Songbirds as Biosentinels for Tidal Wetlands Initial results from North and South San Francisco Bay Letitia Grenier, Josh Collins, Jen Hunt, Shira Bezalel, and April Robinson San Francisco Estuary Institute Royce LaTourrette

Problem Statement Mercury bioaccumulation problem in the Estuary Mercury bioaccumulation problem in the Estuary Tidal wetlands restoration on large scale Tidal wetlands restoration on large scale Restoration provides tremendous benefits for wildlife Restoration provides tremendous benefits for wildlife Concern that increased mercury in the food web a possible side effect Concern that increased mercury in the food web a possible side effect

Sentinel Species Approach Direct measurement of Hg problem Direct measurement of Hg problem Methylmercury Methylmercury Food web = wildlife, people Food web = wildlife, people Integrate over appropriate spatial and temporal scales Integrate over appropriate spatial and temporal scales Link to water/sediment processes Link to water/sediment processes

Uses of Sentinel Species Identify areas where mercury bioaccumulation is a problem Identify areas where mercury bioaccumulation is a problem Habitats Habitats Areas slated for management actions Areas slated for management actions Track change in food web mercury over time Track change in food web mercury over time

Each sentinel species is specific to one habitat Each sentinel species is specific to one habitat Year-round residents Year-round residents Small home range Small home range Abundant Abundant Important role in food web Important role in food web Habitat-based Hg Monitoring Peter LaTourrette

Grenier 2004 Habitat-specific Sentinel Species

Salt PondTidal Marsh Comparisons within a Species before after

Tidal Marsh Song Sparrows salt marsh brackish marsh salt marsh samuelis maxillaris pusillula San Pablo Bay Suisun Bay San Francisco Bay Marshall and Dedrick 1994

Upland and Tidal Marsh gouldiiuplandmaxillaris brackish marsh Iron sulfide Mineral Research Co. Iron oxide Iconofile

Grenier and Greenberg 2005 Continent-wide Data Set Tidal Marsh Sparrows

Petaluma Guadalupe Alviso Tidal marsh songbirds Tidal marsh songbirds 5 locations 5 locations September 2006 September 2006 Mercury in blood (wet weight) Mercury in blood (wet weight)

Bird Blood Higher than Fish Tissue Relative to Trophic Level Sparrow (median 0.31 ug/g ww, n = 37) ~ 6x small fish mean (RMP 2005 data), despite both being secondary consumers Sparrow (median 0.31 ug/g ww, n = 37) ~ 6x small fish mean (RMP 2005 data), despite both being secondary consumers Yellowthroat (median 0.42 ug/g ww, n = 4) ~= striped bass (RMP 2003 data) Yellowthroat (median 0.42 ug/g ww, n = 4) ~= striped bass (RMP 2003 data) Wren (0.82 ug/g ww, n = 1) ~ leopard shark median (RMP 2003 data) Wren (0.82 ug/g ww, n = 1) ~ leopard shark median (RMP 2003 data)

Mercury Varied by Species Marsh Plain: aerial insect and spider food chain Marsh Plain: more epibenthic food chain (transient) South Bay data

Higher Hg in North Bay Marshes Song Sparrow

Unpublished data provided by Darell Slotton Combined FMP and RMP data Combined FMP and RMP data Highest concentrations in South Bay fish Highest concentrations in South Bay fish Mississippi Silverside Data from Darell Slotton and Ben Greenfield

Higher Variability in North Bay Song Sparrow

H 1:  Elevation leads to  Mercury Lower, newer, subsided marshes Higher, older marshes, with more variable elevation

Elevation Proxy for Proxy for Frequency of wetting/drying Frequency of wetting/drying Tide Tide Groundwater Groundwater Amount of organic matter (peat) Amount of organic matter (peat) Marsh age Marsh age

Implications of Marsh Plain Elevation Affects connectivity to slough/bay food web(?) Affects connectivity to slough/bay food web(?) Slowly increases as restored marshes age Slowly increases as restored marshes age Need long-term monitoring Need long-term monitoring Elevation of marsh plain Food web connectivity Fish HgBird Hg H 2:

Summary Sentinel species directly measure the mercury problem at appropriate scales of space and time Sentinel species directly measure the mercury problem at appropriate scales of space and time Songbirds can be used to monitor Hg in nearly every tidal marsh across the Estuary within the same species Songbirds can be used to monitor Hg in nearly every tidal marsh across the Estuary within the same species Initial songbird Hg data suggest several hypotheses for future study Initial songbird Hg data suggest several hypotheses for future study

Next Steps Wider regional survey of sentinel species Wider regional survey of sentinel species Test hypotheses by Test hypotheses by Comparing different types of marshes Comparing different types of marshes Monitoring restoration projects Monitoring restoration projects Studying diets with stable isotopes Studying diets with stable isotopes Riparian areas, coastal fog belt Riparian areas, coastal fog belt Consider Hg effects on passerines Consider Hg effects on passerines

Acknowledgements Thanks to the following funding sources: Santa Clara Valley Water District, State Coastal Commission, San Francisco Foundation Bay Fund, Regional Monitoring Program for Trace Substances, San Francisco Estuary Institute. Thanks to the following funding sources: Santa Clara Valley Water District, State Coastal Commission, San Francisco Foundation Bay Fund, Regional Monitoring Program for Trace Substances, San Francisco Estuary Institute.

Scott Haefner