Assessment of Mercury Contamination and Bioaccumulation in Sarasota Bay

Size: px

Start display at page:

Download "Assessment of Mercury Contamination and Bioaccumulation in Sarasota Bay"

Dominic Stevens
6 years ago
Views:

1 Assessment of Mercury Contamination and Bioaccumulation in Sarasota Bay EMECS 9 August 29 th 2011 Yongseok Hong 1,2, Erik Rifkin 2, Randall S. Wells 3,4 Peter Hull 4, Edward J. Bouwer 1 1 Geography and Environmental Engineering, Johns Hopkins University, Baltimore, MD, USA 2 National Aquarium Conservation Center, National Aquarium in Baltimore, Baltimore, MD, USA 3 Chicago Zoological Society, Brookfield, IL, USA 4 Mote Marine Laboratory, Sarasota, FL, USA

2 Inorganic Hg deposition Hg Cycling in Environment Atmospheric Deposition Hg 2+ Hg o Hg Hg 2+ Hg 2+ Hg 2+ Demethylation Hg 2+ Methylation by Microorganisms CH 3 Hg + CH 3 Hg + Low Hg Concentrations High High Hg Concentrations Low Benthic Organisms CH 3 Hg + Plankton

3 Research Objectives High mercury levels in top predators, such as small cetaceans and tuna, are often reported and can cause health problems. Human consumptions of the Hg contaminated fish and the top predators may raise health problems. Better understand the fate and transport of Hg in ecosystems and Hg accumulation in small cetaceans to protect the animals

Watershed size 1200 km 2 Length 90 km long Average depth 2 m

4 Sarasota Bay Sarasota Bay is a coastal lagoonal system formed by a necklace of barrier islands. Watershed size 1200 km 2 Length 90 km long Average depth 2 m Population approximately 600,000 More than 1,400 different native species of plants and animals inhabit the Bay area.

Sarasota Dolphin Research Program Research since 1970 and extensive and robust data set Research on wild dolphin ecology, social behavior, foraging,

5 ppm) and skin (2 ppm). (Bryan et al., 2007)

5 Sarasota Dolphin Research Program Research since 1970 and extensive and robust data set Research on wild dolphin ecology, social behavior, foraging, communication, health, and habitat use Previous study in Sarasota Bay suggested that dolphins accumulated high levels of Hg concentrations in their blood (~0.5 ppm) and skin (2 ppm). (Bryan et al., 2007) Reference Bryan CE, Christopher SJ, Balmer BC, Wells RS Establishing baseline levels of trace elements in blood and skin of bottlenose dolphins in Sarasota Bay, Florida: Implications for non-invasive monitoring. Science of Total Environment 388:

6 Method

7 Field Experiment (November, 2010; June, 2011) 82 45'0"W 82 40'0"W 82 35'0"W 82 30'0"W 27 30'0"N Palma Solar Bay 27 30'0"N 27 25'0"N ± Sarasota Bay Bowles Creek 27 25'0"N!! Gulf of Mexico Whitaker Bayou 27 20'0"N Study Area!! Hudson Bayou 27 20'0"N Kilometers 82 45'0"W 82 40'0"W 82 35'0"W 82 30'0"W

8 Field Experiment In-situ & time integrative measurement of Hg 2+ and CH 3 Hg + in sediment and overlying water : DGT probes deployment (Hong YS, Rifkin E, Bouwer EJ Environmental Science and Technology 45: ) Temperature, ph, oxygen concentrations, conductivity (salinity) Sediments, overlying water, seagrass, benthic organisms (clams, snails), plankton, and dolphins diet fish Lab analysis: THg and CH 3 Hg +, Se

9 DGT Probes <Water DGT probes: 2 weeks> <Water DGT probes in water> <Sediment DGT probes: 1 week>

10 Environmental Sample Collection Plankton Net SSD : Sediment Sampling Device Greg fishing plankton

11 Environmental Sample Collection Tulip Snail Quohog Turtle Grass

12 Environmental Sample Collection <fishing with trowel> <fishing with rod>

13 Results and Discussion

14 Sediment Overlying Water General Water Quality Parameters Parameters Values ph Salinity (g/l) 35 D.O. (mg/l) Temp ( o C) 22 (Nov) 30 (June) DOC (mg/l) TSS (mg/l) VSS (mg/l) FSS (mg/l) Water content (%) POC (%) AVS (umol/g) Fe 2+ (umol/l), porewater

15 Hg Concentrations in the Ecosystem Total Hg concentrations (ng/g w.w.) Sample Standard % MeHg Reference Average Range Deviation Overlying water (ng/l) a Sediment porewater (ng/l) a Sediment a Sea grass ~ 13 a Zoo plankton a Benthic organisms ~ 48 a Mullet fish >80 a Pinfish >80 a Spotted seatrout >80 a Dolphin blood ~100 b Dolphin skin ~100 b a: Present study b: Bryan CE, Christopher SJ, Balmer BC, Wells RS Establishing baseline levels of trace elements in blood and skin of bottlenose dolphins in Sarasota Bay, Florida: Implications for non-invasive monitoring. Science of Total Environment 388:

16 Comparison with Other Environments-Bioconcentration Bioconcentration Factor ( BCF) Hg inorganisms( ng / g) Hg inwater ( ng / g) Overlying Water vs Plankton Sediment Porewater vs Benthic Organisms Log BCF(THg) Log BCF(MeHg) Log BCF (THg) Log BCF (MeHg) Reported log (MeHg BCF in overlying water) 4.8 Long Island Sound, USA (Atlantic Ocean) 4.6 North Sea, Europe (Atlantic Ocean) Fitzgerald et al., Chem. Rev. 107,

17 Comparison with Other Environments - Biomagnification The rates of biomagnification across the food webs were similar despite the differing foodchain coverage. Environment Hg species slope Lancaster Sound, Canada Total Hg 0.2 Northern Baffin Bay, Canada Total Hg 0.2 CH3Hg the Gulf of Farallones, California, USA Total Hg 0.32

18 Risk Assessment of Dietary Hg Exposure of Resident Bottlenose Dolphins in Sarasota Bay, FL Total Dose ( g d 1 kg 1 ) Fish IngestionRate( kg d 1 Hg Conc in Fish( DolphinBodyWeight ( kg) ) g kg 1 ) HQ Total Dose TRV HQ<1, good; HQ>1, no good Toxicity Reference Value: 16 µg kg -1 d -1 for mammalian species (USEPA, Wildlife exposure factors handbook. EPA/600-R ) Dolphin body weight (kg) Fish feeding rate (kg d -1 ) Mullet Pinfish Spotted seatrout fish uptake rate (g kg -1 d -1 ) Hg uptake rate (µg d -1 ) Hg dose (µg kg -1 d -1 ) HQ

19 Risk Assessment of Dietary Hg Exposure of Resident Bottlenose Dolphins in Sarasota Bay, FL Human Study: Blood mercury concentrations above 200 μg/l showed adverse health effects for human (WHO/IPCS, 1990). Blood mercury levels of bottlenose dolphins in Sarasota Bay is about 500 μg/l, but still HQ was smaller than 1. The TRV (16 µg kg -1 d -1 for mammalian species) may need to be updated. WHO/IPCS (1990): Methylmercury. Environmental Health Criteria No 101, World Health Organisation, International Programme on Chemical Safety (IPCS), Geneva, Switzerland, 1990.

20 Conclusions Observe comparable bioconcentration factors and biomagnification rate. Probably, the factors and rates across the ecosystems were similar despite the differing food-chain coverage and geographic locations. Although current risk assessment model suggests that Sarasota resident bottlenose dolphins are safe from dietary Hg exposure, the blood Hg levels show that the dolphins may encounter potential health risks associated with dietary Hg exposure. Future Work The risk assessment model should be revised. Modeling the observations, link the atmospheric Hg deposition to top predators blood Hg levels. Help regulators to revise Hg release (TMDL) to environments for the protection of wild life and human.

21 Acknowledgement Dr. Edward Bouwer Dr. Erik Rifkin Chuck, Greg, Pete at Mote Marine Lab, FL Bouwer group members

22 Comments and Questions

Methylmercury Bioavailability and Dynamics in the Streams of Piasa Creek Watershed: New Methods 1 of Sam

Methylmercury Bioavailability and Dynamics in the Streams of Piasa Creek Watershed: New Methods of Sampling and Analysis Basic Information Title: Project Number: 2007IL161B Start Date: 3/1/2007 End Date: