Mercury in Maryland Ecosystems STACK April 10 2019 Andrew Heyes Management Questions If we reduce inorganic Hg emissions will it have an impact on methylmercury concentrations in fish? How will we know if methylmercury concentrations in fish are responding to reductions in Hg emissions? What else can we do to mitigate the impact of Hg on aquatic organisms and fisheries? General Caveat’s How is mercury cycling responding to changes in climate? How are changes in land-use impacting Hg cycling? Primarily – how is net Hg methylation impacted? Castro and Sherwell 2016 Only half the story as about 50 % falls as dry deposition a) 12 MD00 SERC T-Hg Concentration MD08 10 MD99 Frostburg 8 Beltsville -1 Mercury Concentration 6 in Precipitation T-Hg ngL 4 2 0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 MD00 b) 160 MD08 Precipitation 140 MD99 120 100 Precipitation -1 80 cmY 60 40 20 0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 14 c) T-Hg Deposition MD00 12 MD08 MD99 10 -2 Mercury Deposition 8 6 T-Hgug m 4 2 0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 Mercury Concentration in Precipitation a) 10 Annual T-Hg Concentration 8 -1 6 4 SERC L ng T-Hg MD00 2 0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 10 b) Annual T-Hg Concentration 8 -1 Frostburg 6 4 T-Hg ng L ng T-Hg MD08 2 0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 12 Annual T-Hg Concentration c) 10 -1 8 Beltsville 6 4 T-Hg ng L ng T-Hg MD99 2 0 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 Young of the Fish Year Study Site Latitude Longitude Map Number Sharptown-nanticoke 38.53876 75.72741 1 Plum-Point Head of Bay 39.48696 76.11385 2 Mill Town Patuxent River 38.63302 76.69111 3 White Perch Eagle Harbor Patuxent River 38.57051 76.68219 4 Tuckahoe Lake 38.96854 75.94462 5 Piney Reservoir 39.70842 79.0018 6 Savage River Reservoir 39.54327 79.13751 7 Liberty Reservoir 39.44576 76.88376 8 Prettyboy Reservoir 39.65239 76.74183 9 Bass Cash Lake 39.03199 76.79729 10 Lake Lariat 38.37774 76.42265 11 Deep Creek 39.55807 79.35482 12 Loch Raven 39.46250 76.57814 13 250 Largemouth Bass Mean 200 Hg Concentration 2008 2009 2010 150 2011 wet wt) 2012 -1 2013 2014 100 2015 Hg(ng g 2016 2017 50 0 Cash LakeLake Lariat Deep CreekLoch Raven Liberty Reservoir Tuckahoe Lake Prettyboy Reservoir Savage River Reservoir Piney Reservoir- Frostburg 25 Nanticoke 20 ) -1 15 White Perch 10 Hg (ng g (ng Hg 5 0 2008 2010 2012 2014 2016 2018 Year 250 Cash Lake 200 ) Largemouth -1 150 Bass 100 Hg (ng g 50 0 2008 2010 2012 2014 2016 2018 Year 90 Savage Reservoir 80 70 Fish Size 60 50 Fish Length (mm) Length Fish 40 30 2008 2010 2012 2014 2016 2018 Year Largemouth Bass 300 Savage Reservoir 250 ) 200 -1 Fish Hg 150 Hg (ng g 100 50 0 2008 2010 2012 2014 2016 2018 Year Factors that control mercury methylation and methylmercury in biota 1) Activity of Hg methylating bacteria 2) Availability of mercury for methylation 3) Connectivity of sites of methylation to food web 4) Length and structure of the food web Mercury Methylation Mercury methylation is a biological process performed by bacteria and some fungi. Hg methylation primarily occurs in anaerobic bacteria such as sulfate and iron reducers and methanogens. Methylating bacteria are in competition with other bacteria for available carbon and electron acceptors such as sulfate and iron. The availability of mercury to bacteria is controlled by chemical ligands such as sulfide and organic ligands such as thiols. Need to create the ideal setting for methylation to occur. What is that setting? + available carbon for bacteria Impact of Land-use 110 109 Hydrology of the Streams 7 7000 6 Watershed 109 6000 5 5000 ) 3 4 4000 Spring Flow 3 3000 Flow(m 2 2000 Precipitation (mm) Precipitation 1 1000 Started Ag 0 0 Reforestation 12/1/06 4/1/07 8/1/07 12/1/07 4/1/08 8/1/08 12/1/08 Started in 2014 7 6000 6 Precipitation Watershed 110 Flow 5000 5 4000 ) 3 4 3000 3 Winter 2000 Flow(m 2 Recharge Precipitation (mm) Precipitation 1 Dry Summer 1000 0 0 12/1/06 4/1/07 8/1/07 12/1/07 4/1/08 8/1/08 12/1/08 Total-Filterable-Hg concentrations in surface water of two SERC watersheds 14 110 12 109 -1 10 8 6 Filterable Filterable T-Hgng L 4 2 0 1/1/2007 1/1/2008 1/1/2009 1/1/2010 1/1/2011 1/1/2012 1/1/2013 1/1/2014 Filterable MeHg Concentrations in Stream water 2007-2013 10 1 -1 0.1 Filterable Filterable MeHgng L 0.01 110 109 0.001 1/1/2007 1/1/2008 1/1/2009 1/1/2010 1/1/2011 1/1/2012 1/1/2013 1/1/2014 Average Filt-MeHg 2007-2013 W110 1.4 -1 1.2 1.0 0.8 F-MeHg0.6 ng L 0.4 0.2 0.0 Jan Feb March April May June July Aug Sept Oct Nov Dec Schematic Model of Biogeochemical Proces in Riparian Zone Forested Decrease in Hg Bioavailability with Low nitrate reduction of DOC? High Hg Agriculture Carbon Pool Transformations Stream High nitrate Lower Hg Respiration Denitrification Sulfate reduction Timing of processes are different between the two watersheds We do not have a good handle on fluxes to Bay from small streams Estimates of 18,000 small streams How representative are the two SERC streams? Is the between difference in watershed methylmercury production reflected in the biota? 600 110 500 400 -1 300 109 200 MeHgg ng 100 0 2016 Data Amphipods Isopods 1000 800 109 -1 110 600 400 T-Hg ng g ng T-Hg 200 0 What about Lakes, Reservoirs and Chesapeake Bay? Aeration of bottom water? Hypoxic Volume Mercury methylation moves from sediment to bottom water? H1- Aeration decreases net MeHg production by reducing hypoxic volume H2 - Aeration increases MeHg because of mixing of increased circulation through sediment porewater. Current Study in Rock Creek 0.4 MeHg in Water 0.3 RC-1 Deep RC-1 Surface -1 0.2 MeHgng L 0.1 0.0 7/6/2018 7/10/2018 7/14/2018 7/18/2018 Low Resuspension High Resuspension MeHg ng g-1 d.w. MeHg ng g-1 d.w. 0 1 2 3 4 0 1 2 3 4 0 0 5 5 10 10 15 15 Depth (cm) Depth (cm) 20 20 25 25 Me199Hg ng g-1 d.w. hr-1 Me199Hg ng g-1 d.w. hr-1 0.00 0.02 0.04 0.06 0.08 0.00 0.02 0.04 0.06 0.08 0 0 5 5 10 10 15 15 Depth (cm) Depth (cm) 20 20 25 25 Phytoplankton Blooms Nutrients Hg Algal Bloom Bacteria MeHg Other factors of interest? How about selenium? YOY study Mercury in fish and Se:Hg Molar Ratios 4.0 3.5 3.0 2.5 2.0 1.5 1.0 MolarHgconcentration 0.5 0.0 0 10 20 30 40 50 Molar Se Concentration Missing information Dry deposition – throughfall? Stream and reservoir food webs? Chesapeake Bay food web? Current importance of anoxic bottom water? Climate change? Shift in nutrient status and methylation? Impact of restoration activities? Urban loading? Conclusions We have made some progress in understanding mercury cycling but we need to do a lot more to make informed management decisions .