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