Thesis Defenses

Thesis Abstract:

Habitat use can affect ecological and biological processes, such as resource use, survival, and reproduction. For many species, habitat use can vary with season as their energetic needs change, for example increasing foraging area in the energetically costly reproductive season. In this study, we sought to understand the seasonal and temporal scales of spiny lobster (Panulirus interruptus) habitat use in a southern California ecosystem by integrating habitat surveys using GIS (Global information system), lobster demographic surveys, and diet analysis using stable isotopes. We focused on the California spiny lobster (Panulirus interruptus) because the species uses a variety of habitats at different seasonal and spatial scale and is economically and ecologically important. Results indicated that Bird Rock had a higher density of lobsters than Big Fisherman Cove and intertidal habitat recorded higher density of individuals than subtidal habitat at both sites during nocturnal high tides. At Bird Rock, the proportion of females to males, and the reproductive condition of the females is greater than that at Big Fisherman Cove. I detected a distinct seasonal change in the diet of spiny lobsters, such that a higher diversity of prey resources were consumed in the summer than in the winter during nighttime high tide movement from the subtidal to the intertidal, specifically lobsters at Bird Rock foraged on the mussel beds that are present at the site. Seasonal foraging in the intertidal habitat acts as a diet subsidy for the spiny lobsters during the reproductive season, a time of high energetic cost. The differences in the reproductive condition of the population are likely due to the presence of the mussel bed at Bird Rock, which is a valuable prey resource for many species of lobster. Understanding fine scale spatial and seasonal habitat needs of target species can help create better protected areas, not only for the spiny lobster, but other critically important species.

Ann is a masters student in the Phycology and has been working under the co-advisement of Dr. Mike Graham and Dr. Diana Steller. She grew up in the forests and on the water of the Great Lakes in northern Michigan, but the lakes weren’t quite enough to satisfy her curiosity. While studying Natural Resource Management and Conservation at Colorado State University she explored policy and research in rangelands, forestry, and anthropology. This led to opportunities to study in Australia focusing on tropical ecology and how to take terrestrial research techniques and apply them to managing natural resources above and below the water. After achieving her Bachelor of Science, she crisscrossed the country working for the National Park Service as a sea turtle technician and for the Catalina Environmental Leadership Program teaching students and sharing her love of nature, ecology, and- especially- seaweed and plants. During her time on Catalina, Ann watched kelp forests on the island disappear in a matter of months and be replaced with a thicket of invasive sargassum. A desire to understand what happened to Catalina’s kelp forests drove her to pursue a masters and became the topic of her thesis. At Moss Landing Marine Labs in addition to her thesis work, she has traveled to study kelp forests in Baja Mexico and Chile, interned at the Monterey Bay Aquarium as their herbarium technician, and assisted with the marine botany course. She has also has been the curator for the MLML Research Museum, which included cataloging and caring for MLML’s historic collections, presenting at conferences on behalf of the museum and her own research, and working to develop the education and outreach side of the collection. Ann hopes to continue working where everything – research, management, outreach – is connected.

Thesis Abstract:

Off the south west coast of North America, kelp forests are facing both warmer waters and introductions of new species. This study examined how the reproductive strategies of giant kelp, Macrocystis pyrifera, and the invasive fucoid Sargassum horneri may have contributed to the interactions of these species on Catalina Island during the 2014 heatwave and 2015/16 El Niño. In 2018-2019 monthly field surveys were conducted to observe current density, demography, temporal variability of vegetative vs. reproductive biomass investment, and temporal variation in gamete release for both species. Field observations were complimented with experimental lab cultures growing M. pyrifera with and without S. horneri. The lab experiments sought to test the effect of temperature on competition between these two species at their microscopic life stages, and what role temperature plays in gamete genesis. Peaks in Macrocystis biomass occurred in summer and coincided with peaks in zoospore production, however there was only a weak correlation between individual size and zoospore production. Conversely, Sargassum biomass and reproductive output peaked between February and April when this seaweed invests heavily in reproduction before the end of its lifespan. Macrocystis produced more propagules per individual at its peak reproductive period than Sargassum. Sargassum released all of its gametes in the spring and grew quickly from the microscopic to juvenile stage. In the lab Macrocystis development was affected mostly by temperature and less by settlement density. Macrocystis sporophyte production decreased with higher temperatures whereas Sargassum zygotes developed more quickly with increases in temperature. The results and observations of this study would indicate that temperature plays a large role in the developmental success of each of these species. The unique events that preceded the record 2015-16 El Niño likely contributed to Sargassum dominating the seascape. If temperatures are anomalously high this will be exacerbated in the future if Macrocystis gametophytes are unable to complete fertilization and develop sporophytes. The high propagule production of Macrocystis and its potential for large area dispersal could provide influxes of gametophytes to deforested areas, particularly in La Niña years, regenerating these habitats. Further research focused on how high ocean temperatures impact Macrocystis resilience and kelp forest connectivity could inform how these ecological processes are changing due to climate change. This can aid in better understanding to manage the trajectory of current and future introduced species, such as invasive Sargassum horneri.

Thesis Abstract:

Many marine species select sites for reproduction based on habitat suitability, environmental tolerances, and oceanographic conditions, in order to enhance development or survival of their offspring. For many species living in the deep sea, it is unknown which factors influence this aspect of the reproductive process. In this study, the occurrence and influences of oviposition site selection were determined for the brown catshark, Apristurus brunneus, and filetail catshark, Parmaturus xaniurus, in the greater Monterey Bay region, providing novel insights into specific habitat preferences and depth distributions. Video footage from the Monterey Bay Aquarium Research Institute (MBARI), and the National Oceanographic and Atmospheric Administration’s Southwest Fisheries Science Center Fisheries Ecology Division (NOAA-SWFSC-FED) was utilized to predict suitable oviposition habitat using MaxEnt presence-only modeling, identify attachment substrates and faunal associations using qualitative observations, and determine depth and habitat preferences using tests of independence and Manly’s selectivity indices. The greater Monterey Bay region was determined as a nursery for both A. brunneus and P. xaniurus on the basis of meeting all oviparous nursery qualifications: high densities of egg cases deposited in the same region, habitat was benthic, oviposition sites were continually used, and no juvenile sharks were observed in the vicinity of egg cases. Complex geographic and environmental features such as rugosity and depth were shown to influence oviposition sites of A. brunneus and P. xaniurus. An increase in rugosity indicated higher predictive habitat suitability. The primary depth range of oviposition sites for both species was 150–199 m, with relatively more A. brunneus egg cases in the 100–149 m range, and more P. xaniurus egg cases observed at deeper depths (200–300 m). Depth ranges for both species are similar and were expanded based on MBARI video observations  (A. brunneus = 87–550 m, P. xaniurus = 99–524 m). Areas of greatest predicted habitat suitability were indicated on the shelf break and upper to mid slope of the Monterey Canyon and in adjacent canyons. MaxEnt model output indicated higher induration (i.e., rockier) habitat was the main driver of oviposition site selection. Structure forming marine invertebrates (SFMI) such as corals and sponges were identified as important faunal attachment structures, with egg cases of both species occurring significantly more often on sponges than other substrates. Nurseries are critically important habitat and this research is necessary for influencing habitat-based management. The vulnerability of these and other species prompts further research concerning the use of SFMI as oviparous nurseries for potential essential fish habitat (EFH) designation.

Growing up, June always loved being underwater. Long summer days were spent at the local pool in Virginia, where she swam along the bottom pretending to be a SCUBA diver and scouring the “seafloor” looking for treasure: forgotten toys, hair ties, and even a coin or two. Then on a fateful snorkel trip to the ocean with her family, 10-year-old June loved swimming with the fish so much, that she decided that she wanted to be an “Oceanographer Scientist” when she grew up! Mind you, she did not know exactly what an oceanographer did, but she liked that it had the word “ocean” in it, and “scientist” sounded impressive. 

From then on, all of her academic pursuits were focused on reaching her goal of becoming an “Oceanographer Scientist”. In high school, she crashed “Take Your Daughter to Work Day” events at NOAA, conducted extra science fair projects, and even studied Latin for four years in hopes that it would help her learn scientific nomenclature. In college, June majored in Biological Sciences for her B.S. degree at Virginia Tech and learned that she was actually more interested in ecology, not oceanography! She participated on any research project she could involving the words “water”, “fish”, or “snorkel”, and spent many days surveying streams for fishes in the mountains of Virginia.

Now, as June graduates with her M.S. in Marine Science from Moss Landing Marine Laboratories and CSU Monterey Bay, she can finally say that she accomplished her childhood dream. When not conducting research, you can find June SCUBA diving - for real now - within the kelp beds of California.

Thesis Abstract:

In marine systems, fishes excrete dissolved nutrients rich in nitrogen, a biolimiting nutrient essential for regulating primary production and macroalgal growth in the ocean. Often overlooked in attempts to explain the variability in kelp forest productivity, relatively little is known about the magnitude and patterns that drive nutrient excretion from fishes, especially in temperate kelp forests. I investigated the supply of nutrients excreted by the dominant fishes (30 species representing ~85% of total fish biomass) on nearshore rocky reefs in California. Using rapid field incubations, I measured the amount of dissolved ammonium (NH₄⁺) released per individual (n = 460) as a function of body size and developed predictive models relating mass to excretion rates at the family-level. I then combined the family-specific predictive equations with data on fish density and size structure around the northern Channel Islands characterized from visual SCUBA surveys conducted from 2005-2018. Mass-specific excretion rates ranged from 0.01 – 3.45 µmol g^-1 hr^-1, and per capita ammonium excretion ranged from 5.9 – 2765 µmol per individual per hr. Ammonium excretion rates scaled with fish size; mass-specific excretion rates were greater in smaller fishes, but larger fishes contributed more ammonium per individual. When controlling for body size, ammonium excretion rates differed significantly among fish families with the highest excretion by surfperches (Embiotocidae). On an areal scale, the fish community in the northern Channel Islands excreted a substantial amount of ammonium to the kelp forest (mean: 131.3 µmol · m^-2 · hr^-1), and spatiotemporal variability (range: 59.84 – 247.9 µmol · m^-2 · hr^-1) was driven by the establishment of marine protected areas (MPAs), geographic and temporal shifts in the overarching fish community structure, and environmental and habitat characteristics. Results suggest that fish-derived nutrients may provide an important and underrepresented nutrient source to kelp beds, particularly during low-nutrient periods (e.g. seasonal or climatic events), and that fishing may interfere with these nutrient cycling pathways. Areal rates of ammonium excretion – consistent with those reported for tropical reefs, but among the first measured in temperate systems – reveal that fishes may play a critical role in supporting the resiliency of kelp forest ecosystems.

Thesis Abstract:

Knowledge of when animals feed and the energetic costs of foraging is key to understanding their foraging ecology and energetic trade-offs.  Despite this importance, our ability to collect these data in marine mammals remains limited.  In this thesis, I address knowledge gaps in both feeding detection and fine-scale diving energetic costs in a model species, the California sea lion (Zalophus californianus).  In Chapter 1 I developed and tested an analysis method to accurately detect prey capture using 3-axis accelerometers mounted on the head and back of two trained sea lions.  An acceleration signal pattern isolated from a ‘training’ subset of synced video and acceleration data was used to build a feeding detector. In blind trials on the remaining data, this detector accurately parsed true feeding from other motions (91-100% true positive rate, 0-4.8% false positive rate), improving upon similar published methods.  In Chapter 2, I used depth and acceleration data to estimate the changing body density of 8 wild sea lions throughout dives, and used those data to calculate each sea lion’s energetic expenditure during descent and ascent at fine temporal scales.  Energy expenditure patterns closely followed the influence of buoyancy changes with depth. Importantly, sea lions used more energy per second but less energy per meter as dive depth increased, revealing high costs of deep diving.  Combined, these chapters further our understanding of California sea lion foraging ecology and provide new methods to aid similar future studies.

Emily has loved marine invertebrates since visiting aquariums and tide pools as a young child. When she moved away from the ocean, she had pet snails so she could continue to learn about molluscs and slimy things, even though she lived in the desert. Emily received a B.S. in Biology from Pepperdine University, where she had a chance to work as an undergraduate researcher and teaching assistant for 3 years. Her research interests include invertebrate zoology and molecular biology, but she is also passionate about education and reaching underserved populations with marine biological knowledge. Emily will move on to a Ph.D. program in collaboration with the University of Maine, University of New England, and the Bigelow Laboratories under the Maine EPSCoR project to continue working with environmental DNA, this time searching for invasive species on the Maine Coast.

Thesis Abstract:

Environmental DNA (eDNA) is nucleic acids outside of living organisms found in air, soil, water, and ice. It is shed by organisms through waste and other bodily fluids, as well as cells sloughed off the outside of an organism. eDNA breaks down over time, especially when exposed to UV, heat, and bacteria. Scientists can analyze eDNA to identify organisms in an area, though the rate at which it is emanated and decayed seem to vary from organism to organism, complicating interpretation of results. The present study sought to quantify the rates of emanation and decay through a series of in vitro experiments for three species, Mytilus californianus (the California blue mussel), Haliotis rufescens (the red abalone), and Lottia scabra (the rough limpet). I found that eDNA emanation rates varied based on species, size, and activity level, and that rates of decay can be influenced by bacterial activity and time under treatment. This data can be used by scientists and managers to interpret eDNA signals of these commercially or ecologically important molluscs to help protect these species and the communities in which they belong.