Sheetflow Effects and Canal Backfilling on Sediment Source and Transport in Everglades Freshwater Wetlands: Analysis of Molecular Organic Biomarkers Peter Regier 1 , Ding He 1 , Colin Saunders 2 , Carlos Coronado-Molina 2 , Blanca Jara 1 and Rudolf Jaffé 1 (1) Southeastern Environmental Research Center, Florida International University, Miami, FL, United States (2) South Florida Water Management District, West Palm Beach, FL, United States Historic freshwater sheetflow in the Florida Everglades distributed sediment to form a ridge-and-slough landscape. Drainage of wetlands along with reduction and obstruction of flow has degraded topography. The Decompartmentalization Physical Model is a landscape-scale test project to assess options for re-establishing sheetflow and re- engineering barriers to flow in order to restore natural freshwater delivery levels to the Everglades. To validate proof of concept that increased flow will rebuild ridge-slough microtopography, biomarker proxies were established for ridge and slough organic matter sources and monitored in flocculent particulate organic matter (floc) before, during and after high-flow conditions. In addition, sediments were collected from partial and complete canal backfill sites with sediment traps. Four molecular organic biomarkers were evaluated: the aquatic proxy (P aq ), C 20 highly-branched isoprenoids (C 20 HBI), kaurenes and botyrococcenes. Biomarkers were able to successfully differentiate ridge and slough organic matter sources with Paq and C 20 HBI being most effective. Additional years of data are needed to assess the interactive effects of partial and complete canal backfilling and sheetflow on organic matter dynamics. Abstract Acknowledgements This work was funded by the South Florida Water Management District (SFWMD) DPM project. We gratefully acknowledge the DPM Team (Dr. Sue Newman, Dr. Fred Sklar, Eric Cline, Eric Tate-Boldt, Chris Hansen, Fabiola Santamaria, Michelle Blaha) for their assistance with field-work, insightful discussion of results and allowing the use of DPM data for this presentation. RJ and BH acknowledge additional support through the George Barley Chair and McNair Fellowship respectively. Hypotheses 1. Increased sheetflow will preferentially mobilize slough organic matter 2. Sediment trapped in backfilled sites will differ from open canal traps Discussion 1. Biomarkers, particularly Paq, successfully differentiated ridge and slough organic matter inputs in the DPM test plot. 2. Slough material was mobilized by increased sheetflow, supporting Hypothesis 1. 3. Sediment traps collected primarily slough-derived materials during low flow. 4. High flow sediment trap inputs were less “slough-like”. Possible explanations include • Disconnect in entrainment of slough-derived floc and ridge-derived fine POM • Seasonal nutrient inputs from producers of HBI and Botyrococcenes (algae) • Containment structure inputs scraped off and mobilized by increased flow 5. More data are required to fully understand the interactions of backfilling and sheetflow in order to test Hypothesis 2. Summary Our preliminary data indicates that under increased flow conditions, flocculent matter from sloughs is preferentially mobilized. This suggests that increasing sheetflow velocity in degraded ridge and slough wetlands is a viable restoration tool. Results from sediment traps are inconclusive regarding effectiveness of canal backfilling. Two additional years of data will be collected in 2014-2015 and 2015-2016, including two periods of increased flow. More advanced statistical analysis of the collected data is suggested before extensive interpretation of results. Solvent Extraction Column Chromatography GC/MS Freeze-dry floc and sediment Paq Differentiate between ridges and sloughs Kaurenes Indicative of ridges HBI Indicative of sloughs Botyrococcenes Indicative of sloughs Methods 0.0 0.2 0.4 0.6 0.8 1.0 Paq Z4-1 Paq 0 100 200 300 C 20 HBI (μg/gdw) Z4-1 C 20 HBI 0.0 0.2 0.4 0.6 0.8 1.0 Paq Z10-2 Paq 0 50 100 150 200 C 20 HBI (μg/gdw) Z10-2 C 20 HBI 0.0 0.2 0.4 0.6 0.8 1.0 Paq Z5-3 Paq 0 50 100 150 200 250 300 C 20 HBI (μg/gdw) Z5-3 C 20 HBI Before High Flow High Flow After High Flow * Significant Difference: Before, High+After, p≤0.05 * * * 0.0 0.2 0.4 0.6 0.8 1.0 Paq Ridge-Slough Transect - Paq 0 100 200 300 HBI (μg/g dry weight) C 20 HBI 10/2012 (LOW flow) 01/2013 (LOW flow) 10/2013 (LOW flow) 01/2014 (HIGH flow) 0 5 10 15 20 Ridge Ridge-Edge Slough-Edge Slough Kaurene (μg/g dry weight) Kaurenes 0 1 2 3 Ridge Ridge-Edge Slough-Edge Slough Botryococcenes (μg/g dry weight) Botryococcenes Results – Ridge/Slough Fig. 2 • Paq – can distinguish ridge and slough organic matter • HBI – can distinguish ridge and slough organic matter • Kaurenes – indicates ridge material, absent in sloughs • Botyrococcenes – strongly variable with season, present in very low concentrations Fig. 3 • Significant increase in slough-like material for Paq and HBI during and after increased flow • Increase consistent along flowpath Fig. 2: Ridge to Slough transect Fig. 3: Test-plot spatial transect 0 0.2 0.4 0.6 0.8 1 Low High After Low High After Low High After Ridge Slough Sediment Paq Fig. 4: Average Paq – All Samples 0.0 0.2 0.4 0.6 0.8 1.0 Paq Fig. 5: Sediment Traps - Paq CC1 CC2 CB1 CB2 CB3 High Flow Before High Flow After High Flow Results – Canal Fig. 5 • Decrease in Paq during high flow • Backfill sections appear to respond differently to high flow conditions • Experimental site data is not significantly different from controls Fig. 4 • Ridge Paq increased during and after high flow • Slough Paq increased during and after high flow • Sediment Paq decreased during high flow Fig. 1: Study Site Georgia Florida Gulf of Mexico Miami Degraded topography Natural topography Control sites Canal sediment traps Flocculent matter sites Flowpath Z5-3 Z4-1 Z10-2 CB3 CC1 CC2 CB2 CB1 Fig 1.: Map of sampling sites. The experiment plot is located between two levees bisecting Water Conservation Area 3, a peatland with historic ridge and slough topography. Control sites are located outside of the flowpath of sheetflow. Canal sediment traps are located in experimental canal backfill sections of the L67-C canal. Flocculent matter sites are located along the flowpath where flocculent mats were collected. Fig. 2: Floc was sampled along a spatial transect from ridge to slough during low and high flow conditions. Fig. 3: Floc was sampled spatially along the sheetflow path from the culverts (source of flow) to the canal backfill sections. Fig. 4: Combination of ridge floc, slough floc and canal sediment samples separated into before, during and after high- flow treatment. Fig. 5: Sediment trap results for canal backfill sites before, during and after high flow. CC1 and CC2 are control sites located outside of the main sheetflow channel (see Fig. 1). CB1 is open canal, CB2 is partially backfilled and CB3 is completely backfilled. Averages for each flow period are shown as dashed bars. Analytical Methods Molecular Organic Biomarkers a a d b b,c c d b,c p≤0.05