An Interview with Madeline Wedge, Auburn University School of Forestry and Wildlife Sciences

Auburn University
Madeline Wedge, a researcher with the Auburn University School of Forestry and Wildlife Sciences, spoke to Onset about her wetlands research project involving the use of data loggers to determine whether urban land-use near salt marshes impacts fish.

An Interview with Madeline Wedge, Auburn University School of Forestry and Wildlife Sciences

What is the focus of your wetlands research project?

My research involved studying the impact of land-use alterations on wetland ecosystems. In this year-long study, we looked at saltwater marshes in both urban and non-urban environments in the Gulf of Mexico to see if there were any changes in fish habitat or community structure, or if certain fish species were present in one marsh and not another. Urban land-use has been shown to alter salt marshes through changes in the hydrology, sedimentation, and vegetation, but little is known about how urban land-use near salt marshes impacts fish.

In terms of the specific settings, three of the creeks we studied had neighborhoods around them, and three creeks had forest around them. We used Onset's HOBO Conductivity Loggers to measure water salinity and temperature at each site.

How were the loggers deployed?

We deployed one HOBO U24 Conductivity Logger per creek. I used PVC piping as a case for the loggers, which I drilled holes in and used a screw-top for easy access when offloading the data. I attached the PVC pipe to a coated cable and wrapped the cable around a cinder block, which I sunk out to a depth of 4 to 5 feet in each creek during low tide.

People in the residential areas had good access to the creeks, and I didn't want anyone messing with my equipment or possibly stealing it. So, it was important that the loggers were relatively concealed as well.

During deployment, just to make sure I was getting proper data off every time, I had HOBOware installed on my personal laptop. So I'd offload some data in the field and do a quick check with the software to make sure everything was okay.

How often were the loggers taking measurements and being offloaded?

I had the loggers sampling every five minutes. I probably could have gotten away with less frequent measurements, but it was definitely beneficial to have it set more frequently. We let the loggers fill up with 64 days' worth of data, and we'd go out every two months to offload the data. We used a HOBO data shuttle for the offload. During these site visits I'd also try to clean up the logger and case a bit, in case barnacles or other things were growing on them, and then put the loggers right back in.

What has your analysis of the data shown?

Water temperatures ended up being very similar between the urban and reference creeks, while salinity ended up being lower in the urban creeks. The fluctuations in salinity were much more rapid at the urban creeks as well. In these sites, you have a lot of hard surfaces, pavement and roofing, and there are more fresh water inputs vs. the forested sites.

In general, salinity levels during the study ranged from straight freshwater to upwards of 25 parts per thousand.

The data not only gave us a picture of what's happening in the creeks with differences in surrounding land-use, but also allowed us to see what happened when storm systems went through, and what happened to the fish afterwards. This was the real advantage of sampling every five minutes vs. once per hour. It was nice to have more recorded data to show that storms, which I thought would have impact on salinity and temperatures, did in fact have the impact, rather than just saying it anecdotally.

Were there any particular advantages of the HOBO Conductivity Logger for this project?

We thought the size of the logger was an advantage, as smaller loggers would likely be easier to lose. If you had something smaller, it probably could have easily gotten covered with barnacles and I wouldn't have gotten data off of it. The price was also a key advantage, as it allowed us to track salinity and temperature conditions in six different sites.