1. Alexandria Marquardt Oregon State University May 10th, 2013
An Observational and Experimental Investigation of Population and Stage-specific Responses to Salinity in the Pacific Chorus Frog (Pseudacris regilla)
Alexandria Marquardt
Oregon State University
May 10th, 2013

2. Motivation
Anecdotal evidence of Pacific Chorus frog tadpoles in saline (boundary) pools near the ocean
Lacking vegetation
Exposed
Assumed variable salinity levels
In the last few years the Garcia lab has received anecdotal evidence that Pacific Chorus frog (PCF) tadpoles had been found in pools alongside the ocean. PCF typically begin breeding in mid-February with adults utilizing freshwater ponds with emergent vegetation. The pools in question have little to no emergent vegetation and were assumed to have variable salinity levels – some well exceeding what you would expect PCF to be able to survive in. We have begun to call these “boundary pools” as they are on the rock faces and cliffs along the ocean, but not tidally influenced. In other words, they are not inundated by waves.
For this reason we designed a study to determine the tolerance of PCF populations to salinity

3. Hypothesis
Populations will exhibit different tolerance to saline conditions
Older age classes less affected by salinity
Based on the proximity of our populations to the ocean, we hypothesized that the coastal populations would be more tolerant to saline conditions than inland populations. Additionally, since we had initially thought the tadpoles were being washed in by large rain events (since there had been no sightings of egg masses in the boundary pools), we included 2 age classes to determine if there is a stage specific response to salinity.

4. Experimental Design 2x5x5 Fully factorial design 2 age classes
Hatchling & 5 week old
5 populations
Inland (Finley National Wildlife Refuge, Dairy Barn)
Coastal Dune (Baker Beach State Park, South Beach State Park)
Boundary (Fogarty Cr.)
5 salinity treatments
Control, 0.4ppt, 4ppt, 8ppt, & 16ppt
Fully factorial design, 2x5x5.
Total of 300 experimental units

5. Field Surveys and Collection
Collected egg masses – Feb & April 28th
Identified second boundary population May 25th 2013
Variable salinity levels measured at Cape Perpetua (boundary site)
We collected egg masses from the 2 dune and 2 inland populations from Feb and were unable to locate any boundary populations at that time. On April 28th we located the first boundary pool population on a private property near Fogarty Creek. We not only found tadpoles, but also breeding adults and viable egg masses. We collected egg masses from this site. Additionally, we located a second boundary population that exhibited delayed breeding phenology May 25th 2013 at Cape Perpetua.
Cape Perpetua is particularly interesting, because we measured a pool that contained egg masses and tadpoles that measured at ~10ppt. Well above the threshold you would expect them to survive. The pool is in a location to receive large amounts of ocean spray, but has a strong feeding freshwater seep – which makes me wonder how the tide/seep dynamics impact the overall salinity of the pools.

6. Data Collection - Hatchling
Weekly overhead photographs
Analyzed using ImageJ software
Daily checks for mortality
Weekly overhead photographs, daily check for mortality. 150 experimental units

7. Data Collection – 5 week old
Weekly total length measurements
Weekly measurement of Gosner stage
Total length and measured Gosner stage weekly. 150 experimental units

8. Conclusions/Summary Data collection still in progress
Trends show a treatment effect
Waiting to finish boundary population
We are currently still in the process of analyzing the images collected from the hatchling experiment, and due to the late breeding of the boundary pool population we are still running a portion of the experiment. That being said, we have already noticed some trends in the preliminary data. There is a very obvious treatment effect – with the highest two treatments dying in the first few days of the hatchling experiment. We are waiting to determine if there is a population effect until we have a complete data set to work with – especially since the boundary population is our ‘population of interest’.

9. Questions?