Natural and artificial desert spring ecosystems influence on aquatic macroinvertebrate communities in semi-arid New Mexico
Cassandra Miller
Sevilleta National Wildlife Refuge
University of New Mexico 2014 REU
Grinnell College

Abstract:
In arid and semi-arid environments, springs are oftentimes the only stable source of water. Aquatic macroinvertebrates play a large role in the maintenance of these ecosystems. Thus they have a bottom-up influence on the larger ecosystem. This study surveys and compares the aquatic macroinvertebrate community composition in natural and artificial springs on the Sevilleta National Wildlife Refuge. Natural springs had a higher abundance, and a significantly higher richness in comparison to communities in artificial springs. I propose that future conservation efforts should focus on the maintenance of natural springs environments.
Introduction:
In arid and semi-arid environments, springs are oftentimes the only permanent water sources (Stevens & Meretsky 2008). Desert spring ecosystems are small “biodiversity hotspots” in the American Southwest. They support aquatic and riparian ecosystems where groundwater reaches the land surface. In arid lands they provide much of the aquatic environment of the region, and provide disproportionately large services to wildlife than their spatial extent would suggest
(Dudgeon et al. 2006).
Furthermore, springs serve as an important link between aquatic and terrestrial ecosystems. Aquatic macroinvertebrates have been well studied in stream ecosystems, and shown to be ecological engineers (Jones et al. 1987).
Macroinvertebrates intersect many trophic levels as decomposers, producers, and consumers (Wallace & Webster 1996). They also help maintain water quality, thus they have a bottom-up influence on the larger ecosystem.
The Sevilleta National Wildlife Refuge has 40 small springs spread across the landscape. Some of these springs are natural whereas some are artificial drinker wells, remnants of the cattle ranch. Thus far, few surveys have documented the

macroinvertebrate communities present in either the natural or artificial springs.
In this experiment, we set out to see if natural and artificial spring habitats impacted the community composition of aquatic macroinvertebrates. It is likely that community composition would differ between natural and artificial ecosystems. I hypothesized that natural springs would foster more diverse communities because of their unique habitats. In contrast, I predicted that artificial springs would have higher abundance due to their extremely stable environment.
Materials and Methods:
All sample site locations can be located within the Sevilleta National Wildlife
Refuge. Sample sites included 8 artificial springs (Nunn, McKenzie, Gibbs, Goat
Draw, 222 (Tule), West Mesa Tire, and West Mesa Steel) and 5 natural springs
(Cibola, Rio Salado, San Lorenzo, Canyon Ojitos, and Four Springs) (see Figure 1).
Directions to each site can be accessed through Dr. Amy Williams’ thesis (2007).

Artificial Spring
Natural Spring
Figure 1. Location of natural and artificial spring sample sites on the Sevilleta National
Wildlife Refuge. The blue dots represent the natural springs and black dots represent artificial springs that were surveyed.
Aquatic Survey of Macroinvertebrates:
At each sample site, a 15x15 cm quadrat was submerged. Water samples were collected from the area within the quadrat using a 25ml pipette to collect 250ml of water from each site. Using a 300micron sieve, aquatic macroinvertebrates were isolated and placed in ethanol (70%) for preservation. Each sample was taken back to the lab for taxonomic identification.
Analysis of Taxonomic Richness and Abundance:

Aquatic macroinvertebrates samples were identified to the level of genus.
Abundance of each macroinvertebrate present was noted, and evaluated through a t-test to determine the effects that habitat had on the abundance and richness of macroinvertebrates of natural versus artificial aquatic habitats had on the overall abundance and taxonomic richness of aquatic macroinvertebrates. Additionally, a
Shannon-Weiner biodiversity analysis was performed in order to account for the uneven sample sites.
Rapid Habitat Appraisal:
At each sample site a transect was set up 1m, 3m, and 10m away from the water source in each cardinal direction. A 100x100 cm quadrat was placed at each transect to ascertain percent vegetation coverage, vegetation type identification, and presence of scat.
Percent Soil Moisture Appraisal:
At each sample site, a transect was set up 1m, 3m, and 10m away from the water source in each cardinal direction. A soil core was then inserted at a depth of 5 cm at each interval. Soil samples were then weighed in the lab. After weighing, samples were dried for 48 hrs at 80 O C and then reweighed to determine soil moisture percentage.
Analysis of Habitat and Soil Moisture Appraisal:
Data was collected, but no further analysis was performed at the time of this paper.

Results:
Natural spring and artificial spring habitats impacted both the overall abundance and taxonomic richness of aquatic macroinvertebrates. Natural springs on average displayed a trend of higher abundance compared to artificial spring habitat (Figure 2 in appendix). When looked at individually, the results present a more variable trend. It is interesting to note that San Lorenzo Spring had exhibited a noticeably high abundance in comparison to all other samples sites, with 512 individuals (Figure 2 in appendix). Overall artificial springs similar abundance, except for West Mesa (steel) that had 196 individuals.
When analyzing taxonomic richness, natural springs demonstrated a significantly higher taxonomic richness in comparison to artificial springs (P=0.015)
(Figure 3 in appendix). The difference was more pronounced when looking at individual springs. Out of the eight artificial springs, six had 5 or less taxa. In comparison, of the five natural springs only one had less than 5 different taxa.
In order to account for the different number of sample sites, a Shannon-
Weiner Biodiversity analysis was performed to look at evenness. This analysis displayed a similar trend of natural springs having a higher evenness on average in comparison to artificial, but there was no significant difference (Figure 5 in appendix). Altogether, all springs appeared more even than the other two analyses suggested.
Taxonomic identification was categorized to the family level. Collectively from both natural and artificial springs, 21 unique families were identified. Of these

seven were found in both natural and artificial springs, four were only found in artificial springs, and ten were only found in natural springs (Table 1 in appendix).
Discussion:
These results indicate that community composition of macroinvertebrates differs between natural and artificial springs. On average, natural springs had a higher total abundance of individuals in comparison to artificial springs. This was impacted by the fact that out of the five natural springs, four had the presence of
Ostracoda (Table 1 in appendix). In comparison, of the eight artificial springs sampled, only four were found to have Ostracoda. Ostracoda occur in high abundance, which could explain these results.
Natural springs had a significantly higher taxonomic richness in comparison to artificial springs. This may have to do with the fact that natural springs occur in unique ecosystems in comparison to the standard ecosystems in which artificial springs are found in, as they provide more distinct niches for macroinvertebrates to occupy (Figure 6 in appendix). Research by Bogan et. al. indicates that macrohabitat type was the most important factor in structuring aquatic invertebrate communities
(2014). Thus, Future studies should disregard the distinction between ‘natural’ and
‘artificial’ and instead categorize sites by macrohabitat type may prove to be more insightful when attempting to learn the cause of community composition.
The Shannon-Weiner Biodiversity Index illustrated a higher amount of evenness than expected. However, information on community composition cannot be predicted from this. Wallace & Webster’s research in stream ecosystems

demonstrates the strengths in studying community structure based on groups of functional similarities (1996). Future studies should then identify macroinvertebrates to the species level to better understand community interactions within the springs.
In light of the predicted increasing aridity of the region, an attempt was made o see how survivorship of macroinvertebrate communities were responding.
However, insufficient data from past REU students did not allow for this comparison. Since this is a long-term study, methods and data maintenance should be maintained and standardized. Monitoring of macroinvertebrates should be continued to learn about seasonal variation. A data collection of this sort would prove to be useful to future conservation discussion on the Sevilleta National
Wildlife Refuge, as macroinvertebrates play disproportionally large ecological roles in the ecosystem.
Acknowledgements:
Thanks to my mentor, Ayesha Burdett, for her support, encouragement, and expertise. Thanks to Amaris Swann for her unwavering support. Thanks to Sevilleta
LTER and Sevilleta Fish & Wildlife –especially Kathy Granillo. Thanks to NSF,
University of New Mexico, and New Mexico Natural History & Science Museum.
Additionally, thanks to Amy Williams, Briana Albini, Ben Spector, Shane Piaso, the
2014 REU Students, and Briana Albini.
References:

Bogan, M., Noriega-Felix, N., Vidal-Aguilar, S., et. al. 2014. Biogeography and conservation of aquatic fauna in spring-fed tropical canyons of the southern
Sonoran Desert, Mexico. Biodiversity Conservation Online. DOI:
10.1007/s10531-014-0745-z.
Dudgeon, D., Arthington A. H., Gessner M.O., & et al. (2006) Freshwater biodiversity: importance, threats, status and conservation challenges. Biol Rev 81:163–
182.
Jones, C.G., Lawton, J.H., Shachak, M. 1994. Organisms as ecosystem engineers.
Oikos 69:373-86
Myers, Marilyn J., Vincent H. Resh. 1999. Spring-Formed Wetlands of the Arid West:
Islands of Aquatic Invertebrate Biodiversity. In D. P. Batzer, R. B. Radar, and S.
A. Wissiner (eds.) Invertebrates in Freshwater Wetlands of North America:
Ecology and Management. John Wiley and Sons. New York, NY, USA. Pp 811-
828.
Wallace, B., & Webster, J. 1996. The role of macroinvertebrates in stream ecosystem function. Annual Reviews. 41. 115-139.
Williams, A. 2009. An aqueous geochemical and hydrologic study of the springs and wells of the Sevilleta National Wildlife Refuge: Evaluating hydrochemical pathways. Dissertation. University of New Mexico. August 2009.
Appendix:

a) b)
Figure 2. Mean total abundance of macroinvertebrates found in natural versus artificial
springs. On average, a) natural springs tended to have higher abundance of macroinvertebrates compared to artificial springs. However, the difference was statistically significant. Panel b) shows individual spring abundance. Error bars = 1 X SE.

a) b)
Figure 3. Mean taxonomic richness of macroinvertebrates found in natural and artificial
springs. On average, a) natural springs had a significantly higher amount on different taxa in comparison to artificial springs (P=0.015). Panel b) shows individual spring taxonomic richness.
Error bars r= 1 X SE.

a) b)
1,2
1
0,8
0,6
0,4
0,2
0,8258 0,548
0
1,4
1,2
1 0,914
0,8
0,6
0,4
0,179
0,349
0,2
0
0,69
0,636
0
0,839
0,777
0,66 0,668
0,823
1,27
0,708
Artificial
Natural
Figure 5. Shannon-Weiner Biodiversity analysis of evenness between natural and
artificial springs. There was no significant difference of evenness between natural and artificial springs, panel a). Panel b) depicts individual spring S-W biodiversity. Error bars = 1 X
SE.

Table 1. List of all unique taxa found in natural and artificial springs. X’s represent if the family was found present in each spring.

a) b) c) d)
Figure 6. Macrohabitats of springs on the
Sevilleta National Wildlife Refuge. Panel a) is
Cibola Spring and panel b) is Four Springs. Both of these are examples of natural spring habitats that were sampled. Panel C) is Nunn Well and panel d) is West Mesa (steel) Well. Both panels are examples of artificial spring habitats sampled.