Thesis Defense by Heather Barrett-May 24th

The energetic cost of human disturbance on the southern sea otter (Enhydra lutris nereis)

A Thesis Defense by Heather Barrett

Vertebrate Ecology Lab

Friday, May 24th, 2019 at 4 pm

MLML Seminar Room

Heather Barrett is a master’s student under Dr. Gitte McDonald in the Vertebrate Ecology Lab. She graduated from the University of California Santa Cruz in 2009 with a B.S. in Ecology and Evolution and studied abroad in England, France, and Belize. Prior to her research at Moss Landing Marine Labs, Heather interned with the Monterey Bay Aquarium’s Sea Otter Research Program, worked abroad in education, managed data entry and fieldwork with California Department of Fish and Wildlife’s long-term biodiversity assessment in Northern California, and assisted with whale shark research in Mexico. Heather currently is a team member with Sea Otter Savvy and hopes to continue her work with research, science communication, and outreach.

Thesis Abstract:

With increased human populations and tourism in coastal areas, there is increased potential for disturbance of marine wildlife.  Impacts of disturbance are not well understood for many coastal species, such as the southern sea otter (Enhydra lutris nereis). Due to high metabolic rates, sea otters are at particular risk of increased energetic costs due to human disturbance. To investigate effects of disturbance, behavioral scans were conducted over three years to record sea otter activity in response to potential disturbance stimuli at three locations in California: Monterey, Moss Landing, Morro Bay. We developed a hidden Markov model to examine how activity varies as a function of location, time of day, group size, pup to adult ratio, habitat (kelp vs. open water), and occurrence of and proximity to potential disturbance stimuli. We combined our results with published estimates of activity-specific metabolic rates, translating changes in activity state into corresponding energetic costs. Our results indicate that the effects of disturbance stimuli on sea otter behavior are location specific, and vary non-linearly with distance from disturbance stimuli. Our model quantifies the distance-disturbance relationship, and calculates the distance at which the likelihood of disturbance is low: averaged across locations, there is <10% potential disturbance when stimuli are >54 meters away. We also estimate energetic costs(kJ) associated with various disturbance scenarios: for example, daily energy expenditure is expected to increase by 212.53kJ ± 15.75, 154.64kJ ± 13.84 and 62.54kJ ± 5, for Monterey, Moss Landing and Morro Bay, respectively, with six small-craft approaches of 20m for a 27.7kg male otter in kelp with 10 otters and a pup ratio of 0.25. Our analyses represent a novel approach for estimating behavioral responses and energetic costs of disturbance, thereby furthering our understanding of how human activities impact sea otters and providing a sound scientific basis for management.

Thesis Defense by Jessica Jang-March 29th

Reproductive strategies of the Big Skate (Beringraja binoculata, Girard 1855)

with evidence of multiple paternity

A Thesis Defense by Jessica J. Jang

Pacific Shark Research Center

Friday, March 29th, 2019 at 12 pm

MLML Seminar Room

Jessica Jang is a master’s student under Dr. David A. Ebert of the Pacific Shark Research Center (PSRC). She graduated from the University of Washington’s School of Aquatic and Fishery Science (SAFS) in a B.S. in Aquatic Fishery and Science and minors in marine biology and quantitative sciences. After graduation, she interned for the WildFish Conservancy in their Grays Harbor juvenile salmon survey in Westport, Washington surveying potential salmon habitats in the region. After being accepted into MLML, she has been working at the Marine Pollution Studies Lab, working on various projects involving pollutants found in fish and bivalves and occasionally volunteering at the Monterey Bay Aquarium.

 

Thesis Abstract:

Beringraja binoculata is a large skate species commonly caught, raised, and exhibited in public aquaria, especially along the Pacific coast of North America. It is one of two species in the Rajidae family found in the western Pacific able to produce multiple embryos within an egg case. Although recent studies suggest this species might be the most fecund elasmobranch currently known, there are no detailed studies on whether this species’ reproductive strategy is influenced by location and environment (e.g. captive vs. wild). Specimens collected from NOAA Fisheries Resource Analysis and Monitoring Division (FRAM) trawl surveys in 2008 and in 2014-2016 showed evidence that wild egg cases and embryo sizes were larger; 3-4 embryos per egg case were the most common, while 2 was the most common in captivity. Offspring sex ratio was not significant, but more female offspring than males was found in both environments. At approximately 42º North latitude, egg case sizes and embryo numbers peaked suggesting that the region is a suitable habitat to deposit offspring due to strong upwelling conditions from the California current ecosystem. Additionally, captive B. binoculata egg cases (n=10) were raised to observe developmental stages. New morphometric data was added to Hitz (1964) describing the developmental stages of this species. Paternity tests were conducted using microsatellites markers, showing multiple paternity exists within this species and females may store sperm for a minimum of three months in captivity, suggesting that B. binoculata possesses several reproductive strategies.

Thesis Defense by Stephen Pang-April 12th

The effect of sex ratio on the reproductive biology of two sex changing fish (Lythrypnus dalli and Rhinogobiops nicholsii)

A Thesis Defense by Stephen Pang

The Ichthyology Lab

Friday, April 12th, 2019 at 12 pm

MLML Seminar Room

Stephen Pang is a master's student under Dr. Scott Hamilton in the Ichthyology Lab. He graduated from the University of Washington in 2012 with a B.S. in biological oceanography. Prior to starting at Moss Landing Marine Labs, Stephen worked in Idaho and central Washington doing salmonid research. He recently completed the Sea Grant State Fellowship (where he was placed with the Delta Stewardship Council in Sacramento) and has recently joined an environmental consulting firm where he continues his work with salmonids and conservation.

Thesis Abstract:

By targeting the largest individuals in a population, size-selective fisheries can influence the life history traits and population parameters of exploited fish stocks. For protogynous (female-to-male) hermaphrodites, this type of harvest is also sex-selective since it preferentially removes males from the population. These differences in sex-specific survival can lead to populations that are heavily female-biased. While males historically have not been considered a limiting factor when assessing the health of gonochoristic populations, modeling work suggests that reduced male abundance and skewed sex ratios could cause a concomitant decline in the reproductive output of protogynous hermaphrodite populations. This study used two nest-brooding sex-changers, Lythrypnus dalli and Rhinogobiops nicholsii, to examine the effect of operational sex ratio on reproductive and nesting success, growth, and rates of sex change. Fish were outplanted on artificial patch reefs at varying sex ratios and their reproductive output was monitored by photographing eggs laid in artificial nests. Sex ratios ranged from 1:1 to 1:19 male:female. Fish were tagged so that growth and sex change could be determined upon recollection from the artificial reefs. For both L. dalli and R. nicholsii, total egg production, female per capita production, average production per nest, and the number of nests per reef were not affected by sex ratio. By contrast, male per capita production and the percentage of nesting males significantly increased as sex ratios became more female-biased. For R. nicholsii, growth rates were highest for individuals that completed sex change during the experimental period. During the breeding season, the frequency of sex change for R. nicholsii was highest on reefs that were strongly female-biased; there was no effect of sex ratio on the frequency of sex change during the non-breeding season. In L. dalli and R. nicholsii, it appears that males do not limit the reproductive output of heavily female-biased populations—as had been predicted by previous modeling work. Instead, for species that defend demersal nests, intrasexual competition between males (i.e., territory and mate monopolization) or females (i.e. competition for nest space) may limit total production when operational sex ratios are more balanced or more female-biased, respectively. As sex ratios became skewed in favor of females, male-male competition was relaxed and individual males became more reproductively successful; the discrepancy in per capita production between males and females at skewed sex ratios indicates that some females would increase their reproductive success by undergoing sex reversal (as demonstrated by R. nicholsii during the breeding season). It is possible that many of the results on reproductive success from this study are specific to nest-brooding species; this highlights the importance of mating systems and reproductive behavior when considering the impact of fisheries on the population dynamics of exploited populations.

Thesis Defense by Alex Olson – December 3rd, 2018

The Biogeochemical Behavior and Speciation of Mercury in the Sea Surface Microlayer:

Implications for Transport to Watersheds via Fog

A Thesis Defense by Alex Olson

Chemical Oceanography Lab

Monday, December 3rd, 2018 at 10am

MLML Seminar Room

Since graduating from CSU Monterey Bay in 2010 with a B.S. in Marine and Coastal Ecology, Alex has worked as a research diver (UCSC, UCSB), fisheries observer (NOAA) and charter boat captain. As a graduate student in the Chemical Oceanography Lab under Kenneth Coale (now Max Grand), his interests center on mechanisms potentially responsible for the transfer of mono-methylmercury in the surface ocean to coastal marine fog. Specifically, he is studying the thin (100 microns) skin layer of the sea surface, building and tuning equipment to collect and eventually analyze material from this layer in the coastal zone. As a student assistant he worked with MLML's Marine Operations Facility, helping maintain the lab's fleet of small research vessels. Alex also assisted in coastal air-sea interaction studies with the Naval Postgraduate School's (NPS) Meteorology Department, first as a MLML student and currently as an employee. 

Thesis Abstract:

Neurotoxic monomethylmercury (MMHg) found in coastal Central California marine advective fog is thought to be a source of elevated MMHg levels throughout the terrestrial coastal foodweb. While not currently present at hazardous concentrations for human exposure directly (17-54 pM), MMHg in fog along the coast poses potential health and ecosystem threats via food-web bioaccumulation and biomagnification processes. The likely marine source and the mechanism of its transport remain unknown. While 2014 vertical profiles from coastal California show surface waters (<6 m) relatively deplete in MMHg (25-185 fM), similar to other ocean basin , surface grab sampling revealed elevated concentrations of MMHg in the uppermost (top ~100mm) portion of the water column known as the surface microlayer (SML). When corrected for dilution during sampling, this could represent a SML concentration of MMHg as high as 1.3 nM, orders of magnitude greater than the localized seawater and fog water; as well as the first such known measurements. Further refined sampling in 2015 of nearshore and offshore waters of California and Oregon supported 2014 findings, with underlying bulk water and SML concentrations from 16 - 380 fM and 4 – 48 fM respectively (Enrichment factors (EF) of 2.5 – 30) These are the first such measurements of MMHg in the SML to our knowledge. SML concentrations were highly variable, likely due to the variable and patchy nature of the SML and its constituents. This may also account for little variability among different surface areas of glass sampling methods. While not statistically significant, these EFs trend with certain oceanographic conditions (temperature, solar radiation, and fluorescence [Chl-a proxy]) suggesting photodegradation and or photodemethylation as major factors affecting enrichment. Although limited, bubble induced SML sea spray aerosol (SSA) production, and thus the ejection of MMHg into the atmosphere as fog nuclei, was also shown to be a potential contributing mechanism to MMHg in fog. Incubation experiments of acidified bulk seawater points to acidolysis of gaseous Dimethylmercury (DMHg) into MMHg as the major pathway of MMHg into regional marine advective fog. Continued comprehensive monitoring via California coastal fog sampling sites (FogNet) and coastal marine features and processes are needed to establish and discern changes in spatio-temporal patterns of the MMHg marine-terrestrial flux.

Thesis Defense by Laurel Lam – December 4th, 2018

Geographic and habitat-based variation in Lingcod (Ophiodon elongatus) demography and life history along the U.S. West Coast

A Thesis Defense by Laurel Lam

Ichthyology Lab

Tuesday, December 4th, 2018 at 12pm

MLML Seminar Room

Laurel is a Master's student under Dr. Scott Hamilton in the Ichthyology Lab. She graduated from UC Santa Barbara with a B.S. in Aquatic Biology and spent several years working for the CA Department of Fish and Wildlife and the Aquarium of the Bay in San Francisco before starting her master's at MLML. Laurel came into the master's program with an interest in fish population biology and working with local fishing communities, so studying Lingcod life-history along the U.S West Coast seemed like the perfect thesis project for her. Throughout her master's career, Laurel has worked closely with state and federal fisheries agencies and has volunteered on several annual research cruises conducted by the NOAA Northwest Fisheries Science Center. In addition, she assisted with conducting entrainment and impingement surveys at the Moss Landing Power Plant with Tenera Environmental and currently works with the Marine Pollution Studies Lab as part of the Bioaccumulation Oversight Group, which investigates harmful levels of organic and man-made contaminates in recreationally caught sportfish in California.

Thesis Abstract:

Fish populations are known to exhibit spatial variability in life history demography due to factors such as temperature, productivity, habitat, and fishing pressure. However, most stock assessment methods neglect to account for these differences and assume that life history traits are constant and unchanging across space and time. As a result, stocks are managed across broad geographic areas with catch quotas, size limits and other regulations applying equally in all places, running the risk of over- or under-harvesting on a regional scale. In this study, Lingcod (Ophiodon elongatus) were collected throughout their U.S. range from 7 geographically distinct areas (Alaska to Southern California) and two habitat types (high-relief versus low-relief) in collaboration with volunteer anglers, recreational party boats, and the federal West Coast Groundfish Bottom Trawl Survey. I evaluated and compared regional and habitat-based differences in Lingcod size and age structure, growth parameters, timing at 50% maturity, total mortality rates and condition indices. Size structure, growth, and maturity rates were found to exhibit a latitudinal cline, where Lingcod in northern waters grew faster and larger, matured at larger sizes than Lingcod in southern waters. There was no latitudinal trend in total mortality, however, Lingcod from Southern California and Washington had the highest total mortality rates compared to all other regions. Between habitats, Lingcod from rocky high-relief habitats grew faster and larger, matured at smaller sizes, and had higher total mortality than fish from trawlable, low-relief habitats. Condition differences were not significant between habitats and did not follow a latitudinal trend, however Lingcod in the Southern California region were in the best condition. Overall, these findings demonstrate significant latitudinal and habitat-based variability in life history and demography of the West Coast Lingcod stock. Differences in growth, maturity, and condition appear to be strongly linked to coastwide patterns seen in sea surface temperature and productivity, while differences in total mortality and demography seem to be influenced by historic and current fishing pressure.

Thesis Defense by Jen Chiu – August 17th, 2018

Diets and stable isotope signatures of Yellowtail Rockfish (Sebastes flavidus) in central California

A Thesis Defense by Jen Chiu

Fisheries & Conservation Biology Lab

Friday, August 17th, 2018 at 12pm

MLML Seminar Room

Jen Chiu is a Master’s student under Dr. Rick Starr in the Fisheries and Conservation Biology Lab.  She graduated from the University of California, Santa Barbara with a B.S. in Ecology and Evolution and a minor in Asian American Studies.  During her time at UCSB, she assisted with research focusing on the non-consumptive effects of predators on prey in the intertidal zone, coupled with the effects of climate change and habitat complexity.  Prior to beginning her graduate work at MLML, she assisted with fisheries ecology research in the Gulf of Mexico, as well as studied the distribution and biomass of benthic invertebrates in the San Francisco Bay.  In addition to her conducting her thesis work, Jen has been a part of the California Collaborative Fisheries Research Program (CCFRP) throughout her entire time at MLML.  She currently serves as the Lead Field Scientist for MLML and the Statewide Coordinator for the program, where she is responsible for managing the MPA monitoring efforts of all academic partners across the state.  She plans to continue her involvement with CCFRP after her defense.

Thesis Abstract:

Studies of fish diets can be used to improve the understanding of feeding habits, trophic distributions, and the predatory role of a species in an ecosystem.  Identifying the spatial and temporal variability in the diets of fishes can provide useful information for stock assessments and fisheries management. Yellowtail Rockfish (Sebastes flavidus) are an important part of the U.S. west-coast commercial groundfish fishery, and abundant along the central California coast.  The most recent studies of Yellowtail Rockfish diets occurred over 20 years ago and originated primarily from studies in Oregon and Washington.  To provide more current information on trophic ecology from California, I examined the food habits of Yellowtail Rockfish collected near Cordell Bank, the Farallon Islands, and Half Moon Bay in 2013 and 2014 using gut content and stable isotope analyses. Yellowtail Rockfish analyzed in this study were semi-pelagic predators, feeding primarily on tunicates, crustaceans, and teleosts.  Based on δ15N values, fish caught in 2013, on average, were feeding at lower trophic levels than those caught in 2014.  δ13C values indicated that fish caught at the northern-most sites were feeding on more pelagic-influenced carbon sources, while those caught at the southern-most sites were feeding on more benthic-influenced carbon sources.  Yellowtail Rockfish in central California can be described as opportunistic feeders because predation patterns were temporally localized, and diets consisted mostly of transitory prey sources.  The Yellowtail Rockfish diet information presented in this study fills data gaps of a key life history component, and will be useful for future stock assessments.

Watch Jen Chiu’s Thesis Defense below:

Thesis Defense by Natalie Yingling – July 20th, 2018

ATP as a Quantitative Proxy for Living Microbial Biomass: Cellular ATP Content Under Stress

A Thesis Defense by Natalie Yingling

Biological Oceanography Lab

Friday, July 20th, 2018 at 4pm

MLML Seminar Room

Natalie Yingling is a Master’s student under the guidance of Dr. Nick Welschmeyer in the Biological Oceanography lab. She started at MLML in Fall 2015 after earning her B.S. degree in Marine Science with a concentration in biological oceanography from North Carolina State University in Spring 2015. During her time at MLML she has participated in various research cruises, worked as a research assistant for Dr. Welschmeyer as part of the ballast water testing team that works in conjunction with Cal Maritime, was vice president of MLML in 2016 and has participated every year in MLML’s annual open house. In Fall 2018 she will be starting a Ph.D. program at Florida State University in the department of Earth, Ocean and Atmospheric Science. Her thesis focuses on implementing measurements of adenosine triphosphate as a proxy of microbial biomass in stressed and dying cells.

Thesis Defense by Tyler Barnes – June 21st, 2018

Assessing beach variability & shoreline change in Monterey Bay, CA

A Thesis Defense by Tyler Barnes

Geological Oceanography Lab

Thursday, June 21st, 2018 at 12pm

MLML Seminar Room

Tyler Barnes is a graduate student in the Geological Oceanography Lab at MLML. His curiosity in in coastal processes was sparked as an undergraduate at the University of San Diego where he joined a research lab investigating sedimentation in bays with coral reefs in St. John, USVI. Soon after, Tyler began his master’s degree in which his research assesses geomorphologic change on beaches in Monterey Bay using a terrestrial laser scanner (ground-based LiDAR that creates 3-D models of surveyed surfaces). Simultaneously, Tyler has worked as a researcher for Central Coast Wetlands Group where he has assisted on projects monitoring bar-built estuary hydrology/ecology throughout California and completed topographic surveys for restoration projects.

Watch Tyler Barnes’s Thesis Defense below:

Thesis Defense by Catarina Pien – June 29th, 2018

Changes in the elasmobranch assemblage in a California estuary

A Thesis Defense by Catarina Pien

Pacific Shark Research Center

Friday, June 29th, 2018 at 12pm

MLML Seminar Room

Catarina Pien is a Master's student under Dr. David Ebert in the Pacific Shark Research Lab. She received her B.A. in Biological Sciences from Wellesley College, where she spent some time abroad in the Caribbean studying mangroves and their associated species assemblages. After coming to the Moss Landing Marine Laboratories, Catarina continued to work in estuarine systems, focusing her work on the life history and ecology of shark and ray species in Elkhorn Slough. While at MLML, Catarina worked as museum curator for several years, getting to know the many interesting organisms collected and donated over the years, as well as for Tenera Environmental, and the California Department of Fish and Wildlife. She recently started as a Sea Grant State Fellow for the Delta Stewardship Council in Sacramento, where she is helping review science and adaptive management in the Sacramento-San Joaquin Delta. 

 

Thesis Abstract:

Elkhorn Slough is an estuarine system that provides habitat for several elasmobranch species. During the past century, the hydrography and habitat of Elkhorn Slough have dramatically changed. Previous studies suggest shifts in the species composition and habitat usage patterns of elasmobranchs. This study characterizes the elasmobranch species composition, and examines the environmental conditions associated with differences in distribution by sex and life stage. Elasmobranchs were sampled from 2015 –2016 by longline and gillnet. Bat rays (Myliobatis californicus), leopard sharks (Triakis semifasciata), and thornback rays (Platyrhinoidis triseriata) were most commonly observed, and were generally more abundant during the dry seasons and in the mid-slough, where environmental conditions were more similar to those in Monterey Bay. Differences in distribution by sex and life stage were associated with season, zone, and associated environmental variables including temperature and salinity. Historical analyses indicate that changes in the assemblage occurred over decadal time scales, associated with increases in mudflat habitat and large-scale climatic shifts (i.e., Pacific Decadal Oscillation), indicating that both habitat and climatic changes may continue to influence the estuarine assemblage in the future.

Watch Catarina Pien’s Thesis Defense below: