The effects of invasive riparian flora on macroinvertebrate populations in cold water streamsSarah Daggett, Carlye Morris, Jamie Williams, Meaghan Anderson

University of Wisconsin River Falls – Biology Department BIOL 296 Field Research Experience

HYPOTHESIS

We predict that the reaches of the degraded river will have a higher macroinvertebrate FBI score than the

reaches of the restored river. We also predict that the reaches of the degraded river will have lower

macroinvertebrate species richness, abundance, and diversity than reaches of the restored river.

INTRODUCTION

According to Clewall and Aronson (2013), the area of the earth’s

surface presently occupied by invasive species is enormous and has

been increasing substantially each year. Alien and invasive species

compromise ecological functionality and ecosystem wholeness

(Clewell and Aronson 2013). Invasive plant species severely affect the

land they invade. They not only displace plant species living there, but

this can inspire a trophic cascade, changing the populations of

herbivores, arthropods, and other organisms in the ecosystem.

Bottom–up models predict that characteristics of lower trophic levels

control species richness and abundance of higher trophic levels.

(Kappes et al. 2007) Ivanov et al. (2011) claim that plant invasions

and the associated decrease in plant diversity and homogenization of

local flora can alter invertebrate assemblages.

Due to the propensity of many species to undergo aquatic-to-

terrestrial life-stage progression, terrestrial systems may be

particularly sensitive to local aquatic trophic dynamics. (Burkle et al.

2014) Serra et al. (2013) describe similar effects on the aquatic

larvae of terrestrial adult insects. If a plant species invades the riparian

zone and significantly changes its species composition and

physiognomy, it may alter the detritus cycling dynamics, thus

affecting the diversity, trophic structure and dynamics of the stream’s

benthic communities.

MATERIALS AND METHODS

Each of the riparian plant study plots will be located on the river bank near a riffle, in a 1x1 meter square marked off

with tape measures and ribbons. The plot will be approximately parallel to the river bank and located where there is less

than 15% bare ground. The experimenters will use field characteristics to identify the plant species within the study plots

and visually estimate the percentage of biomass all individuals of each species comprise. Non-invasive species

consisting of less than 5% of the total biomass will be documented as “other non-invasive species”. Unknown plants will

be identified to the family or genus using the dichotomous key found in the Guide to Vascular Plants of the Northeastern

United States and Canada by Gleason and Cronquist (1998). One experimenter will fill out a plant identification data

sheet as each of the plant species are identified and then quantified. The biomass of the woody species comprising the

rest of the riparian zone will be estimated and used to supplement the estimate of invasive biomass in both sites.

RESULTS

REFERENCESBurkle, Laura A., Mihaljevic, Joseph R., & Smith, Kevin G. “Effects of an invasive plant transcend ecosystem boundaries through a dragonfly-mediated trophic pathway”.

Oecologia. 2012. 8 Pages. 17 September 2014. <http://link.springer.com/article/10.1007/s00442-012-2357-1/fulltext.html>.

Clewell, Andre F. & Aronson, James. Ecological Resoration 2nd ed. Washington D.C.: Island Press. 2013.

Ivanov, Kaloyan and J. Keiper. Potential impacts of the invasive herb garlic mustard (Alliaria petiolata) on local ant (Hymenoptera: Formicidae) communities in norther

temperate forests. Jeffersoniana. 2011. 14 pages. 8 October 2014. <http://www.academia.edu/3142278/Potential_impacts

_of_the_invasive_herb_garlic_mustard_Alliaria_petiolata_on_local_ant_Hymenoptera_Formicidae_communities_in_northern_temperate_forests>.

Kappes, Heike, Lay, Rebecca, & Topp, Werner. “Changes in Different Trophic Levels of Litter-dwelling Macrofauna Associated with Giant Knotweed Invasion.”

Ecosystems. 2007. 12 Pages. 6 October, 2014. <http://web.b.ebscohost.com.ezproxy.uwrf.edu:2048/ehost/pdfviewer/pdfviewer?sid= a5bdabfd-ca9b-4739-870d-

f54ae70230b1%40sessionmgr114&vid=1&hid=101>.

Serra, Maria Noel, Albarino, Ricardo, and Villanueva, Diaz. “Invasive Salix fragilis alters

benthic invertebrate communities and litter decomposition in northern Patagonian streams.” Hydrobiologia. 2013. 17 Pages. 6 October 2014.

<http://web.b.ebscohost.com.ezproxy.uwrf .edu:2048/ehost/pdfviewer/pdfviewer?sid=bea1ab80-6365-420c-a57d-65f6cf28e828%40 sessionmgr113&vid=1&hid=101>.

Figure 13. The chart on the left shows the percentage of individuals from each family comprising the entire sample population of macroinvertebrates

gathered from the invaded stretch of the South Fork River. The chart on the right shows the percentage of individuals from each family comprising the

entire sample population of macroinvertebrates gathered from the restored stretch of the South Fork River.

DISCUSSION

The results of our t-test comparing the mean Family Biotic Index (FBI) of macroinvertebrates from the invaded versus restored sites indicated a

statistically significant difference. Based on these results we have accepted both of our hypotheses about the detrimental effect of invasive riparian

flora on aquatic macroinvertebrate health. The invaded reach had a FBI of 4.04 (mean of 3.96, 3.93, 4.02, and 4.23) and the restored reach had a

FBI of 3.51 (mean of 3.48, 3.76, 3.09, and 3.71). These results indicate that macroinvertebrates with a lower tolerance value of organic pollution

and other disturbances were able to colonize the restored stretch more readily than the invaded stretch. In addition, there was higher species richness,

abundance, and diversity in the restored stretch.

The flora within 0-4 meters from the stream bank was more diverse than the riparian buffer zone beyond. Within the immediate bank, the percentage

of invasive species was 31.25%. (mean of 25, 35, 40, and 25%) Taking into account the riparian buffer zone beyond the streambank, which had

anywhere from 40-85% invasive species (mainly buckthorn and tartarian honeysuckle [Lonicera tatarica]), the estimated invasive floral biomass

ranged from 35.6% (pre-invasive) to 58.1% (invasive). This data demonstrates the complexity of the invasive species epidemic. Even in a pre-

invaded ecosystem it can be very difficult to eradicate all of the invasive flora. To compound the problem, at least one invasive species was found

at all of the sampling sites along the restored reach of the South Fork. Wild Parsnip, known for the phytophotodermatitis it produces in humans, was

found within one meter of the stream bank at the restored site. While this was not one of the invasive species our project focused on, it poses dangers

to the native plant, invertebrate, and animal communities of the ecosystem.

Our results support a growing body of evidence of the need for restoration and other natural resource improvement projects to be backed by sound

scientific research and data analysis. Despite the improved health of the restored stretch of the river as observed by increased macroinvertebrate and

native plant diversity and pollution-intolerant species, threats to the ecosystem were present. Without ongoing monitoring and maintenance, the

restored stretch of the South Fork River could revert, at least partially, to a pre-restored state.

Future research projects could further our understanding of the relationship between invasive species and cold-water ecosystem health.

Comparing the restored stretch of the South Fork to an unrestored stretch outside of city limits could prevent any urban influences on results.

Studying the effect of different invasive species on macroinvertebrate communities could provide a clearer picture of which species are a more

significant threat to the health of these communities. Finally, repeating this study at different points in time could provide insight into how the

assemblages of these plant and cold water stream communities change over time- with or without human influence.

Invasive species are a threat to any ecosystem they colonize, including cold-water streams. Only through vigilant monitoring and innovative removal

efforts can we protect this valuable resource and the communities that reside within.

Figure 3. Invaded stretch of the South Fork River with labeled sampling sitesFigure 2. Forest ecosystem invaded by buckthorn

Figure 4. Restored stretch of the South Fork River with labeled sampling sites

Invaded Site- Insect ID Data Sheet

Order Family # Specimens FBI Value Extended Value Reach #

Amphipoda Gammaridae 100 4 400 R1

Diptera Athericidae 1 2 2 R1

Trichoptera Hydropsychidae 1 4 4 R1

Ephemeroptera Baetidae 1 4 4 R1

Plecoptera Perlodidae 1 2 2 R1

412 / 104 FBI: 3.96

Restored Site- Insect ID Data Sheet

Order Family # Specimens FBI Value

Extended

Value Reach #

Amphipoda Gammaridae 27 4 108 R3

Trichoptera Hydropsychidae 29 4 116 R3

Trichoptera Brachycentridae 19 1 19 R3

Trichoptera Limnephilidae 1 4 4 R3

Coleoptera Elmidae 3 4 12 R3

Diptera Athericidae 12 2 24 R3

Ephemeroptera Baetidae 4 4 16 R3

Coleoptera Dryopidae 1 5 5 R3

Plecoptera Perlidae 5 1 5 R3

Diptera Chironomidae 1 6 6 R3

315/102 FBI: 3.0882

Figure 15. Equipment used during macroinvertebrate sampling and plant

identification steps of the project

Figure 9. Equipment used for randomizing specimens

Two plant invasive species are abundant along riparian zones in western Wisconsin. These are glossy buckthorn (Frangula alnus) and

garlic mustard (Alliaria petiolata). Glossy buckthorn can contribute to bare soil conditions and a thick canopy that will shade the stream

and alter the nearby ecosystem. According to Ivanov et al. (2011), the displacement of native understory plant species associated with

the presence of garlic mustard and the creation of near-monospecific stands in the areas where this species occurs are likely to alter

resource availability, habitat quality and microclimate and thus affect organisms from different trophic levels. We intend to study the

effects of invasive species on nearby aquatic macroinvertebrate populations.

The study will be conducted on four study plots located in two different sites, one degraded and one restored three years ago. The

invasive ecosystem (degraded site) extends along the South Fork of the Kinnickinnic River for several hundred meters upstream of the

3rd street bridge on the UW-River Falls campus. The length of this stream includes a large number of glossy buckthorn, with garlic

mustard and several native species comprising the remainder of the plant community. The restored ecosystem site is located at the

South Fork near highway 29, approximately 3 miles east of River Falls. The beginning of this reach is located directly south of the

parking lot, and extends several hundred meters upstream. The major plant species in this area are native grasses and forbs. We will

gather macroinvertebrates from each site and quantify the biomass of plant species in the adjacent riparian zone. We define an invasive

ecosystem as one with 40% or more of the floral biomass in the riparian zone consisting of invasive species. A restored ecosystem has

15% or less of invasive plant species comprising the riparian zone of the reach. Ecosystems having between 15 and 40% are considered

to be pre-invaded ecosystems that are at high risk of becoming invasive ecosystems without human intervention.

Sample populations of macroinvertebrates will be

gathered from riffles in the stream. Four experimenters

will be spaced apart equally within the riffle. Each

experimenter places a D-net about 30 cm away from their

toes. For 20 seconds they shuffle their feet and disturb the

substrate of the river. The nets will then be immediately

removed from the river and the contents will be placed in

a wide shallow tray filled with a half inch of water from

the river. Representative samples of aquatic insect larvae,

riffle beetles and larvae, and aquatic crustaceans will be

removed using tweezers and placed into a jar of ethyl

alcohol to preserve them for later identification. Each of

the jars will be labeled using tape and permanent marker

with information identifying the site (invaded or restored)

and riffle (1-4) where they were gathered. At each of the

eight study plots, approximately 125 macroinvertebrates

will be gathered. The specimens will be taken back to the

lab and sorted into groups of morphologically similar

individuals from each site. Using a dissection microscope

and an aquatic macroinvertebrate identification key, the

individuals will be identified to the family.

Gammaridae 33%

11%

9%3%

4%

Brachycentridae 23%

4%

0%

6%

1%

0%2%3%1%1%

Invertebrate Biodiversity of Restored Stretch of Stream

Gammaridae Athericidae Hydropsychidae Baetidae Perlodidae

Brachycentridae Elmidae Tipulidae Chironomidae Dryopidae

Sialidae Tabanidae Haliplidae Simuliidae Limnephilidae

Gammaridae 88%

1%

1%

2%

1%1%

4%

Invertrebrate Biodiversity of Invaded Stretch of Stream

Gammaridae Athericidae Hydropsychidae Baetidae

Perlodidae Brachycentridae Elmidae Tipulidae

Chironomidae Dryopidae Sialidae

Figure 8. Experimenter using a plant key to identify

unknown floraFigure 7. Riparian plant study plot

Figure 6. Experimenters electing representative sample

of insect larvae

Figure 5. Experimenters using D-nets to gather macroinvertebrates

Figure 14. Experimenter preparing equipment for

macroinvertebrate gathering

Figure 11. Macroinvertebrate diversity

from restored site

Figure 10. Macroinvertebrate diversity

from invaded site

Invaded Site- Plant ID Data Sheet

Plant Name Native/Invasive % Biomass Reach #

Lonicera tatarica Invasive 20 R3

Solidago Native 30 R3

Lamiaceae Pre-Invasive 5 R3

Alliaria petiolata Invasive 15 R3

Urticaceae Native 10 R3

Asteraceae Native 15 R3

Other Forbs Native 5 R3

Native Total % 60% Invasive Total % 40%

Table 3. Sample insect identification data sheet from restored site

Table 2. Sample insect identification data sheet from invaded site

Table 1. Sample plant identification data sheet from invaded site

Figure 1. A restored cold water stream riparian zone