[1]: What's Cracking: Investigating Gull Predation on Pismo Clam Populations at Pismo Beach.

Ryan Bloom†★§, Marissa Bills§, Ben Ruttenberg§

Department of Biological Sciences, Frost Support, §Santa Rosa Creek Foundation Support, Speaker

Pismo Clams (Tivela stultorum) were once abundant on Pismo Beach until the 1980s when populations declined. However, recent years have seen a notable increase in their numbers. With the potential return of these clam populations to their legal size, we sought to investigate the factors that contribute to their predation, such as humans, otters, and avian sources. This study focused on quantifying the extent of avian predation. We observed a specific clam-dropping predation behavior, where shorebirds/seabirds dropped clams onto compact sand to crack them open, allowing them to feed on the clam. Our research aimed to identify the species of avian predators involved, the size of clams they targeted, and the spatial distribution of predation on the beach. Through surveys on Pismo Beach, we found that Western Gulls (Larus occidentalis) were the sole avian predators engaging in this behavior. The median clam size targeted was 71 millimeters, and predation almost entirely occurred in areas of the beach in which cars were not allowed. Based on this spatial trend, we hypothesize that anthropogenic disturbance from vehicles is a major factor influencing predation frequency. Future work will further explore the impact of Off-Highway Vehicles and other environmental factors on gull predation.

[2]: Quantifying the Putative Therapeutic Serving Size of Commercial Probiotic Foods: A Survey

Reina Knowles, Hannah Rome, Marie Yeung

Department of Biological Sciences, Speaker

Lactic acid bacteria (LAB) are non-pathogenic, gram-positive, facultative anaerobes with probiotic properties of interest to the food and supplement industries. Many genera of lactic acid bacteria, especially in the genus Lactobacillus, are utilized in fermented food products to yield cultured foods with live active cultures. Consumption of cultured food products is often recommended by healthcare practitioners, but there is little evidence to support what serving size of a cultured food will yield therapeutic probiotic effects. In this study, we aim to quantify the putative probiotic cells in eight groups of commercially available cultured food (yogurt, kefir, sauerkraut, etc.) comprising 40 samples using multiple culture-dependent and -independent methods. Preliminary data was obtained from three products - cream cheese, yogurt brand A, and yogurt brand B. The number of gram-positive rods and cocci was $6.4\times10^7$, $1.5\times10^6$ , and $9.6\times10^7$ cells/g respectively, using a direct microscopic count method. These products were diluted and plated on selective MRS agar, which yielded $\lt10^6$, $\lt10^5$, and $6.5\times10^7$ CFU/g, respectively. Based on the results from yogurt brand B, it was calculated that one 150g serving would yield a putative therapeutic dosage of approximately 9.75 billion cells. To enumerate viable but non-culturable Lactobacillus, preparation is underway to perform quantitative Polymerase Chain Reaction with PMAxx viability dye using a primer set specific for the genus. Several Lactobacillus spp will be used to establish a PCR standard curve to aid in accurate quantification. The average probiotic cells per gram of sample will be calculated, which will then be used to determine the effective serving size of each food group based on current literature consensus of 5-10 billion CFU per serving for therapeutic effect. Data from this study has the potential to guide healthcare clinicians' recommendations on the consumption of probiotic cultured foods.


Carolyn Key★§, Benjamin Ruttenberg

Department of Biological Sciences, §Santa Rosa Creek Foundation Support, Speaker

The Pismo clam (Tivela stultorum) is an important recreational fishery species on the California Central Coast. They supported a thriving recreational fishery until the 1980s when Pismo clam populations in California declined and the last legal-sized clam was found on Pismo Beach in the early 1990s. Recently, Pismo clam populations have been increasing and the poaching, or illegal take, of these clams also appears to be increasing. As human interactions with clams are becoming more prevalent with the population recovery, we wanted to understand how much the public knows about the fishing regulations and how knowledge varies with demographic information, such as zip code and age. We additionally sought to document how much the public handles Pismo clams without intentionally fishing for them. We conducted two surveys: a regulation knowledge survey where we surveyed beachgoers on Pismo Beach about their knowledge of Pismo clams and observational surveys, where we documented beachgoers interacting with clams. These surveys help illuminate what the public knows about this species and how much they interact with them. This information can help improve future public outreach and hopefully reduce illegal take.

[4]: The Northern Elephant Seals of Piedras Blancas: a story of recolonization, movement, and monitoring

Mackenzie Davidson1★§, Katie Saenger, Kathleen Curtis2, Brian Hatfield3, Heather Liwanag1, Tim Bean1

1 Department of Biological Sciences, 2 Friends of the Elephant Seal, 3 U.S. Geological Survey, Western Ecological Research Center, §Santa Rosa Creek Foundation Support, Speaker

Northern elephant seals (Mirounga angustirostris) are an example of conservation success, having bounced back from near extinction to a total population of more than 200,000 individuals. Recolonization of northern elephant seal rookeries (breeding sites) at different times presents a unique opportunity to analyze marine mammal population dynamics across the species range and within individual rookeries. The Piedras Blancas rookery in San Simeon, CA was recolonized by northern elephant seals in the early 1990s and demonstrated exponential growth through 2010. The objectives of this study were to: (1) determine whether the Piedras Blancas rookery is approaching carrying capacity (k), which is an indicator of the maximum number of individuals a habitat can support, and (2) explore how abundance of northern elephant seals varies between beaches with differing abiotic characteristics across years. Using published data from past censuses (Lowry et al. 2014), our own ground census data, as well as drone images, we are analyzing the total estimated northern elephant seal abundance at Piedras Blancas and its established beaches during the breeding seasons from 1990 through 2025. Initial analyses have shown an exponential increase in northern elephant seal numbers from 1990 to 2019, with a leveling off around 2020-2023, possibly indicating the rookery has reached carrying capacity. We hypothesize that abiotic beach characteristics such as topography, available area, and location within the rookery will have direct impacts on northern elephant seal abundance. Clarifying how these characteristics affect seal abundance will allow us to predict whether unestablished beaches nearby might provide suitable habitat for future colonization. Understanding the growth of this rookery will provide a better understanding of northern elephant recovery and will help inform conservation and local management efforts for this ecologically and culturally important species.

[5]: Sea Otter Foraging on Pismo Beach: Interactions Between Southern Sea Otters and Pismo Clams

Isa Mattioli†★§, Marissa Bills§, Ben Ruttenberg

Department of Biological Sciences, Frost Support, §Santa Rosa Creek Foundation Support, Speaker

Pismo clam (Tivela stultorum) populations were previously abundant on the California central coast before declining dramatically in the late 1970s and 1980s. However, recently their population has been increasing. The southern sea otter (Enhydra lutris nereis) was hunted to near extinction in the 1800s, leading to a dramatic reduction of their range, including their extirpation from Pismo Beach. Their population has since been recovering, and they are repopulating historic range locations including Pismo Beach in the 1970s, which coincided with the decline in clam populations locally. Since sea otters are an important predator of Pismo clams, we sought to explore the potential impact of sea otter predation on Pismo clam population abundance and recovery by conducting sea otter foraging surveys on Pismo beach. Our preliminary results suggest that sea otter foraging occurs at the north-most point of Pismo Beach, with the majority of their diet consisting of Pismo clams.

[6]: Analyzing the Effect of Sterically Hindered Carboxylic Acid Catalysts in Colloidal COF-300 Synthesis using Electron Microscopy

Zoe Jackson Delos Angeles1★, Leslie Hamachi2

1 Department of Materials Engineering, 2 Department of Chemistry and Biochemistry, Speaker

Covalent organic frameworks (COFs) are a class of highly porous and crystalline polymers that have applications in molecular separations and gas storage. COFs are especially desirable due to the ability to finely control the pore size of the polymer. Historically, COF research has focused on controlling the topology through changing the monomer functionality, or post-synthetic functionalization to tune chemical affinity. Colloidal COF synthesis facilitates error correction and allows for improved materials quality. We hypothesize that developing new colloidal methods to change particle size while maintaining high materials quality will enable future studies on particle size-dependent COF performance. In this research, we study how steric bulk of our synthesis reagents affects the resulting colloidal COF-300 particle size, and we use characterization techniques, such as scanning electron microscopy, to study the size and shape of the COF particles produced.