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Assessment of mercury bioaccumulation within the lower food web of lakes in the western Great Lakes Region. “Super Odon-8 Hotel”. Kris Rolfhus, Britt Hall, Michael Paterson, and Bruce Monson. Introduction. What controls Hg bioaccumulation in food webs? Food web structure

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Assessment of mercury bioaccumulation within the lower food web of lakes in the western Great Lakes Region

“Super Odon-8 Hotel”

Kris Rolfhus, Britt Hall, Michael Paterson, and Bruce Monson


Introduction web of lakes in the western Great Lakes Region

  • What controls Hg bioaccumulation in food webs?

  • Food web structure

  • Efficiency of transfer

  • Complexity of food web

  • Benthic vs. pelagic source

  • Inputs—processes affecting MeHg synthesis, transport

  • Atm deposition

  • Methylation rate

  • Speciation

  • Microbial abundance, activity

  • S, OM

  • Transport to base of food web


Trends observed in bioaccumulation studies web of lakes in the western Great Lakes Region

…within systems of similar [MeHg], trophic structure and transfer efficency may be most important…

…in systems that differ in multiple properties, MeHg supply to base of food web appears to be most important…


  • Why focus on lower food web? web of lakes in the western Great Lakes Region

  • Largest extent of bioaccumulation is in LFW

  • (water to particles in particular)

  • Least studied in terms of structure, function

  • …data sets are sparse, incomplete, and scattered

  • Pelagic:

  • Water/Seston/Zoops/Preyfish/Piscivores

  • Benthic:

  • Sediment/Invertebrates/Preyfish/Piscivores

  • Measures: MeHg, THg, 15N, 13C, ancillaries


Bioconcentration Factor (BCF) web of lakes in the western Great Lakes Region

accumulation due to respiratory/dermal source

= [tissue]/[water]

Biomagnification Factor (BMF)

accumulation due to dietary source only

= [tissue]/[diet]

Bioaccumulation Factor (BAF)

accumulation due to all sources

= [tissue]/[given trophic level]

…not all BAF’s are consistent or relevant…


  • Speciation Matters… web of lakes in the western Great Lakes Region

  • Use of MeHg rather than Total Hg…

  • Methylmercury is the accumulating form…

  • Data are less abundant for a number of reasons…

  • Difficulty/cost of MeHg analysis

  • Historically THg data


  • What are the important questions? web of lakes in the western Great Lakes Region

  • What has a bigger influence on predatory fish Hg,

  • trophic structure or supply of aqueous MeHg?

  • What is extent of spatial variation in

  • LFW bioaccumulation?

  • 3. Is benthic or pelagic food web more important?


Data Sets web of lakes in the western Great Lakes Region


Sublethal & reproductive effects on fish web of lakes in the western Great Lakes Region

USEPA fish criterion for

MeHg (0.3 µg/g)

Voyageurs National Park--Northern Pike


Mukooda Lake web of lakes in the western Great Lakes Region

Ryan Lake

181 ng/g

943 ng/g

Yellow Perch

17 ng/g

197 ng/g

Zooplankton

3.5 ng/g

8.3 ng/g

Seston

< 0.045 ng/L

Water

0.30 ng/L

2004 Collection


VOYA Trophic Transfer Efficiency web of lakes in the western Great Lakes Region


Aqueous MeHg Concentration web of lakes in the western Great Lakes Region


Seston MeHg Concentration web of lakes in the western Great Lakes Region

N/A

N/A


Bulk Zooplankton MeHg Concentration web of lakes in the western Great Lakes Region

N/A

N/A


Seston/Water BAF Comparison web of lakes in the western Great Lakes Region

BAF range: 0.90

8-fold

N/A

N/A


Zooplankton/Water BAF Comparison web of lakes in the western Great Lakes Region

BAF range: 0.71

(5-fold)

N/A

N/A


BAF Comparisons web of lakes in the western Great Lakes Region

N/A

N/A


  • Conclusions (thus far)… web of lakes in the western Great Lakes Region

  • BAFs are fairly consistent among contrasting sites

  • Sources of MeHg BAF variation to food web:

  • Aqueous [MeHg] 2.0 log units

  • Water to Seston 0.9

  • Seston to Zoop 1.0

  • Zoop to Preyfish 1.0


  • What’s next… web of lakes in the western Great Lakes Region

  • Sediment BSAFs involving benthic invertebrates

  • Compile further data from the literature

  • (do we have yours?)

  • Compare THg to MeHg BAFs

  • What is controlling [aqueous MeHg]?


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