Tahoe Divers Conservancy

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A review of the threats to Lake Tahoe from aquatic invasive species.

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Tahoe Divers Conservancy

  1. 1. Tahoe Divers Conservancy Lake Tahoe Aquatic Invasive Weeds Report
  2. 3. Invasive Aquatic Weed Survey and Removal Project <ul><li>Most boaters and recreationists have by now heard of Eurasian watermilfoil , an aggressive and invasive aquatic weed that is spreading around Lake Tahoe’s shoreline and now into the Truckee River. </li></ul><ul><li>This invasive weed grows very quickly, forming dense mats of vegetation that restrict boating, swimming, fishing, and water skiing. It also competes aggressively with native aquatic plants and degrades water quality and aquatic habitats. </li></ul><ul><li>To compound the problem, this aquatic weed is difficult to control. While there are a variety of methods available, including mechanical harvesting, insect bio-controls, drying and/or freezing the water body, and chemical control, no single method will do the job in Lake Tahoe. Mechanical harvesting, most commonly used by local marinas, actually helps spread the weed by releasing plant fragments that float away and establish new populations in nearby marinas and beaches. </li></ul><ul><li>In an effort to remove Eurasian watermilfoil from Lake Tahoe and the Truckee River watershed, the Tahoe Divers Conservancy will train divers to identify, survey, and hand-remove the aquatic weed. Hand–removal is somewhat labor intensive, but is very effective at removing the plant by the roots, reducing the spread by plant fragments, and minimizing disturbance to the lakebed. Project start date was set for Fall 2006. </li></ul>
  3. 4. <ul><li>Until 1994, no surveys for rooted aquatic macrophytes had been conducted, particularly with a goal of documenting the presence of non-native species. Early reports (1975) of Watermilfoil species near Taylor Creek did not identify the species of Myriophyllum, nor were vouchers or photographic records made. </li></ul><ul><li>However, severe impacts from aquatic plants were observed in the Tahoe Keys by the end of the 1970’s and early 1980’s, during which time mechanical harvesting was begun. The US Department of Agriculture/ Agricultural Research Service conducted surveys periodically from 1995 to 2006 (Anderson and Spencer 1995; Anderson and Spencer 1996; Anderson 1997). The most recent USDA-ARS survey of the entire 72 mile lake shoreline was completed in the fall, 2006. Specimen vouchers were made and all locations are geo-referenced. </li></ul>
  4. 5. Near the Tahoe City Dam
  5. 6. Area around outlet
  6. 7. Taylor Creek Marsh
  7. 8. East Shore – Marla Bay
  8. 9. 2006-2007 Work Program <ul><li>The Tahoe Divers Conservancy members recognize that invasive weed infestations occur within the Lake Tahoe basin that reduce the biological, recreational and economical value of the land and have a negative impact upon the environment by suppressing native plant species. A coordinated approach to identifying sites, developing responses and educating the public will result in a more effective effort to reduce or eliminate invasive weed infestations. Responses to invasive weed infestations may include mechanical, biological, chemical and/or cultural control methods that could minimize further invasive weed infestations in the Lake Tahoe basin. </li></ul><ul><li>Accomplishing the above goals will require the following: </li></ul><ul><li>1. EDUCATION : Increase public and staff awareness of invasive weeds. </li></ul><ul><li>2. EXCLUSION : Exclude invasive weeds from the Lake Tahoe basin. </li></ul><ul><li>3. PREVENTION : Prevent the establishment of new invasive weed infestations and spread of existing invasive weed infestations. </li></ul><ul><li>4. CONTROL : Promote the effective management or eradication of designated weeds. </li></ul><ul><li>5. INFORMATION EXCHANGE : Share technical information regarding control methods, locations, new infestations, project success amongst parties and with other regional and local weed management areas. </li></ul><ul><li>6. COOPERATION : Facilitate development of cooperative agreements for local weed management areas which include opportunities for shared funding sources, resources, materials, personnel including volunteers, expertise, equipment, etc. </li></ul>
  9. 10. DESCRIPTION OF METHOD <ul><li>Diver hand-pulled removal assisted by vacuum suction removal involves an underwater diver pulling the plant out by the roots, then ‘feeding’ it into a 3-6” intake suction hose that transfers the entire plant and associated water up to the water surface to a screen or collection box attached to the side of the workboat. The dredge engine is usually a 5 to 8 horsepower Honda or Briggs & Stratton. Sediment type, visibility, and thoroughness in removal of the entire plant, particularly the roots, affect the speed at which plants are uprooted. The screen/basket separates the pulled plant material from the associated water, which then passes back into the water column. The plant material is retained on the screen and, after a threshold amount builds up, is conveyed onto an approved on-shore dry disposal area. </li></ul>
  10. 11. Underwater Visual Identification
  11. 12. FLOW CHART AND RATING Proximity of other milfoil infestations (within 50 miles) Bottom is mud or silt Draw down <10’ Plant life on the bottom? Go through Lower Priority Rating Process No No No No Yes Yes Yes Yes Go to Top Priority Rating Process Waterway is navigable, or used by boats, or has homes, or open to the public
  12. 13. Work Program Specifics I. Site Preparation: Survey, Water Quality Measurement, Disposal Site Selection <ul><li>All divers shall ensure their equipment is thoroughly clean before entering the Lake, and that all equipment under their responsibility is cleaned after the end of the fieldwork before moving it from the project or Lake area. </li></ul><ul><li>Before removing any EWM, divers will conduct an underwater survey of Emerald Bay to: </li></ul><ul><li>Determine the aerial extent, density and volume of EWM targeted for removal, noting locations of EWM plants that are flowering or seeding; </li></ul><ul><li>Identify other aquatic plants present and their locations; </li></ul>
  13. 14. Curlyleaf Pondweed <ul><li>The Curlyleaf pondweed ( Potamogeton crispus ) is an aquatic plant with blue-green leaves that attach to spaghetti-like stems which produce small flowers that rise a few inches above the surface of the water . Considered a deep water plant (up to 30 feet), it often colonizes in shallows. The plant can tolerate extreme low-light conditions and cold water temperatures. It grows actively in winter months, reaches maximum density in late spring, and dies back in mid-summer. It can reproduce by seed, but primary reproductive means is through turions [i ] , which are produced in late spring, and by rhizomes [ii ] . Turions remain dormant in the sediment through summer until cooling water temperatures trigger germination in the fall. </li></ul><ul><li>[1] Turion- a swollen bud of many water plants that contains stored food. It becomes detached from the parent plant, enabling to survive the winter. </li></ul><ul><li>2 Rhizome- a horizontal underground stem, with leaves and buds, that serves as a storage organ </li></ul>
  14. 15. Eurasian Watermilfoil (Myriophyllum spicatum ) <ul><li>The Eurasian watermilfoil ( Myriophyllum spicatum ) is an aquatic plant species that forms in ponds and lakes in both shallow and deep water environments up to about 30 feet. </li></ul><ul><li>It requires stagnant to slow moving water to thrive but can also tolerate brackish water. The plant is rooted in bottom sediments and grows to the surface, usually 3-10 feet and up to 30 feet. </li></ul><ul><li>It forms dense mats of bright green, feathery leaves at the water surface which restrict light to the below water environment and restrict waterways. It thrives in areas that have been subjected to various natural and manmade disturbances that have threatened native species and therefore allow space for the plant to colonize. It does not spread rapidly to areas where natives plants are well established. The plant reproduces primarily by rhizomes and fragments. </li></ul>
  15. 16. Pathways of Plant Introduction <ul><li>The Eurasian watermilfoil ( Myriophyllum spicatum ) and Curlyleaf Pondweed ( Potamogeton crispus) is likely introduced to the Lake Tahoe Basin by boats, trailers, personal watercraft, contaminated construction equipment and to a lesser extent improper disposal of personal fish/plant aquariums. </li></ul><ul><li>From: WORKPLAN SPECIFICATIONS FOR PROPOSALS TO CONDUCT A FEASIBILITY STUDY FOR VARIOUS MANAGEMENT OPTIONS OF INVASIVE AQUATIC WEEDS, LAKE TAHOE, CALIFORNIA & NEVADA - Prepared For: Department of the Army, United States Army Corps of Engineers, Sacramento District </li></ul>
  16. 17. Effectiveness and Duration <ul><li>Diver hand-pulling, assisted by vacuum suction removal, can be highly effective under appropriate conditions. Removal efficiency depends on sediment condition, density of aquatic plants, and underwater visibility. This technique works well to control early low-level infestations of EWM or other aquatic weed species. </li></ul><ul><li>This technique immediately clears the water column of nuisance plants and is site and species specific. A high degree of control, lasting more than one season, is possible when complete removal has been achieved. It is most useful in hard-to-reach places and in sensitive areas where disruption of sediments must be minimized. Plant parts are collected for later disposal, minimizing the spread of fragments, important for milfoil control. The vacuum assistance helps a diver cover a much larger area than ‘unassisted’ hand-pulling, and works well in soft sediments. Potential turbidity increases and bottom disruption depend on hydrosoil structure, and are usually confined and short-term. </li></ul>
  17. 18. Regional Transport Perspective
  18. 19. Physical Control <ul><li>Hand-harvesting with divers and rake-harvesting are viable options for eliminating smaller populations of invasive aquatic weeds. The use of water level alterations, shade barriers, bottom barriers and suspended blocking have been used to some extent at Lake Tahoe and in other areas to control invasive aquatic weed populations. </li></ul><ul><li>From the diver’s perspective in working on both sites in 2006, we have found that we can be very effective with hand removal. It doesn’t disturb the bottom substrate as much as we thought it would. The turbidity that we create by pulling the roots is very little compared to the turbidity we create just with our fin motion on the bottom. </li></ul><ul><li>The effectiveness of hand-harvesting physical control has shown to have little if no potential effects on other Lake species or the lake bottom. Diver’s are most effective at the hand-harvesting when we can place approximately 10 pounds of debris in each goodie bag. Without constant surfacing, divers can pile the bags into one or several areas on the lake bottom and then retrieve them with a float bag at one time to haul them onto a vessel </li></ul>
  19. 20. II. Diver-Assisted Hand Removal <ul><li>Divers will remove as much EWM biomass as possible within the designated time in a manner that will minimize escape of fragments during initial collection, and dedicate time to gather the majority of floating fragments, as reasonably practicable before the close of each day’s removal operation. </li></ul><ul><li>Divers will assist in tracking effort, including recording the estimated volume of haul-out. Disposal refuse site will weigh each load taken from the transfer site, and relay weights to contracting agency within one day after disposal. </li></ul><ul><li>Turbidity will be monitored by designated staff pre-, during, and post-project removal activity. </li></ul>
  20. 21. Hand Harvesting
  21. 22. Mechanical Control <ul><li>Mechanical control methods include mechanical harvesting, wind-powered circulators (windmills), cutting, rotovation, and rototilling. As early as the 1980's, Tahoe boat marinas have employed the use of large-scale mechanical harvesters in weed infested areas. The use of such equipment may temporarily reduce plant biomass in localized areas, but has the potential to exacerbate the spreading of invasive aquatic weed species. Divers have looked into the use and effectiveness of large scale harvesting equipment and decided that for this project they would not be cost effective or efficient for any use in either Emerald Bay or Ski Run Marina. </li></ul>
  22. 23. Mechanical Harvesting
  23. 24. Certification Program <ul><li>The Tahoe Divers Conservancy has instituted a Invasive Aquatic Plant Diver Certification program for this project. </li></ul><ul><li>Invasive Aquatic Plant Diver Certification - PADI </li></ul><ul><li>Certification Outline - Distinctive Specialty Course </li></ul><ul><li>ChapterTitleAuthor </li></ul><ul><li>I.Course Overview Phil/Doug </li></ul><ul><li>II.Course Requirements Phil/Sharon/Doug </li></ul><ul><li>III.Student and Instructor Equipment Requirements Phil/Sharon/Doug </li></ul><ul><li>IV.Academics* Phil/Karl/Doug </li></ul><ul><li>V.General Open-Water Considerations Phil/James/Doug </li></ul><ul><li>VI.Open-Water Sessions Phil/Sharon/Doug </li></ul><ul><li>AppendixGeneral Phil/Doug </li></ul><ul><li>*referencing the PADI Instructors manual on Section II. </li></ul>
  24. 25. Underwater Slates
  25. 26. Help Stop the Alien Invasion Extermination Techniques: <ul><li>Are you providing free rides to aliens? Don't be an alien helper, watch out for hitchhikers. Zebra mussels have already invaded the Great Lakes and the Mississippi River. Other lakes and streams in Wisconsin are at risk. Check the ways you think zebra mussels can get from one body of water to another. </li></ul><ul><li>Boaters use their boats in several places without cleaning them with hot water. </li></ul><ul><li>Kids, mucking in a lake, slosh over to a different lake and empty out their boots. </li></ul><ul><li>Anglers take their bait buckets from lakes to rivers and empty them into the waters. </li></ul><ul><li>Someone gets bored with a pet zebra mussel and releases it in a new home. </li></ul><ul><li>Ducks, with muddy feet, fly off to new watery homes. </li></ul><ul><li>Water plants get stuck on boats or other equipment and are carried to different bodies of water. </li></ul>
  26. 27. REFERENCES <ul><li>Anderson, LWJ and DF Spencer. 1995. Survey of Lake Tahoe for presence of </li></ul><ul><li>Eurasianwatermilfoil. In . USDA/ARS Annual Report, Aquatic Weed Control Investigations. p. 27-32. </li></ul><ul><li>Anderson, Lars W.J. The Invasion of Eurasian watermilfoil ( Myriophyllum spicatum ) and Curlyleaf pondweed ( Potamogeton crispus ) </li></ul><ul><li>in Lake Tahoe: The Risks of Benign Neglect. </li></ul><ul><li>Anderson, LWJ and DF Spencer. 1996. Survey of Lake Tahoe for presence of </li></ul><ul><li>Eurasianwatermilfoil. In . USDA/ARS Annual Report, Aquatic Weed Control Investigations. p. 52-56. </li></ul><ul><li>Anderson, LWJ 1997. Myriophyllum spicatum at Lake Tahoe: Spirng and late summerpopulations outside the Tahoe Keys Marina. In . USDA/ARS Annual Report, Aquatic Weed Control Investigations. p. 59. </li></ul><ul><li>Anderson, Lars W.J. Clarification on Corps & Proposed Milfoil Study. E-mail. 10-01-06. </li></ul><ul><li>Aquatic Invasive Species: Curlyleaf Pondweed. The State of Indiana Department of Natural Resources. </li></ul><ul><li>http:// www.in.gov/dnr/invasivespecies/CURLYLEAFPONDWEED.pdf </li></ul><ul><li>California Invasive Plant Council: Myriophyllum spicatum . The University of California at Davis. Http:// ucce.ucdavis.edu/datastore/detailreport.cfm </li></ul><ul><li>Chandra, S. 2003. The impact of nonnative species and cultural eutrophication on the Lake Tahoe food web over time. PhD thesis. University of California, Davis. </li></ul><ul><li>Invasive Plant Species: Eurasian Water Milfoil (Myriophyllum spicatum). Wisconsin Department of Natural Resources. http://www.dnr.state.wi.us/invasives/fact/milfoil.htm </li></ul><ul><li>Land and Resource Management Plan, Comprehensive Evaluation Report: Lake Tahoe Management Unit. United States Department of Agriculture: Forest Service. </li></ul><ul><li>Non-Native Freshwater Plants: Eurasian Milfoil. Washington State Department of Ecology. http:// www.ecy.wa.gov/programs/wq/plants/weeds/milfoil.html </li></ul><ul><li>Plant Conservation Alliance: Eurasian Watermilfoil. National Park Service. http://www.nps.gov/plants/alien/fact/msp1.html </li></ul><ul><li>Policy and Planning Guidance for Conducting Civil Works Planning Studies. U.S. Army Corps of Engineers. December 28, 1990. </li></ul><ul><li>Progress Report: Federal Actions At Lake Tahoe; FY 2003-2005. Lake Tahoe Intragency Partnership. May 2006. </li></ul><ul><li>San Francisco Estuary Institute, April 2004. Aquatic Pesticide Monitoring Program, Review of Aquatic Pest Control Monitoring Methods For California Waters. </li></ul><ul><li>Spencer, DF and J Madsen. 1996. Eurasian watermilfoil in Lake Tahoe and the Truckee River. In USDA/ARS Annual Report Aquatic </li></ul><ul><li>Weed Investigations. P. 57-59. </li></ul><ul><li>Vander Zanden, S Chandra, BC Allen, JE Reuter, & CR Goldman. 2003. Historical food web structure and restoration of native fish communities in Lake Tahoe (CA-NV) basin. Ecosystems 3: 274-288. </li></ul><ul><li>Vanni, MJ, KK Arend, MT Bremigan, DB Bunnell, JE Garvey, MJ González, WH Renwick, PA Soranno, and RA Stein. 2005. Linking landscapes and food webs: effects of omnivorous fish and watersheds on reservoir ecosystems. BioScience 55: 155–167. </li></ul><ul><li>Washington State Department of Ecology. Aquatic Vegetation Survey Methods. www.ecy.wa.gov/programs/wq/plants/management/survey.html . </li></ul>
  27. 28. Other Invasives
  28. 29. Zebra Mussel <ul><li>Alias (scientific name in Latin): Dreissena polymorpha </li></ul><ul><li>Home Land (Origination): Ponto-Caspian region of western Russia </li></ul><ul><li>Arrival Date: They were first found in the Great Lakes on June 1, 1988. They were accidentally introduced to North America in ballast water from a boat that traveled across the ocean. </li></ul><ul><li>How to Identify: Polymorpha, means &quot;many forms.&quot; Zebra mussels come in many colors. Most are white or cream-colored with jagged brown or black stripes. However, some individual mussels have been found that are all-white, all-black, or have stripes going the other direction. Zebra mussels are members of the phylum Mollusca (mol-US-ka), or mollusks. Mollusca comes from the Latin word, mollis, meaning soft. Slugs, snails, octopuses, clams, and oysters are all mollusks. Mussels are bivalve mollusks. Bivalves have two shells that are held together by a strong ligament. </li></ul>
  29. 30. Dynamic Mapping http://nationalatlas.gov/dynamic/dyn_zm.html#
  30. 31. Rapid Spread of Zebra Mussels
  31. 32. Attack on Native Ecosystem
  32. 33. Truckee River Watershed
  33. 34. Zebra Mussel vs. 2 Inch Pipe
  34. 35. Life Cycle
  35. 36. Zebra Mussel Trap
  36. 37. Mussel Monthly Check-up
  37. 38. Web Based On Line Reporting Form
  38. 39. Caspian Area of Invasives
  39. 40. New Zealand Mudsnail
  40. 41. Spread of Mud Snail in Western States
  41. 42. Crayfish kill-off
  42. 43. Spread in One Decade
  43. 44. Nevada Counties
  44. 45. Spread in the Great Basin
  45. 46. Effected California Areas
  46. 47. polymorhpa vs. bugensis
  47. 48. Variations
  48. 49. polymorhpa vs. bugensis
  49. 50. Tahoe Divers Conservancy Green Boat Project
  50. 51. <ul><li>Design specification to log over 24,000 operational hours as the primary vessel serving as the TDC research and work platform while monitoring the marine resources of Lake Tahoe. </li></ul><ul><li>During the 20 year life of the vessel it is estimated that we will use 185,000 gallons of diesel fuel. To reduce the environmental impact of this operation several changes are proposed: </li></ul><ul><li>Use of bio-diesel fuels only. </li></ul><ul><li>Lubricating Oils- Only re-refined oil is utilized on the boat, this oil reduces the need to exploit new oil resources. Additionally the oil filter system on the boat, a &quot;Purafiner&quot; system super cleans the engine oil while removing contaminants which reduced oil change cycles by 78%. </li></ul>
  51. 52. <ul><li>Electrical Generation- Battery storage and a 110/220 volt inverter provide cabin electrical service which has reduced generator run time by 65%. </li></ul><ul><li>Bulbous Bow- Hull modifications to the vessel are proposed to be performed. The installation of a &quot;Bulbous Bow&quot; reduces friction and wake resistance on the displacement hull as it travels through the water. This increased efficiency allows the vessel to travel farther while operating at the same engine RPM and fuel consumption. The predicted fuel savings will averaged 18%. This increase in efficiency will result in less fuel being consumed per trip and correspond in reduced exhaust emissions. </li></ul>
  52. 53. FINIS

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