Copper Sensitivity in Glochidia:
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Copper Sensitivity in Glochidia: Assessing the Effect of Water Composition on the Sensitive Larvae of Freshwater Mussels. Patricia Gillis. Introduction - Freshwater Mussels. 70% of North American freshwater mussels are either endangered, threatened or in decline

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Patricia gillis

Copper Sensitivity in Glochidia:

Assessing the Effect of Water Composition on the Sensitive Larvae of Freshwater Mussels

Patricia Gillis


Introduction freshwater mussels

Introduction - Freshwater Mussels

70% of North American freshwater mussels are either endangered, threatened or in decline

Their decline is attributed to a number of factors including:

- loss of habitat

- decline in fish host populations

- invasive species

- over harvesting

- environmental pollution


Patricia gillis

Introduction - Lifecycle of Freshwater Mussels


Introduction contaminants as threats to mussels

Introduction – Contaminants as Threats to Mussels

  • Field surveys find that populations are skewed towards older individuals – failed recruitment?

  • Early life stages most sensitive to contaminants.

  • Recovery strategies for endangered mussels indicate the need to assess the impact of waterborne contaminants.


Introduction copper and the blm

Introduction – Copper and the BLM

  • Like all molluscs - freshwater mussels are especially sensitive to copper.

  • Concerns whether current water quality regulations for copper would protect the sensitive early life stages.

  • Copper bioavailability is influenced by water composition → Biotic Ligand Model (BLM).


Introduction biotic ligand model

H+

Gill or Biotic Ligand

Ca2+

Na+

Na+

organic

complexes

H+

Mn+

NOM

M

.

inorganic

complexes

Ca2+

HCO3-

active

influx

Cl-

renal

excretion

chlorides

hydroxides

carbonates

sulphides

passive

efflux

Chemistry

Physiology

Toxicology

Regulatory needs

Introduction - Biotic Ligand Model

Paquin et al., 2002. Comp. Biochem. Physiol.


Introduction biotic ligand model1

H+

Gill or Biotic Ligand

Ca2+

Na+

Na+

organic

complexes

H+

Mn+

NOM

M

.

inorganic

complexes

Ca2+

HCO3-

active

influx

Cl-

renal

excretion

chlorides

hydroxides

carbonates

sulphides

passive

efflux

Chemistry

Physiology

Toxicology

Regulatory needs

Introduction - Biotic Ligand Model

Paquin et al., 2002. Comp. Biochem. Physiol.


Part i

Part I

Assessing the Copper Sensitivity of Glochidia

A

B


Part i goals

Part I - Goals

  • Examine copper sensitivity in glochidia from both common and endangered species of freshwater mussels.

  • Investigate the influence of water composition (hardness, DOC) on the sensitivity of glochidia to copper.

  • Determine if current water quality regulations for copper protect glochidia.

A

B


Methods collection and holding of mussels

Methods - Collection and Holding of Mussels

  • Gravid mussels were collected under a Species at Risk Permit (SECT 06 SCI 007).

  • Mussels were held in the lab at 10oC (in order to prevent the release of glochidia).

  • Mussels were fed a commercial shellfish diet (4.6x106 cells mL-1 day-1).

A

B


Patricia gillis

0.5 mm

0.5 mm

Methods - Conducting Toxicity Tests with Glochidia

  • Collect glochidia from mature mussel

  • Expose glochidia to a range of copper

  • concentrations (vary water composition)

A

B

  • Assess glochidia viability→EC50

  • (if they close - they are viable)

+ salt =

ASTM 2006. Guidance for Conducting Laboratory Toxicity Tests with Freshwater Mussels


Acute copper toxicity in glochidia

A. ligamentina

40

L. siliquoidea

L. recta

30

Copper EC50 (mg/L)

20

10

0

Species

Acute Copper Toxicity in Glochidia

Exposures conducted in reconstituted soft water

Error bars represent 95% confidence intervals around the EC50s

Gillis et al., AQ TOX. In Press


Acute copper toxicity in glochidia1

A. ligamentina

40

L. siliquoidea

L. recta

E. torulosa rangiana

E. triquetra

L. fasciola

30

O. subrotunda

P. fasciolaris

V. fabalis

Copper EC50 (mg/L)

20

10

0

Species

Acute Copper Toxicity in Glochidia

Endangered (Canadian)species to right of dashed line

Exposures conducted in reconstituted soft water

Error bars represent 95% confidence intervals around the EC50s

Gillis et al., AQ TOX. In Press


Patricia gillis

Water Composition Affects Copper Sensitivity

(E.triquetra)

Soft Water = 40 mg CaCO3/L, Hard Water = 165 mg CaCO3/L

‘Low’ Dissolved Organic Carbon (DOC) = 0.3-0.6 mg C/L, ‘High’ DOC = 1.6-1.7 mg C/L

*Bars with different letters are significantly different from each other

Gillis et al., AQ TOX. In Press


Comparison of water quality regulations and copper sensitivity of glochidia

Comparison of Water Quality Regulations and Copper Sensitivity of Glochidia

  • Employed the USEPA online version of the copper BLM

  • to derive exposure-specific water quality criteria.

  • Input pH, DOC, Ca, Mg, Na, K, SO4, Cl, and alkalinity into BLM.

  • When a parameter varied (e.g. pH 7.4-7.8) entered the full range.

  • Criterion Maximum Concentrations (CMC) were derived for each type of exposures.

  • Compare BLM derived criteria to the observed 24 h Cu EC50s.


Comparison of water quality regulations and copper sensitivity of glochidia1

Comparison of Water Quality Regulations and Copper Sensitivity of Glochidia

aCMC = Critical Mean Concentration as derived from the USEPA’s BLM


Comparison of water quality regulations and copper sensitivity of glochidia2

Comparison of Water Quality Regulations and Copper Sensitivity of Glochidia

aCMC = Critical Mean Concentration as derived from the USEPA’s BLM

bCCME = Canadian Council of Ministers of the Environment

Copper Guideline for hardness up to 120 mg CaCO3/L equivalents = 2 µg/L,

for hardness 120-180 mg CaCO3/L equivalents = 3 µg/L


Part i conclusions

Part I - Conclusions

  • Glochidia are very sensitive to copper in reconstituted soft water with the EC50s of 2 endangered species <10 µg/L.

  • Copper sensitivity was significantly affected by water composition: increased hardness and additions of Aldrich Humic acid decreased copper toxicity.

  • Glochidia are protected by current copper water quality regulations, but protection may only be marginal in soft waters with very low concentrations of DOC.


Patricia gillis

Part II

BLM-style Exposures with Glochidia and Copper


Part ii conclusions

Part II - Conclusions

  • Sensitivity to Cu decreases with increasing water hardness. →EC50 3 fold higher in moderately-hard compared to very soft water

  • Natural DOC provides significant protection from Cu toxicity. →EC50 5 fold higher when DOC increased from <1 to 4.4 mg C/L

  • An increase in pH reduces Cu sensitivity. →EC50 >2 fold higher at pH 7.7 compared to pH 6.0

  • Glochidia can only endure limited range of water composition. → Balanced water chemistry appears to be important


Patricia gillis

Acknowledgments

Scientific Input and Lab Assistance

Josef Ackerman, Gerry Mackie, Chris Wood,

Rebecca Mitchell, Astrid Schwalb, Kelly McNichols

Research Funding

Copper Development Association

Department of Fisheries and Oceans (Species at Risk)

World Wildlife Fund (Endangered Species Recovery Fund)


Patricia gillis

Thank-you


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