The late spring storms of the previous day had moved eastward, leaving in their wake flooded farm fields and saturated roadside wetlands. At dusk, we loaded the Ford Escort wagon and headed South from Sioux City, IA. We bumped along the maze of farm roads intent upon listening for croaks and snores in the night. At one roadside wetland, I heard my first congress of Spadefoot toads. The sound was deafening, invoking everything that a “congress of snoring toads” brings to mind. Around the corner, in a low spot of a corn field, a lone Spadefoot toad called for a mate; he was joined by a rather enthusiastic Copes Gray tree frog and several chorus frogs. The congress down the road provided a rolling base to these more melodic anurans.
Monday, February 2, 2015, is World Wetlands Day. Wetlands exist in many different shapes and sizes and in many different geographies: coastal margins, mountain valleys, beaches and rocky shores, estuarine wetlands where tidal saltwater and freshwater mix, and inland wetlands (1,2). Some of them are ephemeral, some of them permanent. Wetlands serve many different functions, from providing habitat and food for plants and animals to offering protection from floods and maintaining water quality. One acre of one-foot deep wetland is estimated to hold 330,000 gallons of water (3). Coastal wetlands are important for reducing storm erosion by reducing tidal surge and buffering the wind, and in the US alone, this benefit has an estimated value of 23.2 billion USD each year (4,5).
Many wetlands are important for maintaining water quality. Wooded riparian wetlands next to streams and ponds can reduce pollution and trap sediment, removing substances such as nitrogen, phosphorus, and pesticides from agricultural runoff before they reach surface waters (2,3). Removing these compounds from agricultural runoff can help preventing the development of smelly, eutrophic lakes and toxic algal blooms such as the one in Lake Erie in 2014 that affected drinking water for the city of Toledo, forcing residents to turn to bottled water (6).
The water purification functions of wetlands depend upon several factors including vegetation and the microbial community of the wetland. The microbes that are found in wetlands are responsible for catalyzing most of the chemical transformations that clear the nitrogen, phosphorus, pesticides and other compounds from the water before it returns to the ground water or enters nearby surface water (1). In fact, wetlands are so effective at purifying water that artificial wetlands are being created to filter and treat waste water and water polluted from mining activities (1).
Monitoring the microbial populations is an important aspect of monitoring water quality, whether monitoring the health of the wetland microbial community or monitoring for the presence of unwanted bacteria. This kind of field work benefits from quick, portable assays. Traditionally, microbiologists have obtained water samples and returned to the laboratory to culture and count organisms, with this process taking at least 24 hours. The delay to results prevents quick action to limit recreational access to unsafe waters, or if the health of an ecosystem is at stake, it can delay the implementation of measures to restore a community of beneficial microbes in an ecosystem.
Researchers at UCLA have recently tested a more portable assay method for detecting fecal indicator bacteria (FIB) with the goal of monitoring beach wetlands to protect swimmers and surfers. This method, covalently linked immunogenic separation/adenosine triphosphate technique (COV-IMS/ATP), was compared to traditional culture techniques and more elaborate assays such as qPCR. In this method, magnetic beads are covalently attached to antibodies specific for FIB. The beads are mixed with a water sample where they capture the targeted bacteria. The FIB are lysed and an ATP-dependent luciferase reaction is used to quantitate the FIB present in the sample. In study, the researchers used the BacTiter-Glo™ Microbial Cell Viability Assay and the GloMax® 20/20 Luminometer. Results from the pilot study indicate that this highly portable assay compares favorably to the traditional methods, but is less time consuming (results can be obtained in about an hour), and the COV-IMS/ATP assay doesn’t require the same scientific expertise as the qPCR method, making it accessible to a wider community of individuals who might be interested in water-quality monitoring (7).
As fresh water sources and growing populations continue to collide, understanding and protecting wetlands becomes increasingly important for maintaining clean water sources for natural habitats, human consumption and recreation. Faster and more responsive methods for monitoring the beneficial and harmful microbial communities of wetlands and other water sources are necessary. Bringing molecular tools like luciferase assays into the field is a first step.
- Carter, V. US Geological Survey. National Water Summary on Wetland Resources. USGS Water Supply Paper 2425 [Internet: http://water.usgs.gov/nuwsum/WSP2425/hydrology.html accessed 1/31/2015]
- Evans, R., Gilliam, J.W., Lilly, J.P. (1996) Wetlands and Water Quality. North Carolina Cooperative Extension Service [Internet: bae.ncsu.edu/programs/extension/evans/ag473-7.html accessed 1/31/2015]
- Miller, B.K. Wetlands and Water Quality. Dept. of Forestry and Natural Resources. School of Agriculture. Purdue University Cooperative Extension Service [Internet: https://www.extension.purdue.edu accessed 1/31/2015]
- S. Department of the Interior. Chapter 8 Coastal Louisiana [Internet: www.doi.gov/pub/opec/wetlands2/v2ch8.cfm accessed 1/31/2015]
- World Wildlife Fund. The Value of Wetlands [Internet: panda.org/about_our_earth/about_freshwater/intro/value accessed 1/31/2015]
- Arenschield, L. (2014) Curbing phosphorus would quickly slash algae in Lake Erie. The Columbus Dispatch. [Internet: http://www.dispatch.com/content/stories/local/2014/08/19/Lake-Erie-algae-phosphorus-runoff-water-quality.html accessed 2/1/2015]
- Zimmer-Faust, A.G. et al. (2014) Performance and Specificity of the Covalently Linked Immunomagnetic Separation-ATP Method for Rapid Detection andEnumeration of Enterococci in Coastal Environments Envir. Micro. 80, 2705–14.
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