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.

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.

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.

Thesis Defense by Evan Mattiasen – June 6th, 2018

Effects Of Hypoxia on the behavior and physiology of juvenile state temperate reef fishes (genus: Sebastes)

A Thesis Defense by Evan Mattiasen

Ichthyology Lab

Wednesday, June 6th, 2018 at 4pm

MLML Seminar Room

Thesis Abstract:

The progression of climate change is predicted to cause large-scale changes to ocean chemistry (i.e., shifts in temperatures, salinity, ocean acidification, etc.) within the California Current. Forecasts from climate models and oceanographic observations indicate an increase in the frequency and duration of hypoxic events in the coastal zone, which have the potential to affect marine biodiversity and fisheries. Many studies have shown that exposure to extreme low dissolved oxygen (pO2) conditions can have deleterious effects on fish in early life stages, such as inhibition to growth and reproduction. Rockfish (Sebastes spp.) are a diverse group of species composed of fishes with varying life history characteristics. This study aims to determine how exposure of two species of young-of-the-year (YOY) juvenile rockfishes will perform under chronic exposure to varying dissolved oxygen levels. Copper rockfish (Sebastes caurinus) and Blue rockfish (Sebastes mystinus) are two closely related species that differ in early life history traits. Copper rockfish have a short pelagic duration that begins with parturition in the spring and ends with recruitment to the kelp forest canopy after 1-2 months. Blue rockfish have a longer pelagic duration that begins in the winter and ends with recruitment to the benthic kelp forest habitat after 3-6 months. I compared how behavior and physiology were affected under chronic exposure to low pO2 at four treatment levels (ambient = 9.0 mg O2 L-1, moderate = 6.0 mg O2 L-1, low = 4.0 mg O2 L-1, hypoxic = 2.0 mg O2 L-1). Behavioral tests were aimed at identifying changes in exploratory behavior (i.e., escape response trial), predator detection through olfactory perception (i.e., olfactory choice test), and changes in turning preference (i.e., behavioral lateralization). Physiological tests focused on determining changes in hypoxia tolerance (critical oxygen tension, pCrit), the capacity for aerobic activity (i.e., aerobic scope), and ventilation rates. Changes in growth rates of both species were also measured. The findings of this study indicate that both species express sensitivity to low pO2; however, the strength of the response differed between species. Copper rockfish exhibited decreased growth rates and reduced absolute lateralization following chronic exposure to the lowest oxygen levels. Behavioral tests did not differ with treatment for blue rockfish. Additionally, growth rates for Blue rockfish followed the opposite trend of Copper rockfish where individuals in the lowest oxygen treatment grew more than those in the control treatment. Both species exhibited decreases in aerobic scope and increases in ventilation rates with decreasing oxygen levels. Copper rockfish had a lower tolerance of hypoxia and weaker acclimation response compared to Blue rockfish as measured by critical oxygen tension threshold (pCrit). A lower pCrit for fish exposed to low oxygen conditions indicates the potential for acclimation to those conditions. Despite the physiological changes that occurred for both species in low oxygen conditions, these results provide evidence of acclimation to chronic hypoxia. Species with a greater capacity for acclimatization are potentially those with life history characteristics where larvae/juveniles have a higher probability of exposure to low oxygen conditions, leading to either acclimatization in the field or pre-adaptation to hypoxia over multiple generations. The differences expressed by each species suggest that acclimatization to changing ocean conditions may vary across closely related species, leading to winners and losers under future ocean conditions. Overall, increases in strength and frequency of coastal hypoxia events may have severe impacts on juvenile stage rockfishes that reside in kelp forests. While this study highlights adaptations to low oxygen, extended exposure to hypoxia decreased fitness of individuals through metabolic and aerobic depression, and changes to behavior. The information gathered in this study is critical for advancing the understanding of how these economically valuable species will fair in the future, and the information presented here will help inform policy makers to protect populations at risk.

Thesis Defense By Cody Dawson – May 7th, 2018

Phenology and the Response to Disturbance of the fucoid, Stephanocystis osmundacea

A Thesis Defense by Cody Dawson

Phycology Lab

Monday, May 7th, 2018 at 4pm

MLML Seminar Room

Cody Dawson is a Master's student in the Phycology Lab under the expert tutelage of Mike Graham. He received his BS in Biology from Humboldt State University where he was mainly working with invertebrates and predator-prey dynamics. Upon joining MLML in 2014, he discovered a love for seaweed which led him to a project surrounding their physiology that would become his life for the next 3 years. With the completion of his MS, he will be moving onto to study the trophic ecology of nearshore ecosystems in the Alaskan Beaufort Sea at the University of Texas at Austin as a part of his PhD.

Thesis Abstract:

Nearshore rocky ecosystems along exposed shorelines experience frequent disturbances due to turbulent swells and wave action. These disturbances directly affect subtidal algal communities that provide biogenic habitat along the coast. This habitat shapes faunal communities by providing refuge through structural complexity. In central California, kelps are the most notable providers of biogenic habitat, but, seasonally, a prolific fucoid, Stephanocystis osmundacea, adds a considerable amount of habitat into the environment. While diminutive and bushy during the winter, this alga produces canopy-forming reproductive fronds during the spring and summer months that add to the biogenic refuge. The purpose behind this study was to understand how the frequency and timing of disturbances affect the physiology of Stephanocystis. This was accomplished by performing manipulations on the reproductive and vegetative tissues of the alga, including: full reproductive removal (-R), haphazard vegetative blade damage (-V), no removal (C), and damage of both reproductive and vegetative structures (-All). Using measurements of changes in total length (cm) as a proxy for biomass allowed for an in situ assessment of the response by the alga. This external response measurement was coupled with stable isotope analysis of internal response using carbon and nitrogen as a bioindication of fitness. Removal of reproductive fronds during spring elicited a dormancy response, while damage to the vegetative tissue reduced growth, possibly by limiting overall photosynthetic capacity. These results suggest that spring frond growth is important to reproductive fitness and removal can stimulate a life history trade-off between reproduction and survival. Winter manipulations elicited no response due to the dormancy period of this species. Enrichment values for ∂C and ∂N were consistent with reported values for other brown algal species but, because of the timing of extraction, the internal chemistry of the individuals rebounded and the ability to detect a response was lost. Both the natural and manipulated populations had similar ∂C and ∂N when separated by tissue and time of year, which indicates that while the alga may be impacted from an external perspective, it will recover internally and stay as a viable part of the reproductive population. Understanding how these seaweeds respond to biomass loss provides a better perspective of disturbance effects on this species and the ecosystem it helps support.

Thesis Defense by Suzanne Christensen – March 19th, 2018

Chemical competition between microscopic stages of Macrocystis pyrifera and five native kelp species: does giant kelp always lose?

A Thesis Defense by Suzanne Christensen

Phycology Lab

Monday, March 19th, 2018 at 12pm

MLML Seminar Room

Suzanne Christensen came to the United States from Sweden in 2004 where she began her educational journey at Foothill College in CA. She transferred to San Jose State University where she was able to attend a few classes at MLML as an undergrad before graduating with a B.S in marine biology in 2010. A year later she joined the MLML community as a graduate student in the Phycology lab. During her time at MLML, Suzanne worked as graduate student assistant for the marine ecology class for one semester and she also worked for the MLML Front Desk for almost all of her time at the laboratories. In addition she also worked for Tenera Environmental for a few months as a research assistant in 2015 before finding out she was about to be a mom. After welcoming the new addition to her family, Suzanne worked part-time at the end of 2016 helping coordinate the Friends of Moss Landing Marine Labs program. She began fulltime employment in 2017 in Santa Cruz, CA, culturing algae and purifying algal pigments that are used to conjugate antibodies.

Thesis Abstract:

The giant kelp Macrocystis pyrifera is often considered competitively dominant to other kelp species due to its high productivity. However, on the microscopic level, previous studies found that Macrocystis can be inferior to other kelp species through microscopic interspecies chemical competition. Recruitment failure can be caused by neighboring kelps because there is no species’ specificity in the stereochemistry of the signaling chemical used during reproduction to initiate spermatozoid release; therefore, Macrocystis spermatozoid release is pre-empted by that of its competitors. To date, this interaction has been tested between Macrocystis and only one other kelp taxon, Pterygophora. To test whether Macrocystis is always chemically outcompeted microscopically, I investigated the competitive outcome, by tracking sporophyte production, between Macrocystis and five native kelps using laboratory studies. Tests with Pterygophora californica and Ecklonia arborea showed asymmetric results indicating that Macrocystis was the inferior kelp. Studies using Alaria marginata and Egregia menziesii found symmetric results where both competing species did poorly in the presence of Macrocystis. Lastly, when Macrocystis was settled with Postelsia palmaeformis, there was no significant difference in sporophyte production between polycultures and monocultures for either species. These results indicate that the competitively superior species will vary depending on the specific species interaction . Studying how Macrocystis competes with species microscopically is essential to understanding its recruitment and subsequent population structure which provides the biogenic habitat in the dynamic kelp forest.

Funding:

MLML John H. Martin Scholarship, COAST graduate award, Myers Trust grant, SJSU Graduate Equity Fellowship, H. T. Harvey Memorial Fellowship, and David and Lucille Packard Foundation.

Thesis Defense by C. Ryan Manzer – December 12th, 2017

Physical Factors Influencing Phytoplankton Abundance in Southern Monterey Bay

A Thesis Defense by C. Ryan Manzer

Physical Oceanography Lab

Tuesday, December 12th, 2017 at 4pm

MLML Seminar Room

Thesis Abstract:

As the base of almost all marine food webs, phytoplankton play a dominant role in determining the productivity of marine ecosystems. Recent studies have highlighted the dynamic variability of phytoplankton abundance in nearshore ecosystems over synoptic time scales. The inability of satellite ocean color monitoring to resolve chlorophyll values at a resolution less than 1 km and a reliable temporal resolution of ~8 days means this data cannot adequately capture the impact of nearshore dynamics on chlorophyll abundance and distribution. Therefore, a greater understanding of the physical mechanisms that contribute to this variability is required to assess impacts of current as well as future weather patterns on these ecosystems. In this study, chlorophyll fluorescence data from a nearshore location in the south Monterey Bay is used to identify the timing and duration of increases in phytoplankton concentrations.  Physical parameters, including wind stress and water temperature were analyzed to determine whether upwelling and/or upwelling relaxation events correlate with observed blooms. A significant negative correlation between water temperature and chlorophyll was found for the two summer seasons studied (2012, 2013) which suggess that increases in chlorophyll concentrations are more likely due to advection than biological reproduction. The results of this study suggest that phytoplankton are advected into the southern Monterey Bay during wind relaxation events of great enough magnitude to disrupt dominant circulation patterns. These impacts are site specific and demonstrate the degree to which the ecological subsidies can vary over small spatial ranges at synoptic scales.

Thesis Defense by Christian Denney- December 1, 2017

Characterization of a new stero-video tool to survey deep water benthic fish assemblages with comparison to a remotely operated vehicle

A Thesis Defense by Christian Denney

Fisheries and Conservation Biology Lab

December 1st, 2017

MLML Seminar Room

 

Christian Graduated from UC Davis in 2009 with a BS in Biology and an interest in population and community dynamics. As an undergraduate, he spent a quarter studying at Bodega Marine Lab where he worked with Dr. Stephen Morgan and PhD candidate Sarah Gravem studying predator-prey interactions. After graduating, he worked for a year with CA Department of Fish and Wildlife monitoring lakes and streams for invasive fish species before joining Rick Starr's Lab at Moss Landing Marine Labs in 2010. At Moss Landing, he studied competitive interactions of juvenile Blue Rockfish (Sebastes mystinus) and worked on the California Collaborative Fisheries Research Program. These experiences in population and community dynamics and fisheries research led him to focus his thesis work on designing the methodology for using a new visual survey tool for monitoring deep water fish assemblages. This research will hopefully lead to improved monitoring for populations that are currently under-studied.

Thesis Abstract:

Increasing use of ecosystem-based management strategies, which are often applied to broad geographic areas and preclude extractive activities, are creating a need for rapid, cost-effective monitoring of large areas. Visual surveys are increasingly being used to meet this need. In this thesis, I examine a new tool for surveying fish assemblages in deep-water habitat: a stereo-video lander. In Chapter 1, I evaluate methodological choices and their impact on the data collected. In Chapter 2, I compare the video lander with a Remotely Operated Vehicle (ROV). In characterizing the new stereo-video lander, I found a negligible effect of bait on the number of fish observed or on the number of species observed. The rotating camera system yielded density estimates slightly lower than those determined by a stationary camera but the rotating camera system produced less variance with the same number of surveys. In comparing the lander and the ROV, both measured similar densities for most species. Furthermore, I found that estimates of the variance in fish density were similar for the two tools given a comparable sampling effort (i.e., number of sites surveyed). Differences in community assemblage were found to be significant between the two tools. Because of the similarity in results and ability to quickly perform surveys and move on to new areas, the lander represents a new option when considering visual tools for deep-water research.

Thesis Defense by Devona Yates- December 8th, 2017

Spatial Variation of Invertebrate Survival in Central California Kelp Forests

A Thesis Defense by Devona Yates

Ichthyology Lab

December 8th, 2017

MLML Seminar Room

 

Devona graduated from the University of California Santa Cruz (UCSC) in 2008 with a B.S. in Marine Biology. Before coming to Moss Landing Marine Laboratories in 2012, Devona spent four years as a scientific diver for the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO) at University of California Santa Cruz, a long-term ecosystem research and monitoring program whichconducts research in nearshore oceanography, ecological interactions, population replenishment (recruitment), population genetics, and the diversity and structure of ecological communities in central-northern California kelp forests. As an undergraduate, Devona was an assistant research diver under the supervision of PhD candidate Jan Freiwald and Dr. Mark H. Carr (UCSC), where she used acoustic telemetry and SCUBA surveys to study the movement and homerange size of temperate reef fishes, and aided in the development of microsatellite markers for a parentage analysis on adult kelp greenling (Hexagrammos decagrammus)1. Devona’s extensive amount of time spent underwater observing kelp forest organisms and their natural habitats with PISCO (over 600 coldwater dives), combined with her interest in population and community ecology led her focus of her Masters thesis on predator- prey interactions and the cascading effects of fish predation on lower trophic level organisms. This research will use tethering experiments and underwater habitat surveys in order to quantify mortality rates of invertebrate prey as a function of MPA protection status and habitat type along the Monterey Peninsula.

 

Thesis Abstract:

Human induced shifts in predator abundances are well documented in ecosystems all over the globe, yet the extent to which predators regulate prey populations in marine ecosystems is not fully understood. Marine reserves, a type of no-take Marine Protected Area, are effective at allowing fish populations to reestablish inside their boundaries. Since individuals targeted by fishing tend to be larger and occur at higher trophic levels, the establishment of marine reserves often results in an increase in predatory fish, and the potential to impact populations of their prey via consumptive and non-consumptive effects. In 2007, several new reserves were added to two existing marine reserves (30+ years protection) in central California, creating a network of marine reserves that prohibiting fishing. Knowledge on the recovery of predatory fishes inside these reserves and their potential effects on invertebrate prey are not well understood. By conducting field surveys and empirical predation assays (i.e., tethering experiments) inside and outside of marine reserves, I provide new evidence detailing the direct and indirect effects of changes in predator abundance for kelp forest communities. Densities of invertebrate predator fishes (i.e., invertivores) were 1.5x higher and biomass was 2.8x greater inside no-take marine reserves compared to nearby areas open to fishing. The increased abundance of predators translated to a significant reduction in survivorship of two species of decapod crustaceans, the coonstripe or dock shrimp, Pandalus danae, and the cryptic kelp crab, Pugettia richii. Shrimp mortality rates were 4.6x higher, while crab mortality rates were 7x greater inside reserves. Video analyses indicated that predatory fishes were more numerous (fmax) in the video footage and arrived sooner (tinst) to tethering arrays in reserve sites. Major shrimp predators inside reserves were Hexagrammos decagrammus (31%), Embiotoca lateralis (16%), Scorpaenichthys marmoratus (10%), and small sculpins in the family Cottidae (9%). Strike rates per hour were similar across sites, except strike rates by small sculpins, which were 14x greater inside reserves than outside. The majority (71.5%) of predation events on crabs were attributed to Octopus rubescens, based on analysis of the remains of the carapace following predation events.  Results from this research demonstrate that the removal of predatory fishes via fishing has profound effects on invertebrate populations, and may be affecting other populations of organisms within the surrounding community.