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Description
Quagga mussels are an aquatic invasive species capable of causing economic and ecological damage. Despite the quagga mussels’ ability to rapidly spread, two watersheds, the Salt River system and the Verde River system of Arizona, both had no quagga mussel detections for 8 years. The main factor thought to deter quagga mussels was the stratification of the two watersheds during the summer, resulting in high temperatures in the epilimnion and low dissolved oxygen in the hypolimnion. In 2015, Canyon Lake, a reservoir of the Salt River watershed, tested positive for quagga mussel veligers. In this study, I used Landsat 7 and Landsat 8 satellite data to determine if changes in the surface temperature have caused a change to the reservoir allowing quagga mussel contamination. I used a location in the center of the lake with a root mean squared error (RMSE) of 0.80 and a correlation coefficient (R^2) of 0.82, but I did not detect any significant variations in surface temperatures from recent years. I also measured 21 locations on Canyon Lake to determine if the locations in Canyon Lake were able to harbor quagga mussels. I found that summer stratification caused hypolimnion dissolved oxygen levels to drop well below the quagga mussel threshold of 2mg/L. Surface temperatures, however were not high enough throughout the lake to prevent quagga mussels from inhabiting the epilimnion. It is likely that a lack of substrate in the epilimnion have forced any quagga mussel inhabitants in Canyon Lake to specific locations that were not necessarily near the point of quagga veliger detection sampling. The research suggests that while Canyon Lake may have been difficult for quagga mussels to infest, once they become established in the proper locations, where they can survive through the summer, quagga mussels are likely to become more prevalent.
ContributorsLau, Theresa (Author) / Fox, Peter (Thesis advisor) / Neuer, Susanne (Committee member) / Abbaszadegan, Morteza (Committee member) / Arizona State University (Publisher)
Created2018
Description
Some cyanobacteria, referred to as boring or euendolithic, are capable of excavating tunnels into calcareous substrates, both mineral and biogenic. The erosive activity of these cyanobacteria results in the destruction of coastal limestones and dead corals, the reworking of carbonate sands, and the cementation of microbialites. They thus link the biological and mineral parts of the global carbon cycle directly. They are also relevant for marine aquaculture as pests of mollusk populations. In spite of their importance, the mechanism by which these cyanobacteria bore remains unknown. In fact, boring by phototrophs is geochemically paradoxical, in that they should promote precipitation of carbonates, not dissolution. To approach this paradox experimentally, I developed an empirical model based on a newly isolated euendolith, which I characterized physiologically, ultrastructurally and phylogenetically (Mastigocoleus testarum BC008); it bores on pure calcite in the laboratory under controlled conditions. Mechanistic hypotheses suggesting the aid of accompanying heterotrophic bacteria, or the spatial/temporal separation of photosynthesis and boring could be readily rejected. Real-time Ca2+ mapping by laser scanning confocal microscopy of boring BC008 cells showed that boring resulted in undersaturation at the boring front and supersaturation in and around boreholes. This is consistent with a process of uptake of Ca2+ from the boring front, trans-cellular mobilization, and extrusion at the distal end of the filaments (borehole entrance). Ca2+ disequilibrium could be inhibited by ceasing illumination, preventing ATP generation, and, more specifically, by blocking P-type Ca2+ ATPase transporters. This demonstrates that BC008 bores by promoting calcite dissolution locally at the boring front through Ca2+ uptake, an unprecedented capacity among living organisms. Parallel studies using mixed microbial assemblages of euendoliths boring into Caribbean, Mediterranean, North and South Pacific marine carbonates, demonstrate that the mechanism operating in BC008 is widespread, but perhaps not universal.
ContributorsRamírez-Reinat, Edgardo L (Author) / Garcia-Pichel, Ferran (Thesis advisor) / Chandler, Douglas (Committee member) / Farmer, Jack (Committee member) / Neuer, Susanne (Committee member) / Arizona State University (Publisher)
Created2010
Description
Plastic pollution has become a global threat to ecosystems worldwide, with microplastics now representing contaminants reported to occur in ambient air, fresh water, seawater, soils, fauna and people. Over time, larger macro-plastics are subject to weathering and fragmentation, resulting in smaller particles, termed ‘microplastics’ (measuring < 5 mm in diameter), which have been found to pollute virtually every marine and terrestrial ecosystem on the planet. This thesis explored the transfer of plastic pollutants from consumer products into the built water environment and ultimately into global aquatic and terrestrial ecosystems.
A literature review demonstrated that municipal sewage sludge produced by wastewater treatment plants around the world contains detectable quantities of microplastics. Application of sewage sludge on land was shown to represent a mechanism for transfer of microplastics from wastewater into terrestrial environments, with some countries reporting as high as 113 ± 57 microplastic particles per gram of dry sludge.
To address the notable shortcoming of inconsistent reporting practices for microplastic pollution, this thesis introduced a novel, online calculator that converts the number of plastic particles into the unambiguous metric of mass, thereby making global studies on microplastic pollution directly comparable.
This thesis concludes with an investigation of a previously unexplored and more personal source of plastic pollution, namely the disposal of single-use contact lenses and an assessment of the magnitude of this emerging source of environmental pollution. Using an online survey aimed at quantifying trends with the disposal of lenses in the US, it was discovered that 20 ± 0.8% of contact lens wearers flushed their used lenses down the drain, amounting to 44,000 ± 1,700 kg y-1 of lens dry mass discharged into US wastewater.
From the results it is concluded that conventional and medical microplastics represent a significant global source of pollution and a long-term threat to ecosystems around the world. Recommendations are provided on how to limit the entry of medical microplastics into the built water environment to limit damage to ecosystems worldwide.
A literature review demonstrated that municipal sewage sludge produced by wastewater treatment plants around the world contains detectable quantities of microplastics. Application of sewage sludge on land was shown to represent a mechanism for transfer of microplastics from wastewater into terrestrial environments, with some countries reporting as high as 113 ± 57 microplastic particles per gram of dry sludge.
To address the notable shortcoming of inconsistent reporting practices for microplastic pollution, this thesis introduced a novel, online calculator that converts the number of plastic particles into the unambiguous metric of mass, thereby making global studies on microplastic pollution directly comparable.
This thesis concludes with an investigation of a previously unexplored and more personal source of plastic pollution, namely the disposal of single-use contact lenses and an assessment of the magnitude of this emerging source of environmental pollution. Using an online survey aimed at quantifying trends with the disposal of lenses in the US, it was discovered that 20 ± 0.8% of contact lens wearers flushed their used lenses down the drain, amounting to 44,000 ± 1,700 kg y-1 of lens dry mass discharged into US wastewater.
From the results it is concluded that conventional and medical microplastics represent a significant global source of pollution and a long-term threat to ecosystems around the world. Recommendations are provided on how to limit the entry of medical microplastics into the built water environment to limit damage to ecosystems worldwide.
ContributorsRolsky, Charles (Author) / Halden, Rolf (Thesis advisor) / Green, Matthew (Committee member) / Neuer, Susanne (Committee member) / Polidoro, Beth (Committee member) / Smith, Andrew (Committee member) / Arizona State University (Publisher)
Created2020