effect comes from urban residential developments that occur around the feeder streams and the lake itself. From the study, other activities going about the lake and its feeder streams, give a perfect atmosphere for eutrophication to occur (Report on Swan Lake 4).

Further, the analysis by ADEC in October 1996 and April 1997 on the waterfowl staging area at the Swan lake Spit shows the presence of fecal coliform bacteria. However, the cause of the bacteria does not point to human activities as other researchers have often found out. However, the level, of bacteria in the lake has not recorded any high numbers. According to the analysis, the level of bacteria stands low (Report on Swan Lake 6). The low level of bacteria shows that raw sewage do not enter the lake and if it does it does not enter in any significant amount that might negatively affect the lake. The Montana Department of Fish, Wildlife and Parks (FWP) the occurrence of non-native fish in the lake, the listing of Bull trout by the FWP as an endangered species within the lake points to eutrophication that occurs at the lake. Swan Lake has over the years considered as a stable and healthy home for the bull trout population (Last, Smol, & Birks p 48). Prior to the closure of Bigfork Dam Fish in 1993, evidence shows that the angler was caught by the FWP net survey efforts. The angler might have found its way to the Swan Lake through the Bigfork Dam fish.


Historical logging that goes around the lake contributes to low level of dissolved oxygen within the lake making the lake have high-level siltation. According to the Montana 303(d) done by the Montana Department of Environmental Quality, the lake appeared as one to the most impaired water bodies in 1996. According to the department, the impairment come from siltation, organic enrichment and dissolved oxygen. The revised version of the study in 2002, the effect downgraded to “threatened” with siltation listed as a major effect of the impairment. The organic enrichment became discarded in 2002 list as probable cause category to avoid any form of redundancy. The siltation listed in 2002 pointed to accumulation of inorganic materials and organic materials that come specifically from organic carbon to the lake bottom sediments.

There was transplanting of Mysis shrimp in the Swan Lake in 1968 and 1975 to help in providing a food source for benthic feeding fishes like the trout and kokanee salmon. The transplant proved bad for the long run safety of the lake. Mysis shrimp, when become established in the area, can affect the lake’s food web (Marinov & Brebbia 281). The introduction of the Mysis shrimp sets complex interactions with processes that advance eutrophication. Mysis selectively feeds on cladoceran zooplankton of a particular size. Through benthic feeding, it would normally stir sediments and thus stimulate the release of the phosphorous.

Eutrophication within the Swan Lake can have been evidenced by the progressive growth and encroachment of aquatic plants on recreational uses of the Swan Lake. The aquatic plant provides growth find an ample environment when the nutrients level increase to a certain level (Gilbert 89). The aquatic plant growth gives an overview of the natural aging process that the lake currently undergoes. According to the Environmental Superintendent of the City, the Swan Lake has consistently faced filling up with plant growth, organic-rich deposits and sediment from creeks that feed into the lake.

In the modern time, the advent of septic system has proved cost effective in water treatment. However, poor septic system can turn out to negatively affect the water treatment leading to eutrophication. Septic failures that might arise from several factors including, improper initial design, permeability of the soil and improper drainage can affect the water. Whenever septic system is put into place, they require regular maintenance and checking in order to ensure proper functioning and positive results (Marinov & Brebbia 283). Further, it becomes imperative to ascertain the lifespan of the system in order to avoid the system failures and eventual leaching of nutrients into the ground water.

The above discussion points to several factors that give eutrophication an ample atmosphere to thrive. As noted earlier, the Swan Lake has witnessed high productivity in terms of planktonic growth and alien species. At the same time, the natural species of the lake has faced difficulties surviving in the lake waters. Further, the extensive aquatic plant bed within the lake provides another proof that the lake undergoes the eutrophication process at a high rate than earlier anticipated. Most of the researchers have come to the conclusion that the lake bottom of the Swan contains sediments that have accumulated due to the on-going pollution, human activities, and other related factors. In addition, to strengthen the case, the lake has consistently recorded low dissolved oxygen on the bottom and as a consequence have only allowed for the adaptation of warm water fish.

Swan Lake and the contagious marshland around it have since received more attention from the Sitka District Coastal Management as Area Meriting Special Attention (AMSA). The recognition has led to several proposals that aim to enhance fisheries and recreation in and around the lake by the City and the Department of Fish and Games. Further, the renewed efforts by the locals to pick up trash, verify sanitary sewer links show some of the positive plans rolled by the local government and the local community to remedy the situation. In addition to the above initiatives, several organization and volunteers have come together to create an annual community Spring clean-up in collaboration with the local government. Therefore, despite the eutrophication that has persisted within the lake; steps that the local government, the community, and the non-governmental organization have taken can pass as a good pointer to the efforts of saving the lake.

However, much of the efforts should broaden to include other countries that share the same problem. Trans-boundary initiatives and frameworks would provide a longer lasting solution than the local initiatives since the nature of pollution, and the nature of the lake makes it difficult to limit their effect. Most water bodies locations stand either at the tropical or subtropical regions making the solving the problem through trans-boundary initiatives more effective.

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