Zebra Mussels in Texas: Implications for Southern States Robert F

Zebra Mussels in Texas: 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 Colorado River, 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

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