The Effects of Eutrophication and Salinization on Methane

The Effects of Eutrophication and Salinization on Methane Production in Urban and Rural Lakes Rebecca Kiekhaefer Dr. Carla Koretsky, Thesis Chair Dr. Alan Kehew Denisha Griffey Davina Wyman

Introduction ¡ Eutrophication http: //bhargavikorlipara. edublogs. org/files/2012/05/eutrophication-19 y 5997. jpg

Introduction ¡ Redox Stratification http: //ucce. ucdavis. edu/files/repository/calag/fig 5702 p 56 athumb. jpg

Introduction ¡ ¡ Methane: Greenhouse gas Methanogenesis l l Anaerobic bacteria break down organic matter

Introduction http: //www. dnr. state. wi. us/org/water/fhp/lakes/under/mixing. htm

Introduction ¡ Salinization l Road Salt ¡ l l l ~ 95% Na. Cl 23 million tons used nationwide (2005). Acute chloride toxicity Water density changes, affects mixing http: //i 00. i. aliimg. com/photo/v 0/109074356/Road_Salt_De_Icing_Ice_Melter_extra. jpg

Purpose ¡ ¡ Determine the effects of lake salinization on methane production. Determine the effects of eutrophication on methane production.

Hypothesis ¡ High salinization will lead to redox stratification, which will cause increased methane production.

Field Site: Asylum Lake ¡ ¡ Located in an urban setting in Kalamazoo, MI. Groundwater fed kettle lake in outwash sediments and sandy soil. Area: 0. 2 km 2 Depth: 14 m

Field Site: Wintergreen Lake ¡ ¡ Located in a rural setting, part of the Kellogg Biological Station in Augusta, MI. Groundwater fed kettle lake in outwash sediments and sandy soil. Area: 0. 16 km 2 Depth: 5 m

Methods: in situ ¡ Sample Dates l l l ¡ 17 November 2012 Wintergreen Lake 18 November 2012 Asylum Lake 8 December 2012 Asylum Lake YSI Multiprobe Sonde l l l Temperature DO p. H Conductivity 0. 5 meter intervals

Methods: in situ ¡ Water Sample Collection l l l 4 samples at 1 meter intervals Filtered using 0. 2 μm filter 2 samples were preserved with concentrated nitric acid

Methods: Methane Samples ¡ Pre-Sample Preparation: l l New 60 m. L serum vials were rinsed. New rubber stoppers were boiled in 1 M Na. OH solution. 1 Na. OH pellet was placed in each vial. Brine blanks were created in the lab using super saturated Na. Cl and water bubbled with helium.

Methods: Methane Samples ¡ in situ: l l Sample water drawn in 140 m. L plastic syringe. Injected into vial from bottom up using rubber tubing. Sample capped with minimal air bubbles. DI field blanks were collected.

Methods: Methane Samples ¡ Post-Sample Preparation: l l Samples were purged with helium while inverted. 15 m. L of helium was injected into each. 15 m. L of water was expelled into an empty syringe. Samples were stored upside down.

Methods: ex situ ¡ UV-Vis Analysis: l ¡ Ion Chromatograph Analysis: l ¡ Alkalinity Chloride Gas Chromatograph Analysis: l Methane GC IC

Results

Results Koretsky et al. , 2011

Results

Results

Results Sample Bubble Size Methane Concentration (µM) W 3 A 1 1. 66 1 none W 3 B 2 1. 68 2 o A 4 A Nov 2 1. 55 3 o A 4 B Nov 2 1. 59 4 O A 6 A Nov 5 1. 72 5 O A 6 B Nov 2 1. 74 A 13 A Nov 4 131. 66 A 13 B Nov 2 208. 98 Bubble Size

Discussion ¡ Estimations indicate 40% of methane produced in lakes such as Wintergreen Lake and Asylum Lake is released into the atmosphere. ¡ Asylum Lake: l l 1 m containing high methane concentrations surface area of 0. 2 km 100 µM of methane 120 kg of methane per year ¡ Methane is released via ebullution (bubbles). ¡ Much more methane might be released from these lakes. Strayer & Tiedje, 1978

Conclusions ¡ Higher salinity and higher methane concentrations in Asylum Lake. l Could be the result of other factors ¡ Asylum Lake appears to mix some between November and December. ¡ Bubbles in methane samples do not appear to cause any difference in measured methane concentration.

Conclusions ¡ ¡ There is not nearly enough data in this study to draw significant conclusions about the lakes. Future analysis of these lakes will indicate more. l More samples over a full year to show trends in both salinity and methane production

Acknowledgements ¡ Thanks and consideration are extended to these people and organizations for their help with this project: l l l l Dr. Carla Koretsky Dr. Alan Kehew Denisha Griffey Allie Wyman Ryan Sibert UGA Marine Sciences Western Michigan University ¡ ¡ Department of Geosciences Lee Honors College BBC Sherlock