Brennan Davis University of New Mexico

 Seasonal drought is predictable; organisms can adapt.  Supra-seasonal drought is unpredictable and unrelenting.  Drought can increase ion concentrations in natural waters. Graph: Lake, 2003

 New Mexico is in a period of severe supra-seasonal drought.  On the Sevilleta NWR, three springs have dried completely from 2012 to 2013.

 Diatoms are photosynthetic organisms.  They are widespread, prolific and diverse.  Diatoms are good indicator organisms, as they are sensitive to changes in water quality.

 How has diatom diversity changed from 2012?  How has drought affected ion concentrations?  How does water quality and chemistry affect diatom density?

 1 spring and 10 drinkers on the Sevilleta National Wildlife Refuge.

 Three water samples were collected from each source.  Field instruments were used to collect water quality measurements at the time of sampling.

 Sample twice at each water source. Sampler choice depends on substrate.  Process samples.  Prepare slides. Identify diatoms and calculate density.

 4 transects performed at each water source.  Percent cover of vegetation and scat, as well as rough ID performed.  Gives insight into nutrient inputs and water usage.

Final stress: 9.95 Ordination of Relative Abundance

Nitzscia perminutaPlanothidium lanceolatum Achnanthidium spp. Rhopalodia gibbaEpithemia spp.

 Water quality measures, such as turbidity and salinity, varied from each water source.  Three different substrate types were sampled.  Surrounding habitat varied by water source; vegetation and scat levels were inconsistent.

 Three different substrate types were sampled.  Flat steel, sediment and wood substrates were sampled; the substrate differed at each source.

 Reminder: drought can increase concentration of ions in water.  Ions that facilitate algal growth: Cu, V, and Ni, among others not present in refuge waters.

 Observed diversity increased from 2012 to Differences in experimentation.  Ion concentrations have increased from 2012 to  Increases in beneficial ions may lead to higher diatom density. Drought may therefore benefit some diatoms to a point.

 Sample over time to observe diatom reactions to drought on a temporal scale.  Test water chemistry over time to observe changes in ion concentrations.  Perform vegetation and scat transects at time of water and diatom sampling.  More sampling will also contribute to more robust data.

Lead P.I.: Dr. Scott Collins Mentor: Dr. Rebecca Bixby Program Manager: Amaris Swann Field Partner: Briana Albini