Mangrove ecosystems that depend on phosphate nutrients in the Everglades can be found growing over karst substrate at the ecotone between seawater and freshwater—ground zero for saltwater intrusion. (Photo: K. Jimenez)
Congratulations to Dr. Hilary Flower! Hilary has rapidly published a great series of three papers exploring the geochemical outcomes of saltwater intrusion into freshwater environments. Check out Hilary’s work here, here, and here.
Sea levels are rising on account of climate warming that is very real and very now. Most of us understand that rising seas inundate land, flood coastal cities, and threaten human infrastructure. Yet sea level rise has another less visible but perhaps equally dramatic outcome: the intrusion of saltwater into freshwater aquifers, ecosystems, and drinking-water wells. With salts come many chemical changes to water, and to the way water interacts with soils and sediments. Working in the karst limestone system of the Florida Everglades, Hilary investigated how saltwater intrusion affected the sorption and desorption dynamics of phosphate to and from sediments. Importantly, Hilary found that karst sediments lose their capacity to sorb phosphate at the very onset of saltwater intrusion, when the water interacting with sediments is <1% seawater! Rather, sediments desorb (lose) large, immediate pulses of phosphate as soon as they are hit with small amounts of seawater. These findings are critically important because they show that the chemical environment on which organisms and food webs depend is very sensitive to the unseen outcomes (e.g., saltwater intrusion) that ultimately arise from climate change.
The ability of sediment to adsorb phosphate declines sharply at the onset of saltwater intrusion, when the water mixture is less than 1% seawater. The blue and red show phosphate adsorption on two different rock types. These data are from the second article in Hilary’s series (Estuarine, Coastal and Shelf Science 184 (2017) 166-176)
Hilary’s work also highlights the value of interdisciplinary cooperation, as she did her chemical analyses with the Lewis Ecosystems Lab while pursuing her PhD in USF Geosciences under Mark Rains.
This landscape in west-central Florida contains a diverse portfolio of wetlands that vary in size, shape, and connectivity. Many of these are geographically-isolated wetlands.
Good things sometimes come in small packages. Check out this article, that the Lewis Lab participated in, on the importance of small wetlands, high in landscapes, for big ecological functions. This work was led by Matt Cohen, at the Univ. of Florida, and emerged from an EPA-hosted working group.
Landscapes consist of a patchwork of many ecosystems, and they provide services such as the generation of biodiversity, maintenance of key plant and animal populations, storage of water to prevent flooding and ensure available water during dry spells, and the capture of nutrients and sediments to prevent pollution of rivers and bays. Analyses in this paper support the concept that the provision of these services by landscapes depends on a portfolio of many wetlands that vary in size, shape, and connectivity. A host of landscape functions, this paper argues, require the portfolio to include geographically isolated wetlands (GIWs). Owing to their landscape characteristics, these GIWs shelter organisms, sequester captured pollutants, and are connected to other ecosystems in landscapes through sometimes hidden avenues, such as through migration and groundwater flow. This finding has important implications for whether legislation and policies concerned with the quality and biotic integrity of larger rivers and bays should include protection of the many small GIWs that help regulate what materials escape landscapes and enter these waterways.
Geographically isolated wetlands tend to be smaller wetlands (solid black line in upper panel), and more circular. Larger wetlands tend to have irregular shapes (larger perimeter:area ratios; green dots) that deviate from circularity, which is important because many ecological functions happen on the edges of ecosystems where reactants and organisms can mix. Despite the irregular shape of large wetlands, it is small wetlands that provide most of the “edge” habitat in a landscape, as the bottom panel shows that as wetland size decline, area drops off before perimeter length does. (Modified from Cohen et al. 2016, PNAS)
Congratulations to Viviana. She won the award for outstanding oral presentation from among 865 student presentations at a major national scientific conference. Way to go, Viviana! She delivered her award-winning presentation at the 2015 SACNAS conference (Society for Advancement of Chicanos/Hispanics and Native Americans in Science) , held in Washington, DC, in October. Viviana presented findings from her master’s degree research, which investigated how the nutrient status and fertility of residential soils is influenced by the manner in which people manage their yards. She generally found elevated levels of some nutrients, organic matter, and microorganisms in soils that receive more frequent applications of reclaimed water than those that are watered less frequently with conventional water. As water supplies grow scarce, many cities increasingly encourage their citizens to use reclaimed water. This resource, however, is chemically distinct from “regular” potable water, and Viviana’s research is beginning to unpeel some of the unintentional consequences of its use.
When groundwater is conserved, soil carbon in wetlands recovers up to a point. At severe cutback in groundwater use, returns to wetlands are marginal and uncertain.
Check out our recent paper on restoring wetland carbon sequestration when water is conserved!!!
Climate change and water pollution. What causes them? At a fundamental level, these and other undesirable changes to our environment result from the mobilization of particular chemical elements. Accelerated delivery of carbon to the atmosphere, for instance, is the direct cause of climate change. Nature’s ecosystems do have one powerful way to slow down the mobilization and cycling of many elements, and that is to store them in soil organic matter, which is the partially decayed remains of plants, microorganisms, and organic materials exuded by all life forms.
Wetlands are quite impressive reservoirs for soil organic matter and the chemical elements that it stores. Because wetland soil is flooded for long periods of time, organic matter decomposes slowly, and wetlands thus have the capacity to sequester large quantities of carbon and other elements. Unfortunately, voracious water consumption by humans has lowered water tables and dried out wetlands in many areas, resulting in a loss of soil organic matter, and the release of carbon and other polluting elements to the atmosphere, rivers, and seas.
So what might happen if humans appropriated less water. Could wetland soil carbon recover as well? This is a difficult question to answer because there are many steps—each rife with uncertainty—between conserving water and restoring carbon cycles. In this recent paper, the Lewis Lab used an approach called error propagation to investigate whether one could detect changes in wetland soil carbon storage, amid all the noise and uncertainty, when human reliance on a groundwater aquifer was reduced. It appears that increased amounts of carbon in wetland soils may be detectable in the initial stages of water conservation, but that severe cutbacks in aquifer use to the point of human privation may be marginally less helpful for wetland soils.
Bert in a Juncus needlerush salt marsh near Tampa Bay
Congratulations to lab member Bert Anderson! Bert is a PhD candidate who received this year’s Outstanding Teaching Assistant award for the Department of Integrative Biology. Bert set the bar high for excellence in teaching. He more than just assisted, but helped innovate by creating new material and better learning experiences for our undergraduate students. Bert contributed to course design, and developed a feedback system so that student perspectives on courses could be used in solutions for course improvement. He has improved biology education in our department. Great job!
See our recent paper that links increases in urban water use with impaired ecosystem service provided by rural wetlands located in the water-extraction zone.
Cities use water…lots of water. Urban water demand is one of the most confounding issues of our time, because a city can demand so much water that supplies are stretched thin. “Water wars” erupt, as cities are pitted against each other and against other economic sectors like agriculture and extractive industries in scrambles to get dwindling water resources. The losers in these wars are often out-of-sight natural ecosystems, from which excessive amounts of water are extracted in an effort to satisfy all competitors. In a recent publication by the Lewis Lab, we shine a light on these ecosystems. We document how increases in water demand by a large metropolis (the Tampa Bay region of Florida) diminishes the water balance of rural wetlands, as well as the amount of carbon and nitrogen stored in the soils of those wetlands. Typically, wetland soils hold huge reserves of carbon and nitrogen, and the impairment of this “storage” service results in carbon and nitrogen pollution of air, streams, and bays.
A cypress swamp, one of many wetland types. Resulting from groundwater extraction, this swamp is degraded, as indicated by falling cypress trees and the loss and subsidence of organic soil. (Photo: TF Rochow)
Congratulations to Kirsti Martinez! Kirsti is one of only 260 undergraduate sophomores and juniors in the United States to receive the prestigious Barry M. Goldwater Scholarship for the 2015-2016 academic year. Congratulations are especially in order because this award does not simply recognize merit. Applicants had to write a competitive, rigorous research proposal, as well. Kirsti is a member of the Lewis Lab working on her Honors thesis, which investigates how leaf litter inputs from forest trees affect soil properties in upland and wetland habitats. Additionally, she is a member of Dr. Luanna Prevost’s lab, also in our department, where Kirsti participates in biology education research that investigates how biology and ecology are taught at the undergraduate level. Read the press release.
Prairie pothole wetlands in central North America. Credit: Ducks Unlimited. Taken from the National Science Foundation website.
Wetlands come in all shapes and sizes, and one form is the “geographically isolated wetland,” or GIW. Often, GIWs occur in complexes that reach across broad expanses, such as the prairie potholes shown here, which span the central plains of North America. Vernal pools in California, cypress domes in Florida, and pocosins in the Carolinas also occur as vast numbers of small basins scattered across broad landscapes. Wetlands perform many valuable services, such as filtering sediment and pollutants, and thereby protecting lakes, rivers, and bays situated further downhill. But recently, GIWs have come under attack based on the assumption that because they are “isolated,” they do not provide these valuable services. This attack has been so sweeping that the US Supreme Court recently stripped GIWs of many protections, ruling that they don’t fall within the scope of the Clean Water Act. The Lewis Lab participated in a review article, led by John Marton of Indiana University, emphasizing that GIWs are anything but isolated, as they communicate with their surroundings through the movements of organisms and flows of nutrients and groundwater. Our article discovered that GIWs indeed provide services that should place them within the scope of the Clean Water Act. Read it here.
Kristen Langanke, Jeannie Mounger, and Sandy Voors at the USF Undergraduate Research Colloquium.
Great job to the undergraduate researchers in the Dept of Integrative Biology at USF, who presented their posters yesterday at the USF Undergraduate Research Colloquium! Members of our lab presented three posters with authors including Sandy Voors, Kirsti Martinez, Kristen Langanke, and Jeannie Mounger. Thanks to faculty members Christina Richards and Luanna Prevost, and PhD student Bert Anderson, for mentoring these works!!
Congratulations to Bert Anderson, who just passed the PhD proposal examination, and has advanced to the status of PhD candidate. Bert’s research will examine how biogenic habitat modification alters organic matter dynamics in hypersaline coastal salt pans. Now the real work begins!