Presentation on theme: "Saving our lakes by using wind, solar and/or electric powered water circulators."— Presentation transcript:
Saving our lakes by using wind, solar and/or electric powered water circulators
Lake eutrophication Natural and Cultural eutrophication Increase in nutrients = increase plant and animal life Once a lake becomes eutrophic, problems starts to occur, including fish kill, odors, abundant aquatic plants… algae bloom!
Aquatic plants in the littoral zone at different trophic stages of a lake
Typical results of a lake infested with milfoil Oxygen profile of Loch Garry
TSI index – Loch Garry status ParameterResults Transparency (Secchi)0,8m Chlorophyll-a 17,0 g/L Total phosphorus 0,059 mg/L or 59 g/L Oligotrophic poor in nutrients and biologically non- productive. Rich in oxygen. Mesotrophic Transition status between oligo and eutrophic. Slight oxygen depletion. Eutrophic Rich in nutrients, biologically very productive. Oxygen depletion often observed at bottom. Hyper-eutrophic Pea-soup condition; Poor water transparency less than 1m. Very low in oxygen. ParametersCarlson TSI Total Phosphorus63 Chlorophyll-a58 Secchi transparency63 MEAN : 61
Eurasian milfoil Myriophyllum spicatum is a perennial, submersed, vascular plant. The plant can grow up to 6.5 m in height and once it reaches the surface it grows laterally to form a dense canopy. The inflorescence (flower spike), usually a few inches tall, is the only part of the plant that grows out of the water. Once established, it tends to form a dense wall of vegetation.
Milfoil reproduction In the fall, the plants are reduced to root crowns, and survive winter on non-structural carbohydrate (starches and sugars) storage. The crowns sprout in the spring and develop into adult plants that flower in mid to late July. It is not uncommon to see this plant overwinter in its evergreen state, as it tends to be quiescent with little metabolic activity in northern climates. Although it produces viable seeds, its primary means of reproduction is through vegetative propagation; stolons and fragmentation, both natural and induced (accidental cuttings from animals, human activities, wave action, or other factors).
Problems associated with Eurasian milfoil Multiple species stands are important in maintaining adequate habitat for aquatic life. Fish use these types of stands as shelter and feeding grounds, as a diversity of insects and prey inhabit these areas. When M. spicatum invades these areas, the dynamic changes as M. spicatum invasions most often result in successful competition against native lake flora. Once established, M. spicatum often becomes the dominant specie, rendering the surrounding aquatic habitat inadequate for other plant or animal species, as fish rarely use dense stands of vegetation with more than 250 stems/m2. The usually dense stands of invasive plants provide healthy nesting grounds for noxious insects, such as mosquitoes that thrive in stagnant waters. Also, these monospecific stands provide poor habitat for waterfowl. Along with ecological problems that are found as a result of exotic species invasion lie economical problems. Lakes, and their surrounding properties, suffering from the intrusion of such macrophytes see their value diminish Canopies and dense stands of aquatic vegetation restrict swimming, water skiing, fishing and boating. Commercially, these macrophytes have an impact on commercial boating, power generation from hydro-electrical dams, water supplies (drainage and filtration systems), flood control and housing development since they inhibit water flow, obstruct waterways and impede upon activities.
Eurasian Milfoil control techniques Herbicides Herbicides, such as 2,4 D or Fluridone, are only a short term solution. More and more studies show that they have major negative impacts such as die-offs of native vegetation, increases in green algae and/or cyanobacteria (blue-green algae), and effects on invertebrates and fish through loss of habitat. As the plants die off, new organic matter is generated, resulting in an increase in biological oxygen demand. This demand creates a severe oxygen depletion which may cause winter and summer fish kills, toxic gas production, odours and foul taste. Although the interaction of these chemicals within the food chain and effects on humans is not fully known, many scientists are reconsidering the use of these chemicals. Even though this technique is still used in the United States, more and more Lake Conservation Associations and lake users are mobilizing to ban the usage of herbicides and are moving towards ecological means of control. We strongly discourage the use of herbicides. Algae bloom (possibly cyanobacteria) could result from the high nutrient levels made readily available following the sudden death of milfoil. Human health, aquatic ecosystem balance and the lakes overall quality could be at risk.
Weed harvesters Weed harvesters are also a short term solution. Experience acquired on many lakes has shown that the actual density of milfoil doesn’t decrease with this technique. Harvestings usually have to be done 3 to 5 times during the summer to keep the surface free of emerging stems. These costly machines (lowest price encountered was $80 000 US) are very expensive to operate.
Biological control Biological control, which involves the introduction of one species to control another, has been used in a number of cases. Since 1991, a North-American aquatic weevil (Euhrychiopsis lecontei) has been studied as a potential biological control agent for M. spicatum. This weevil, which uses the milfoil as a primary food source directly affects milfoil and is thereby species specific. Since the feeding source (sediments) of the milfoil is not affected the lake’s trophic status might deteriorate with the addition of new layers of dead milfoil at the sediment level. Therefore, oxygen consumption could increase due to higher biological activity and beneficial living aquatic organisms could be lost. No data is available to compare lakes trophic status before and after the introduction of the weevils. We believe that milfoil cannot be fully eliminated in large lakes, thus reintroduction of milfoil in treated areas is most likely probable. The cost of this technique is unusually expensive.
Water draw down This technique, usually performed during summer or just before winter, could be possible in reservoirs. By drying out the littoral zone of the lake or by bringing down the water level in order to eliminate the plants by freezing, milfoil (and most aquatic plants) could be controlled in shallow areas. But because reservoirs are also the water source for the towns, we believe that this technique cannot be considered in many cases for the following reasons: Reduction of total water volume could result in water shortage While using this technique, oxygen levels might decrease to anoxic levels due to the decomposition of a large volume of organic matter (dead plants and aquatic organisms) Native aquatic plants, needed to colonize the lake, will also be reduced or eliminated Reduction and/or elimination of fish habitat will result in the loss of many fish species Reduction and/or elimination of invertebrates that are part of a balanced aquatic ecosystem In a eutrophic lake, the addition of nutrients through decomposition might create other problems such as major algae blooms and might deteriorate a lake to the point of making it reach rapidly the hyper-eutrophic status
Solutions Electric, Wind and Solar powered water circulators
Water aerators/circulators This technique has shown to be in accordance with every ecological principle that is known and that must be considered in any lake restoration program. oxygen = animal life = diversity of aquatic organisms = balance in aquatic ecosystem = control of Eurasian milfoil overgrowth Most importantly, this technique is not just specific to milfoil control (as with many other techniques) it reverses the overall eutrophication process of a lake. Through this process, weeds, algae and organic matter become an available source of nutrients primarily for animals (as opposed to plants), including fish. The primary energy source in a lake no longer benefits mostly plant life, but is distributed more uniformly throughout a balanced aquatic food chain.
Given that milfoil spreads via fragments, to what extent does the action of the impeller create fragments that can spread by laminar flow? If the water circulators are installed during the summer (when the milfoil stems have reached the near surface) a negligible amount of fragments could be produced. Motorboats and vegetative fragmentation will create more fragments than a water circulator. We have seen lakes where motorboats are prohibited that became completely infested with milfoil within a period of less than 3 years. Natural reproduction of milfoil by vegetative fragmentation is an unsolvable problem for lake managers that want to control milfoil propagation once the plant is established. Actually, the risk of milfoil propagation is greatly reduced with water circulators. We have observed in most cases a drastic drop in milfoil density and total length of stems around the water circulators. The return of oxygen recreates a favourable environment for competition at the sediment level for the same source of nutrients (through bacterial and invertebrate activity) and a reduction of available nutrients through oxidation.
Oxygen/temperature Taken from a lake that also has a maximum depth of 80 feet. In milfoil stand without circulators In milfoil stand with circulators During summer, high water temperatures measured at the surface of a milfoil stand will promote multiple periods of flowering and fragmentation. Example: On July 31st 2005, the surface temperature in this milfoil stand at Loch Garry went up to 31oC, thus promoting flowering and fragmentation. At this same site, 1.5m below the water surface, the water temperature was only 23 oC. An ascending water flow, created by wind or solar powered circulators, will prevent extreme water temperatures, therefore limiting the number of flowering periods in a given summer.
Does photosynthesis, induced by creating an ice-free (and snow) area during winter, influence milfoil? Wisconsin DNR describes Eurasian Water Milfoil as being opportunistic since it is adapted for rapid growth early in spring. Stolons, lower stems, and roots persist over winter and store the carbohydrates that help milfoil claim the water column early in spring, photosynthesize, divide, and form a dense leaf canopy that shades out native aquatic plants. Its ability to spread rapidly by fragmentation and effectively block out sunlight needed for native plant growth often results in monotypic stands. We believe that, by creating open areas during winter, photosynthesis continues to occur. This, with a combination of control factors (temperature, oxygen, water movement, reduction of nutrient level) will oblige the plant to use up some of its stored carbohydrates. Come spring, milfoil growth would then occur at a slow pace, allowing competition between milfoil and native plants.
What are the impacts on other aquatic plant species? The impacts are variable. From our observations, sites that offered a thin sediment layer (3-6 inch) came back to their original sandy bottom, colonized by species usually found in oligotrophic lakes (such as Eriocolon septangulare) or not colonized at all due to an insufficient amount of nutrients for plant survival. In areas with thicker sediment layers, we found a variety of Pondweeds, Vallisnerias and Canada Waterweed, but not in dense formations usually encountered in eutrophic lakes. The new plant community is always in low density and size (or length) when using this technique. We would think that openings in milfoil stands would create opportunities for other invasive species to take over, but since this technology is not specific to a particular plant specie but mostly on what they thrive upon (nutrients), it is the overall trophic status of the lake that is being reversed (what is referred to as induced oligotrophication of a lake).
Oligotrophic Mesotrophic Eutrophic Hyper- eutrophic Lake Echo in a natural state Lake Echo trophic status with todays nutrient inputs from watershed Total phosphorus before (1998) and after using wind powered water circulators (1999 to 2003). 2003 1999/2001 2000 1998
Before and After at Lake Schryer, (Montpellier,Quebec)
Which model to use and how many water circulators? We have used in the past 1 water circulator per 1 to 7 hectare (2,5 to 17acres). Depends on depth, application (algae or plant control), nutrient levels, average wind speed, etc… Our new wind powered water circulator, specially designed for lakes exposed to high winds