Habitat conditions for the endangered Zuni bluehead sucker, Catostomus discobolus yarrowi, Zuni Mountains New Mexico: Continuous monitoring and hydrogeochemistry of springs

Authors: Frus, Rebecca*, Crossey, Laura, Bixby, Rebecca

Year: 2015 (xlvii)

Abstract

Spring fed ecosystems in arid environments have been identified as isolated islands that provide stable habitats for endemic species. The Zuni bluehead sucker (ZBS), Catostomus discobolus yarrowi, is the only endemic fish species still found in the Zuni River, tributary to the Little Colorado River. In 2014, the ZBS was federally listed as endangered as it has lost over 90% of its habitat range; populations have been reduced to 4 isolated spring fed sections of the Rio Nutria, New Mexico. This research focuses on three of the ZBS habitats to understand hydrogeochemical controls (major ion chemistry and stable isotopes, ÁŽÂ´¹⁸O and ÁŽÂ´D) on habitat suitability. In addition, multi-season continuous monitoring (CM) data (specific conductance (SC), water temperature, dissolved oxygen (DO)) are reported. Major ion chemistry was analyzed for water samples collected at each site and was compared to regional groundwater chemistry. Two of the habitat sites are determined to have major contributions of water supplied from the Permian San Andres/Glorieta (Psg) aquifer, while the third site has waters supplied from the Triassic Chinle Formation (TRc). In addition, all sites have contributions from local shallow alluvium aquifers (Qa) found in their respective creek beds. Geochemical mixing models show that the habitats are a mixture of these water sources TRc or Psg and Qa, with dry seasons having as much as 99% of the water supply from the spring waters (TRc or Psg). Stable isotopes of ground waters (TRc: ÁŽÂ´¹⁸O=-13.48 to -12.14 and ÁŽÂ´D= -94.83 to -92.029ÁŽÂ´; Psg: ÁŽÂ´¹⁸O =-11.84 to -10.50 and ÁŽÂ´D=-87.60 to -83.37) indicates that the spring waters are recharged predominately through snow melt. The shallow alluvium waters (Qa: ÁŽÂ´¹⁸O= -12.829 to -9.82 and ÁŽÂ´D=-92.13 to -76.07) can be recharged through both rain and snow events and undergo evaporation during warm seasons. CM of water temperatures show that TRc spring waters (5-13Á‚°C with peak in mid-September) have seasonal variability but temperatures are dampened and timing is different when compared to the Qa (2-18Á‚°C with a peak in mid-July). CM of SP shows that Qa waters are impacted by precipitation events (Qa: SP= 630 to 185Á‚µS/cm) while TRc ground water has very slight response to precipitation events (TRc: SP=490 to 520Á‚µS/cm). CM of Qa waters, with no spring inputs, have a mean DO=1.6 mg/l, while ZBS habitats with TRc waters having a mean DO=5.7 mg/l. These results indicate that spring waters input re-aerated waters to the ZBS habitat which helps to maintain tolerable DO levels. Without the perennial input from spring waters, habitats for the ZBS would either dry completely during warm seasons, or become stagnant anoxic water bodies unable to maintain ZBS. This research demonstrates the importance of maintaining groundwater resources for these essential aquifers. For the persistence of the species, encroaching development as well as impacts of a warming climate should be considered in natural resource management.