Industry update on nitrogen removal programs across the United States: What d...
Thesis powerpoint DD
1. Effects of Growing Season Flow
Regime on Stream Periphyton
Growth in a Coastal Plain Stream
David Diaz, M.S. Candidate, Ecology
Advisors Dr. Paul V. McCormick, Dr. Alan
Covich
Thesis Defense: September 18th 2015
2. Outline
Background: Rationale and site
description
Part 1: Influence of discharge and
nutrient availability on periphyton
biomass and composition
Part 2: Effects of discharge-grazer
interactions on periphyton biomass
and composition
Conclusion
3. Rivers and streams
Ecosystem services
Human and environmental water
needs
Environment flows
9. Outline
Background
Part 1: Influence of discharge and
nutrient availability on periphyton
biomass and composition
Part 2: Effects of discharge and grazer
interactions on periphyton biomass
and composition
Conclusion
13. Hypotheses
Study 1: Higher periphyton
accumulation at lower discharge due
to reduced shear stress
Study 2: More nutrient limitation at
lower discharge.
◦ Phosphorus is limiting nutrient
14. Methods- Experimental
design
Study 1:
◦ 5 discharge treatments across 15 channels
3 replicates : L, ML, M, MH, H (20 fold range across
treatments)
4 tiles/channel, 2-3 days for 28 Days
Samples processed for AFDM, chl a and other
pigments
Study 2:
◦ Same discharge treatments
Nutrient enrichment : Control, Phosphorus,
Nitrogen + Phosphorus
Sampled every 2-3 days for 33 days. Processed for
AFDM, chl a and other pigments
15. Analysis
Biomass accumulation patterns modeled
using polynomial regression
◦ Growth rates estimated from linear
coefficients
◦ Rates compared among treatments using
95% confidence intervals
ANOVA analysis and Tukey’s
significance test to compare maximum
values of AFDM, chl a and for pigment
concentrations.
25. 0
0.5
1
1.5
2
2.5
3
3.5
4
Control P N+P
Pigmentconcentration
(nmol/cm2)
Diatoms
0
5
10
15
20
25
30
35
Control P N+P
Pigmentconcentration
(nmol/cm2)
0
5
10
15
20
25
30
35
Control P N+P
H
MH
M
ML
L
0
0.5
1
1.5
2
2.5
3
3.5
4
Control P N+P
H
MH
M
ML
L
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Control P N+P
Pigmentconcentration
(nmol/cm2)
Green Algae
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Control P N+P
H
MH
M
ML
L
Total Pigments Day 4
Day 4
Day 4 Day 33
Day 33
Day 33
26. Part l Summary
Greater accumulation of AFDM (higher
AI ratio) at higher discharge
Diatom dominance in all treatments.
Higher relative abundance of green
algae in lower treatments
Nutrient enrichment effect greatest at
higher discharges
27. Background
Part 1: Influence of discharge and
nutrient availability on periphyton
biomass and composition
Part 2: Effects of discharge and
grazer interactions on periphyton
biomass and composition
Conclusion
29. Hypothesis
Snail grazers can limit periphyton
biomass under a range of periphyton
growth conditions related to discharge.
30. Methods
Marked and weighed snails
◦ Used similar ambient density for
treatments
3x2 factorial design. 3 discharge
treatments (L,M,H)and 2 grazer
treatments.
31. Analysis
Accumulation patterns modeled using
polynomial regression
◦ Average growth rates estimated from linear
coefficients
◦ Rates compared among treatments using
95% confidence intervals
2-way ANOVA and Tukey’s significance
test used to compare maximum values of
AFDM, chl a and for pigment
concentrations.
Snail growth
37. 0
5
10
15
20
25
30
L M H
Pigmentconcentration
(nmol/cm2)
Ungrazed
Grazed
Total Pigments Day 4
0
2
4
6
8
10
12
L M H
Pigmentconcentration
(nmol/cm2)
Ungrazed
Grazed
Diatoms Day 4
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
L M H
Pigmentconcentration
(nmol/cm2)
Ungrazed
Grazed
Green Algae Day 4
0
5
10
15
20
25
30
L M H
Total Pigments Day 33
*
Grz=.011*
Dch=.008*
Grz x Dch= .045*
0
2
4
6
8
10
12
L M H
Diatoms Day 33
*
Grz=.011*
Dch= .025*
Grz x
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
L M H
Green Algae Day 33
*
*
Grz=.582*
Dch=.152*
Grz x Dch=.464
38.
39. Part ll Summary
AFDM and chl a pigment
concentrations increased with
discharge. Diatom dominance in all
discharge treatments.
Grazers had greater effect at higher
discharges
Snail growth rate decreased with
higher discharge
40.
41. Conclusion
Rapid periphyton accumulation potential
during the summer growing season
◦ High light availability
◦ Stable flow regime
Local flow conditions control periphyton
patterns
◦ Accumulation rates and maximum biomass
◦ Mat heterotrophy
◦ Taxonomic composition
Grazers exert limited control over
periphyton
42. Implications
Climate Change: Drought duration and
frequency influence stream primary
production
Human water Use: Changes
in instream flows affect periphyton
spatial patterns
Lower flow conditions may become
more common in the future
Food web dynamics
43. Acknowledgements
• Special thanks to Dr. McCormick and Dr.
Covich
• Jones Center Staff and Students
• Chelsea Smith, J.R Bolton, Steve Shivers
• Committee- Dr. Steve Golladay, Dr. Mary
Freeman, Dr. Susan Wilde
• Dr. Matt Waters
Outline
I’ve divided my talk into four sections
Background on my topic and the stream that I worked in.
Rivers and Streams
Ecosystem Services- water purification, nutrient cycling, primary production, habitat for aquatic biota
Human use of water resources for consumption, irrigation, energy production
Increased human water consumption coupled with finite freshwater supplies makes it difficult to balance human and ecological needs for water.
Environmental flows
Aquatic ecologists recognize that the flow regime is a key driver of ecosystem function for rivers: Determines the type physical habitats and affects geomorphology of streams over time. Physical structure in turn affects the movement and persistence of aquatic biota.
Environmental Flows- Management frameworks aim to find the range of flow conditions needed to maintainhealthy aquatic systems. This frame work can help us understand compatibility between the water needs of human and natural systems.
Lower Flint River Basin (example)
*The lower Flint River Basin (LFRB), located in Southwestern Georgia is one of the most productive agricultural regions in the U.S.
*Since the 1970s the regional economy has depended on row-crop agriculture supported by center-pivot irrigation, which increased water withdrawal from both surface and groundwater sources.
*Prolonged dry periods are projected to be more common as a result of global climate change in Georgia. The LFRB has experienced periods of below normal rainfall, including three droughts, during the past decade
*Withdrawals often coincide with seasonally decreased summer low flows, exacerbating the conserquences of low flows during the summer.
Seasonal flow patterns in a coastal plain stream Hydrograph
Black water systems- During the winter and spring months, we observe a lot of run off and a lot of DO matter coming into the stream, with very low light availability, which can limits periphyton growth.
During the summer is the best opportunity of periphyton growth, because of the surface ground water connection , much of the water is clear ground water as opposed to stained surface water inputs. These are the periods of the years when the potential for periphyton growth is greatest in this stream. Flow regimes during summer are being altered by discharge.
Question- Under these seasonally favorable conditions for periphyton growth, what effect does discharge have on periphyton growth and composition?
Flow Ecology
My study was focused on the effects of the flow regime on periphyton growth.
Periphyton is a complex mixture of algae, bacteria, and fungi that is attached to submerged surfaces in most streams. It is a primary energy source in most lotic food webs, regulate nutrient spiraling can influence chemical and physical habitat conditions for stream organisms.
In excess quantities can be considered a nuisance. May negatively affect water clarity, limit growth of submerged aquatic vegetation, alter habitat quality, and affect invertebrate grazing communities and food web dynamics.
Hypothetical relationship between flow and periphyton in coastal plain streams
Flow influences factors that can affect algal growth and biomass both directly and indirectly through its influence on temperature, light and nutrient availability
As I’ll describe in more detail later, my study focused primarily on the direct effects of flow, which can be positive or negative. Positive because it can increase the supply of algal cells/propogules, and negative because faster flow environments can increase turbulence and sheer stress.
Flow affects periphyton through its influence on nutrient supply rates. Discharge influences the concentration and uptake potential of nutrients by benthic communities. Higher water discharge has the potential to increase nutrient supply rates and decrease the diffusive boundary layers for higher nutrient uptake by algae. These changes in nutrient availability can regulate rates of primary production.
Stream grazers can also play an important role in controlling periphyton growth, and I was interested in how that influence might be affected by the flow regime.
Site
My study was conducted in the lower portion of Ichawaynochaway Creek , a 5th order tributary of the Lower Flint River.
Jones Center during the summer and late fall of 2014.
Experimental Stream Facility
Flow through system, where water was pumped to channels to the stream.
Discharge in individual channels controlled by spigots
Channels lined with clay tiles that were used to sample periphyton growth
Temperatures held constant across treatments
Methods
Randomly selected from 4 sections. Decrease variation in conditions. Tiles scraped and placed upside down.
Used standard protocols for sampling.
AFDM- Total organic matter ( an estimate of overall periphyton biomass including photo and heterotrophic components), chla – algal biomass, and pigments associated with algal composition.
Nutrient enrichment- reinitiated 5 discharge treatments. Added slow release fertilizers in panty hose bags for enrichments. This allowed for slow leaching.
Samples processed for same parameters as study one
X axis=time , y –axis=AFDM, each point represents the mean for 3 replicate channel discharge treatment +-one standard error.
Throughout the course of the experiment, AFDM tended to increase, with increasing discharge. * Discharge had a positive effect on AFDM .
Based on our regression models, the growth rates were higher at the higher discharge treatments, which was contrary to our expectations
Chla on the other hand, did tend to be lower at the higher discharge treatments, particularly as the study progressed. This was more consistent with our expectations. In this case initially there was no major trends, but at the end there were higher chla concentrations in lower discharges.
Polynomial- linear was accumulation phase and quadratic term was the sloughing phase/ reduced chl a
Ex: accumulation rates based on linear coeff were similar for all treatments earlier in the study but then there was a significant quadratic term for higher discharge treatments, which resulted in lower biomass compared to lower treatments towards the end of the study
The maximum AFDM also increased with discharge, while maximum cholorphyll values tended to be higher in the lower discharge. What we observed was a shift toward a more heterotrophic assemblage with increasing discharge.
This is shown here using the calculated AI ratio which is AFDM/Chla. Higher AI ratios indicate a more heterotrophic community while lower ratios indicated a more autotrophic community. The AI ratios tended to be higher at the higher discharge treatments, particular towards the end of the study where we saw higher AFDM and lower chla values.
Pigment analysis is in part showing diatom dominance (in term of relative abundance) in all treatments but increased green algal abundance in low flows.
Nutrient study- more nutrient dissolution of nutrients… potential for more nutrient dissolution if more water blasting through bags. Where nutrients important by self? (no, when controls were compared to nutrient additions, regardless of discharge, there were no significant differences – used max biomass for afdm and chl a).
Was there an interaction with discharge? (no replication, cannot test for it significantly)
Higher discharge= Higher AFDM. In higher discharges nutrient enrichment had higher AFDM
Stream grazers often limit algal biomass but may not be able to respond to a rapid increase in algal growth rates that exceeds herbivory rates. The purpose of this study is to investigate how summer low-flow conditions affect algal growth and biomass and the ability of stream herbivores to respond to changes in this food resource.
Grazers regulate periphyton biomass and growth through ingestion and physical disturbance.
The majority of studies have concluded that algal biomass almost always declines in the presence of herbivores, though the outcome can often depend on the type of alga and herbivore involved
Discharge was the most influential parameter. In some treatments there appeared to be differences between grazers
Pigments- Grazing effects intensified with increasing discharge as indicated by a significant interaction term between these two factors (F=2.870, p=.045).
Snail growth declined with increased discharge despite the fact that there was more periphyton biomass for consumption at high discharge.
previous studies have shown higher energy/metabolic expendetures
Flow can have a direct negative affect on grazers. Effects more complicated than I originally thought.
Answers to the research objectives can provide insight into the linkages between reductions in stream discharge and periphyton growth and biomass. Exploring factors that promote rapid algal growth will provide a better understanding of the ecological impacts of human water consumption and low flows on lotic systems.
This research provides greater insight into how alterations to summertime flow regimes affect periphyton ecological conditions within the LFRB. These results will increase understanding of the relationship between discharge and periphyton abundance and composition in order to predict the effects of changing flow regimes on stream ecology. Our study highlights the significance of flow and nutrient effects on algal biomass, particularly in agricultural areas where present and future anthropogenic modifications can greatly alter lotic systems
In the stream we previously observed that high biomass is positively related to lower flows which provided a basis for our initial hypothesis. We surmised that reduced flow and associated scouring increase attached algal biomass by reducing sloughing of algal cells from substrata. In our experiment, however, we found that higher flows had greater AFDM accrual. Results presented here demonstrate that flow has the potential to alter the composition and growth rates of periphyton in a controlled experiment.
