No abstract

Increasing temperatures and decreasing precipitation will likely result in a decrease in spring discharge for highly productive volcanic aquifer-spring systems.ABSTRACT: Medicine Lake Highlands/Fall River Springs Aquifer System, located in northeastern California, is home to some of the largest first-order springs in the United States. This work assesses the likely effects of projected climate change on spring flow. Four anticipated climate futures (GFDL A2, GFDL B1, CCSM4 rcp 8.5, CNRM rcp 8.5) for California, which predict a range of conditions (generally warming and transitioning from snow to rain with variable amounts of total precipitation), are postulated to affect groundwater recharge primarily by changing evapotranspiration. The linkages between climate variables and spring flow are evaluated using a water balance model that represents the physics of evapotranspiration and recharge, the Basin Characterization Model. Three of the four climate scenarios (GFDL A2, GFDL B1, CCSM4 rcp 8.5) project that by the year 2100, groundwater recharge (and consequently decreased spring flow) will decrease by 27%, 21%, and 9%, respectively. The fourth scenario (CNRM rcp 8.5) showed an increase in recharge of 32% due to a significant increase in precipitation (27%). Evapotranspiration increases due to a shift in the type of precipitation and a longer growing season. While the likelihood of each scenario is outside the scope of this work, unless total precipitation increases dramatically in the future, increased temperatures and decreasing precipitation will likely result in reduced spring flows, along with warmer water temperatures in downstream habitats.

Microbes inhabiting the guts of phylogenetically "lower" termites and the closely related woodfeeding roach Cryptocercus have attracted the attention of numerous biologists and microscopists for well over 100 years [1]. The combined metabolic activities of hindgut microbes-which include representatives of bacteria, archaea, as well as protists (microbial eukaryotes)-allow their termite hosts to survive on a diet that consists exclusively of wood [2]. The great majority of studies based on microscopy have focused on the protists (comprising mostly parabasalids and oxymonads), not only because of their relatively large size, but also because of the enormous structural complexity and bizarre morphologies present in many species [3,4]. Additionally, a number of different lines of evidence indicate that the protists (not the bacteria) carry out enzymatic cellulose degradation for the termite host, as well as produce hydrogen gas [2,3,5]. Many species of hindgut protists are seen to associate with symbiotic bacteria on their surface, and in cytoplasmic vacuoles [6]; these are thought to provide their protist host (as well as the termite host) with fixed nitrogen in the form of amino acids and other nitrogenous nutrients, while free-swimming spirochetes fix dinitrogen from air [2].Despite their great structural, evolutionary, and ecological importance, termite hindgut protists-and more recently, their associated symbiotic bacteria-have been studied almost exclusively with light microscopy and TEM (as well as molecular techniques), while studies of morphology with SEM and studies of metabolism using isotopic tracers and NanoSIMS have been rare or nonexistent. Difficulty in fixing whole protist cells from these environments for high vacuum analysis and imaging with high energy electron or ion beams is likely due to their large size (some up to 200 microns long), lack of a rigid cell wall, enormous structural complexity, and the presence of numerous fine-scale structures (some protist species may have tens of thousands of flagella).Here, we will describe a new approach for SEM and NanoSIMS imaging and analysis of hindgut microbes. The technique relies on two new, simple chemical fixation methods that produce very high quality preservation that retains overall cellular shape (similar to what is observed in light microscopy), fine structures such as flagella (and many newly discovered surface features), as well as membrane integrity of both protists and associated bacteria. Both methods require dilution of hindgut microbes in Trager Medium U buffer [7], and immediate exposure to fixative. The first method uses only osmium tetroxide as a fixative-introduced first as a vapor, followed by direct contact with cells (approximately 1% v/v). This suspension of fixed cells is then introduced over Millipore Isopore membrane filters (with a 1, 3, or 5 micron pore size) held in Swinnex cartridges affixed to 10 ml syringes. The cells concentrated on filters are then rinsed in buffer and dehydrated with an ethanol series (50%, 70%, 90%,...