Thesis Defense by Holly Doerr – July 21 Livestream

 

"Species-specific transcriptomic responses of juvenile rockfish (Sebastes) to simulated future upwelling conditions"
A Thesis Defense by Holly Doerr

The Ichthyology Lab

MLML Live-Stream | July 21, 2021 at 2 pm

Holly graduated from the University of Missouri – Columbia (MU; MIZZOU) in 2016 with a B.S. in Biological Sciences. During her time at MU, she worked under the guidance of Dr. Elizabeth Bryda in her Comparative Medicine lab at the MU College of Veterinary Medicine and investigated the effects of exposure to a common brain parasite (Pseudoloma neurophilia) on the behavior of larval zebrafish for her undergraduate capstone projects, and also assisted then PhD student Daniel Davis with his research investigating the ability for a common probiotic (Lactobacillus plantarum) to mitigate stress-induced dysbiosis in the gut microbiome of adult zebrafish. Holly began the Moss Landing Marine Laboratories (MLML) Masters program in the fall of 2016, initially joining the Biological Oceanography Lab and later switching to join the Ichthyology Lab at MLML and the Logan Lab at CSUMB in April of 2018 after realizing her interests were better suited studying marine fish physiology. During her time at MLML, she thoroughly enjoyed countless friendships and the ability to help on at least 10 other lab and thesis projects both at the bench and in the field. Likewise, during this time Holly also served three semesters as student body vice president, volunteered at 4 Open House events on the food committee, in the puppet show and in both the Bio Oce and Ichthyology labs, and was employed in a variety of roles - including one year as Student IT Help Desk Assistant, a little over a year as a research technician on a Ballast Testing project, two semesters as a TA, and two years as a Naturalist/Deckhand for Sea Goddess Whale Watching in Moss Landing, CA. In January of 2021 she moved to North Carolina with her husband where she finished up her thesis writing and is currently employed part-time as a research technician on UNC - Chapel Hill's shark surveys. After graduation, Holly looks forward to spending more time pursuing hobbies of swimming, hiking, camping, painting and reading, and exploring North Carolina with her husband and two dogs!

Thesis Abstract:

Anthropogenic climate change is predicted to trigger large-scale changes in ocean chemistry over the next few decades. These conditions may be exacerbated in coastal upwelling regions where strong, seasonal increases in pCO2 and hypoxia are expected to intensify under climate change. Nearshore rockfishes (genus Sebastes) may already be adapted to fluctuating upwelling environments along the west coast of North America, but further shifts in ocean chemistry could push individuals beyond their physiological thresholds. I examined the effects of future upwelling conditions by simulating fluctuating vs. static levels of combined high pCO2 and low dissolved oxygen (DO) on the gill transcriptomes of three juvenile rockfish congeners with different life histories: copper rockfish (Sebastes caurinus), gopher rockfish (S. carnatus) and black rockfish (S. melanops). Juveniles were collected and exposed to static-ambient (DO= 8mg/L; pH=8.0), static-moderate (DO=4.0mg/L; pH=7.5), static-extreme (DO=2.0mg/L; pH=7.3), or two fluctuating treatments that alternated between ambient and extreme conditions every 8 days, simulating upwelling and relaxation cycles. Gill tissue was sampled from fish following 13 weeks of exposure to each treatment. De novo transcriptome assemblies were constructed for each species, and compared for quality, completeness, and mapping rates across all samples.  The copper rockfish reference assembly was selected to map and compare differential gene expression for common orthologs across all species. I found significant changes in gene expression (edgeR, FDR<0.01) under all pair-wise comparisons of static vs. fluctuating treatments, with fluctuating treatment responses containing larger overall numbers of differentially expressed genes. Likewise, significant changes in gene expression of fishes from fluctuating-relaxation conditions vs. static-ambient may reflect persistent evidence of stress response after “recovering” from upwelling, or acclimatory preparation for subsequent upwelling exposure. Highly species-specific transcriptional responses appear to be related to life history differences and suggest the possibility of greater tolerance to future ocean chemistry in black rockfish, which was not reflected in the other species. Likewise, correlations of physiological data from the same copper and gopher rockfish to their respective expression responses suggest that these congeners rely on different molecular mechanisms to cope with environmental stressors. Comparing transcriptomic responses of rockfish exposed to static vs. fluctuating future upwelling conditions provides insights into the ways in which climate change will impact an ecologically and economically important group of marine fishes in North America.

Thesis Defense by Melissa Naugle – July 23 Livestream

 

"Effects of Land-Based Sources of Pollution on Coral Thermotolerance"
A Thesis Defense by Melissa Naugle

The Invertebrate Ecology Lab

MLML Live-Stream | July 23, 2021 at 10 am

Melissa Naugle graduated from University of Maryland, College Park in 2016 with a B.S. in Environmental Science and Policy. During her time at UMD, she had the opportunity to participate in a coral monitoring internship in Thailand where she learned to SCUBA dive. After that experience, Melissa knew she wanted to pursue marine science research. After graduating, she began a research position at Georgetown University, where she studied how disturbance affects the community ecology and population genetics of salt marsh arthropods. Melissa began her Master’s at California State University, Monterey Bay and Moss Landing Marine Labs in 2018 in the Logan Lab and the Invertebrate Ecology Lab. She studies coral responses to stress and is interested in using genomics to learn more about coral conservation. During her time at MLML, Melissa has taken part in multiple outreach activities including a mentorship program she led called Future Leaders in Marine Science, which aims to teach marine science to high schoolers at North Monterey County High School. She served on MLML student body as CSUMB representative. She also served as a MLML liaison, and later as co-chair of the Monterey Area Research Institution’s Network for Education (MARINE). Melissa has also worked at the Monterey County Public Health Laboratory, processing PCR tests for COVID-19 and later sequencing SARS-CoV-2 viral RNA to monitor variants across Monterey County. After graduating from MLML, Melissa will begin a PhD with the Reef Restoration and Adaptation Program and Southern Cross University to study genetic markers of coral bleaching on the Great Barrier Reef.

Thesis Abstract:

Phenotypic plasticity is one way that species may cope with stressful environmental changes associated with climate change. Reef building corals present a good model for studying phenotypic plasticity because they have experienced rapid climate-driven declines in the past twenty years, often with differential survival among individuals during heat stress. One potential reason for underlying differences in thermotolerance may be due to differences in baseline stress levels. Stress associated with pollution has been shown to produce synergistic effects with heat stress, exacerbating the physiological damage of heat stress. Conversely, it is possible that mild pollution stress could prepare corals to better cope with heat stress via cross tolerance mechanisms. Cross tolerance occurs when a mild stressor prepares an organism for more extreme, subsequent stress, reducing the impact of that stressor on the organism. To examine these two possibilities, acute heat stress experiments were conducted on Acropora hyacinthus from five sites around Tutuila, American Samoa with differing pollution impact. Bleaching responses were measured visually, using photographic assessment to estimate chlorophyll content, and using pulse amplitude fluorometry to measure photosynthetic efficiency. Endosymbiont community composition was assessed at each site using quantitative PCR. RNA sequencing was used to compare differences in genes expression patterns prior to and during heat stress. Symbiont communities differed among sites, with heat tolerant Durusdinium dominating in areas with higher pollution impact and heat sensitive Cladocopium more common in pristine areas. Pollution stress may induce a shift towards Durusdinium thereby enhancing resistance to subsequent heat stress in the near term. Gene expression patterns showed few differences correlating to site or pollution level. Thermotolerance, however, did affect gene expression patterns, both during heat stress and in control conditions. In this thesis, I present potential mechanisms underlying coral thermal tolerance in pollution-impacted areas. My results highlight the importance of measuring pollution impacts on thermotolerance and identifying heat tolerant corals in “non-pristine” areas and their potential to seed nearby reefs following bleaching events.

Melissa Naugle Presents: “Effects of Land-Based Sources of Pollution on Coral Thermotolerance”