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28 Research products, page 3 of 3

  • European Marine Science
  • Research software
  • Other research products
  • 2013-2022
  • eScholarship - University of California

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  • Open Access English
    Authors: 
    Lowman, Heili Eileen;
    Publisher: eScholarship, University of California
    Country: United States

    Coastal regions lie along a dual ecotone: the boundary of terrestrial and marine ecosystems and at the convergence of fresh and saltwater aquatic ecosystems. These ecotones are biogeochemically active regions that are stimulated by the supply and transport of organic material by way of their aquatic linkages. My dissertation addresses questions of organic matter and nutrient supply, retention, and transformation in the coastal regions of the Santa Barbara Channel with a focus on maintaining sufficiently high nitrogen concentrations to support primary production of kelp forests during low nutrient periods. To examine fluctuations of nitrogen concentrations in nearshore marine waters, and their relationships with physical and biological factors, I conducted intensive sampling for ammonium concentrations during the summer season and found a distinct periodicity in concentrations throughout the full water column in relationship to the tidal cycle. To determine if permeable marine sediment is a source of dissolved inorganic nitrogen to the overlying water column, I conducted a multi-year series of nutrient flux measurements using flow-through sediment bioreactors containing sediment collected near kelp forests and found that they are a source of ammonium and total dissolved nitrogen during the summer season. To investigate organic matter supply to marine sediment, I analyzed coastal sediment samples for evidence of terrestrial organic matter input before, during, and after a period with considerable rainfall that followed a 5 year drought, and I found evidence in both stream and marine sediment of terrestrial organic matter inputs becoming increasingly varied and less degraded over time. Using a Santa Barbara Coastal LTER dataset, I examined carbon and nitrogen in giant kelp tissue to evaluate patterns in nutritional content as they relate to changes in seawater temperature and larger oceanographic indices. I found that the nutritional content of giant kelp tissue collected in the Santa Barbara Channel has declined over the past 17 years, and this decline is correlated with increasing seawater temperatures and fluctuations of the North Pacific Gyre Oscillation index.

  • 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: 
    Freedman, Ryan;
    Publisher: eScholarship, University of California
    Country: United States

    Spatial management is a popular tool for resource managers to protect and conserve natural resources. However, a number of emerging threats are testing the ability of these tools to address management needs. Marine protected areas and slow speed zones are popular tools employed by resource managers to mitigate anthropogenic threats; however climate change and whale ship strikes represent new threats that may complicate the benefits of these tools. This dissertation examines the efficacy of incentivizing slow vessel transits to reduce cetacean mortality risk and the application of MPAs to mitigate climate change. A trial program to monetarily incentivize slow transits through the Santa Barbara Channel showed high compliance compared to a similar voluntary program. During incentivized transits, the large majority of ships maintained a 12 knot transit speed as determined by the program guidelines. An incentivized program may be key in reducing risk to whale mortality and reducing ships speeds; however scaling up this program may face financial difficulty.Marine Protected Areas have been claimed to offer additional protection to areas affected by climate change. However, a recent warm water marine heatwave changed the fish community’s abundance, biodiversity, and recruitment around the Channel Islands. While the ecological community changes across strong longitudinal biogeographic patterns, forecasts built from GLMs with environmental conditions predict shifts in species abundance. Upwelling and cool waters coming to the surface may mitigate warming ocean conditions in the region but marine protected areas showed no increased resilience to acute climate affects like marine heatwaves.

  • 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: 
    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: 
    Iacuaniello, Caroline Marie;
    Publisher: eScholarship, University of California
    Country: United States

    Mesopelagic fishes are of utmost importance to the health of global oceanic ecosystems. These fishes comprise the largest known marine biomass, and are a vital source of food many economically important fish and marine mammals. Further, they serve as a major component of the biological carbon pump, moving food items through the water column via diel migration. Though significant effort has gone into understanding species diversity, and positioning in marine food webs, the microbial component of these animals remains poorly characterized. Symbiotic microbial populations associated with the gastrointestinal (GI) tract assist the host with nutrient uptake, digestion, defense against pathogenic microbes, but can also be detrimental to host health as parasites or pathogens. This study investigates the normal intestinal microbiota of wild mesopelagic fish to determine community diversity and distribution across multiple host families with varying migratory and dietary lifestyles. The results presented here indicate that midwater fish have unique microbial communities from fish of other pelagic zones, where, for example, mesopelagic hosts show enrichment in Betaproteobacteria and Gammaproteobacteria microbial classes. Within mesopelagic fish families, major differences were seen: Gonostomatidae are enriched in three Mycoplasma taxa, Stomiidae had highest alpha diversity, Melamphaidae had the highest abundance of Planctomycetes, and Myctophidae gut communities were enriched in Betaproteobacteria. This study brings new understanding to the microbial ecology of the mesopelagic, and demonstrates that despite sharing space in the water column, mesopelagic fishes contain different microbial communities. Clearly, life history traits must be considered in addition to environment in order to better understand the mesopelagic ecosystem. Mesopelagic fishes are of utmost importance to the health of global oceanic ecosystems. These fishes comprise the largest known marine biomass, and are a vital source of food many economically important fish and marine mammals. Further, they serve as a major component of the biological carbon pump, moving food items through the water column via diel migration. Though significant effort has gone into understanding species diversity, and positioning in marine food webs, the microbial component of these animals remains poorly characterized. Symbiotic microbial populations associated with the gastrointestinal (GI) tract assist the host with nutrient uptake, digestion, defense against pathogenic microbes, but can also be detrimental to host health as parasites or pathogens. This study investigates the normal intestinal microbiota of wild mesopelagic fish to determine community diversity and distribution across multiple host families with varying migratory and dietary lifestyles. The results presented here indicate that midwater fish have unique microbial communities from fish of other pelagic zones, where, for example, mesopelagic hosts show enrichment in Betaproteobacteria and Gammaproteobacteria microbial classes. Within mesopelagic fish families, major differences were seen: Gonostomatidae are enriched in three Mycoplasma taxa, Stomiidae had highest alpha diversity, Melamphaidae had the highest abundance of Planctomycetes, and Myctophidae gut communities were enriched in Betaproteobacteria. This study brings new understanding to the microbial ecology of the mesopelagic, and demonstrates that despite sharing space in the water column, mesopelagic fishes contain different microbial communities. Clearly, life history traits must be considered in addition to environment in order to better understand the mesopelagic ecosystem.

  • Open Access English
    Authors: 
    Kelley, Mark B.;
    Publisher: eScholarship, University of California
    Country: United States

    Early American notions of sympathy, largely shaped by Adam Smith’s theory of rational self-interest and fellow feeling, undergird the period’s dominant narrative tropes, socio-political philosophies, and economic ideologies. In this dissertation, I argue that investments in sympathy structure two “domestic” cultural ideals on a watery globe. The first ideal is of a seamlessly productive shipboard society. The second ideal is of an essentially familial national order. To advance these ideals, common sailors, women writers, and political policymakers uphold sympathy as a corrective to sea-based geological or cultural unruliness. In other words, each asserts that domestic stability in a transoceanic system may be gained via a perfection of moral feeling. As I show in two sections, these discrete sentimental narratives on land and at sea confirm antebellum domesticity’s oceanic entanglements. My first section highlights a shipboard domestic ideal that results from oceanic labors that power a U.S.-backed oceanic economy. Specifically, isolated vessels’ socio-material structures direct sailors’ bodies towards affectively cohesive labor. In short, proper feeling at sea is a technical skill as well as a social one. In this system, ideal “sentimental seamen” know exactly how to feel, how to labor, and how to describe those feeling labors. Sailors use novel materialist, labor-based sentimental forms to stake their relative claims to this economic and social ideal. Ultimately, sentimental seamen embody the forms of regulated and monetized feeling that structure age of sail vessels as historical and literary spaces. My second section tracks an antebellum domestic ideal that results from the nation’s reliance on oceanic cultures and economies. Namely, landed writers debate the domestic nation’s place in a “family of nations” via competing definitions of the “villain of all nations.” Within these debates, “pirates of sympathy” are maritime subjects whose incompatibility with state power is due to their supposed incapacity for moral feeling. For some, such figures’ removal protects an ideal national family; for others, the pirate embodies the effects of state violence. As I conclude, this figure’s pervasive literary-historical presence reflects the antebellum era’s shifting and conflicting moral compasses, particularly in relation to maritime slavery and its inheritances. In tracking sentimental seamen and pirates of sympathy, I place two “domestic” ideals on a watery globe. One is a model for ideal domestic laborers at sea. The other is a foil for ideal domestic citizens on land. Both of these figures are defined by their relation to interior, domestic attachments that ripple across and within transoceanic space. In turn, the study of sentimental seamen and pirates of sympathy provide a glimpse of a field I am tentatively calling “terraqueous domestic studies.” Overall, this field treats early American domestic interiority and attachment as fashioned by earth and water together.

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

    The marine leeches of California are found on many host species, but the biology, distribution, and ecology of these leeches is not well understood. In this thesis I describe two previously unknown species: the leeches Mysidobdella californiensis, found on mysid shrimp hosts in Bodega Bay, CA, and Heptacyclus cabrilloi, found on giant kelpfish in San Pedro, CA. I also describe a method that addresses the problem of measuring the size of leeches, which is considered to be difficult because of the inconsistencies in the body proportions of soft-bodied invertebrate organisms. I utilize digital photography to measure leech size and use maximum- likelihood estimation to fit a model of size/age cohort distributions to a sample of leeches.