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31 Research products, page 3 of 4

  • European Marine Science
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  • eScholarship - University of California

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  • Open Access English
    Authors: 
    Friedman, Jonathan Katzenstein;
    Publisher: eScholarship, University of California
    Country: United States

    Navigation, localization, and targeting while completely submerged in the ocean are all extremely difficult due to the lack of a proficient sensor. The highly conductive nature of salt-water results in severe radio-wave attenuation precluding the use of RADAR. Naturally occurring noise sources, high energy costs, long-wavelengths, and surface turbidity restrict the use of SONAR imaging to low resolutions, depths, and far fields. The ocean's dark, turbulent, and silty disposition impedes optical imaging.Nature knows another better way. Apteronotus Albifrons is a nocturnal oceanic fish that cannot rely upon optical notions of vision to navigate, hunt, or avoid predators. Instead, it relies upon an electroreceptive capability achieved through a dense grid of electric field (Voltage) sensors arrayed along both sides of the body and concentrated around the head. It emits an electric field into the water and senses the self-induced forces down its sides. Objects in the vicinity that differ in conductivity from the background ocean environment disturb the field, redistribute the current, and hence the spatial distribution of voltages measured by the fish.This dissertation chronicles the effort to produce an engineered sensor which mirrors the biological phenomenon of electroreception and demonstrate its ability to "visualize" targets with different conductivities from the background ocean environment at very high resolution by detecting perturbations in a quasi-static electric field (electrostatics). This culminates in the first Biomimetic Electrostatic Images (BEI) and demonstrates the potential of the technology to provide significant advances in underwater scientific enterprises, military applications, as well as in medicine.

  • Open Access English
    Authors: 
    Hernandez, Rebecca Noemi;
    Publisher: eScholarship, University of California
    Country: United States

    With the ubiquity of parasites, many hosts have been selected to decrease parasite infection success by employing behavioral defenses, such as avoidance of infected habitats/conspecifics, grooming, grouping, altering swimming behavior, or even self-inducing behavioral fevers. California killifish, Fundulus parvipinnis – common to southern California and Baja California estuaries – are typically exposed to several trematode species that use them as 2nd intermediate hosts. At least one of these trematodes substantially impacts killifish fitness. We also know killifish likely perceive trematode infectious propagules (cercariae). However, we do not know whether they employ behavioral defenses. We experimentally exposed killifish (originating from two San Diego wetlands) individually and in groups to two of their trematode species: Euhaplorchis californiensis – which infects the killifish brain and manipulates host behavior to increase predation rates – and Small Cyathocotylid, which infects connective and muscle tissues. To assess killifish behavioral response to exposure, we quantified several behavioral traits: average number/type of potential defensive behaviors (PDBs), activity, vertical position in the water column and group size before and during exposure to parasites. Our results showed that killifish individually-exposed (both previously infected and naïve) to parasites increase their average number of PDBs, but not their activity. However, in groups, parasite-exposed killifish increase both their average number of PDBs and activity. Conversely, neither average vertical position (in either experiment) nor group size was influenced by parasite exposure. In sum, parasites can alter killifish behavior after infection, but also during anti-parasite behavioral defense, with implications for host-parasite coevolution, and host social and ecological interactions.

  • Open Access English
    Authors: 
    Cahyani, Ni Kadek Dita;
    Publisher: eScholarship, University of California
    Country: United States

    The exceptional concentration of marine biodiversity in the Coral Triangle is among the best-known biogeographic patterns in the ocean. Marine biodiversity peaks in the islands of Eastern part of Indonesia and the Philippines, the heart of the Coral Triangle, and significantly decreases moving away from this global biodiversity hotspot. However, data supporting this pattern largely come from fishes, corals and larger metazoans, and exclude smaller organisms that comprise the majority of marine biodiversity. This study utilized Autonomous Reef Monitoring Structure (ARMS) and DNA metabarcoding to examine biodiversity patterns of marine communities across Indonesia, the largest and most biologically diverse region of the Coral Triangle. In Chapter 1, I examine eukaryote biodiversity patterns of marine communities across Indonesia. Results demonstrate that smaller cryptofauna display similar biodiversity patterns to larger metazoans; the most diverse parts of Indonesia had more diversity per unit area, and greater heterogeneity and beta diversity across all spatial scales, individual ARMS, reefs, or regions. The results show that processes shaping biodiversity hotspots appear consistent in marine and terrestrial ecosystems, and across size and spatial scales. In Chapter 2, I examine patterns marine bacterial diversity across Indonesia, comparing microbial diversity to eukaryotic and metazoan diversity from ARMS. Results showed strong regional differentiation in microbial communities. Microbial diversity tracked eukaryote and metazoan diversity, and displayed a significant pattern of isolation by distance, strongly indicating that associations with larger eukaryotes and physical limitations to dispersal differentiate microbial communities in the Coral Triangle. These results are counter to the hypothesis that “everything is everywhere, but the environment selects”, and provide novel insights into the processes shaping marine microbial diversity in the world’s most diverse marine ecosystem. In Chapter 3, I re-examine data from Chapter 1 to determine how strategies for marine ecosystem monitoring in Indonesia could be developed to yield the best results for the least cost, allowing resource managers to harness the power of metabarcoding to better monitor this region’s biodiversity. Comparisons of cytochrome oxidase 1 (COI) and 18S rRNA metabarcoding data across three separate organismal size classes recovered from ARMS indicate that metabarcoding the 100 �m size fraction with COI captures the largest amount of diversity at the highest resolution. Results indicate that metabarcoding the 100 �m size fraction with COI provides the most accurate and economical approach to monitoring diversity in megadiverse regions where limited research investment precludes sequencing multiple size fractions with multiple metabarcoding markers. Combined, the results of this thesis demonstrate the power of ARMS and metabarcoding for the study and monitoring of marine biodiversity, providing new tools for the study and management of the exceptional marine biodiversity of the Coral Triangle.

  • Open Access English
    Authors: 
    Kwan, Garfield Tsz;
    Publisher: eScholarship, University of California
    Country: United States

    Ionocytes are specialized epithelial cells that excrete or absorb ions across an epithelium to regulate ionic, osmotic and acid-base levels in internal fluids. These ionocytes perform a wide range of functions (e.g. osmoregulation, pH regulation, and calcification) across various organs (e.g. gill, skin, inner ear). As atmospheric CO2 levels rise and oceanic pH levels fall, teleosts may increase their investment on ionocytes to survive in future ocean conditions. But generally speaking, the gill, skin, and inner ear ionocytes within marine teleost are not well characterized. This dissertation contains research spanning five southern Californian teleosts: the Blacksmith Chromis punctipinnis, the Yellowfin Tuna Thunnus albacares, the White Seabass Atractoscion nobilis, the Pacific Mackerel Scomber japonicus, and the Splitnose Rockfish Sebastes diploproa. In Chapter II, I investigated the individual and group behavioral responses of the Blacksmith, a temperate damselfish, after exposure to CO2-induced low-pH conditions. In Chapter III, I describe a novel technique used to quantify skin ionocytes in larval fishes. In Chapter IV, I applied the Chapter III’s technique to document developmental patterns in the skin and gill ionocytes of larval Yellowfin Tuna. In Chapter V, I investigated larval White Seabass response to hypercapnia by monitoring oxygen consumption rate and quantifying ionocyte abundance and relative ionocyte area across development. In Chapter VI, I characterized two types of inner ear ionocytes responsible for otolith calcification in the Pacific Mackerel. In Chapter VII, I investigated whether future CO2 /pH conditions would affect the gill and inner ear ionocytes of Splitnose Rockfish. Altogether, this work across the multiple teleosts demonstrates that ionocytes 1) have the plasticity to respond to external pH stress, 2) are sufficient to maintain internal homeostasis despite significant differences in CO2/pH levels, and 3) differ greatly in protein, morphology, and function depending on the tissue in question.

  • Open Access English
    Authors: 
    Rivera Sotelo, Aida Sofia;
    Publisher: eScholarship, University of California
    Country: United States

    Coral coverage reduction of up to 90% became a barometer of planetary health in the last three decades. As a result, coral scientists anticipate coral extinction with catastrophic effects on life in the oceans and propose direct interventions to rehabilitate ecological functions and extend corals’ lives. Some scholars have offered a critical approach to coral restoration’s naturalization of corporate forms of responsibility (Moore 2018) and controversies among coral scientists about what coral restoration can achieve (Braverman 2018). My dissertation draws upon twenty months of immersive study as a volunteer for the Center of Research, Education, and Recreation (CEINER) in the Rosario archipelago (part of the Corals of Rosario and San Bernardo Nature Reserve). CEINER simultaneously works on coral restoration and the assisted reproduction of endangered fish species. In addition, I volunteered for other coral restoration and reef checks in Isla Fuerte, Santa Marta, Taganga, and San Andrés. I also attended and presented posters and papers at international conferences on conservation biology, coral science, and ecological restoration. My work with scientists and other residents and visitors in the Rosario archipelago has pushed my analysis beyond extinction’s recognition to consider the migration of coral and fish further and deeper in the ocean. Using the word “migrations,” I intend to reframe the terms of destruction from planetary accounts to elusive ecologies—for both scientists and artisanal fishers. I explore different and co-incidental sea compositions, undecidable temporal horizons in coral reproductive urgencies, and more ways through which various islanders grow coral and fish in this sea. My research conceptually integrates and advances discussions surrounding extinction, managerial juridical frameworks, and environmental and animal studies. Throughout my dissertation, I build a vocabulary to think and imagine affective sea ecologies and unlikely, partial, and strategic collaborations among coral restoration scientists and other islanders.

  • Open Access English
    Authors: 
    Cavole, Leticia;
    Publisher: eScholarship, University of California
    Country: United States

    Fish and fishers are affected by the environmental conditions they experience throughout their lives, from daily, annual to decadal time scales. Currently, the oceans are changing fast, as global warming increases the temperature of the water and reduces oxygen levels within it. However, there is still an important knowledge gap about how these shifting conditions influence wild populations of fish, especially in the early life stages of tropical species inhabiting mangrove lagoons or for adult fishes dwelling in the deep ocean. In this dissertation, we use the chronological and chemical properties of otoliths – calcified structures within the inner ear of fish – to investigate how temperature correlates with fish growth, to improve our understanding of their populations, and to develop proxies for hypoxia exposure in deep-sea fishes. Chapter 1 asks how the water temperature inside mangrove lagoons regulates the first year of growth for yellow snappers in the Gulf of California. We found that these animals grow faster in warmer waters until they experience a thermal threshold (~ 32° C) beyond which their growth rate is reduced. Chapter 2 tests the effects of extrinsic (water chemistry and temperature) and intrinsic (growth rate and taxonomy) factors on otolith chemistry. Using distinct species from Galápagos (yellow snapper and sailfin grouper) and the same species (yellow snapper) between Galápagos and the Gulf of California, we observed that extrinsic factors seem to be more important than intrinsic factors as influences on otolith microchemistry. Chapter 3 examines the population structure of yellow snappers in the Gulf of California and Galápagos mangroves by using otolith microchemistry and genetic analyses in tandem. These methodologies were complementary and helped to elucidate a source-sink metapopulation structure for Galápagos snappers, and a self-recruitment scenario for the Gulf snappers, with important implications for the mangrove management at these ecosystems. Chapter 4 explores the use of fish as mobile monitors of hypoxic conditions in Oxygen Minimum Zones (OMZs). Surprisingly, fishes with distinct life-history traits (longevity and thermal history) and from different OMZs (NE Pacific and SE Atlantic), but exposed to comparable low oxygen conditions, exhibited high similarity in their otolith chemistry. These findings may provide a baseline for tracking the ongoing expansion of OMZs. Lastly, Chapter 5 inquires how fishers’ local ecological knowledge (LEK) in the Galápagos Archipelago can help to elucidate the effects of climate variability on fish. We observed that LEK is in line with the scientific literature regarding distributional shifts in marine species and anomalous weather conditions during strong El Niño years.

  • Open Access English
    Authors: 
    Werner, Leah Kimberly;
    Publisher: eScholarship, University of California
    Country: United States

    Richly productive polar marine ecosystems are hypothesized to have evolved within the last ~30 million years through the rise of diatoms to ecological dominance and diversification of distinctive polar fish, sea birds, seals and whales. Today, short diatom-based food chains support substantial fish biomass, but whether polar fish production is high enough to sustain current industrial fishing is unknown. To this end, we compared ichthyolith accumulation rates (IAR), a proxy for fish production, across ocean ecosystems to trace the development of global fisheries stocks over the past 1.8 million years. We find that the magnitude of polar fish production, based on the flux of fish teeth to deep-sea sediments, is an order of magnitude lower than seen in subtropical and tropical sites. We suggest that polar fish production is systematically suppressed by extreme seasonality, phenological mismatch, low functional redundancy, and extreme glacial-interglacial climatic variability in the high latitude oceans. Comparisons of our Pleistocene data to similar records from the Eocene and Oligocene oceans (~42-28 Ma) show that fish production in high latitudes has been consistently low for the last 30-40 Ma relative to most of the tropical and subtropical locations. We conclude that the stock crashes observed in the polar regions over the past several decades reflect overexploitation of ecosystems that have had low fish production for tens of millions of years.

  • Open Access English
    Authors: 
    Berta, Veronica Zsazsa;
    Publisher: eScholarship, University of California
    Country: United States

    Amines were measured by aerosol mass spectrometry (AMS) and Fourier Transform Infrared (FTIR) spectroscopy during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) cruises. Both AMS non-refractory (NR) amine ion fragments comprising the AMS CxHyNz family and FTIR non-volatile (NV) amine measured as primary (C-NH2) amine groups typically had greater concentrations in continental air masses than marine air masses. Secondary continental sources of AMS NR amine fragments were identified by consistent correlations to AMS NR nitrate, AMS NR m/z 44, IC non-sea salt potassium, and radon for most air masses. FTIR NV amine group mass concentrations for particles with diameters <1 μm showed large contributions from a primary marine source that was identified by significant correlations with measurements of wind speed, chlorophyll a, seawater dimethylsulfide (DMS), AMS NR chloride, and ion chromatography (IC) sea salt as well as FTIR NV alcohol groups in both marine and continental air masses. FTIR NV amine group mass concentrations in <0.18 μm and <0.5 μm particle samples in marine air masses likely have a biogenic secondary source associated with strong correlations to FTIR NV acid groups, which are not present for <1 μm particle samples. The average seasonal contribution of AMS NR amine fragments and FTIR NV amine groups ranged from 27% primary marine amine and 73% secondary continental amine during Early Spring to 53% primary amine and 47% secondary continental amine during Winter. These results demonstrate that AMS NR and FTIR NV amine measurements are complementary and can be used together to investigate the variety and sources of amines in the marine environment.

  • Open Access English
    Authors: 
    Spies, Brenton Tyler;
    Publisher: eScholarship, University of California
    Country: United States

    This project is directed towards implementing aspects of the tidewater goby recovery plan in coordination with, and funded by, the US Fish & Wildlife Service (USFWS) through a Section 6 Cooperative Agreement awarded to the University of California, Los Angeles on May 15, 2015. The primary focus of this dissertation was to developed a quantitative framework to complete a metapopulation viability analysis (MVA) for the endangered tidewater gobies in the genus Eucyclogobius. Modeling tidewater goby metapopulation dynamics is an essential component in constructing long-term management plans rangewide throughout the California Coast. This dissertation examines more closely how these dynamics affect viability, connectivity, and long-term persistence of tidewater goby metapopulations throughout the California coast. In the first chapter of this dissertation, I conducted annual population surveys (2014, 2015, and 2017-2018) in 117 estuaries and lagoons to assess the current health and status of the tidewater gobies in five of the six Recovery Units, spanning from Bodega Bay to San Diego, CA. This massive effort has provided continuous coastal surveys over four years, and over 300 observations, which helped create the framework for a robust and comprehensive presence/absence dataset to help inform metapopulation management and recovery actions. In the second chapter of this dissertation collated all existing rangewide occupancy data, metapopulation descriptors, wetland site characteristics, and repository specimen collections into an open access database. This database will provide critical information relative to the federally endangered tidewater gobies and help inform the metapopulation viability analysis model developed in this study, as well as support continued research on the conservation and management of these incredible fish species and the coastal wetland ecosystems they inhabit. In the third chapter of this dissertation I review the general biology, conservation status, habitat impacts, and metapopulation dynamics of the northern tidewater goby (Eucyclogobius newberryi) and southern tidewater goby (Eucyclogobius kristinae). In addition, I demonstrate the effectiveness of a Bayesian approach to provide a flexible method to generate metapopulation viability analyses and provide a detailed summary of the MVA model framework, including limitations, required corrections, and future amendments that need to be addressed in order to meet the recovery criterion envisioned in the recovery plan.

  • Open Access English
    Authors: 
    Pagniello, Camille;
    Publisher: eScholarship, University of California
    Country: United States

    Marine protected areas (MPAs) have been established worldwide to protect coastal ecosystems and the species inhabiting them. However, it is difficult to quantify whether these areas are adequately protecting the targeted species. Current monitoring methods, such as diver surveys, allow fish species to be identified in situ, but are known to alter fish presence and behavior. Other methods, such as acoustic telemetry, are relatively invasive, requiring the implantation of a transmitter tag into the fish. Additionally, both these approaches are laborious and expensive, relying on good weather and a talented pool of fisherman and divers. Methods that are non-invasive, such as passive acoustics, offer good spatial and temporal coverage, but ascribing specific calls or sounds to the species creating them is difficult, particularly for fishes. Camera deployments allow for in situ observations of behavior, diversity and frequency of occurrence of a wide variety of animals but are often hindered by low-light and battery limitations. Here, I developed passive acoustic and optical imaging tools to study sound-producing fish that allow improved performance over contemporary methods. These tools were used to study chorusing fish in protected kelp forests along the southern California coast. First, an autonomous Wave Glider was equipped with a passive acoustic recorder to map the distribution of five soniferous fish spawning aggregations. The fish choruses started near sunset and ended before sunrise, and were almost exclusively recorded offshore of kelp forests. Second, a low-cost underwater optical imaging system that utilizes a consumer-grade camera to capture high-quality images in low-light aquatic habitats without artificial lighting was designed and developed. The system was used to captured >1,500 images per day over 14 days, which revealed biologically important behaviors as well as daily patterns of presence/absence. Lastly, an underwater controlled source of known position was used to improve an acoustic localization algorithm to track fish to a resolution of a few meters. The fish remained outside of the MPA while vocalizing. This work demonstrates the promise of these tools to non-invasively monitor animal behavior, biodiversity and frequency of occurrence in MPAs as well as other nearshore areas.