Thesis Defenses

Thesis Defense by Victoria Dickey – November 30th

Jackson Hoeke

 

"The Distribution of Microplastics in Marshlands Surrounded by Agriculture Fields: Elkhorn Slough (CA)"
A Thesis Defense by Victoria Dickey

Geological Oceanography Lab

Zoom | Live-Stream | November 30th, 2022 at 4:00 pm PDT

Bio

Victoria joined Moss Landing Marine Labs in 2018 after earning a BS in Oceanography at Hawaii Pacific University. She is in the Geological Oceanography lab under Ivano Aiello’s advisement and has enjoyed building skills in GIS, grain size analysis, and operating the Scanning Electron Microscope. Victoria came up with the idea to sample sediment to find microplastics after driving past the fields of plastic mulch on her way to school every day. She is a strong advocate for ocean conservation and has played a role in the local chapter of the Surfrider Foundation as well as on the advisory council for the Monterey Bay National Marine Sanctuary. Victoria believes strongly in the necessity of communicating science and conservation to people of all ages and demographics and hopes to continue to build that skill in her future careers.

Thesis Abstract

The wide-spread use and subsequent recycling of plastics in the agriculture industry promotes improper disposal and poses a threat to important wetland habitats. When plastics degrade, they break up into smaller pieces that pose serious threats to organisms that ingest them and to habitats they settle in. This study quantifies the estimated concentration, types, and lengths of microplastics (< 5mm plastic particles) in the marsh environments of Elkhorn Slough, California’s second largest estuary. Replicate samples of marsh soil samples were extracted from seven Elkhorn Slough marshes at varying distances from the head and the mouth of the estuary and potential sources of agricultural plastic. Using a safe and cost-effective density separation technique, microplastics were separated from the soil, identified, and counted on micro-filters using a dissecting microscope, then further analyzed with a Scanning Electron Microscope equipped with an Energy-Dispersive Spectrometer (SEM/EDS) to analyze surface microstructures and the elemental compositions of the particles. Two main microplastic morphotypes, fragments and fibers were observed. The average concentration of microplastics estimated by this study is ~1600 particles per kg of wet soil, which is comparable to the average concentration of microplastics found in the sediment of the Venice Lagoon. Fragments are statistically smaller but more abundant (making up 85% of microplastics found) than fibers and with an average length of ~85 µm and ~500 µm respectively. Fragment lengths at agriculture sites are larger than the rest of the sampling sites, indicating a shorter residence time in these locations and highlighting agriculture plastics as a potential source. All microplastics found in collected samples exhibit signs of weathering, like pitting and fractures on the surface.  This study explores the particle size distributions of microplastics and the sediment they were sampled from to highlight the similarities in the physical influences controlling their distributions. Importantly, the federally protected Monterey Bay National Marine Sanctuary exchanges an extensive tidal range with Elkhorn Slough. This study identifies potential sources of microplastics to the Monterey Bay National Marine Sanctuary and the surrounding shores with an emphasis on the agriculture industry.

Thesis Defense by Hannah Bruzzio – August 30th (Zoom)

Taylor Azizeh

 

"Effects of Ocean Acidification and Hypoxia on Stress and Growth Hormone Responses in Juvenile Blue Rockfish (Sebastes mystinus)"
A Thesis Defense by Hannah Bruzzio

Ichthyology Lab

Zoom | Live-Stream | August 30th, 2022 at 2:00 pm PDT

Bio

Hannah Bruzzio is a graduate student in the Ichthyology Lab at Moss Landing Marine Labs. In the spring of 2018, she got her BS from the College of William & Mary in Williamsburg, VA. While there she completed her honor’s thesis researching particle interactions with the gill arch/gill raker morphology of the American shad to investigate the fluid dynamics of filter-feeding fish. She joined MLML in the fall of 2018. 
For her master’s thesis, Hannah looked at how the environmental stressors of ocean acidification and hypoxia affects the hormonal stress response of juvenile blue rockfish. In addition to her research, Hannah worked as the MLML Environmental, Health and Safety assistant under Jocelyn Douglas. She also designed the open house t-shirts for 2019, 2020 and 2022. She also volunteered at the Monterey Bay Aquarium where she worked with the jellyfish and schooling fish husbandry staff. In April of 2022, Hannah returned to the east coast to accept a job at the Institute of Marine and Environmental Technology (IMET) as the Senior Biological Technician for their Aquaculture Research Center (ARC) in Baltimore, MD. There she maintains populations of Atlantic salmon, Tilapia, Rainbow trout, Nurse Shark, Blue gill, Hybrid striped bass, Blue crab, White-leg shrimp and Zebrafish for use in a wide range of RAS-aquaculture based research projects.

Thesis Abstract

Global climate change is causing increasing ocean acidification (OA) and deoxygenation (hypoxia) of coastal oceans. Along the coast of California, where upwelling is a dominant seasonal physical process, these environmental stressors often co-occur and are intensified in nearshore ecosystems. For juvenile nearshore fishes, who spend a crucial developmental life stage in coastal kelp forests during the upwelling season, these stressors are experienced concurrently and may have large implications for fitness. Environmental stress can set off an endocrine response, which impacts physiology, energy allocation, growth, and behavior. To test the effects of climate change on juvenile blue rockfish, I measured the endocrine response to single and combined stressors of OA and hypoxia after one week of exposure. Assays of cortisol and IGF-1 hormone responses, served as proxies for stress and growth, respectively. Full organismal effects of environmental stressors were evaluated using a scototaxis (i.e., light/dark anxiety) behavior test, and measures of physiological changes in maximum metabolic rate (MMR) and body condition (i.e., Fulton’s K condition index). I found that peak (~1 hour) cortisol levels were highest in the single stressor low pH (7.3 pH), followed by the combined stressor (7.3 pH and 2.0 mg/L O2) and then the single stressor hypoxic treatment (2.0 mg/l O2). This high peak cortisol associated with low pH may indicate the role of cortisol in acid-base regulation. Only the low DO (dissolved oxygen) group did not exhibit a recovery of cortisol levels by the end of one week. There was no observable difference in IGF-1 in juvenile blue rockfish after a week of exposure to any of the pH or DO stressors. When cortisol levels were high, the same fish had low levels of IGF-1, and when cortisol levels were lower, the same fish had highly variable levels of IGF-1. At one-week of exposure, cortisol exhibited a positive relationship with MMR, such that higher stress levels were associated with greater oxygen consumption by the fish. MMR values themselves were highest in the low DO fish, which subsequently also had slightly higher cortisol levels at one-week. Juvenile blue rockfish were largely robust to any behavioral changes associated with stress across treatments. Hypoxic treatment fish had significantly lower body condition than fish from treatments with ambient DO levels after one week. Overall, the results indicated that pH levels influenced hormonal stress physiology, while DO levels contributed to observed differences in metabolism, body condition, and behavioral anxiety in juvenile blue rockfish. I was unable to tease apart and classify whether OA and hypoxia work in an additive, antagonistic, or synergistic way. Continued research should include more experimental stressor treatment levels of varying intensity of both individual and combined treatments as well as upwelling/relaxation fluctuating treatment levels. Elucidating the effects of climate change on fish endocrine response and physiology is important for fish population management and can help inform stock assessment models of blue rockfish in a rapidly changing ocean.

 

Hannah Bruzzio Presents: Effects of Ocean Acidification and Hypoxia on Stress and Growth Hormone Responses in Juvenile Blue Rockfish (Sebastes mystinus)

Thesis defense by Caroline Rodriguez – August 22nd (Zoom)

Taylor Azizeh

 

"Measuring the Impact of Thermal Stress on Coral Reef Resilience in Hawaii Using Large-Area Imagery"
A Thesis Defense by Caroline Rodriguez

Marine Environmental Physiology Lab | Invertebrate Ecology Lab

Zoom | Live-Stream | August 22nd, 2022 at 3:00 pm PDT

Bio

Caroline Rodriguez graduated from Duke University with a B.S. in Environmental Sciences in 2013 and completed internships at the North Carolina Coastal Federation and the Maryland Sea Grant Research Experience for Undergraduates (REU) program. After graduating, Caroline was chosen for the Chesapeake Conservation Corps program and spent two years working as a water quality technician and outreach coordinator for the Arundel Rivers Federation in Edgewater, Maryland. Caroline then spent two and a half years serving as a Peace Corps Volunteer in Nicaragua where she co-taught natural science courses in rural elementary schools and co-led environmental projects including school gardening and environmental summer camps. 

After the Peace Corps, Caroline began her M.S. in Marine Science in the Marine Environmental Physiology Lab at California State University Monterey Bay and the Invertebrate Ecology Lab at Moss Landing Marine Labs. Caroline was awarded the NOAA Center for Coastal Marine Ecosystems (CCME) Graduate Fellowship, which funded her thesis research. During her time in the CCME Fellowship program, Caroline completed a NOAA Experiential Research and Training Opportunity (NERTO) at NOAA Pacific Islands Fisheries Science Center in Honolulu, Hawaii where she developed a workflow to generate accurate growth, survival, and recruitment estimates for thousands of coral colonies using large-area imagery. She built on this work for her master’s thesis and investigated coral population dynamics for the dominant coral species across the Hawaiian archipelago and assessed the impact of thermal stress on coral populations. In addition to her research work, Caroline worked at the MLML Front Desk throughout her time at MLML, helped lead the Future Leaders in Marine Science mentorship program at the North Monterey County High School, and served as the CSUMB representative on the MLML Student Body. In 2022, Caroline was selected for the John A. Knauss Marine Policy Fellowship Program and moved to Washington, D.C. to work with NOAA’s Office of International Affairs. She hopes to continue working with diverse communities at the intersection of science and policy to advance equitable ocean and coastal policy.

Thesis Abstract

Coral reefs worldwide are declining due to several anthropogenic stressors, but rising ocean temperature is the most serious threat to coral reef persistence. Developing models that document changes in coral communities following thermal stress events and project trends in reef recovery is crucial in identifying resilient reefs. Traditional approaches to generating the coral vital rates necessary for demographic modeling are time consuming and field intensive; however, by leveraging Structure from Motion photogrammetry, we can accurately track populations over time at a large spatial scale. In this study, we assessed the population dynamics of the dominant coral species across the Hawaiian archipelago and investigated the impact of thermal stress on coral populations. The annual growth, survival and recruitment of 3,852 coral colonies (5,636 unique colony-level transitions) for 3 genera was recorded at 16 sites spanning the Hawaiian archipelago across 14 intervals from 2013 to 2019, including 3 bleaching events. These data were used to parameterize integral projection models to determine the impact of thermal stress on population growth. Degree Heating Week output from the NOAA Coral Reef Watch daily global 5km satellite was used to estimate thermal conditions at each site by calculating temperature stress severity (the mean of all maximum thermal anomalies) and frequency (number of thermal stress events per 10 years). We found that all three coral genera, which have different morphologies and life-history strategies, had negative population growth rates. As expected, smaller colonies experienced faster growth, but large colonies had a high probability of shrinking, due to partial mortality. Therefore, it may be biologically advantageous for larger colonies to fragment into smaller pieces and avoid total mortality. Population dynamics were primarily driven by coral growth and survival and should be targeted in future restoration and adaptation projects. Additionally, across all taxa, population growth rates (λ) varied spatiotemporally, but most sites exhibited a declining population growth rate (λ < 1). While increased severity and frequency of thermal stress events negatively impacted the population growth rate of massive Porites corals, there was no signal of this effect on encrusting Montipora corals. We demonstrate that despite variations in the responses observed among taxa, there is an overall expected population decline across the Hawaiian archipelago. While coral population growth rates are higher following bleaching events, signifying recovery, the projected increase in both the severity and frequency of thermal anomalies may overwhelm corals’ ability to recover and threaten coral population persistence.

Caroline Rodriguez Presents: “Measuring the Impact of Thermal Stress on Coral Resilience in Hawaii Using Large-Area Imagery”

Thesis Defense by Katie Neylan – August 12th (Seminar Room/Zoom)

Taylor Azizeh

 

"Evaluating a microalga (Schizochytrium sp.) as an alternative lipid source in fish-free feeds for sablefish (Anoplopoma fimbria) aquaculture"
A Thesis Defense by Katie Neylan

Ichthyology Lab

Zoom | Live-Stream | August 12th, 2022 at 1:00 pm PDT

Bio

Katie graduated from CSU Monterey Bay in 2016 with a B.S. in Marine Science. While there, Katie worked for a few MLML Ichthyology lab graduate students. Her undergrad research included two main projects: "Investigating the condition of surgeonfish along a nutrient gradient in the southern line islands" and "Examining the effects of size-selective mortality on sex change in a protogenous hermaphrodite species of goby, rhinogobiops nicholsii". Following her graduation, Katie worked for California Department of Fish and Wildlife (CDFW) as a Scientific Aid and collected data for the California Recreational Fisheries Survey in Santa Cruz, CA. 

Katie joined the Ichthyology lab at MLML in Fall 2018 and is co-advised by Dr. Scott Hamilton and Dr. Luke Gardner. Katie was awarded the California Sea Grant Graduate Research Fellowship in 2019, which funded her thesis research. For her thesis, Katie designed a feed experiment to test a microalga as an alternative lipid source in fish-free feeds for sablefish (Anoplopoma fimbria) aquaculture. She presented the results of her thesis research at the 2022 Aquaculture America conference. Katie is looking forward to pursuing a career in resource management and policy after completing her degree at MLML.

Thesis Abstract

Alternative feeds for finfish aquaculture are critical for the sustainable expansion of the aquaculture industry. Fish that are farmed for human consumption are often carnivorous; therefore, the industry uses wild-caught forage fish as a primary ingredient in farmed fish feeds in the form of fish meal (FM) and fish oil (FO). With the aquaculture industry expanding, alternative ingredients are needed to safeguard fisheries' sustainability and future aquaculture development. While some alternative feed ingredients have been identified, it is necessary to improve the existing options and identify alternative ingredients with higher concentrations of omega-3 polyunsaturated fatty acids (PUFAs). This study was designed with six feed treatments to test a microalga, Schizochytrium sp., as an alternative feed ingredient for sablefish (Anoplopoma fimbria). The two fish ingredient control diets are called +FM+FO (contains both FM and FO) and -FM+FO (contains FO). The fish-free diets completely replace FO with flax oil (FF Flax) or a combination of flax oil and low, moderate, or high inclusion of Schizochytrium sp. (FF LowSc, FF ModSc, and FF HighSc) in the feeds. After a five-month feeding trial, sablefish condition metrics, whole-body proximate composition, and apparent digestibility coefficients were not different across diet treatments. In contrast, sablefish growth was influenced by treatment, with the high microalga-inclusion diet (FF HighSc) performing as well as the fish-ingredient controls. Fillet fatty acid profiles were also influenced by diet treatment, generally reflecting the fatty acid profiles of the feed. Total PUFAs were higher in the fish-free diets than in the controls. These results suggest Schizochytrium sp. can increase PUFA concentrations in fish fillets, while not compromising fish health and growth, making it a viable ingredient for alternative sablefish feeds.

 

Thesis Defense by Alora Yarbrough – July 22nd (Livestream)

Keenan Guillas

 

"The impacts of climate change on blackeye goby (Rhinogobiops nicholsii) stress responses, reproduction, and offspring fitness"
A Thesis Defense by Alora Yarbrough

Ichthyology Lab

Zoom | Live-Stream | July 22nd, 2022 at 4:00 pm PST

Bio

Alora Yarbrough is a graduate student in the Ichthyology Lab at Moss Landing Marine Labs (MLML). She received her BA in Biology from Pepperdine University in 2017. While there, she completed an undergraduate honor's thesis researching the effects of variable incubation conditions on the development of the California grunion which she presented at the Western Society of Naturalists Annual Meeting, the Joint Meeting of Ichthyologists and Herpetologists, and the Society for Integrative and Comparative Biology's Annual Meeting. After graduating, she completed internships with Heal the Bay at the Santa Monica Pier Aquarium and with Disney World's Animal, Science, and Environment Program in Florida. She then accepted a position in Dr. Scott Hamilton's lab at MLML in the fall of 2018.

For her Master's thesis, Alora examined how climate change affects the stress response, reproduction, and offspring fitness of blackeye gobies, a demersal reef fish common off the west coast of the United States and Mexico. In addition to her master's work, Alora joined the MLML IT department as a Help Desk Technician in 2019 through which she implemented projects such as the Student Life Website and headed the first media committee for the annual Open House fundraiser. In April 2022, Alora returned to southern California to join the Yelon Lab at the University of California, San Diego (UCSD) as a staff research associate supporting research investigating cardiac development in zebrafish.

 

Thesis Abstract

Climate change poses a major threat to marine ecosystems and the organisms living within them. Along with warming and sea level rise, the increasing intensity of ocean acidification and hypoxia events in coastal environments is of large concern. Weakened immune function, tissue damage, and altered reproductive output are only some of the detrimental effects of decreased pH in ocean waters. Hypoxia has also shown major consequences including decreased aerobic scope, altering predator-prey interactions, and inducing hyperventilation. Additionally, animals living in eastern boundary currents, such as off the coast of California, experience a regional phenomenon known as upwelling. As surface waters are directed offshore due to wind patterns, deep, acidic, hypoxic water is brought up to the surface magnifying the effects of ocean acidification and hypoxia for up to two weeks at a time. Both low pH and low amounts of dissolved oxygen (DO) characterize stressful conditions for many marine species. Under stress, one of the main hormones organisms will produce to maintain homeostasis is cortisol, therefore cortisol can act as a marker to determine the relative stress an animal is under. This study evaluated the stress response of adult female blackeye gobies when under both acute and chronic climate change stress by measuring muscular cortisol concentrations at specific time points while under one of four treatments: control (8.1 pH; ~9 mg/L O2), low DO (8.1 pH; 2.0 mg/L O2), low pH (7.3 pH; ~9 mg/L O2), and a combination of low DO and low pH (7.3 pH; 2.0 mg/L O2). In addition, the stress response differs for organisms at varying life stages. Notably, some larval fish species rely entirely on maternally derived hormones supplied by the yolk sac. An increase in cortisol in the yolk supply may impose developmental disadvantages on the larvae, but there is also evidence that it can better equip offspring to face the stressors experienced by their mothers. Therefore, the relationship between maternal and egg cortisol concentrations was investigated with females laying clutches under each of the four treatments. After laying, clutches were split to be incubated under the same conditions their mothers experienced or the control treatment. At 1 day post hatch, offspring physiological fitness was evaluated based on morphometric characteristics and standard metabolic rate. This study found adult female blackeye gobies experiencing acute stress tend to have higher cortisol concentrations than those under chronic stress. When evaluating how stress is translated generationally, a positive relationship between maternal and egg cortisol concentrations was found. However, blackeye gobies were not able to successfully fertilize eggs under the low pH treatment. In addition, clutches with higher initial cortisol concentrations showed trends of increased time to hatching and standard metabolic rate and decreased length and weight at 1 day post hatch. The results of this study suggest decreased pH and dissolved oxygen are harmful to both adult and larval blackeye gobies. Due to the disruption of successful reproduction under low pH and the developmental and physiological disadvantages under low DO, future populations of blackeye gobies could suffer greatly as anthropogenic climate change progresses.

 

Alora Yarbrough Presents: “The impacts of climate change on blackeye goby (Rhinogobiops nicholsii…