Understanding and managing urban aquatic ecosystems has to begin with good information about their distribution and about characteristics like size and shape (hydrography). We've just received word that our paper on this topic, led by post-doc Meredith Steele, has been accepted for publication in Ecological Applications! One simple thing that makes this paper significant is the spatial extent of Meredith's analysis (100 cities across the whole US). A second simple thing about this paper is what the data show: urban water bodies (lakes, ponds, wetlands) are of moderate size. That is, in comparison to undeveloped land outside cities, there are fewer very large and fewer very small water bodies. The more complicated thing we want to know is how these differences arise. One possibility is that cities are located near particular types of water bodies. A second possibility is that, during urban development, we remove small (and large?) water bodies, and build medium-sized ones. We use some subtler patterns in our data to distinguish among these processes, and ask how their importance might change over time. This paper is the first of several papers Meredith has in review or in prep that will deal with other scales and other aspects of urban hydrographic change. Very exciting! And congratulations Meredith!
Congratulations are due to Ewan Isherwood, who successfully defended his MS thesis this morning at FIU! Ewan's research addresses the distinctness of vegetation communities (ridges and sloughs) in the Florida Everglades, with a particular focus on how these these distinct communities become more blended as a result of hydrologic modification and microtopographic flattening. To do this, Ewan developed statistical proxies of distinctness using multivariate techniques, and applied them across our Everglades-wide sampling regime.
A few weeks ago, Dr. Todd Kana delivered a new instrument to the River Center. The Membrane Inlet Mass Spectrometer, which Todd designs and builds, measures dissolved gases directly from water samples. We had one of these instruments in our lab at FIU, and used it to study denitrification in the Floridan Aquifer and in spring-fed and blackwater rivers.
Yesterday, Todd returned to us to train about 8 people from the River Center and other labs on the use of the new instrument, which is a slightly different model than the old MIMS. We also had lunch with about a dozen people where we discussed the different applications of the MIMS, including the different gases it can measure and the different kinds of samples it can measure (air, water; field samples, in line experiments, etc.). We are very excited to have this new capability in the lab, and look forward to all of the neat things we will learn with it!
Megan Fork's paper on DOC and denitrification, published in Ecosystems, is now available online. This work, which comes from Megan's MS thesis, uses a natural gradient in dissolved organic matter (DOC) concentration to understand how terrestrially-derived DOC influences aquatic denitrification. We found that this DOC does not directly stimulate or inhibit denitrification, but that denitrification becomes more limited by DOC as DOC concentrations increase. The explanation for this counter-intuitive finding is that DOC reduces light, and therefore the release of labile DOC by macrophytes and algae. This paper provides additional evidence for the importance of in-stream primary production for denitrification in larger rivers, and has implications for how aquatic ecosystems may respond to future changes in DOC. Read the whole thing here, and congratulations Megan!
A belated congratulations to soon-to-be alumni/ae Tim Covino and Meredith Steele! Tim has accepted a position as an assistant professor in the Department of Ecosystem Science and Sustainability at Colorado State University. Meredith has accepted a position as an assistant professor in the Department of Crop and Soil Environmental Sciences at Virginia Tech. Both begin their new gigs in January 2014. Hooray!
A big welcome to Chelsea Clifford, the newest PhD student in the Heffernan lab. Chelsea is supported by a Graduate Research Fellowship from the National Science Foundation. She received her BA in Biology from Carleton College in 2010, and has worked for the MacAurther Agro-ecology Research Station and the Chesapeake Bay Foundation. Chelsea's interests are primarily in the ecology and biogeochemistry of designed, altered, and restored ecosystems.
New paper on hydrologic feedbacks in the Everglades has been published in PLoS One. In this study, we develop a mathematical model of interactions between peat accumulation, vegetation productivity, soil elevation, and water flow. We show that the resulting feedbacks can cause spontaneous divergence of ridges and sloughs, and that these feedbacks act differentially with direction. The model provides a range of predictions that we are hoping to test with data from our Everglades monitoring project. You can download the paper here.
In between collecting data and writing papers, we do have to eat. Happily, Durham is a great place to do that. There are lots of really creative and exciting restaurants ranging from the casual to the refined, many of them with a focus on updating southern cuisine. We have a great farmer's market, and many restaurants place a lot of emphasis on local sourcing of there food. A fleet of food trucks peddle everything from dumplings to pizza to raw foods. No wonder Durham was recently named Tastiest Town by Southern Living magazine!
Tim Covino, along with McGlynn Lab grad students Kendra Kaiser and Erin Seybold, organized a demonstration day at our field site in New Hope Creek. The New Hope Creek project involves continuous monitoring of water chemistry and other variables to understand processes going in the terrestrial watershed and within the stream itself. Tim, Kendra, and Erin, along with many other members of the River Center, took this opportunity to educate members of the community about the things we measure, how we measure them, and why.
Kris Voss of the Bernhardt lab helped find and identify stream invertebrates.
As you can see, the recent rains had NHC running pretty high and turbid. One of the things we are hopnig to understand at NHC is how these floods influence metabolic processes and nutrient cycling.
Chelsea Clifford has accepted an offer to enter the PhD program at the Nicholas School as a member of the Heffernan lab. Chelsea is a graduate of Carleton College, has worked on Chesapeake Bay restoration and land use effects in central Florida, and is the recipient of a National Science Foundation Graduate Research Fellowship. Congratulations Chelsea, and welcome to Duke, the River Center, and the Heffernan Lab!
|The Heffernan Lab at Duke University||