Amphibian ranavirus dynamics in an industrially altered landscape
Danna M. Schock2nd International Symposium on Ranaviruses
Knoxville TN, 27-29 July 2013
Map from the Washington Post
Fort McMurray, AlbertaOilsands, boreal forest, big money & big politics
RV dynamics like prevalence& frequency of outbreaks
Habitat characteristics, Wetland classification
Contaminant levels in amphibian tissues and breeding ponds
Population biology & biomarkers of (chronic) stress
Proximity to disturbancesCan wood frogs be used to monitor ecosystem health in the oil sands?
Establishing field sites – 2012 & 2013
1)Wood frogs breeding at the site
2)In close proximity to air monitoring stations
3)Geographically representative of the landscape*
4)Safe to work
Priority placed on identifying wetlands suitable for long-term monitoring of the oil sands region of Alberta.
Atmospheric deposition and pulses of contaminants into amphibian breeding ponds in the spring
Photo: Dave Cooper, Calgary Herald
Snow sampling March 2013
wood frogs boreal chorus frogs
Canadian toads
Ranaviruses detected widely in wood frogs
12/27 (44%) sites positive at least once from 2010 – 2013
Positive wetlands from Fort Resolution to Fort McMurray
● PCR and/or characteristic lesions and carcasses (~2,200 samples still to screen, including most samples from 2013)
Ranaviruses detected widely in wood frogs
Ranavirus-related die-offs at remote sites (helicopter access only) and highly disturbed sites
Die-offs take place last week of June/first week of July
● irrespective of type of site
● irrespective of spring thaw
Ranaviruses detected widely in wood frogs
The majority of carcasses are tadpoles Gosner stages 37 - 40
All positives sequenced to date are FV3-like
● MCP4/5 primers
● but see Schock et al. 2008 Copeia re “hidden” variability of northern isolates
● additional characterization in progress by J. Brunner
Data collectedBasic information• Species• Snout-Vent-Length• Gosner stage (tadpoles), weight (terrestrials)• Physical abnormalities
Tissue samples• toe/tail clips (several times/year, screen for
RV, Bd)• lethal whole body, once/year, screen for
contaminants and evidence of stress
Water quality• pH & conductivity (handheld meters)• In-depth analysis (3x per active season)
including hardness, and 26 metals, 74 PAH, and 60 NA
Narratives of 3 wetlands
• Jetliner – loss of entire age class
• Tower Road – repeated die-offs, no apparent change in population biology (yet?)
• Gateway – why hasn’t ranavirus been detected here (yet)?
Results – an evolving story
Distribution of mass of terrestrial wood frogs in 2013 at 6 intensively studied sites.
Mass (g)
Jetliner
# o
f in
div
iduals
Jetliner
Jetliner
Wood frog egg masses at Jetliner May 2011
Jetliner Pond
Mass (g) of terrestrial wood frogs 2011 - 2013
2011
2013
2012
# o
f in
div
iduals
Mass (g)
Distribution of mass of terrestrial wood frogs in 2013 at 6 intensively studied sites.
Mass (g)
Tower Road
# o
f in
div
iduals
Tower Road
Tower Road
Distribution of mass of terrestrial wood frogs in 2013 at 6 intensively studied sites.
Mass (g)
Gateway
# o
f in
div
iduals
Gateway
Gateway
Size at metamorphosis is another indication of population health
Snout-vent length (mm) of Gosner Stage 44 wood frogs in 2013
F5,159 = 17.287, P < 0.01aa
b
A role for environmental transmission?
Unrelated 2011 lab study:
Only wood frog tadpoles in reference wetland water and aged tap water became infected.
FV3: apparently “killed” by something in the OSPM water?
Tadpoles in the OSPM water: 85%+ survival Gateway
A role for invertebrates in ranavirus transmission?
• Impede transmission by scavenging carcasses quickly?
• Facilitate transmission or persistence – leeches ?
What about nutrient/energy cycles in these wetlands?
• Die-off years vs non-die-off years?
• Different invertebrate species assemblages?
Data to come:
PCR screening of 2,200+ tissue samples for ranavirus
Water and tissue contaminant analyses
Bio-markers of (chronic) stress – metabolomics, CORT
Other fitness correlates – triglycerides & glycogen
PCA and Regression analyses
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