Sunday, April 9, 2017

MEB Seminar Series | Grad Student Presentations | 4/11, 12 PM, AHF Torrey Webb Room

Jayme Smith, PhD Candidate
PI: Dr. David Caron
Title: "Dissolved Algal Toxins in Southern California Waters"
Abstract: Harmful algal blooms (HABs) have been increasing globally, particularly along the North American west coast, threatening marine wildlife, human health, and commercial fisheries. HAB species of particular concern in southern California waters include those of the dinoflagellate genus Alexandrium (saxitoxin producer) and Dinophysis (okadaic acid producer), and diatom genus Pseudo-nitzchia (domoic acid producer). Toxic strains of these species produce toxins that cause illness and sometimes death in humans and marine wildlife. We utilized a new technique called Solid Phase Adsorption Toxin Tracking (SPATT) to monitor dissolved algal toxins at several locations along the southern California coast. SPATT has the advantage of integrating dissolved algal toxins present in the water throughout the deployment period, providing information about events that may occur between discrete sampling periods. We utilized SPATT for short studies at Catalina Island and on temporary offshore moorings, as well as a long-term study at our Newport Beach Pier HAB monitoring station. SPATT samples were analyzed for saxitoxin, and domoic acid and a subset of samples were tested for okadaic acid. Our data revealed the regular occurrence of at least one algal toxin at all study sites. Algal toxins were present in at least 64% of samples from our long-term site. Perhaps more concerning, we found that multiple toxins often co-occurred, presenting an increased risk to human and wildlife health.
Xiaoshen Yin, PhD Candidate
PI: Dr. Dennis Hedgecock
Title: "Mapping genes determining Type-III survivorship in the Pacific oyster Crassostrea gigas"
Abstract: The Pacific oyster Crassostrea gigas has a high mortality during its early life stages (type III survivorship). Previous mapping of genetic factors affecting viability (quantitative trait loci, vQTL) has revealed ~7-13 vQTL in each family of Pacific oysters. Estimated genetic inviability caused by vQTL ranges from 96% to 99%, which accounts for the high early mortality in the Pacific oyster. However, these previous studies used low-density linkage maps, which make it hard to pinpoint genomic regions containing vQTL accurately. To resolve this issue, I constructed high-density linkage maps with single nucleotide polymorphism markers (SNPs), generated from Illumina sequencing (genotyping-by-sequencing, GBS). The linkage map has an average interval between markers of 0.65 cM, about 12 times denser than previous linkage maps. Using these high-density linkage maps, I discovered 9-14 vQTL in six F2 families and estimated cumulative genetic mortality to be 96%-99%, which is consistent with previous studies. High-density linkage maps, on the other hand, more narrowly localize vQTL peaks caused by recessive viability mutations than did low-density maps, improving the accuracy of vQTL mapping. Finally, high-density linkage maps are effective in teasing apart multiple deleterious mutations and their genetic effects under broad vQTL peaks.

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