Impact of Dissolved Oxygen and Flow Rate on Watercress Germination and Growth

A study by Claire Cleveland and Dr. Laurie Mauger explores the effects of dissolved oxygen concentration and flow rate on watercress germination and growth. The research includes ecological markers, existing evidence, hypothesis, experimental design, and anecdotal results indicating that watercress thrives better in flowing environments with augmented oxygen concentration compared to stagnant conditions. Experimental setups such as circulation and aeration were employed to simulate natural stream flow. Notably, anecdotal observations showed reduced growth in environments with increased dissolved oxygen.

• Watercress
• Germination
• Growth
• Dissolved Oxygen
• Flow Rate

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1. Effects of Dissolved Oxygen Concentration and Flow Rate on Watercress Germination and Growth by Claire Cleveland and Dr. Laurie Mauger

2. Ecological Markers Watercress growth patterns were noticed during United States Forest Service (USFS) water rights surveys, Dixie National Forest 2012 Specificity of growth indicated potential for an ecological marker Ecological markers Test models of abundance and distribution Locate possible abnormalities in conditions Locate possible contamination sites Groundwater markers Flow rate Abundance Year round availability Water quality

3. Existing Evidence Correlation between effluent quality and spring sources (Kothandaraman and Ewing 1969) Watercress specificity to spring headwaters Dorset and Hampshire England (Crisp 1970) Sacromento Mountains, New Mexico (Goerndt et al. 1985) Anecdotal evidence of the effect of flow rate on growth Inverse relationship between dissolved oxygen concentration (DO) and water temperature (Slack 1971) Relationship between flow rate and DO (Hupp 1982) Connections between oxygen depletion events and emergent aquatic plant species (Caraco and Cole 2002, Caraco et al. 2006)

4. Hypothesis Watercress germination and growth will be higher in flowing and augmented dissolved oxygen concentration environments than in stagnant and unaltered dissolved oxygen concentration environments.

5. Experimental Design Control (F): circulation, no aeration Simulates naturally occurring stream flow Stagnant (S): no circulation, no aeration Stagnant + O2 (S+): no circulation, aeration Flowing + O2 (F+): circulation, aeration Three replicates were run for each environment Dormant (seeds) Germinated sprouts (two cotyledon leaves, 1.0 cm in height) Growth quantified as live growth mass above the soil surface at 21 days

6. Anecdotal Results Mean Growth (g) of Dormant and Germinated Watercress in Variable Environments Environment Dormant Growth (g) Germinated Growth (g) F (circulation, no aeration) F+ (circulation, aeration) S (stagnant, no aeration) S+ (stagnant, aeration) 0.000 (0.000) 0.004 (0.004) 0.024 (0.001) 0.005 (0.004) 0.183 (0.040) 0.057 (0.045) 0.099 (0.026) 0.110 (0.043) Figures in parenthesis represent the standard deviation of the mean. Yellow, splotchy leaves and diminished growth observed in augmented DO environments

7. Statistics R 2.15.2 was used to perform all statistical analysis Experimental data adhered to a normalized distribution Statistical analysis included ANOVA Type II, post hoc tests elimination of zero values by addition of 0.0001 g log 10 transformation Graphically presented data is not transformed

8. Statistical Results Overall, augmented DO did not have a statistically significant effect on watercress growth p-value = 0.73

9. Statistical Results Overall, a small but statistically significant relationship was found between flow and watercress growth p-value = 0.0057 Flowing water had a modestly positive effect on overall watercress growth

10. Statistical Results Inverted relationships were found for the effect of flowing water on dormant versus germinated watercress growth p-value = 0.0087 Germinated watercress showed increased growth in flowing water Dormant watercress showed a decrease in growth in flowing water

11. Statistical Results The effect of augmented DO was negative overall, but degree of effect was significant p-value = 0.015 Augmented DO has a more strongly negative effect on flowing environments than on stagnant environments

12. Hypothesis Assessment Flowing environments showed a modestly positive effect on watercress growth overall Germinated positive Dormant negative A negative relationship between watercress growth and augmented DO was clearly demonstrated for both dormant and germinated watercress specimens Germinated large effect Dormant small effect Flowing large effect Stagnant small effect

13. Related Research Optimal watercress growth was found at spring headwaters and seeps with low topography and flow rates < 0.91 cm/sec (Goerndt et al. 1985) DO found low at high elevations and shows a negative relationship with taxon richness of stream macroinvertebrates (Jacobson 2008) Evidence found supports likelihood of finding watercress at high elevations Patterns originally observed by USFS at locations above 9000 ft elevation Reduced diversity may allow ecological niche for watercress to fill

14. Future Direction Watercress does show some specialist type attributes Strong preference for low DO Strong preference for flowing waters, but not too much flow Specificity of growth patterns suggestive of additional attribute not yet found Potential for watercress as ecological indicator for Flow rate Abundance Source and year round availability Water quality Additional parameters not yet found

15. References Caraco, N. F., J. J. Cole. 2002. Contrasting impacts of a native and alien microphyte on dissolved oxygen in a large river. Ecological Applications 12(5): 1496-1509. Caraco, N., J. Cole, S. Finley, C. Wigand. 2006. Vascular plants as engineers of oxygen in aquatic systems. Bioscience 56(3): 219-225. Crisp, D. T. 1970. Input and output of minerals for a small watercress bed fed by chalk water. Journal of Applied Ecology 7(1): 117-140. Fumetti, S., P. Nagel, B. Baltes. 2007. Where a springhead becomes a springbrook a regional zonation of springs. Fundamental and Applied Limnology 169(1): 37-48. Goerndt, D. L., S. D. Schemnitz, W. D. Zeedyk. 1985. Managing common watercress and spring/seeps for Merriam s turkey in New Mexico. Wildlife Society Bulletin 13(3): 297-301. Hupp, C. R. 1982. Stream-grade variation and riparian-forest ecology along Passage Creek, Virginia. Bulletin of the Tory Botanical Club 109(4): 488-499. Jacobsen, D. 2008. Low oxygen pressure as a driving factor for the altitudinal decline in taxon richness of stream macroinvertebrates. Oecologia 154(4): 795-807. Kothandaraman, V., B. B. Ewing. 1969. A probabilistic analysis of dissolved oxygen-biochemical oxygen demand relationship in streams. Water Pollution Control Federation 41(2): R73-R90. Slack, K. V. 1971. Average dissolved oxygen: measurement and water quality significance. Water Pollution Control Federation 43(3) Part 1: 433-446.