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Bitter Lake National Wildlife Refuge (NWR), Chaves County, New Mexico, harbors at least 19 different aquatic macroinvertebrates in spring systems, wetland units, and channels. Of these 19 invertebrate taxa, 3 are endemic and federally listed: Noel’s amphipod, Koster’s springsnail, and Roswell springsnail. These organisms are dependent upon several environmental factors which have not been well-studied, locally. Environmental factors such as water temperature, dissolved oxygen, specific conductance, pH, and depth are thought to influence macroinvertebrate communities. Furthermore, pollutants especially from oil and gas, stochastic events such as fire, and invasive species are known to effect water quality parameters and potentially aquatic macroinvertebrate taxa. Therefore, I investigated species-environmental community interactions for benthic macroinvertebrates at Bitter Lake NWR, and specific water quality parameters that could influence Noel’s amphipod abundances and springsnail abundances. Twenty-four monitoring sites were sampled for springsnails between 2014-2017 with a benthic grab trap quarterly across 3 systems: Sago Springs, Snail Unit, and Bitter Creek. Noel’s amphipod were sampled at 37 monitoring sites with the inclusion of 13 additional monitoring sites in the Rio Hondo. At each monitoring site, specific
conductance, dissolved oxygen (mg/l), water temperature (ºC), depth (cm), and pH were measured to obtain associations of Noel’s amphipods, and springsnails with each parameter utilizing Canonical Correspondence Analysis (CCA), Generalized Linear Mixed Effects Models (GLMMs), and Classification and Regression Trees. Species-environmental factors were teased out utilizing a CCA, with bloodworm (order: Diptera) having the strongest association with salinity on the environmental gradient. Caddisflies, mosquito larvae, physidae, beetles, orange amphipods, and copepods were associated with the site Bitter Creek. However, Noel’s amphipod was negatively correlated with Bitter Creek and preferred sandy substrates with vents, and rushes and sedges. Springsnails were negatively correlated with all environmental gradients except for temperature and were associated with the season Spring and saltgrass. Based on GLMMs Noel’s amphipod was significantly influenced by dissolved oxygen, depth, and water temperature (p-values <0.001) where pH and salinity were not statistically significant. Springsnails were influenced by all water quality parameters (p-values < 0.001). Based on Classification and Regression Trees, approximately 46% of Noel’s amphipods were most abundant in cooler water, whereas springsnails preferred specific ranges of a water temperature less than 20.6 ºC, a depth greater than 7.92 (cm), and a pH less than 7.87. With this knowledge I plan to implement these results to enhance current monitoring efforts by selecting more sites with more variability of water quality parameters and less species occurrences (e.g. sites where endangered species are not found) to obtain more robust conclusions of habitat and endangered species habitat use. Furthermore, current monitoring efforts include two springsnail species as one. Therefore, I wanted to investigate the efficacy of an external morphological character to discern these two species in the field utilizing a field dissecting microscope. I utilized the initial observations of Taylor (1987) that operculum color can differentiate Roswell springsnail and Koster’s springsnail. Roswell springsnail is assumed to have an amber operculum color and Koster’s springsnail is assumed to have an opaque operculum color. Therefore, I separated springsnails by operculum color and verified my observations with another individual. I then utilized genetic analyses via Sanger Sequencing to determine species identity. I found that we had a field assigned ratio of 59:41 (amber:opaque) and a genetic ratio of 99:1 (Koster’s springsnail:Roswell Springsnail. Therefore, studies based on operculum color should be suspect, and a third party should replicate my work to verify if these species are in fact differentiated by operculum color if this trait is going to be utilized in monitoring efforts at Bitter Lake NWR.



Invertebrates, community ecology


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