Management Recommendations for
Loch Erin
Lenawee County, Michigan
1996
Aquest Corporation
5212 Berneda Drive
Flint, Ml 48596
Contents
Introduction …………………………………………………………… 2
Eutrophication …………………………………………………….. 2
Water Quality Concerns in Lakes …………………………………. 3
Improving Water Quality ………………………………………………. 4
Aquatic Plant Problems ………………………………………………. 4
Description of Loch Erin ………………………………………………. 6
1996 Sampling Program …………………………………………… 6
Results and Interpretation …………………………………………… 7
1996 Water Quality Results …………………………………… 7
Trophic State Index …………………………………………… 10
Aquatic Plants in Loch Erin …………………………………… 11
Erosion Problems in Loch Erin …………………………………… 11
Conclusions & Recommendations …………………………………… 12
Areas of Concern …………………………………………………… 12
Specific Recommendations: …………………………………… 13
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Introduction
Eutrophication
Eutrophication refers to the natural process whereby lakes slowly become increasingly productive of plant, algae, microbe and animal life. Eventually, a lake will fill in with debris, sediments, and decaying plants and animals and become a wetland or even a meadow. Although it is natural for lakes to undergo eutrophication, human activities can greatly accelerate the process, causing premature aging. For this reason, the eutrophication rate of lakes is a key consideration and an important basis for lake management planning.
Lakes that have been little affected by eutrophication are called oligotrophic lakes. Oligotrophic lakes have clean, clear water with few algae. Addition of nutrients (fertilizers) to oligotrophic lakes causes algae to increase. When nutrient levels become sufficiently high, algal blooms frequently turn the water green and cloudy and the lake is said to be eutrophic. Mesotrophic lakes have characteristics intermediate between oligotrophic lakes and eutrophic lakes. Lakes characterized by extremely high nutrient concentrations and severe algal blooms are called hypereutrophic lakes. Lakes of different trophic statuses also differ in many other characteristics (see the attached sheet on "The Trophic Spectrum").
Although increased algal growth supports increased growth of other organisms in eutrophic lakes, including sport fish and fish-food organisms, eutrophication is usually considered undesirable. Most Lake Residents prefer the cleaner, clearer water of oligotrophic lakes. Fish production is commonly higher in eutrophic lakes. These productive lakes often support excellent bass and panfish fisheries. Fish kills occur in some severely eutrophic (hypereutrophic) lakes, when dissolved oxygen in the water becomes depleted by the decomposition of dead algae and other materials. Blooms of blue green algae in eutrophic and hypereutrophic lakes can cause fish to have an unpleasant odor and taste. Blooms of toxic blue-green algae can cause problems for swimmers and for animals that drink algae-filled water.
The "fuel" for eutrophication is usually phosphorus. Phosphorus is an essential element or nutrient for plant and algae production. Relative to other plant and algae nutrients, it is usually found in the shortest supply and is the most Limiting. Consequently, efforts to slow or reverse eutrophication typically concentrate on reducing the availability of phosphorus. There are a variety of phosphorus control techniques that can be used to slow or reverse eutrophication of lakes. Some seek to control phosphorus inputs from out-side the lake, while others make phosphorus already in the lake less available for algal growth.
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Water Quality Concerns in Lakes
Poor Water Clarity
Poor water clarity is primarily an aesthetic problem, although it can sometimes be a safety issue or contribute to other lake management problems. Poor water clarity makes water appear turbid (muddy). Turbid water favors the growth of nuisance rooted plants, such Eurasian watermilfoil, over more desirable native plant species. Water clarity problems can result from dense growth of microscopic suspended algae (phytoplankton), from eroded soils in runoff, or from bottom sediments resuspended by wind, waves or boats.
Blue Green Algae
Blue green algal blooms are a particularly serious problem for lakes. Bloom-forming blue green algae float and often produce extremely dense masses of algae, frequently resembling split-pea soup. Dying blooms stink, and often release pigments that look like oil slicks. Decomposition of dense algal blooms can lead to dissolved oxygen depletion. High densities of certain common bloom-forming blue greens can become toxic, posing a hazard to swimmers and to livestock and pets that may drink them. Total phosphorus, pH and alkalinity measurements help to identify factors that contribute to blooms of blue green algae. Remediation of blue green algae problems may consists of either measures to reduce productivity of all algae, usually by reducing phosphorus availability, or measures to favor other algae over blue green species.
Low Dissolved Oxygen Concentrations
Low dissolved oxygen concentrations pose a threat to aquatic life. Depleted dissolved oxygen in deep waters is a frequent consequence of eutrophication. Loss of oxygen from bottom waters makes lakes unsuitable for cold-water fish species (salmonids, cisco, etc.) and leads to processes that further promote eutrophication. Depletion of oxygen from surface waters can eliminate most or all fish species and many types of invertebrates. Low oxygen concentrations result from the consumption of oxygen, which can be caused by such materials as decomposing algae, resuspended anoxic sediments, materials in runoff, and discharges of untreated sewage or certain industrial wastes.
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Bacterial Contamination
Bacterial contamination results in conditions that are unsafe for swimming and other body-contact recreation. Bacterial contamination problems nearly always result from contamination of the water by fecal material from humans or animals. The indicator bacteria used to detect contamination are common inhabitants of animal digestive tracts. Contamination from human sources usually results from failed or inadequately designed septic systems. High densities of geese and other waterfowl can also contribute to bacterial contamination. Remediation of bacterial problems usually consists of removing the source of contamination.
Improving Water Quality
The potential for water quality improvement differs greatly between lakes. Relatively dramatic improvements are attainable in some lakes if the correct management actions are taken. Selecting the correct technique requires a careful analysis of the characteristics of the individual water body. The specific problem, and the causes of the problem, must be identified before appropriate corrective measures can be selected. There is no single management approach that works for every lake. For example, replacing septic systems with sewers is a highly successful technique for managing some types of lakes, but not for others. Unfortunately, there are a few lakes that are unlikely to respond to any known techniques for improving water quality.
Aquatic Plant Problems
Many midwestern lakes have problems with excessive growth of rooted aquatic plants. In moderate amounts, aquatic plants provide many benefits to lakes. Rooted plants (macrophytes) provide structure necessary for the fishery and help to stabilize sediments, thereby reducing resuspension of sediments and recycling of nutrients in shallow parts of the lake. Dense plant growth near the lake bottom causes few problems, but when plants grow densely to and along the water surface they interfere with boating, swimming, water skiing, fishing and other forms of recreation. Widespread dense plant growth throughout the water column can contribute to fisheries composed of stunted panfish, by providing such dense cover that it is difficult for sport fish (i.e., bass) to capture smaller prey fish.
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Many factors contribute to aquatic plant problems, but the most important ones are (1) invasion by exotic plants, and (2) accumulation of nutrient-rich sediments. Exotic aquatic plants (i.e., plants that do not naturally occur in this area) often produce particularly severe problems. Exotic species, such as Eurasian watermilfoil (Myriophyllwn spicatum L.) and curly leaf pondweed (Potamgeton crispus L.), expand rapidly to replace native vegetation and form dense monospecific beds. Compared with most native aquatic plants, these exotic species concentrate their stems and leaves at the water surface. Thus they interfere with recreation to a much greater degree than comparable quantities of native plants. Not all lakes are equally likely to be severely affected by exotics: lakes with highly developed shorelines and those used intensely for recreation are most susceptible.
Most aquatic plants are rooted and typically derive essential limiting plant nutrients from the sediments. In lakes with sediment too nutrient poor to support much plant growth, a variety of techniques can be used to prevent the accumulation of nutrients. In general, the same measures used to prevent cultural eutrophication can reduce sediment accumulation. Many lakes in southern Michigan have probably always had fertile sediments. Reservoirs, in particular, often have sediments that are relatively nutrient rich due to their origin as terrestrial soils. Once sediments have become sufficiently nutrient rich to support luxuriant plant growth, there is little likelihood that any lake management technique will be able to remove enough nutrients to restrict plant growth.
The need to manage aquatic vegetation arises when vegetation cover and biomass become sufficiently high to disrupt the natural balance of a lake and interfere with recreation. Excessive growth of aquatic plants interferes with nearly all forms of recreation and causes many biological problems. Dense plant growth at the water surface impedes exchange of gases between the air and water, thereby contributing to nighttime dissolved oxygen depletion and large daily pH fluctuations, conditions which are detrimental to fish and other aquatic life. Production of desirable sport fish (e.g., largemouth bass) is maximal at intermediate levels of plant cover and biomass. Excessive plant cover makes it difficult for larger fish to capture smaller food fish, which can lead to reduced production of larger piscivorous fish and to stunted populations of small forage fish.
Management of problem aquatic plant growth should be carried out in such a way as to preserve desirable aquatic vegetation. Selective techniques control problem species with minimal effect on desirable ones. Desirable vegetation can also be preserved by limiting the application of control techniques to areas where they are needed. In general, some areas in every lake should be set aside for little or no management in order to preserve species that are sensitive even to selective controls.
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Description of Loch Erin
Loch Erin is a 605-acre impoundment in Lenawee County, Michigan. Wolf Creek, Onsted Creek and Geddes Creek contribute water to the lake. Wolf Creek is the largest tributary to the lake, and contributes the greatest quantity of water to the lake. The lake drains over a concrete spillway into the continuation of Wolf Creek.
1996 Sampling Program
During 1996, water Samples were collected from 6 locations on 2 dates. Water sample locations are shown in Figure 1. Samples were collected on May 16 and September 4, 1996. Weather conditions were recorded on each sampling date. The Secchi disk depth (a measure of
Figure 1. Water quality and bacteria sampling locations.
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water clarity) was measured at each location. Water temperature and dissolved oxygen (concentration and percent saturation) were measured at the surface and just above the bottom. A sample of the surface water was collected from each location and returned to the laboratory for measurement of pH, alkalinity, conductivity, total dissolved solids, turbidity and total phosphorus. Samples for bacteria (E. coli) counts were collected on September 4, 1996 from six locations (see Figure 1). Bacterial samples were evaluated to determine the safety of the lake for body contact recreation (e.g., swimming); thus these samples were collected near shore, usually between the shore and swimming rafts.
Results and Interpretation
1996 Water Quality Results
Tables of water quality data for 1996 are appended to the back of this report. A guide to
Interpreting water quality measurements is also attached.
Temperature
Surface temperatures ranged from 12.7 to 25.5'C (55 to 78'F). Surface temperatures at all stations were similar. The lake was essentially unstratified, even at the Deep Hole Site (Site 3), due to the shallowness and size of the lake.
Temperature values indicate: normal seasonal temperature changes, no vertical
stratification.
Dissolved Oxygen
Surface and bottom water were well oxygenated (>85% saturated) in May at most locations. Exceptions were the bottom water in Bay "X' and the Deep Hole, which were slightly less oxygenated, and Geddes Creek, where the surface and bottom waters were both well below saturation (71 and 56%, respectively). Moderately low dissolved oxygen concentrations in Geddes Creek probably reflected the input of organic matter or other materials that consume oxygen from the creek. None of the May values was low enough to be a cause for concern.
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In September, dissolved oxygen concentrations were near saturation in Onsted Bay, Drive "N' Bay and Geddes Creek, and lower elsewhere. The concentrations in the Deep Hole and Limerick Bay sites were high enough to support aquatic life, but not by a large margin. Dissolved oxygen was almost totally depleted in Goose Bay, even at the surface, leading to conditions that would not support most aquatic life. Since the condition was localized, more mobile organisms (e.g., fish) were probably able to avoid the ill effects of depleted oxygen by moving out of the area. The cause of low oxygen levels is unknown. Depletion of dissolved oxygen from the entire water column typically occurs due to either: (1) an influx of oxygen consuming material (e.g., decomposable organic matter), or (2) conditions that reduce oxygen production by algae.
Determining the duration of low oxygen concentrations should be a top priority for future water quality monitoring. If oxygen depletion is infrequent, no further action may be necessary. If depleted dissolved oxygen is a frequent condition, it may be desirable to identify the specific cause and consider possible remedial measures.
Dissolved oxygen values indicate: Substantial algal production, sufficient oxygen for aquatic life in surface waters in most locations. Moderately low dissolved oxygen in Limerick Bay and Deep Hole sites. Depleted dissolved oxygen in Goose Bay during September is a cause for concern.
Secchi Disk Depths and Turbidity Measurements
Water clarity in Loch Erin was uniformly poor in May, as indicated by Secchi disk depths of only 0.45 to 0.7 meters. The May sample was taken at a time when the lake level was very high due to runoff from recent spring rains. Turbidity measurements at this time were very high, indicating high concentrations of suspended material,. Water clarity was slightly better in September, when Secchi disk depths ranged from 0.8 to 1.5 meters. Turbidity measurements indicated correspondingly lower concentrations of suspended material. Better than average water clarity in Limerick Bay and Goose Bay at the time of the September sample suggests that oxygen depletion probably resulted from an input of dissolved material or an algal inhibitor, rather than from an influx of suspended materials. Algal bloom conditions were noted only at the Geddes Creek location in September. Otherwise, poor water clarity is more the result of suspended sediments than algae. Likely sources of suspended sediments include bank erosion, sediment loading from tributaries, and resuspension of bottom sediments.
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Secchi disk depths and turbidity measurements indicate: Poor water clarity throughout
the lake, probably due primarily to suspended sediments.
Alkalinity and pH
Alkalinity and pH values were within normal ranges for a moderately alkaline (hard water) lake. Alkalinity values ranged from 159 to 191 mg CaCO3/L. Values of pH ranged from 7.7 to 8.4. Values of pH and alkalinity from most in-lake locations were similar to one another. In September the pH in Goose Bay was slightly lower than at other sites, which suggests that microbial respiration probably contributed to dissolved oxygen depletion in the Bay.
For temperatures above 20'C, free carbon dioxide (CO2) concentrations were calculated from pH and alkalinity measurements to provide an index of whether C02 depletion may be facilitating dominance by blue-green algae. Free carbon dioxide concentrations were well above the threshold for carbon-dioxide limitation (approximately 13 µmoles/L).
Alkalinity and pH values indicate: Loch Erin is a moderately alkaline, hard lake water.
Free carbon dioxide levels indicate little possibility of carbon-dioxide limitation of algae.
Conductivity and total dissolved solids
Conductivity and total dissolved solids values ranged from 425 to 480 µS/cm and 305 to 344 PPM, respectively. These values are moderate for a productive lake in southern Michigan. Differences between sites were insignificant.
Conductivity and total dissolved solids values indicate: moderate content of
dissolved materials in water.
Total Phosphorus
Total phosphorus (TP) concentrations ranged from 0.020 to 0.041 mg P/L. Total phosphorus levels at sites I through 5 were very similar. Phosphorus concentrations in Geddes Creek were consistently lower than at other locations, whereas those in Limerick Bay and Goose Bay were
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higher. Apparently there are sources of phosphorus loading to Limerick Bay and Goose Bay that are sufficient to result in elevated phosphorus concentrations in these embayments. Since no tributaries enter these embayments, likely phosphorus sources are runoff from the immediate drainage area of the lake or internal phosphorus recycling (ie., release from sediments).
Total phosphorus measurements indicate: Moderate phosphorus concentrations, relatively low phosphorus concentrations in Geddes Creek, higher concentrations indicate significant phosphorus loading to Limerick Bay and Goose Bay.
Bacteriological Analysis
Bacterial counts (E. coli) taken immediately after the Labor Day holiday were below the detection limit (4 CFU/100 mL) at all locations. Based on these measurements the lake was safe for body contact recreation at all locations.
E. coli measurements indicate: no evidence of bacterial contamination at any site.
Trophic State Index
Based on the late-summer (September) Secchi disk depth at the Deep Hole Site, Carlson's Trophic State Index for Loch Erin is 53. Carlson's Index ranks lakes from I to 100 based on how eutrophic they are. The value of 53 classifies Loch Erin as a moderately eutrophic lake. Summer total phosphorus concentrations of 0.025 to 0.026 mg P/L yield a trophic state index of 47, which classifies Loch Erin as a mesotrophic lake just below the eutrophic threshold. When the trophic index based on Secchi disk is larger than that based on total phosphorus, it usually indicates that non-algal material is contributing significantly to poor water clarity. In this case, trophic indices based on Secchi disk depth overestimate the actual degree of eutrophication. Common sources of non-algal turbidity are eroded soils in runoff and bottom sediments resuspended by wind, waves or boats. In Loch Erin, Secchi disk depths indicate poor water clarity at all shallow stations and exhibit several different seasonal patterns, suggesting several independent sources of turbidity.
Trophic State measurements indicate: Loch Erin is meso-eutrophic. Non-algal sources of
turbidity contribute significantly to poor water clarity.
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Aquatic Plants in Loch Erin
Loch Erin currently supports relatively
Few species of submersed aquatic plants
and relatively little aquatic plant growth.
Aquatic plant surverys in May and
September found only five aquatic plant
Species (Table 1). Relatively little area was
occupied by aquatic plants. In May curly leaf pondweed was locally dense, particularly in Wexford Bay and Limerick Bay, but covered only a relatively small fraction of the shallows of the lake. The only other aquatic vegetation encountered in May was a small patch of water smartweed found on the eastern side of Limerick Bay. In September, the smartweed remained, and small amounts of curly leaf pondweed, coontail and water lilies were found near the mouth of Wolf Creek.
Poor water clarity currently limits the abundance and production of submersed plants in Loch Erin. Although this reduces the need for aquatic plant control, it also favors canopy-forming nuisance species, such as Eurasian watermilfoil and curly leaf pondweed. Given the aggressive nature of curly leaf pondweed and its tolerance for poor water clarity, its distribution can be expected to expand considerably in the future. Improvements in water clarity would favor more desirable plant species, but would also allow plant growth over a much larger fraction of the lake. Planting of native plant species could help to slow the spread of exotic aquatic plants, including curly leaf pondweed, but: (1) it would be difficult to establish desirable plant species under current turbid conditions, and (2) lake residents are likely to view increased plant growth, even of native species, as undesirable. As no long-term control techniques for curly leaf pondweed currently exist, it is probably desirable to continue using current short-term management practices to control curly leaf pondweed growth where it interferes with recreation. Should other management efforts improve water clarity or exotic plants become widespread in Loch Erin (so that residents would be willing to accept native plants in lieu of exotics) planting of native aquatic plants may be desirable.
Erosion Problems in Loch Erin
Bank erosion is a major problem in Loch Erin. Fine textured, easily-eroded soils, relatively long wind fetches and wintertime ice scour have led to severe bank erosion in many locations around the lake. Shoreline erosion adds to the poor water clarity in the lake and contributes
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sediments that accumulate in the deeper portions of the lake, reducing lake depth and adding to the potential habitat for aquatic plants.
The most serious erosion problems occurred in the southeastern arm of the lake, particularly along undeveloped shorelines. An attempt to control erosion by planting herbaceous marsh vegetation near the outlet structure to had failed. While better planting techniques might improve the success of such efforts, the energy regime in most parts of Loch Erin is probably too great for herbaceous plantings. Planting of woody vegetation, such as shrubby willows, has a much greater likelihood of success. A technique such as brush mattressing (description included with report) that can successfully establish woody vegetation in relatively high energy environments is recommended for Loch Erin. The cost of such techniques is low, provided that volunteer labor is used.
Failure of armored shorelines was also evident in a number of locations. Some of the failures appeared to be the result of designs inadequate for the energy regime. The Loch Erin LEPOA may wish to develop guidelines that promote durable shoreline protection. Rip-rap guidelines should address such things as slope angles, rip-rap size, and the use of infiltration barriers. Seawall guidelines should recommend depth of penetration into the substrate and appropriate toe protection.
Conclusions & Recommendations
Loch Erin is a shallow, turbid impoundment. Water clarity is poor, but much of the turbidity comes from suspended sediments rather than algae. Algae blooms are apparently not widespread, as algal bloom conditions were noted in only one location. Aquatic plant coverage and diversity are low, although curly leaf pondweed causes localized problems in the Spring. As this plant species spreads, aquatic plant problems will increase. Current problem areas are listed below.
Areas of Concern
Depletion of dissolved oxygen in Goose Bay. This phenomenon is an indicator of pollution or severe eutrophication and should be closely monitored. Determining the duration and extent of dissolved oxygen depletion should be a high priority for future monitoring.
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Severe Bank Erosion. Severe bank erosion exists at many locations around the shoreline of Loch Erin. Erosion contributes to poor water clarity, moves nutrients and sediments into the lake, and, in some areas, threatens roads or other structures.
Elevated Phosphorus Concentrations in Limerick Bay and Goose Bay. Elevated phosphorus concentrations in Limerick and Goose Bays indicate significant local sources of phosphorus. Continued unabated, these inputs may accelerate eutrophication in the associated bays, producing some or all of the impacts associated with advancing eutrophication. Efforts to identify and reduce phosphorus inputs from the immediate watershed of these embayments would be desirable.
Potential invasion by Eurasian watermilfoil or Zebra Mussels. Invasion of Loch Erin by Eurasian waterrnilfoil or zebra mussels would create serious problems for the lake. Conditions in the lake are well suited to the growth of Eurasian watermilfoil. If it invades the lake it will greatly increase aquatic plant problems and the cost of aquatic plant control. It is not equally clear that the lake would provide a good environmental for zebra mussels, but if they were to become established they would probably exacerbate existing lake management problems. Increased water clarity due to zebra mussels would allow the abundance of aquatic plants to expand greatly, and selective effects on the algal community would likely lead to problematic blooms of blue green algae. Efforts should be made to educate lake residents about the risks posed by these organisms and to encourage the thorough cleaning of boats and trailers to prevent their introduction.
Specific Recommendations:
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is also recommended. Given the energy regime of the Loch Erin shore, a technique such as brush mattressing is recommended. Detailed instructions for installing brush mattressing are provided with this report.