The Ecology of Signal Crayfish in Two Large Ultra-Oligotrophic Ecosystems: Crater Lake and Lake Tahoe

Invasive species have become an increasing problem in the Western United States particularly when there are multiple stressors (e.g., invasive species and eutrophication) occurring to ecosystems. Invasive omnivores can present unique problems for aquatic ecosystems by having both direct and indirect impacts on native benthic invertebrates and vertebrates. Omnivorous crayfish, for example, strongly influence littoral habitats and biota with their foraging habits, creating both direct and indirect effects on trophic interactions in aquatic systems. Once they invade, these crayfish can ultimately dominate freshwater ecosystems. This dissertation investigates the distribution, density changes, and the direct and indirect impacts of the invasive signal crayfish (Pacifastacus leniusculus) in two oligotrophic lentic ecosystems in the western United States; Lake Tahoe (CA-NV) and Crater Lake (OR). In chapter 1, I investigate the distribution, movement, and feeding behavior of invasive signal crayfish in Crater Lake. This lake population presents a unique opportunity to understand the movement of crayfish in a recently expanding population. I used minnow traps and snorkeling to determine crayfish distribution and stable isotope ratios of δ13C and δ15N to determine the flow of organic matter through the food web, trophic position, and percent benthic reliance. Depth gradient minnow traps demonstrate that crayfish densities can live as deep as 250 m. Trap and snorkel surveys from 2008 to 2013 indicate an expansion of crayfish from 44% to 78% of the littoral zone. Summer water temperature in Crater Lake has been warming, which may increase the recruitment of individuals and expand habitat availability for growth. Between 1965 and 2014 the nearshore surface temperature increased by 3.5°C. Principal component analysis revealed a positive relationship between crayfish occupation and cobble and boulder habitats of the lake. Crayfish in the littoral zone rely heavily (97.4%) on littoral-benthic carbon sources indicating their potential for impacting native invertebrate communities and the overall dynamics of Crater Lake’s ecosystem. Our findings indicate, however, that deeper water crayfish also may rely on littoral benthic energy resources. Crayfish movement to deeper waters may be subsidizing generally nutrient poor, deep-water habitats with littoral energy through excretion and egestion, where physical conditions are stable and natural perturbation is low.In Chapter 2, I quantify the influence of this early, expanding invasion in Crater Lake to littoral zone ecology by evaluating their influence on zoobenthic consumer biomass and basal algal biomass. Benthic invertebrate biomass was 77% lower in hard substrate and 78% lower in soft substrate areas with crayfish present than in crayfish-absent locations. Using Bayesian, stable isotope mixing models, dietary preferences of crayfish at three locations with varying crayfish densities were quantified. Only slight variations in crayfish diet were detected between the three locations where crayfish have been established, the outer boundary of crayfish expansion, and the middle of the crayfish population indicating that crayfish. Despite differing densities, crayfish are feeding on similar food sources, particularly benthic invertebrates. At low crayfish densities (0 to 10), benthic invertebrate numbers were 222.3±36.6 individuals m-2, while chlorophyll a was 16.8±5.8 mg m-2. At high densities of crayfish (>50), benthic invertebrates had low mean density 3.0±4.2 individuals m-2, while chlorophyll a biomass was high 226.7±48.1 mg m-2. Crayfish are impacting native invertebrate communities and periphyton biomass in Crater Lake by changing trophic interactions in the lake’s littoral zone and altering the lake’s food web.In Chapter 3, I focus on the benthic environment and biodiversity of Lake Tahoe and regional lakes (Donner Lake, Marlette Lake, and Fallen Leaf Lake. Signal crayfish were introduced into the Central Sierra Nevada region of the United States in the late 19th to early 20th century. I used a long-term data set to document highly variable crayfish densities in the littoral zone of Lake Tahoe, showing an increase during the summer months linked to an increase in water temperature (R2 = 0.69, P<0.001). Crayfish responded to site-specific characteristics of the nearshore rather than to lake-wide characteristics; local stream discharge was the only factor that explained a positive increase in lake densities (P< 0.04). Trophic niche models developed from stable isotope measurements of crayfish and nongame fish indicate that crayfish influence the dietary breadth (e.g. niche area) of nongame fish consumers. Crayfish feeding behavior may be forcing nongame fish to feed on a broader set of food resources when crayfish are present. Stable isotope analysis also indicates an overlap of crayfish niche area with other nongame fish and amphibians, indicating interspecific competition between organisms. Our study highlights that local factors influence cold-water crayfish movement and densities in large lakes, as well as potential direct and indirect influences on nongame fish consumers in the littoral region, potentially affecting native biota and ecosystem function. This research has significant implications for understanding the direct and indirect impacts of signal crayfish in oligotrophic food webs, particularly on benthic invertebrate densities. It expands on the current understanding of expansion of signal crayfish and the factors that influence crayfish density. Future research will need to focus on better understanding the life history and mechanisms controlling this species if they are to be controlled in lakes of the Western United States

So, You Want to 3D Print a Landscape? An Outline of Some Methods

https://digitalcommons.cedarville.edu/alum_books/1435/thumbnail.jp

So, You Want to 3D Print a Landscape? An Outline of Some Methods

https://digitalcommons.cedarville.edu/alum_books/1453/thumbnail.jp

What Has to Change for Forests to be Saved? A Historical Example From the United States

This article looks at the conservation of American forests in the nineteenth and twentieth centuries to cast light on the prospects for global forest conservation in the twenty-first. At the beginning of the nineteenth century, Americans understood their forests as good only for cutting. By the end of the century a national scheme existed for comprehensive and permanent forest conservation. This new scheme became possible thanks to changes in scientific knowledge, the ideological self-image of the country, political institutions, and the imagination and moral commitments of citizens and social movements. A look at the changes that laid the foundations of national forest conservation might help to show what would have to happen for international forest conservation to emerge. Alternatively, it might highlight differences between those past developments and present circumstances, showing how past is not prologue. In this case, the upshot is some of both

Mount Mazama and Crater Lake : A Study of the Botanical and Human Responses to a Geologic Event

Crater Lake, located in the southern Cascade mountains of Oregon, is the seventh deepest lake in the world. Unlike a majority of the deepest lakes in the world, found in continental rift valleys, Crater Lake is in the caldera of a volcano. For the young at heart and mind, those willing to descend (and ascend) about 700 feet to Cleetwood Cove can undertake a boat tour of Crater Lake. From the boat, Crater Lake is more than just a beautiful blue lake; it becomes the inside of a volcano, where the response of people and plants to a geologic event can be investigated. The catastrophic eruption of Mount Mazama 7,700 years ago affected both plant and human populations. Before pumice and ash from the volcano blanketed the landscape like freshly fallen snow, the forests to the east of Mount Mazama were dominated by ponderosa and lodgepole pine. Within the immediate vicinity of the volcano all life was obliterated; the force of the eruptive material toppled vegetation and buried it with ash and pumice. Through the recovery process of succession, life has slowly returned to Crater Lake. Forests surrounding the lake are now dominated by mountain hemlock, whitebark pine, and lodgepole pine. These plants not only depict the process of succession, but also of adaptation to a volcanic environment. Factors restricting establishment and growth of plants are controlled by the nonliving environment. Climate, geologic activities, elevation, and time all contribute to the availability of water, soil, nutrients, and sunlight, which directly affect plant growth. Heavy winter snows, which linger until July, and very little summer rain, control soil moisture and the length of the growing season at Crater Lake. Volcanic activity dictates the parent material, which with time breaks down forming soil. The properties of the soil determine its ability to hold water and the concentrations and availability of nutrients. Pumice soils provide developing plants with low nutrient supplies and affect the growth of plants with extreme surface temperature fluctuations. Volcanic cinder has a very low capacity to hold water and nutrients, thus restricting plant growth. People have lived in the Pacific Northwest for at least the last 10,000 years. Direct archaeological evidence of life near Mount Mazama is scarce. Those occupation sites closest to the volcano were covered with pumice and ash from the climactic eruptions. Sites protected from the eruptive material and sites farther away provide archaeologists a glimpse into the cultures of the Basin and Range Province. People living around Mount Mazama were predominantly nomadic; their survival depended on available resources. The catastrophic eruption of Mount Mazama and the subsequent devastation of the land disrupted their lives. As the environment recovered from the eruption, the people also recovered. They were forced to find alternative food sources, fuels, and shelters. The indigenous people's perceptions of this natural disaster are understood indirectly through the use of archaeological data and folklore. Their stories tell of angry gods and stalwart ancestors. Llao, the God of the underworld, and Skell, the God of light, were often at war, Llao from Mount Mazama and Skell from Mount Shasta. Although the origins of such legends are difficult to trace, they emphasize the perceptions of those who lived in the shadow of this mystical volcano. People's limited understanding of the volcano thus triggered their reverence for the place

1950-07-28 (The OCE Lamron)

Student newspaper for Oregon College of Education, 1950-07-28. Newspaper includes campus, local and national news stories and photographs. For additional information about this collection see: http://digitalcommons.wou.edu/studentnewspapers

An investigation of volcanic depressions. Part 1 - Geologic and geophysical features of calderas Progress report

Preferred classification of calderas and volcano- tectonic depressions based on relative amounts of lava and proclastic eject

Chemical differentiation by mineralogical buffering in crustal hot zones

Chemical diversity in convergent margin magmas is a product of igneous differentiation in crustal hot zones, vertically extensive regions characterised by a low-volume (<20%) mobile melt phase dispersed in a crystal-rich mush. Chemical reaction between buoyant, percolating melts and the surrounding mush leads to chemical buffering by the local mineral assemblage. Where this assemblage has low thermodynamic variance (e.g. six mineral phases plus melt and H2O-CO2 fluid) the resultant multiply saturated melts will show limited chemical variability. Plutonic xenoliths from many volcanic arcs, as well as exhumed arc crustal sections, testify to the ubiquity of low-variance, broadly gabbroic, mineral assemblages. Here I use the concept of multiple saturation to explore the chemical consequences of percolative reactive melt flow in crustal hot zones using data from published experimental studies on a wide variety of different starting materials. I show that the common, low-variance hornblende gabbronorite assemblage clinopyroxene-hornblende-orthopyroxene-magnetite-plagioclase-ilmenite (CHOMPI) coexists with fluid-saturated melt over a wide range of pressure (1–10 kb) temperature (800–1050 °C) and fluid composition (molar fraction H2O, XH2O, of 1.0 to 0.3). The CHOMPI stability field is bounded by the following: the appearance of garnet at high pressure, the hydrous haplogranite granite liquidus at low temperature, and amphibole breakdown at high temperature and low pressure. CHOMPI melts cover a wide compositional range (54–74 wt% SiO2; 4.4–0.1 wt% MgO) that can be parameterised in terms of five independent variables: pressure, temperature, fO2, molar CO2/H2O in the fluid and melt K2O content. The compositional diversity and broad stability field of CHOMPI-saturated melts make them extremely common in the rock record. Melt composition parameterisations can be inverted to recover pressure (±1.3 kb), temperature (±16 °C) and fluid molar CO2/H2O (±0.43) of CHOMPI-saturated melts. If a natural magma composition can be shown to lie on or close to the CHOMPI saturation surface then the conditions under which that melt was last in equilibrium with this mineral assemblage can be established. I apply this method of magma source thermobarometry and hygrometry to the most recent eruptions from 15 Cascades arc volcanic centres. Calculated pressures range from 1.3 to 5.8 kb (5–21 km depth) with significant along-arc variation. Temperatures correlate with pressure and match independent estimates of eruption temperatures from mineral thermometry with the exception of two eruptions where significant (≤10°C) cooling occurred during pre-eruptive magma storage. Fluid XH2O is in the range 0.47–0.92 and inversely correlates with pressure. Mineralogical buffering of melt chemistry in hot zones is proposed as an important mechanism of chemical differentiation in volcanic arcs. Mineralogical buffering can operate at the low-melt fractions observed in geophysical surveys of arc crust, providing an alternative to traditional concepts of assimilation-fractional crystallisation and liquid lines of descent that operate most effectively in melt-rich systems