Mercury in Mosquitofish of the Greater Everglades: Changes in Biogeochemistry and Trophic Complexity over Time and Space -- R-EMAP

Transcription

1 Mercury in Mosquitofish of the Greater Everglades: Changes in Biogeochemistry and Trophic Complexity over Time and Space -- R-EMAP Peter Kalla, Joel Trexler, Curtis Pollman, Brooke Sargeant, Daniel Scheidt, Yong Cai, Guangliang Liu, Xiaoping Yin GEER 2010

2 Mosquitofish Mercury, 1995 & 2005 CORE AREA (Scheidt and Kalla 2007)

3 Mosquitofish Mercury, 1995 & 2005 Wet Season 40% of marsh > 100 ng/g % of marsh > 100 ng/g

4 Mercury, Wet Season 2005 (Scheidt & Kalla, 2007)

5 Surface Water THg (ng/l) (Scheidt and Kalla 2007) Surface Water MeHg (ng/l)

6 Optimal Biogeochemical Conditions for Elevated Mercury in Mosquitofish Surface water SO4: mg/l Bulk density: g/cm 3 Soil TP: mg/kg Surface water DOC: 7 35 mg/l Surface water ph: 6.6 < ph < 8.0

7 Mosquitofish Mercury vs. Surface Water Sulfate,

8 Mercury in Age 3 Largemouth Bass from 100 Florida Lakes

9 CART Model of Mercury in Mosquitofish in the Everglades 77 ng/g thg 138 ng/g thg r 2 N # Splits # Imputes fold cross-validation r 2 = 0.451

10 Mosquitofish Hg CART Model Terms Term Number of SS SS Splits Sigmoid SO4 in surface water 3 117,267 Sigmoid ph 0 0 Total Phosphorus 4 81,618 Chlorophyll-a 1 3,606 DOC 2 29,628 Methyl Mercury 3 69,482 Total Mercury 2 32,926 Bulk Density 1 13,369 Total Mercury in soil 2 70,640 Methyl Mercury 4 20,678 Total Mercury in floc 1 13,212 Methyl Mercury 1 6,979 Chlorophyll-a 0 0 TOTAL ,404 Major variables: SO4 > TP (water) > thg (soil) mhg (water)

11 Recursive Partitioning Modeled Gambusia Hg vs. Observed Concentrations

12 Biogeochemical Prediction of Mosquitofish Mercury Ln fish Hg = f (time, sigmoid SO 4, soil Hg, soil TP, TOC/DOC)

13 Model Prediction vs. Observed Concentration Aggregate r 2 = 0.33

14 Predicted Mosquitofish Mercury for 2005

15 Predicted Changes in fish Hg for 2005 with 50 % and 20 % SO 4 reduction

16 Predicted Changes in fish Hg for 2005, at 50% Sulfate Reduction Largest circles are +/-17 ng/g.

17 THgFish BAFMeHg THGSW MeHgSW BAFTHG BAFMeHG MeHgPE MeHgPF MeHgPB TCSD FDOCPW DOCSW AFDWSD BDSD COND CLSW SO4SW SO4PW H2SPW depth APASW CHLASW TPSW TPFC TPSD1 EVERGLADES ECOSYSTEM ASSESSMENT PROGRAM

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19 Methylation and the Food Web in Periphyton: Optimal Abiotic Conditions (Scheidt and Kalla 2007)

20 Trophic Hypothesis R-EMAP interaction web hypothesis Used path analysis to test food-web hypothesis Density-mediated bioaccumulation considered because mercury not measured for each food-web component Hydrology, Periphyton TP, species composition, and biomass, macroinvertebrate infauna, small herbivorous and omnivorous fish and large macroinvertebrates

21 Trophic Hypothesis R-EMAP interaction web hypothesis Model Infauna - Periphyton Herbivores - Periphyton Omnivores - Periphyton Omnivores - Infauna Omnivores - Herbivores Bottom-up mechanisms Bottom-up and Top-down mechanisms 7

22 Trophic Hypothesis R-EMAP interaction web hypothesis Model 1: All bottomup effects Infauna Omnivores Herbivores Periphyton Biomass Diatoms + Green Algae Time Since Flooding Periphyton Phosphorus

23 Trophic Hypothesis R-EMAP interaction web hypothesis Infauna Omnivores Herbivores Model 6: Both bottom-up and top-down effects Periphyton Biomass Diatoms + Green Algae Time Since Flooding Periphyton Phosphorus

24 Food-Web Hypothesis R-EMAP interaction web Model Number of Parameters BIC Bollen-Stine X

25 Food-Web Hypothesis R-EMAP interaction web Infauna Mercury in Mosquitofish Herbivores Model 1: All bottom-up effects Periphyton Biomass Diatoms + Green Algae Hypothesis: all effects are density mediated Time Since Flooding Periphyton Phosphorus

26 Food-Web Hypothesis R-EMAP interaction web Model Number of Parameters BIC Bollen-Stine X merc merc

27 All Bottom up Effects Omnivore Density Periphyton TP Time Since Flooding Direct Indirect Total Direct Indirect Total Periphyton Biomass Relative Abundance (Diatoms + Green Alg) Infauna Density Herbivore Density Omnivore Density

28 All Bottom up Effects Mosquitofish Hg Periphyton TP Time Since Flooding Direct Indirect Total Direct Indirect Total Periphyton Biomass Relative Abundance (Diatoms + Green Al) Infauna Density Herbivore Density THg mosquitofish * Adding top-down effects does not change these results

29 Food-Web Hypothesis R-EMAP interaction web Both nutrient and hydrological effects propagate through the food web to effect omnivore density all effects are indirect No indirect density-mediated effects were documented for mosquitofish mercury; direct effect of hydrology was noted Future models should consider biomass and uptake-mediated hypotheses

30 Conclusions, Synthesis, Hypothesis, and Implications Mercury in mosquitofish declined, but remains above acceptable limits for about half of the system. Methylation is affected locally by relatively small changes in sulfate, phosphorus, and organic carbon. Bioaccumulation of mercury is dampened or amplified by food web effects, which vary widely throughout the system. Synergistic effects of driving methylation in complex food webs should be avoided when modifying water deliveries.

31 Acknowledgements: Don Axelrad Elmar Kurzbach, Bob Johnson Len Scinto, Joe Boyer Brenda LaSorsa Tim Fitzpatrick Danny Adams, Pam Betts Mel Parsons, Phyllis Meyer, Jerry Ackerman Jenny Richards

32 Recent Program Publications R-EMAP 2005 Web Site at FIU Poster 67 Thursday -- Richards, Gann, et al. G. Liu et al ES&T ES&T B. Sargeant et al Marine & FW Ecol Oecologia