Background

Literature Cited Acknowledgements

Discussion

Special thanks to the Strecker Aquatic Ecology Lab and Portland State Center for Lakes and Reservoirs. Field and laboratory funding from Edward D. and Olive C. Bushby Scholarship,Sonoma County Fish and Wildlife Commission Student Scholarship, and field sampling help from California Sea Grant and Watershed Stewards Program AmeriCorps members.

Community Structure of Macroinvertebrates from Intermittent Streams: Diversity and Evenness Evaluations

Oliviah Franke, Amelia Johnson, Angela StreckerEnvironmental Science & Management, Portland State University

1) Isbell, Forest, et al. Nature 526.7574 (2015): 574-577.2) Leigh, C., et al. (2015). Ecological research and management of intermittent rivers: an historical review and future directions. Freshwater Biology.3) Merritt, R.W., and Cummins, K.W. (Editors). 2008. An introduction to the aquatic insects of North America. 4th edition. Kendall Hunt Publishing. 4) Rundio, D. E. (2009). Hydrobiologia, 620(1), 91-108.5)Washington, H. G. (1984). Diversity, biotic and similarity indices: a review with special relevance to aquatic ecosystems. Water research, 18(6), 653-694.6) Meyer, John R. "Ephemeroptera." General Entemology NC State University. Mar. 2016.

• Community structure is important when analyzing resiliency of an ecosystem. ₁

• Resiliency of streams in the face of global climate change will have benefits for organisms that inhabit the streams₁, as well as humans that utilize ecosystem services.

• Freshwater is a fundamental biological need and its supply varies geographically- specifically in intermittent rivers. ₂

• Benthic macroinvertebrates are great indicators of stream quality, and act as a integral part of the food webs in this ecosystem. ₄ Changes in these communities could have drastic effects on higher trophic species such as salmon.

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Objectives

Results

• Assess macroinvertebrate community structure by comparing Shannon diversity and evenness index values across two intermittent creek sites in Northern California. ₅

• Discuss factors that impact these index values, as well as resiliency of the sites. ₅

• Provide valuable information to improve management of these two creeks. Creeks with higher diversity and evenness should maintain priority for climate change management.

There are many factors that impact the analysis of community structure including sampling methods and size, depth and duration of sampling, time of year and organismal life cycles, and taxonomic level being evaluated (Washington 1984). In this case, these factors were all considered and held constant for each sample. Due to the intermittent nature of these creeks, community structure will likely be greatly impacted across time.Implications: • Mill Creek showed higher diversity and evenness, therefore, would be

predicted to have higher resilience for disturbance events related to climate change.

• Over half of the most dominant taxon of Mill Creek reaches fall under the Ephemeroptera order (Baetidae, Ephemerellidae, Heptageniidae), which are especially sensitive to water quality (Meyer 2016).

• Management of these intermittent creeks should take community structure of organisms into consideration when making decisions regarding conservation and protection of areas (Leigh et al 2015).

Improvements: • With more time sampling techniques would be improved. Samples

would be repeated across a time period to evaluate seasonality as recommended in Washington 1984.

• Future experiments could increase the number of streams sampled and compared as well as increasing the number of reaches.

• Further research would allow for in depth exploration of geographical and land-use variation in the watershed.

Figure 2: Box plot for calculated H’ diversity index by

creek (n=4). Box plot shows median (bold horizontal line,

extents of the box represents the 25th and 75th quartiles,

and minimum and maximum values (whiskers).

• There is a statistically significant difference in Shannon’s diversity index values between the two creeks (H=5.9, d.f. =1, p=0.015) (Figure 3)

• There is a statistically significant difference in evenness values between the two creeks (H=5.9, d.f. =1, p=0.015) (Figure 4).

• Mill Creek has significantly higher diversity and evenness index values than Green Valley creek.

• Over half of the most dominant taxa of Mill Creek fall under the Ephemeroptera order (Baetidae, Ephemerellidae), and over half of the most dominant taxa of Green Valley fall under the diptera order (Simuliidae, Chironimidae)

Figure 3: Box plot for calculated E index by creek (n=4). Box

plot shows median (bold horizontal line, extents of the box

represents the 25th and 75th quartiles, and minimum and

maximum values (whiskers).

Figure 4: mean and standard error reported across two intermittent streams’ H’ diversity index values and evenness index values.

2 streams, each with 4 reaches 3 habitats with 3composited kicknet samples

24 samples

Methods

𝑯′ = −∑[𝑷𝒊 𝒍𝒏𝑷𝒊 ]Where Pi= Number of individuals/total individuals , relative abundance

E=H’/(ln(TR))Where TR=taxon richness

Subsample/ID at habitat scalen=300 (or smaller if <300 individuals)

Use n to estimate total population values by taxon

Use estimates to calculate indices: H’, E at the stream and reach scale

Determine if data values for indices are normally distributed: non-parametric

Apply appropriate statistical test: Kruskal-Wallis

H’ Shannon-WeinerDiversity index

E Shannon-WeinerEvenness Index

KEY AND EQUATIONS

Figure 1: Illustration of field sampling technique.

(Washington 1984)

Mill Creek reach 2

Sampling done in Russian River watershedMarch 2015

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MIL mean GRE mean