Zebra Mussels in : Implications For Southern States Robert F. McMahon Professor Emeritus The University of Texas Department of Biology Center for Biological at Arlington The University of Texas at Arlington Macrofouling Research

South Shore, Lake Texoma Outline • Invasive Biology and Impacts of Zebra and Quagga Mussels • Overview of Past Texas Dreissenid Research • Recent Texas Dreissenid Research • Zebra Mussels in Texas Water Bodies? • Threat to Gulf States • Conclusions Invasive Biology and Impacts of Dreissenid Mussels Zebra and Quagga Mussels • Originally endemic to Europe • Introduced to North America in ~ 1986 • Found in Lake St. Clair and eastern basin of Lake Erie in 1989 • Rapidly spread throughout major US and Canadian drainage systems east of the Rocky mountains • Great Lakes drainage, the Mississippi River, and its eastern tributaries, lower Missouri River, Arkansas River and isolated lakes and rivers • Rapid dispersal through navigable waterways on commercial vessels • Dispersed more slowly to isolated water bodies (i.e., overland transport) • Quagga mussels recently found in Lake Mead, lower , and lakes in southern California • Zebra Mussel recently found in San Justo Reservoir Central California • Most costly macrofouling and ecological pests ever introduced to North American freshwaters Dreissenid Shell Morphology

Zebra Mussel Quaaga Mussel Dreissena polymorpha Dreissena rostriformis bugensis Zebra Mussel Invasion of the US 1988 Zebra Mussel Invasion of the US 1990 Zebra Mussel Invasion of the US 1992 Zebra Mussel Invasion of the US 1994 Zebra Mussel Invasion of the US 1996 Zebra Mussel Invasion of the US 1998 Zebra Mussel Invasion of the US 2000 Zebra Mussel Invasion of the US 2002 Zebra Mussel Invasion of the US 2004 Zebra Mussel Invasion of the US 2005 Zebra Mussel Invasion of the US 2008 2009 Present Quagga Mussel Distribution in the United States

Zebra Mussel Filter Feeding

Frontal Cilia

Cirri Filter Feeding • Zebra and quagga mussels both efficiently filter bacterioplankton (< 1 µm) • Large adults may filter up to 1 L / hr • Average ≈ 1.5 L / Day • 150,000 L / Day at a density of 100,000 mussels / m2 • Results in rapid clarification of infested waters • Removes phytoplankton impacting energy flow through food webs • Quagga mussels are more efficient at filtering bacteria • Leads to eventual replacement of zebra mussels by quagga mussels Filter feeding Impacts

Average Secchi Disk an Chlorophyll a Concentration, Seneca Lake , NY

Area of Submerged Macrophyte Cover, Oneida Lake, NY Maximum Depth of Submerged Macrophytes in Oneida Lake, NY

et al Zhu. ., 2006 Zhu. et al., 2006 Lake Erie Pelagic Benthic Food Web Macrophytes

Dreissenid Mussel Impacts on Aquatic Aquatic macrophyte growth in Lake St. Clair, MI, stimulated by zebra Ecosystems mussels clarifying the water column Dreissenid Life Cycle • Gonochoristic - External Fertilization • Fecundity as high as 1,000,000 eggs per adult female per year • Trochophore (6-20 Hours) • No shell (≥ 40 µm) • Early Veliger (3-4 Days • D-shaped shell (80-100 µm) • Late veliger (1-2 weeks) • Umbonal shell (100-250 µm) • Pediveliger (2-3 weeks) • Develops foot – settles, crawls to attachment site (200-400 µm) Umbonal • Plantigrade (3-4 weeks) Veliger • Byssal attachment – transforms to

mussel shape (250-500 µm) D-shaped Veliger • Juvenile (3-5 Weeks) Umbonal Pediveliger Veliger • Mussel-shaped shell (>400 µm) • Spawning occurs at low levels > 10°C • Spawning maximized at > 18-24°C Plantigrade • Settle in three to five weeks Plantigrade Juvenile Dreissenid Population Dynamics

• Maximum age = 3-5 years depending on population • Maximum adult size = 2.5 – 4.0 cm dependent on population • Growth rate declines with increasing adult size • Survival rate is low across year classes • Adult growth rates and population density dependent on temperature and phytoplankton and bacterioplankton productivity • High fecundity leads to development of massive populations within 3-5 years of initial introduction Water Quality Factors Affecting Dreissenid Mussel Distribution and Invasion

• pH: Inhabit waters with pH < 7.4 • Attain highest densities at pH > 8.0 • Salinity: • Do not spawn or successfully fertilize above 7 ppt • larvae do not develop at > 8 ppt • juveniles and adults do not survive > 5 ppt (14% SW) • Turbidity and Suspended Solids: • Thrive in lower Ohio and Lower Mississippi Rivers at > 80 NTU units • Turbidity unlikely to be a factor in limiting distribution • Organic Enrichment: Does not generally limit distribution except when associated with hypoxic conditions - will accelerate growth • Phosphate Concentration: Found as low as 0.001 mg/L • Nitrate Concentration: Not found below 0.009 mg/L • Calcium Ion Concentration: Not found below 12-15 mg/L Ca • Total Hardness: Not found below 25 mg/L Ca • Alkalinity: Not found below 20 mg/L Ca Water Quality Factors Affecting Dreissenid Mussel Distribution and Invasion (Continued)

• Potassium Ion: • Intolerant of waters with natural potassium concentrations > 30 mg/L K • Flooding and Water Level Variation: • Limited success in rivers prone to extensive flooding and lakes with large annual level fluctuations • Large stable rivers and lakes with reduced level fluctuations are most prone to invasion • River populations sustained by mussel populations in upstream impoundments • Pollution: • Generally as tolerant of industrial and municipal water pollution as are native unionid and Asian clams • Will not invade waters made chronically hypoxic by receipt of organic pollutants Chronic Hypoxia Tolerance

15ºC 25ºC 40 A Dreissena polymorpha A 30 A

20 A A

10 A >40 Days >40

0 (Days)

50 Dreissena rostriformis bugensis B LT 30 B B 20

10 B A B

0 0 5 10 Johnson and McMahon % Air O 2 Saturation Desiccation Tolerance in Zebra Mussels Emersion Tolerance at Different Temperatures and Relative Humidities 400 100% • Summer emersion and LT 350 80% 50 desiccation (<10-20 Days) 300 60% • Temperature and humidity 250 40% dependent responses 200 20% 150 0% 100 Hours Survived Hours 50 0 0 5 10 15 20 25 30 TEMPERATURE (°C)

800 100% 700 80% LT 600 60% 100 500 40% 400 20% 0% 300 200 Hours Survived Hours 100 0 0 5 10 15 20 25 30 TEMPERATURE (°C) McMahon and Ussery Trailered Boats as Zebra Mussel Dispersal Vectors in Southwest US

100th Meridian Boater Movement in Western States Database

Britton and McMahon AFLP Analysis of Dreissenid Mussel Genetic Diversity

F UM J ST NYZ NYQ OB MR BR SL DL ED Zebra Mussels Quagga Mussels VA WL LM DZ DQ Q K H LE MC

•Analyzed genetic diversity Coordinate 2 for 16 zebra mussel and 6 quagga mussel populations •Of various ages of establishment (<3->25 yrs) Coordinate 1 •Compared for genetic differences with AFLP (Amplified Fragment Length Morse and McMahon Polymorphisms) • Could not distinguish populations of either species based on AFLP • All showed high levels of genetic diversity • Suggested that there were no genetic bottlenecks or founder effects in recently established populations • A large number of individuals are required to establish a population

ST F NYQ UM VA J Quagga Mussels LM Zebra Mussels NYZ DQ OB Q MR BR SL DL ED WL DZ K H LE MC Coordinate 2 Coordinate 2

Coordinate 1 Coordinate 1 Morse and McMahon Invasion of Southern Water Bodies by Zebra Mussels

Predicted Zebra Mussel Distribution Based on Average Maximal and minimal Monthly Surface Water Temperatures

• Generally agreed long-term incipient upper thermal limit of zebra mussels was 28-30°C • Generally agreed temperature for initiation of spawning was 16-18°C • These temperature limits were used predict potential zebra mussel distribution in North America based on maximum summer surface water temperatures • Recent successful establishment of zebra mussels Texas requires a re-examination of these assumptions McMahon 1°C Mean Maximum Air Temperature Isotherms (1961-1990) Source: Spatial Climate Analysis Service, Oregon State University

Windfield City Lake Lake Oologah

35°C 33°C Lake Texoma

32°C 34°C Confirmed western quagga mussel populations 35°C Confirmed zebra mussel populations Chronic Thermal 30 Tolerance of Zebra Mussels in the Southwest 25

Ambient Water 20 Winfield City Lake 2008 Temperatures of Lake Oologah 2006 Lake Oologah (OK) Lake Oologah 2007 and Winfield City Lake Oologah 2008 15 Lake (KS) Mean WaterAmbient Daily Temperature (øC)

10

Jun. Jul. Aug. Sept. Oct.

Date McMahon, Leung and Morse 10 hours at 33°C 12 hours at 33°C 14 hours at 33°C

0% Selection 0% Selection Selection for Chronic 50 0% Selection 50 50 42.4% Selection 85.8% Selection Temperature Tolerance 29.2% Selection 40 40 40 in Zebra Mussels 30 30 30

• 25°C acclimated mussels 20 20 20 exposed to a lethal temperature of 33°C Percent Mortality 10 10 10

• Control sample held at 33°C 0 0 0 until 100% mortality ensued 24 48 72 96 120 120+ 24 48 72 96 120 120+ 24 48 72 96 120 120+ • Second sample to 33°C long enough to induce partial sample mortality • Surviving individuals allowed to recover at 25°C • Chronic thermal tolerance at 33°C of surviving individuals retested • Experiment repeated three times

McMahon, et al. Comparison of Median Survival Times Between Zebra Mussels from Winfield City Lake (KS) and Hedges Lake (NY)

900 Shell Length = 15 mm 800 Acclimation Temp. = 20øC 700 WCL Incipient Upper Thermal Limit = 31.7°C

600 WCL Early WCL Late 500 HL 2006 400 HL 2007 300

200 Median Survival Time (h)

100 Near 100% Survival over 672 h 672 over Survival 100% Near Near 100% Survival over 672 h 672 over Survival 100% Near Near 100% Survival over 672 h 672 over Survival 100% Near 0 28 29 30 31 32 33 34 Treatment Temperature (øC) Morse 2009 Zebra Mussels Invasion of Lake Texoma (TX/OK)

• Lake Texoma was considered thermally resistant to zebra mussel invasion • Surface water temperatures reach or exceed 30°C in mid- summer • Much recreational boat traffic from infested water bodies in Oklahoma • Establishing individuals likely to have evolved increased thermal tolerance in nearby southwestern water bodies (KS and OK) • An adult zebra mussel was discovered in the lower end of Lake Texoma, on the Red River on April 3 2009 • Now recorded at numerous sites in the lower end of the lake • Populations are rapidly expanding and increasing in density Zebra Mussel Distribution in Lake Texoma (TK/OK) The Question • If zebra mussels can thrive in the warm waters of Lake Texoma can they invade other Texas Lakes with similar annual temperature profiles? • Through the Quagga-Zebra Mussel Action Plan (Q-ZAP) , the USFWS funded an effort to develop and test a zebra mussel monitoring and risk assessment system for 13 lakes in northeastern Texas receiving recreational boat traffic from Lake Texoma

Texoma

Arrowhead

Ray Roberts Red River Basin Bridgeport Bob Sandlin Lewisville Lavon Wright Basin Eagle Ray Patman Sabine River Basin Mountain Hubbard Lake O’ Tawakoni Fork the Pines Cypress River Basin Caddo Sulphur River Basin Methodology • Monitoring/risk assessment system design requirements • Must be simple, accurate, cost effective, easily applied • Must provide rapid risk assessment and detection • Must be readily applied by Texas Parks and Wildlife personnel • 14 lakes sampled spring and fall 2011 when larvae were present (18-28°C) • Physical data recorded for risk assessment • Temperature data loggers in surface waters (≈1 m) for a year’s period • Recorded ambient water temperature hourly • Ca2+ concentration • pH • O2 Concentration • Plankton net sampling for mussel veliger larvae (60 μm mesh) • Microscopic examination of live samples immediately after collection • Cross-polarized light examination of fixed samples in the laboratory • Molecular qPCR testing (real-time, quantitative PCR) for larval DNA • 197 bp fragment of the rDNA ITS 2 region • John Wood, Pisces Molecular LLC, Boulder, Colorado • Scouring pad pediveliger settlement monitors • Allow rapid detection of settling pediveligers and juvenile mussels • Deployed for 3-4 weeks • Pads examined immediately in the field • Preserved for later, more detailed examination in the laboratory • Use of multiple tests increases likelihood of detection • Allows multiple confirmation of a positive result

2011 Spring & Fall Settlement Sampling

Lake Monitor Monitor Days Monitor Monitor Days Deployment Recovery Deployed Deployment Recovery Deployed Arrowhead Lake 6/1/2011 6/30/2011 29 10/21/2011 11/21/2011 33 Lake Bridgeport 6/1 2011 6/30/2011 29 10/21/2011 11/21/2011 33 Eagle Mountain Lake 6/1/2011 6/30/2011 29 10/21/2011 11/21/2011 33 Lake Lewisville 8/8/2011 7/1/2011 23 10/22/2011 11/19/2011 29 6/8/2011 7/1/2011 23 10/22/2011 11/19/2011 29 Lake Ray Roberts 6/2/2011 6/30/2011 28 10/22/2011 11/19/2011 29 Lake Lavon 6/8/2011 7/1/2011 23 10/22/2011 11/19/2011 29 Lake Texoma 6/2/2011 6/30 /2011 28 10/21/2011 11/19/2011 30 6/8/2011 7/1/2011 23 10/22/2011 11/19/2011 29 Lake Fork 6/8/2011 7/1/2011 23 10/23/2011 11/20/2011 29 Lake Bob Sandlin 6/7/2011 7/5/2011 28 10/24/2011 11/20/2011 27 Lake O’ the Pines 6/7/2011 7/5/2011 28 10/23/2011 11/20/2011 29 Lake Wright Patman 6/7/2011 7/5/2011 28 10/23/2011 11/20/2011 29 6/7/2011 7/6/2011 29 10/23/2011 11/20/2011 29 Risk Assessment Surface Water Oxygen Concentration

14 Lake O2 Concentration 12 -1

L 10 2 8

mg O 6 4 2 0 160 LTX LA LB EML LLE LRR LRH LLV LTA LF LBS LP LWP CL 140 120 100% Air O2 Saturation 100 80 Saturation 2 60 % O 40 Incipient Lower Limit (30% of Air O2 Saturation) 20 0 LTX LA LB EML LLE LRR LRH LLV LTA LF LBS LP LWP CL Lake Surface Water pH

Mean pH 10.0

9.0 Laval Adult Limits Development 8.0

7.0

6.0 pH 5.0

4.0

3.0

2.0

1.0

0.0 LTX LA LB EML LLE LRR LRH LLV LTA LF LBS LP LWP CL Lake Surface Water Calcium Concentration 100. Mean Calcium Concentration 90.0

80.0

70.0 -1

60.0

50.0

40.0 mg Calciummg l 30.0

20.0 Incipient Lower Limit (12 mg Ca l -1) 10.0

0.0 LTX LA LB EML LLE LRR LRH LLV LTA LF LBS LP LWP CL Lake Surface Water Temperature 7 Lake Texoma Temperature and 30 Dissolved O2 with Depth (07/27/2011) 6 29 Temp: NTMWD Intake Temp: Dam Intake 28 DO: NTNWD Intake 5 DO: Dam Intake -1) 27 Data Provided by Texas Dept. of Parks and Wildlife 4 (mg l 26 2

25 3

24 2

23 O Dissolved

22 1

AmbientWater Temperature (ºC) 21 0 20 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Depth (m) Lake Surface Water Temperature

35 Lake Arrowhead Lake Bridgeport

30

25

20

15

Eagle Mountain Lake Lake Lewisville 35

30

25

20

15 Daily Mean Ambient Water Temperature (ºC) WaterTemperature Ambient Mean Daily

6/1 7/1 8/1 9/1 10/1 11/1 6/1 7/1 8/1 9/1 10/1 11/1 12/1 2011 Lake Surface Water Temperature

Lake Lavon 35 Lake Ray Hubbard

30 Data Logger 25 Lost

20

15

35 Lake Ray Roberts Lake Texoma

30

25

20

15 Mean Daily Ambient Water Temperature (ºC) WaterTemperature Ambient Daily Mean

6/1 7/1 8/1 9/1 10/1 11/1 6/1 7/1 8/1 9/1 10/1 11/1 12/1 2011 Lake Surface Water Temperature

35 Lake Tawakoni Lake Fork

30

25

20

15

Lake O' the Pines 35 Lake Bob Sandlin

30

25

20 AmbientWater Temperature (ºC)

15

6/1 7/1 8/1 9/1 10/1 11/1 6/1 7/1 8/1 9/1 10/1 11/1 12/1 2011 Surface Water Temperature

Caddo Lake Lake Wright Patman 35

30

Switch to New Site 25

20

15 Mean Daily Ambient Water Temperature (ºC)

6/1 7/1 8/1 9/1 10/1 11/1 6/1 7/1 8/1 9/1 10/1 11/1 12/1 2011 Mean August Surface Water Temperature

33.0 Mean August 2011 Surface Water Temperature

32.5

Incipient Upper Thermal Limit (32ºC) 32.0

31.5

31.0

Lake Texoma (30.5ºC) 30.5 MeanAmbient Temperture (ºC) 30.0 LTX LA LB EML LLE LRR LRH LLV LTA LF LBS LP LWP CL Lake Water Temperature versus Depth & Capacity

33.0 Depth Capacity

32.5

32.0

31.5

31.0

30.5

30.0

n =14 n =14 Mean August 2011 Temperature (ºC) Temperature 2011 August Mean 29.5 r = 0.304 r = 0.073 p = 0.290 p = 0.0.80 29.0 0 2 4 6 8 10 0.00 0.50 1.00 1.50 2.00 2.50 Mean Depth (m) Acre-Feet (Millions) Risk Assessment Matrix

* Lake O2 pH Ca Temperature Risk Level Arrowhead Lake Suitable Suitable Suitable Suitable HIGH Lake Bridgeport Suitable Suitable Suitable Marginal MARGINAL Eagle Mountain Lake Suitable Suitable Suitable Suitable HIGH Lake Lewisville Suitable Suitable Suitable Suitable HIGH Lake Texoma Suitable Suitable Suitable Suitable HIGH Lake Ray Roberts Suitable Suitable Suitable Suitable HIGH Lake Ray Hubbard Suitable Suitable Suitable Suitable HIGH Lake Lavon Suitable Suitable Suitable Suitable HIGH Lake Tawakoni Suitable Suitable Suitable Suitable HIGH Lake Fork Suitable Suitable Marginal Suitable MARGINAL Lake Bob Sandlin Suitable Suitable Unsuitable Unsuitable POOR Lake O’ the Pines Suitable Suitable Unsuitable Unsuitable POOR Lake Wright Patman Suitable Suitable Suitable Suitable HIGH Caddo Lake Suitable Marginal Unsuitable Suitable POOR

Suitable = Good to excellent for mussels Marginal = Marginal for mussels Unsuitable = Unlikely to support mussels Monitoring for Veligers and Juvenile Settlement Plankton Samples • Microscopic examination of live and preserved plankton samples revealed presence of veliger larvae June – November only at Lake Texoma • Dense veliger concentrations on 2 June (24.0°C) and 30 June 2011 (29.4°C) • Low veliger concentrations on 8/10/2011 (30.7°C), 10/21/2011 (24.5°), 11/19/2011 (16.0°C) • No veligers observed in either spring and fall plankton samples from the 13 other examined lakes

Veligers

Veligers Veliger Shell Lengths

90 06/02/2011 - Mean SL = 175.4 µm 06/30/2011 - Mean SL = 110.1 µm 80 08/10/2011 - Mean SL = 110.6 µm 10/21/2011 - Mean SL = 118.8 µm 70 Veliger Shell 60 Length Distribution Lake Texoma, TX 50

40 06/02/2011 (24.0ºC) 06/30/2011 (30.6ºC) 30

Percentof Sample 08/10/2011 (30.7ºC) 20 10/21/2011 (22.0ºC)

10

0 0 50 100 150 200 250 300 Shell Length (µm) Settlement Monitoring

• Settled juvenile mussels recorded only on Lake Texoma monitors immersed from 6/2/2011 – 6/30/2011 • Mean water temperature = 25.3°C over 28 days of immersion • Juveniles were relatively densely settled on the monitor Settlement Monitoring

15 Lake Texoma Juvenile Settlement Monitor Shell Length Distribution 2-30 June 2011 Mean SL = 1.03 mm ) 12 Shell Growth Rate = 9.64 µm SL / Day (Based on increase in SL to 3.0 mm 28 days post-settlement)

9

6 Percent of Sample (n = 765 3

0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Shell Length (mm) Settlement Density • Numbers of settled juveniles in 10 randomly selected fields (3.142 cm2) under a binocular microscope on both sides of settlement monitor

6 Side 1 (Rope), 16.4 Mussels/3.14 cm2 Field 5 Side 2, 15.8 Mussels/3.14 cm2 Field 4 t = 0.298, n = 20, p = 0.768 3 2

Frequency 1 0 10-12 13-15 16-18 19-21 22-24 8 Combined Sides 7 Mean = 5.12 Mussels cm-2 (±1.40) on monitor = 3,762 (±817) Mussels per 19.5x15.0 cm Monitor 6 = 64,318 Mussels m-2 -2 -1 5 = Settlement Rate of 2,297 Mussels m day 4

Frequency 3 2 1 0 10-12 13-15 16-18 19-21 22-24 Number of Mussels per 3.142 cm2 Field Settlement Monitoring – Late Summer & Fall

• No settled juvenile mussels recorded on Lake Texoma monitors immersed from 8/10/2011 – 8/24/2011 or 10/21//2011 – 11/19/2011 • Viable veligers present in the water column during both periods • Mean water temperatures • 8/10/2011 – 8/24/2011 = 30.12°C ±0.33 • 10/21/2011 – 11/19/2011 = 18.67°C ±1.55 Lake Texoma Veliger Samples: Shell Lengths

90 06/02/2011 - Mean SL = 175.4 µm 06/30/2011 - Mean SL = 110.1 µm 80 08/10/2011 - Mean SL = 110.6 µm 10/21/2011 - Mean SL = 118.8 µm 70 Veliger Shell 60 Length Distribution Lake Texoma, TX 50

40 06/02/2011 (24.0ºC) 06/30/2011 (30.6ºC) 30

Percentof Sample 08/10/2011 (30.7ºC) 20 10/21/2011 (22.0ºC)

10

0 0 50 100 150 200 250 300 Shell Length (µm) Spring and Fall qPCR Results

1e+11 1e+10 Spring 2011 LTX1 = Lake Texoma (06/02/2011) LLV = Lake Lavon (06/08/2011) Plankton LTX2 = Lake Texoma (06/30/2011) LTA = Lake Tawakoni (06/08/2011) 1e+09 Samples LA = Lake Arrowhead (06/01/2011) LF = Lake Fork (06/08/2011) LB = Lake Bridgeport (06/01/2011) LBS = Lake Bob Sandlin (06/07/2011) 1e+08 06/1-8/2011 EML = Eagle Mountain Lake (06/01/2011) LP = Lake O' the Pines (06/07/2011) LLE = Lake Lewisville (06/08/2011) LWP = Lake Wright Patman (06/07/2011) 1e+07 LRR = Lake Ray Roberts (06/02/2011) CL = Caddo Lake (06/07/2011) LRH = Lake Ray Hubbard (06/08/2011) 1000000 100000 Copies/Sample 10000 1000 LTX1LTX2 LA LB EML LLE LRR LRH LLV LTA LF LBS LP LWP CL Lake 1e+11 Fall 2011 LTX1 = Lake Texoma (Not Sampled) LLV = Lake Lavon (10/22/2011) 1e+10 Plankton LTX2 = Lake Texoma (Not Sampled) LTA = Lake Tawakoni (10/22/2011) LA = Lake Arrowhead (10/21/2011) LF = Lake Fork (Not Sampled) 1e+09 Samples LB = Lake Bridgeport (10/21/2011) LBS = Lake Bob Sandlin (Not Sampled) 10/21-23/2011 EML = Eagle Mountain Lake (10/21/2011) LP = Lake O' the Pines (Not Sampled) 1e+08 LLE = Lake Lewisville (10/22/2011) LWP = Lake Wright Patman (10/23/2011) LRR = Lake Ray Roberts (10/22/2011) CL = Caddo Lake (10/23/2011) 1e+07 LRH = Lake Ray Hubbard (10/22/2011) 1000000 100000 Copies/Sample 10000 NS NS NS NS NS 1000 LTX1LTX2 LA LB EML LLE LRR LRH LLV LTA LF LBS LP LWP CL Lake NS = Not Sampled Conclusions

• Zebra mussels appear to have evolved increased thermal tolerance in the warm water bodies of Kansas and Oklahoma • May have allowed zebra mussels to eventually invade Lake Texoma • May allow zebra mussels to invade warm southern water bodies • Lake Texoma could become an epicenter for zebra mussel dispersal to other warm water bodies in Texas and the Gulf States • Because of the increased potential to invade warm water bodies, water bodies in the Gulf States should undergo invasion risk assessment for zebra mussels • Risk assessment indicated that 11 of 13 lakes in northeastern Texas could support zebra mussels • pH, Ca2+ concentration, summer surface water temperature • Nine of 13 Texas lakes appeared to be at high risk of invasion • Boaters appeared to be major vectors for mussel movements between water bodies • Analysis of boater movements (100th Meridian Boater Survey) Conclusions

• Zebra mussel monitoring programs for warm southern water bodies should include: • Juvenile settlement monitors (scouring pad monitors) • Plankton net sampling for veliger larvae • Microscopic examination in field and under polarized light in the laboratory • qPCR for mussel DNA in plankton samples • Positive qPCR must be corroborated by visual evidence of veliger larvae or settling juveniles • Imperative to develop a zebra mussel risk assessment and monitoring programs for southern water bodies in order to identify those most vulnerable to invasion • Allows prevention and education programs to be focused on water bodies most at risk • Allows early detection and rapid response to mussel invasion Acknowledgements

Funding Agency • U.S. Fish and Wildlife Service, U.S. Army Corps of Engineers Research Colleagues • Dr. David K. Britton (USFWS) , John Morse (USFWS) Partners • Texas Department of Parks and Wildlife • Brian Van Zee, Dr. Earl Chilton • Arrowhead Lake State Park (John Ferguson) • Eisenhower State Park (Paul C. Kisel) • Caddo Lake MWA • US Army Corps of Engineers (Brandon Mobley) • US Fish and Wildlife Service Providers of Sites for Settlement Monitor Deployment • Tarrant Regional Water District – Eagle Mountain Lake • Lake Ray Roberts Marina (Bill Williams) • Titus County Freshwater Supply District No. 1 – Lake Bob Sandlin (Judy Barton) • Kelly Creek Marina – Lake Wright Patman (Leon and Shelley Jennings) • Johnson Creek Marina - Lake O’ the Pines (Sam and Lyda Edwards) • Popes Landing Marina - Lake Fork (John Goergen) • Tawakoni Marina (Larry Wright) • Chandler’s Landing Marina - Lake Ray Hubbard (Joel Weiner) • Collin Park Marina - Lake Lavon (Joe Castro) • Cottonwood Creek Marina – Lake Lewisville (Jennifer Morris) • Col. Richard Cary – Caddo Lake • Technical and Field Assistance • M. Colette McMahon (Research Technician) • Wesley Walters (Undergraduate Research Assistant) • Dr. Michael O’Neill (Volunteer) Thanks For Your Attention