Assessing the impacts of methylmercury on piscivorous wildlife: as indicated by the Common Loon, 1998-2000 (Report BRI00-01) 2000 Final Report Submitted to: Maine Department of Environmental Protection Surface Water Ambient Toxic Monitoring Program State House Station 17 Augusta, Maine 04333 Submitted by: David C. Evers, Chris De Sorbo, and Lucas Savoy BioDiversity Research Institute1 23 March 2001 1Send correspondence to: BioDiversity Research Institute, 411 U.S. Route 1, Suite 1, Falmouth, Maine 04105 (207-781-3324) ([email protected]) Assessing the impacts of methylmercury on the Common Loon Page 2 TABLE OF CONTENTS EXECUTIVE SUMMARY:................................................................................................................................................... 3 INTRODUCTION .................................................................................................................................................................. 4 USING BIRDS AS BIOINDICATORS OF MEHG AVAILABILITY ........................................................................................ 5 MERCURY RISK TO LOONS ............................................................................................................................................... 5 STUDY AREA ........................................................................................................................................................................ 6 METHODS.............................................................................................................................................................................. 9 1. COLLECTION OF TISSUES FOR EXPOSURE ASSESSMENT .......................................................................................... 9 2. ASSAYS RELATED TO PHYSIOLOGICAL MEASUREMENTS ...................................................................................... 10 3. COLLECTION OF BEHAVIORAL INFORMATION ........................................................................................................ 10 Explanation of Time-Activity Budget Methods........................................................................................................... 11 Distinguishing/identifying individuals ........................................................................................................................ 12 Nest Sitting: Monitoring with Data Loggers .............................................................................................................. 12 4. IMPACTS ON INDIVIDUAL SURVIVAL ....................................................................................................................... 12 5. TECHNIQUES AND DEFINITIONS FOR REPRODUCTIVE MEASURES ....................................................................... 13 RESULTS AND DISCUSSIONS......................................................................................................................................... 13 A. EXPOSURE ASSESSMENT........................................................................................................................................... 14 1. Common Loon Mercury Profile .............................................................................................................................. 14 2. Yellow Perch Mercury Profile ................................................................................................................................. 16 B. HAZARD ASSESSMENT............................................................................................................................................... 19 1. Physiological Relationship with Mercury............................................................................................................... 19 a. Blood Profiles...........................................................................................................................................................................19 b. Hormones.................................................................................................................................................................................19 c. Developmental Stability ...........................................................................................................................................................21 2. Behavioral Relationships with Mercury................................................................................................................. 22 a. Behavioral relationships with Hg risk ......................................................................................................................................22 b. Geographic and gender differences in behavior .......................................................................................................................22 c. Nesting Period: Behavioral relationships with Hg risk............................................................................................................23 d. Post-hatching Period: Behavioral relationships with Hg risk..................................................................................................27 e. Behavioral Relationships: mercury and energy expenditure....................................................................................................32 f. Adult Behavior Event Analysis................................................................................................................................................32 g. Adult Behavior Summary........................................................................................................................................................34 h. Temperature Dataloggers as measures of adult incubating behavior.......................................................................................34 i. Juveniles: Behavioral relationships with Hg risk .....................................................................................................................35 3. Survival Relationship with Mercury........................................................................................................................ 36 a. Adult Loons..............................................................................................................................................................................36 b. Juvenile Loons .........................................................................................................................................................................37 4. Reproduction Relationship with Mercury .............................................................................................................. 38 a. Egg Development and Hatching Success ................................................................................................................................38 b. Impacts on Overall Productivity..............................................................................................................................................40 C. RISK CHARACTERIZATION ......................................................................................................................................... 42 1. Basis for current established risk categories.......................................................................................................... 42 2. Common Loon Risk Profile .................................................................................................................................... 43 RECOMMENDATIONS ..................................................................................................................................................... 47 ACKNOWLEDGEMENTS ................................................................................................................................................. 49 LITERATURE CITED ........................................................................................................................................................ 49 Assessing the impacts of methylmercury on the Common Loon Page 3 Executive Summary: Anthropogenic inputs of mercury (Hg) into the environment have significantly increased in the past few decades. In conjunction, the current availability of methylmercury (MeHg) in aquatic systems has increased to levels posing risks to human and ecological health. Risk levels vary considerably in response to MeHg availability, which is affected by lake hydrology, biogeochemistry, habitat, topography, and proximity to airborne sources. We selected the Common Loon as the most suitable bioindicator of aquatic Hg toxicity, based on ecological, logistical, and other criteria, including public valuations of natural resources. Opportunistic and probability-based sampling efforts from 1994-2000 indicate New England’s breeding loon population is at unacceptable levels of risk to Hg contamination, particularly in Maine. Based on risk categories developed from the literature and in situ studies by BioDiversity Research Institute and their collaborators, 30% of the breeding loon population in Maine is estimated to be at risk, while 46% of the eggs laid are potentially impacted. Because results from national sampling indicated loons were at most risk from Hg in New England (particularly Maine), we identified several individual- and population-level parameters to better understand the extent of mercury toxicity across Maine. Between 1994-00, we collected 139 abandoned eggs as well as blood