INVERTEBRATE ACTIVITIES IN WETLAND SEDIMENTS INFLUENCE OXYGEN AND NUTRIENT DYNAMICS AT THE SEDIMENT-WATER INTERFACE A thesis submitted to the Kent State University Honors College in partial fulfillment of the requirements for Departmental Honors by Taylor Michael May, 2018 Thesis written by Taylor Michael Approved ______________________________________________________________________, Advisor _____________________________________________________, Chair, Department of Biology Accepted by ___________________________________________________________, Dean, Honors College ii TABLE OF CONTENTS LIST OF FIGURES .............................................................................................................v LIST OF TABLES ........................................................................................................... viii ACKNOWLEDGEMENT ...................................................................................................x CHAPTER: Invertebrate Activities in Wetland Sediments Influence Oxygen and Nutrient Dynamics at the Sediment-water Interface I. ABSTRACT .................................................................................................1 II. INTRODUCTION .......................................................................................2 III. METHODS ..................................................................................................6 Study Sites ....................................................................................................6 Field Sampling and Core Construction .......................................................6 Experimental Design ....................................................................................7 Microelectrode Profile Measurements ........................................................8 Nutrient Analyses .........................................................................................9 Flux Calculations and Statistical Analysis ..................................................9 IV. RESULTS ..................................................................................................10 Oxygen Profiles ..........................................................................................10 Flux Rates ..................................................................................................11 Influence of Density on Fluxes ...................................................................13 Invertebrate Excretion ...............................................................................14 V. DISCUSSION ............................................................................................15 iii Oxygen Introduction ..................................................................................15 Nutrient Fluxes...........................................................................................16 Invertebrate Excretion ...............................................................................18 VI. CONCLUSIONS........................................................................................19 VII. REFERENCES ..........................................................................................21 VIII. FIGURES AND TABLES .........................................................................25 iv LIST OF FIGURES Figure 1. Conceptual diagram of the direct and indirect effects bioturbating invertebrates can have on sediment-surface water nutrient fluxes ..................................................25 2. Diagram of the creation of a U-shaped burrow and the corresponding oxygen introduction (Baranov et al., 2016) ............................................................................26 3. Conceptual model of expected phosphorus fluxes between the oxic and anoxic sediment layers and between the sediment-water interface with the introduction of oxygen into anoxic sediment through an invertebrate burrow (red curved line) .......27 4. Conceptual model of expected nitrogen fluxes between the oxic and anoxic sediment layers and between the sediment-water interface with the introduction of oxygen into anoxic sediment through an invertebrate burrow (red curved line) .......28 5. Conceptual model of expected sulfur fluxes between the oxic and anoxic sediment layers and between the sediment-water interface with the introduction of oxygen into anoxic sediment through an invertebrate burrow (red curved line) ....................29 6. Conceptual model of the experimental design, showing the different treatments, including bioturbator type and relative densities of the three trials ...........................31 7. Top: Representative oxygen profiles of the wetland sediment for the control (zero density) and high densities of both L. variegatus and E. simulans Each color represents one of the four electrodes simultaneously used. Bottom: Photographs v of zero density, high density L. variegatus, and high density E. simulans treatments, illustrating the absence and presence of burrows ....................................32 8. Change in solute flux compared to increasing L. variegatus density in KSU - 2- - sediment. Solutes include NO3 , SRP, SO4 , and Cl . The 95% confidence interval is represented by the shaded area. A positive flux indicates a release of solute into the surface water and a negative flux indicates the removal of solute from the surface water ...............................................................................................37 9. Change in solute flux compared to increasing E. simulans density in KSU - 2- - sediment. Solutes include NO3 , SRP, SO4 , and Cl . The 95% confidence interval is represented by the shaded area. A positive flux indicates a release of solute into the surface water and a negative flux indicates the removal of solute from the surface water ...............................................................................................38 10. Change in solute flux compared to increasing L. variegatus density in OWC - 2- - + sediment. Solutes include NO3 , SRP, SO4 , Cl , and NH4 . The 95% confidence interval is represented by the shaded area. A positive flux indicates a release of solute into the surface water and a negative flux indicates the removal of solute from the surface water ...............................................................................................39 11. Change in solute flux compared to increasing E. simulans density in OWC - 2- - + sediment. Solutes include NO3 , SRP, SO4 , Cl , and NH4 . The 95% confidence interval is represented by the shaded area. A positive flux indicates a release of vi solute into the surface water and a negative flux indicates the removal of solute from the surface water ...............................................................................................40 12. Average fluxes (n=4) of the L. variegatus high density (25,000 worms/m2) in OWC sediment and sand treatments corrected by subtracting the average 0 2- - density flux of the corresponding substrate. SO4 , Cl , and SRP fluxes were all significantly different between the OWC and sand treatments (p<0.001, p=0.017, - and p<0.001 respectively). NO3 fluxes did not differ significantly. A positive flux indicates a release of solute into the surface water and a negative flux indicates the removal of solute from the surface water.............................................................42 13. Average fluxes (n=4) of the E. simulans low density (650 larvae/m2) in OWC sediment and sand treatments corrected by subtracting the average 0 density flux 2- - of the corresponding substrate. SO4 , Cl , and SRP fluxes were all significantly different between the OWC and sand treatments (p=0.01, p=0.007, and p<0.001 - respectively). NO3 fluxes did not differ significantly. A positive flux indicates a release of solute into the surface water and a negative flux indicates the removal of solute from the surface water.................................................................................43 vii LIST OF TABLES Table 1. Average sediment moisture and organic matter as loss on ignition content and initial surface water chemistry at the Old Woman Creek and Kent State University wetlands .....................................................................................................................30 2. Average ê standard deviation dissolved oxygen of the four replicate cores of the zero and high bioturbator density treatments .............................................................33 3. Average ± standard deviation flux rates of each density treatment for the experiment comparing the effects of E. simulans and L. variegatus in KSU sediment. Flux rates were calculated over a 24-day period. A positive flux indicates a release of solute into the surface water and a negative flux indicates the removal of solute from the surface water.............................................................34 4. Average ± standard deviation flux rates of each density treatment for the experiment examining L. variegatus excretion and bioturbation in OWC sediment. Flux rates were calculated over a 17-day period. A positive flux indicates a release of solute into the surface water and a negative flux indicates the removal of solute from the surface water.............................................................35 5. Average ± standard deviation flux rates of each density treatment for the experiment examining E. simulans excretion and bioturbation in OWC sediment. Flux rates were calculated over a 15-day period and an