Category Archives: News

Sandy explaining it, owning it, defending it.

Congrats to lab member Sandy Voors on defending her Master’s degree! Sandy’s M.S. thesis is entitled “Linking Ecosystem Function and Phenotypic Variation in Spartina Alterniflora Salt Marshes”. Sandy did a great study examining the implications of trait variation in a foundation species (S. alterniflora in salt marshes) for the storage and cycling of carbon and nitrogen in marsh soils. She found a complex association among plant traits, soil biogeochemicial properties, and site effects across several marsh ecosystems. This work contributes to an emerging focus on the importance of populations and phenotypes within species as functionally important sources of biodiversity. Sandy was co-advised by Christina Richards, and did this work as part of a collaboration within Randall Hughes’ Marine Biodiversity lab at Northeastern U. Now that the defense is behind her, graduating in May is the next step!

Check out this recent paper outlining a vision for protecting the least-protected, most-imperiled surfaces waters. It was led by Irena Creed from Western Univ in Ontario, with contributions from a large working group, including us.

Valuation of ecosystem services provided by vulnerable headwater streams and wetlands outside of floodplains in the contiguous U.S.

In the U.S., the Clean Water Act protects interstate “Waters of the USA”. Protecting such waters requires stewardship and conservation of small, upland aquatic systems like wetland basins and headwater streams, whose ecological functions (e.g., flood pulse dampening, pollutant retention, biodiversity reservoir) determine the condition of downgradient Waters of the USA. Yet, conserving upland waters is controversial because preserving them can inhibit land development. Into this fray, the U.S. Supreme Court waded with two landmark cases limiting the Act’s application, and the current administration drags their feet administering the Act. This paper describes the scientific basis for how small & vulnerable waterbodies high in watersheds are linked (biologically and geophysically) to the rivers draining those watersheds, and it provides scientifically grounded options for protecting these vulnerable waters as governments struggle to find solutions for stewarding waters that serve as hotspots of ecological function.

Red mangrove propagules growing the field. Kristen reared huge numbers of these in the greenhouse! (photo: newtonsapple.org.uk/truly-amazing-mangroves)

Congratulations to Kristen Langanke on defending her Master’s thesis and graduating with her M.S. Kristen’s thesis was “Response to nitrogen and salinity conditions in Rhizophora mangle seedlings varies by site of origin”. Kristen collected well over 1200 red mangrove (R. mangle) propagules from a variety of mangrove ecosystem sites, and reared them in the greenhouse under varying conditions of salt and nutrient stress. These two forms of stress are likely to intensify with changing sea levels and pervasive coastal nutrient eutrophication. This study was a nice example of examining phenotypic variation in responses to stress. Kristen’s primary advisor was our frequent collaborator Dr. Christina Richards, and she was a member of the Lewis Lab group as well. Great work Kristen!

Visit this page to take the ecological footprint quiz (you can “log in” with a fake email address to play as a guest): http://www.footprintcalculator.org/

Enter data from your quiz here: Data Entry Form
https://goo.gl/forms/7GsRTobTAmrlPWhX2

Explore the ecological footprint database generated by the whole group: Data spreadsheet
https://docs.google.com/spreadsheets/d/11WtCH2ziqnf2EXKnIk6HiIj4bZrYza931PFNCp3sTyY/edit?usp=sharing

Analyze and interpret ecological footprint data
https://goo.gl/forms/m6lPgRoK9lC6vTxh1

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.

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.

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)