M. Clayden, K. Batchelar, B. Wyn and K. Kidd University of New Brunswick, Saint John

Accumulation and effects of mercury in yellow perch and supporting lake food webs in Kejimkujik National Park

Studying mercury (Hg) in Keji’s aquatic ecosystems 1. Changes in Hg concentrations in yellow perch over a decade:

mid-1990’s – 2007 2. Effects of Hg on yellow perch health 2009 – 2010

3. Bioaccumulation of Hg in lake food webs 2006 -2010

Loon

1) Increasing mercury in yellow perch Brianna Wyn, M.Sc. project, 2006-2007

• Examined changes in total mercury (THg) in yellow perch in 16 lakes

• 1996-97 to 2006-07

• Perch Hg ↑ 29% in 10 lakes • ↓ 21% in 3 lakes • Unchanged in 3 lakes • Fish Hg ↓ elsewhere in North America • e.g. Wisconsin, Adirondacks (Hrabik et al. 2002; Dittman & Driscoll 2009)

1) Increasing mercury in yellow perch

Wyn 2008

Wyn B, Kidd KA, Burgess NM, Curry RA, Munkittrick KR (2010). Increasing mercury in yellow perch at a hotspot in Atlantic Canada, Kejimkujik National Park. Environmental Science and Technology;44:9176-81.

1) Why is Hg increasing in Keji perch? • Aerial Hg deposition to Keji

constant since 1990’s • sulfate deposition ↓ • % change in perch Hg related

to acidity, organic carbon • Total N ↑, hypolimnetic O2 ↓ • Bacterial methylation ↑ ? • Greater trophic transfer of

Hg? (Wyn et al. 2010)

2) Studying effects of Hg on yellow perch health K. Batchelar, MSc. Project, 2009-2011

• Effects of Hg on wild fish from remote areas are not well studied

• Based on lab studies, estimated threshold for adverse effects of Hg on fish is ~0.33 µg/g ww in muscle tissue (Beckvar, 2005)

• 57% of Keji perch sampled exceeded this threshold

2) Perch health study lakes in Keji

12 lakes in total

2009

2010

2) Perch general health endpoints Endpoints examined: • Condition • Liver somatic index (LSI) • Macrophage aggregates (MAs)

in liver, kidney, and spleen

Findings: • No evidence condition or LSI was

negatively affected by Hg • Hg may affect female perch health at

the cellular level • Liver MAs contained 2.45X more Hg

than adjacent liver cells • ↑occurrence of MAs with ↑ liver

inorganic Hg (independent of age) • Determined using residuals

(shown in figure) of linear regressions between perch age and MA occurrence

Liver

MAs

MA

2) Perch reproductive health endpoints Endpoints examined: • Gonadosomatic index (GSI) • Germ cell development • Plasma estradiol

concentrations (females)

Findings: • No evidence any endpoints were

adversely affected by Hg

• Perch Hg concentrations were lower than those in lab studies showing Hg effects on reproduction

• Perch were sampled early (Sept.) in their maturation, effects may occur closer to spawning in May

Female

Male

Sections of gonad tissue from perch. Females: Chromatin nucleolar (*), perinucleolar (a), and cortical alveolar (b) oocytes. Males: spermatogonia (1), spermatocytes (2), spermatids (3), and spermatozoa (4).

• Hg exposure may result in ↑ cellular breakdown in Keji perch • No adverse effects on perch reproductive health, or organ and

whole-body level health (LSI and condition)

Keji perch appear to be able to tolerate high Hg concentrations, without major health effects

WHY?

• Perch are known to be tolerant of metal contamination • Other fish species within Keji may be more sensitive • Species used to estimate ~0.33 µg/g ww threshold may be more

sensitive

2) Perch health conclusions

Batchelar KL, Kidd KA, Drevnick PE, Munkittrick KR, Burgess NM, Roberts AP, Smith, JD (In press). Evidence of impaired health in yellow perch (Perca flavescens) from a biological mercury hotspot in northeastern North America. Environmental Toxicology and Chemistry. Batchelar KL, Kidd KA, Munkittrick KR, Drevnick PE, Burgess NM (In review). Reproductive health of yellow perch (Perca flavescens) from a biological mercury hotspot in Nova Scotia, Canada. Science of the Total Environment.

3) Studying Hg biomagnification in lake food webs M.Clayden & B.Wyn, M.Sc. projects, 2006-2011

• Stable isotope analysis is a common technique in ecological research

Trophic position

[Hg]

Slope =

“Biomagnification rate”

• Isotope signatures of tissues indicate: – Feeding habits – Position in the food chain or web (trophic position)

• Nitrogen isotopes used to estimate trophic position • Hg and N isotopes of organisms related in aquatic food webs • Measure MeHg in invertebrates, THg in fish (>90% of THg in fish is in the form of MeHg)

Hilchemakaar

George

Wyn et al. 2006-2007

Clayden et al. 2009-2010

3) Food web study lakes in Keji

Measured Hg and trophic position in fish and invertebrates in 11 lakes in Keji

Trophic position

[Hg]

Lake A Lake B

3) Does Hg biomagnification differ among lakes? If so, could this be due to lake chemistry?

• Rates of Hg biomagnification differed significantly across lakes (ANCOVA, p < 0.001)

• Similar to other less acidic systems (0.13 – 0.23)

• Higher Hg biomagnification rates in lakes with lower TOC, lower calcium, but not related to lake pH (R2 = 0.08, p = 0.42)

R² = 0.5402

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

1.0 10.0 100.0

Bio

mag

nific

atio

n ra

te

Log-TOC (mg L-1)

3) Hg biomagnification is related to lake chemistry

R² = 0.4881

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.10 1.00Log-Calcium (mg L-1)

Lake chemistry data: Environment Canada’s Acid Rain Monitoring Program

Clayden, M.G. K.A. Kidd, B. Wyn, J.L. Kirk, D.C.G. Muir, N.J. O’Driscoll.. (In Review) Rates of mercury biomagnification are higher in lower nutrient lakes. Environmental Science & Technology. Wyn, B. K.A. Kidd, N.M. Burgess, R.A. Curry. 2009. Mercury biomagnification in the food webs of acidic lakes in Kejimkujik National Park and National Historic Site. Can. J. Fish. Aquat. Sci. 66:1532-1546.

• Role of organic matter in Hg bioavailability is enigmatic • Higher nutrients can dilute [Hg], leading to biomass and

growth dilution (Pickhardt et al. 2005; Karimi et al. 2007)

• Higher calcium may decrease bio-membrane permeability (Spry & Weiner 1991)

– linked to lower gill permeability, less Hg uptake by fish (Rodgers & Beamish 1983)

– But diet is more important route of Hg uptake in fish (Kidd & Batchelar 2011)

3) Hg biomagnification rates and nutrients

3) Hg in aquatic invertebrates

• Hg biomagnification rates not related to Hg in perch

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

0.10 0.15 0.20 0.25

Mea

n ye

llow

per

ch lo

g-TH

g (µ

g g-

1 )

Hg biomagnification rate

• More Hg in perch with higher methyl Hg in Limnephilid caddisflies (R2 = 0.31, p = 0.04)

Insectsofiowa.com

• Yellow perch Hg increased 29% in ten

lakes, 1996-97 to 2006-07

• Hg is affecting yellow perch health at a cellular level

• No evidence of reproductive impairment in perch

• Hg biomagnification rates similar to less acidic lakes elsewhere

• Higher Hg biomagnification in lakes with lower nutrient content

Conclusions

Photo Y. Fuchs

Paulina Bahamonde Tim Barrett Ben Barst Neil Burgess Tom Clair Lauren Del Bel Ian Dennis Paul Drevnick

Sam Edmonds Yoann Fuchs Mark Gautreau Nina Gottselig Marc Houle Laurent Jonart Gretchen Lescord Jane Kirk Blaine Mailman

Angella Mercer Chris McCarthy Derek Muir Kelly Munkittrick Nelson O’Driscoll Sally O’Grady Amanda Valois Xiaowa Wang Erin Whidden

Acknowledgements