Effects of Dissolved Oxygen Concentration and Flow Rate

on Watercress Germination and Growth

by

Claire Cleveland and Dr. Laurie Mauger

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

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)

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.

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

Anecdotal Results

Environment Dormant Growth (g) Germinated Growth (g)

F (circulation, no aeration)

0.000 (0.000) 0.183 (0.040)

F+ (circulation, aeration)

0.004 (0.004) 0.057 (0.045)

S (stagnant, no aeration)

0.024 (0.001) 0.099 (0.026)

S+ (stagnant, aeration) 0.005 (0.004) 0.110 (0.043)     

Mean Growth (g) of Dormant and Germinated Watercress in Variable Environments

Figures in parenthesis represent the standard deviation of the mean.

Yellow, splotchy leaves and diminished growth observed in augmented DO environments

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

Statistical Results

• Overall, augmented DO did not have a statistically significant effect on watercress growth

• p-value = 0.73

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

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

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

Hypothesis Assessment

• 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

• Flowing environments showed a modestly positive effect on watercress growth overall• Germinated—positive• Dormant—negative SUPPORTED

REJECTED

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

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

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.