Comparative Population Assessments of Nautilus sp. in the Philippines, Australia, Fiji, and American Samoa Using Baited Remote Underwater Video Systems

The extant species of Nautilus and Allonautilus (Cephalopoda) inhabit fore-reef slope environments across a large geographic area of the tropical western Pacific and eastern Indian Oceans. While many aspects of their biology and behavior are now well-documented, uncertainties concerning their current populations and ecological role in the deeper, fore-reef slope environments remain. Given the historical to current day presence of nautilus fisheries at various locales across the Pacific and Indian Oceans, a comparative assessment of the current state of nautilus populations is critical to determine whether conservation measures are warranted. We used baited remote underwater video systems (BRUVS) to make quantitative photographic records as a means of estimating population abundance of Nautilus sp. at sites in the Philippine Islands, American Samoa, Fiji, and along an approximately 125 km transect on the fore reef slope of the Great Barrier Reef from east of Cairns to east of Lizard Island, Australia. Each site was selected based on its geography, historical abundance, and the presence (Philippines) or absence (other sites) of Nautilus fisheries The results from these observations indicate that there are significantly fewer nautiluses observable with this method in the Philippine Islands site. While there may be multiple possibilities for this difference, the most parsimonious is that the Philippine Islands population has been reduced due to fishing. When compared to historical trap records from the same site the data suggest there have been far more nautiluses at this site in the past. The BRUVS proved to be a valuable tool to measure Nautilus abundance in the deep sea (300–400 m) while reducing our overall footprint on the environment

Sustained increases in atmospheric oxygen and marine productivity in the Neoproterozoic and Palaeozoic eras

A geologically rapid Neoproterozoic oxygenation event is commonly linked to the appearance of marine animal groups in the fossil record. However, there is still debate about what evidence from the sedimentary geochemical record—if any—provides strong support for a persistent shift in surface oxygen immediately preceding the rise of animals. We present statistical learning analyses of a large dataset of geochemical data and associated geological context from the Neoproterozoic and Palaeozoic sedimentary record and then use Earth system modelling to link trends in redox-sensitive trace metal and organic carbon concentrations to the oxygenation of Earth’s oceans and atmosphere. We do not find evidence for the wholesale oxygenation of Earth’s oceans in the late Neoproterozoic era. We do, however, reconstruct a moderate long-term increase in atmospheric oxygen and marine productivity. These changes to the Earth system would have increased dissolved oxygen and food supply in shallow-water habitats during the broad interval of geologic time in which the major animal groups first radiated. This approach provides some of the most direct evidence for potential physiological drivers of the Cambrian radiation, while highlighting the importance of later Palaeozoic oxygenation in the evolution of the modern Earth system

Nutrients, Productivity, and Redox Conditions during Greenhouse Extinctions in the Panthalassic Ocean

Thesis (Ph.D.)--University of Washington, 2014This study aims to better understand the series of events leading up to and following the Permian-Triassic mass extinction as it took place in the Panthalassic Ocean basin, with a particular focus on the oceanographic factors controlling nutrient cycles, redox conditions, and the ecology of the planktonic community. The first two chapters focus on the Opal Creek section, in Alberta, Canada, which records deposition in a slope setting at subtropical latitudes on the northwestern margin of Pangaea. The first chapter of this study uses organic carbon and nitrogen isotopes, as well as the abundant but homogenous conodont community, to infer the presence of a nutrient rich coastal upwelling system along the continental margin, with highly enriched nitrogen isotopes interpreted as reflecting denitrification in a well-developed water column oxygen minimum zone. Subsequent analysis using trace element proxies for redox and productivity, as well as declining nitrogen isotope values, suggest a substantial weakening of coastal upwelling in the earliest Triassic coinciding with the extinction of the benthic sponge fauna and an increase in the sedimentation rate. Marine primary productivity is among the most important variables influencing water column redox conditions and benthic community structure, however it is extremely difficult to estimate from ancient marine rocks. The final chapter of this study aims to develop quantitative tools for estimating paleoproductivity, based on parameters that can be measured or calculated for most marine sedimentary systems. This study uses a compilation of 93 Cenozoic (primarily Quaternary) marine cores for which the sedimentary bulk accumulation rate could be calculated. Accumulation rates of organic carbon, phosphorus and biogenic barium are compared to estimates of primary and export productivity in the modern ocean derived from carbon-14 uptake and satellite measurements of chlorophyll. The resulting equations relating proxy accumulation to productivity can be applied to a wide variety of ancient marine systems, allowing for more quantitative reconstructions of paleoproductvity and comparison to other geochemical proxies for nutrient availability or environmental stress

Thallium isotopic measurements of Gujo-Hachiman and Ubara, Japan and Opal Creek, Canada and thallium isotopic model results across the Permian-Triassic transition

A compilation of the thallium isotopic data (along with previously published geochemical information) from organic-rich shales across the end-Permian mass extinction event, covering the latest Permian and earliest Triassic. Samples are from the Ubara and Gujo-Hachiman outcrops in Japan and Opal Creek outcrop in Alberta, Canada. The thallium isotopic analysis was done to constrain changes in global deoxygenation across the extinction event and link marine anoxia to the extinction. Analyses were done following thallium column chemistry and subsequent measurement on a Neptune inductively coupled plasma mass spectrometer. Modeling of the thallium isotopes was done using a forward geochemical box model in the Stella modeling program. This was used to determine the changes in extent of oxic seafloor necessary to induce the resultant compiled thallium isotope record from the aforementioned sections