abstract: Biodiversity is required to guarantee proper ecosystem structure and function. However, increasing anthropogenic threats are causing biodiversity loss around the world at an unprecedented rate, in what has been deemed the sixth mass extinction. To counteract this crisis, conservationists seek to improve the methods used in the design and implementation of protected areas, which help mitigate the impacts of human activities on species. Marine mammals are ecosystem engineers and important indicator species of ocean and human wellbeing. They are also disproportionally less known and more threatened than terrestrial mammals. Therefore, surrogates of biodiversity must be used to maximize their representation in conservation planning. Some of the most effective surrogates of biodiversity known have only been tested in terrestrial systems. Here I test complementarity, rarity, and environmental diversity as potential surrogates of marine mammal representation at the global scale, and compare their performance against species richness, which is the most popular surrogate used to date. I also present the first map of marine mammal complementarity, and assess its relationship with environmental variables to determine if environmental factors could also be used as surrogates. Lastly, I determine the global complementarity-based hotspots of marine mammal biodiversity, and compare their distributions against current marine protected area coverage and exposure to global indices of human threats, to elucidate the effectiveness of current conservation efforts. Results show that complementarity, rarity, and environmental diversity are all efficient surrogates, as they outcompete species richness in maximizing marine mammal species representation when solving the minimum-set coverage problem. Results also show that sea surface temperature, density, and bathymetry are the top environmental variables most associated with complementarity of marine mammals. Finally, gap analyses show that marine mammals are overall poorly protected, yet moderately exposed to hotspots of cumulative human impacts. The wide distribution of marine mammals justify global studies like the ones here presented, to determine the best strategy for their protection. Overall, my findings show that less popular surrogates of biodiversity are more effective for marine mammals and should be considered in their management, and that the expansion of protected areas in their most important habitats should be prioritized. / Dissertation/Thesis / Doctoral Dissertation Biology 2019

Picophytoplanktonic cells (0.2-2 μm) are the dominant phytoplankters in the largest marine biomes on Earth: the subtropical gyres. The overaching aim of this thesis is to develop algorithms that use remote-sensing observables to map the distribution of the smallest and most abundant member of picophytoplankton, Prochlorococcus, and assess its contribution to the marine carbon cycle. To understand how the photoacclimatory status and growth of Prochlorococcus and its sister genera Synechococcus are influenced by light and nutrients, experiments were conducted in the South Atlantic Gyre (SAG). Results from the manipulation experiments show that, in the central region of the SAG, nutrient addition can induce marked changes in the optical properties of Prochlorococcus cells when subjected to saturating light levels, leading to a decrease in cell abundance, whereas at the gyre periphery no substantive changes in cell growth or optical characteristics were observed. Since light plays a central role in shaping the distribution of cyanobacteria, an empirical algorithm based on relationships between Prochlorococcus abundance and remotely-sensed observables was developed. The outputs were then used in a modified primary production model to predict the vertical distribution of carbon fixation by Prochlorococcus. The models estimate that ∼ 3.4 x 10²⁷ Prochlorococcus cells in the global ocean fix 4.7 Gt C year^-1. Most of the cell biomass and primary productivity is concentrated in the subtropical gyres and areas near the Equatorial Convergence, and 61% of the carbon fixation occurs in the upper water column (0-45 metres), where only 43% of the cells reside. However, in the gyres, carbon fixation is highest (62%) in deeper layers (45-200m), and both cell abundance and carbon fixation show marked seasonal patterns. The models developed in this study provide an unprecedented view of the vertical distribution of Prochlorococcus cells and their corresponding rates of carbon fixation in the global ocean.

abstract: Marine pico-cyanobacteria of the genera Synechococcus and Prochlorococcus carry out nearly two thirds of the primary production in oligotrophic oceans. These cyanobacteria are also considered an important constituent of the biological carbon pump, the photosynthetic fixation of CO2 to dissolved and particulate organic carbon and subsequent export to the ocean’s interior. But single cells of these cyanobacteria are too small to sink, so their carbon export has to be mediated by aggregate formation and/or consumption by zooplankton that produce sinking fecal pellets. In this dissertation, I investigated for the first time the aggregation of these cyanobacteria by studying the marine Synechococcus sp. strain WH8102 as a model organism. I first found in culture experiments that Synechococcus cells aggregated and that such aggregation of cells was related to the production of transparent exopolymeric particles (TEP), known to provide the main matrix of aggregates of eukaryotic phytoplankton. I also found that despite the lowered growth rates, cells in the nitrogen or phosphorus limited cultures had a higher cell-normalized TEP production and formed a greater total volume of aggregates with higher settling velocities compared to cells in the nutrient replete cultures. I further studied the Synechococcus aggregation in roller tanks that allow the simulation of aggregates settling in the water column, and investigated the effects of the clays kaolinite and bentonite that are commonly found in the ocean. In the roller tanks, Synechococcus cells formed aggregates with diameters of up to 1.4 mm and sinking velocities of up to 440 m/d, comparable to those of larger eukaryotic phytoplankton such as diatoms. In addition, the clay minerals increased the number but reduced the size of aggregates, and their ballasting effects increased the sinking velocity and the carbon export potential of the aggregates. Lastly, I investigated the effects of heterotrophic bacteria on the Synechococcus aggregation, and found that heterotrophic bacteria generally resulted in the formation of fewer, but larger and faster sinking aggregates, and eventually led to an enhanced aggregation of cells and particles. My study contributes to the understanding of the role of marine pico-cyanobacteria in the ecology and biogeochemistry of oligotrophic oceans. / Dissertation/Thesis / Doctoral Dissertation Biology 2016

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 126-138). Also available on the World Wide Web.

xv, 99 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / The trochid gastropod Chlorostoma (Tegula) funebralis is found in rocky intertidal habitats along the west coast of North America from Baja California to Vancouver Island. Size-frequency distributions of populations were analyzed along a latitudinal gradient from northern Oregon to Baja California. Populations in California and southern Oregon were dominated by individuals in the juvenile size classes (0.1g-2g). Along the Oregon coast, populations dominated by juveniles were correlated with coastline topography, with protected areas having large numbers of juveniles and exposed areas dominated by larger size classes. The largest size classes (>9g) were rarely present in southern populations. The seasonality of reproduction was investigated in a southern California population and an Oregon population to determine whether continuous reproduction in southern populations increases recruitment success over the year and decreases inter-annual variation in reproductive success. Constant recruitment may cause populations to have a large number of juveniles, the observed pattern in southern populations. Although individuals capable of reproduction were found year-round in both populations, the southern population experienced multiple spawning events over the year, while the northern population experienced only one such event. Constant recruitment may be a strategy to compensate for shorter life spans and smaller sizes of individuals in southern California. To investigate whether variations in predation rates on large adult C. funebralis affect the size structure of populations, the main predators and predation rates for different populations in Oregon were identified. All observed predation events were by the intertidal seastar Pisaster ochraceus . Predation pressure by P. ochraceus varied significantly with site and between sampling dates but did not remove enough C. funebralis from the adult population to have a significant effect on population size structure. To determine the connectivity between populations and the maximum dispersal potential, the mitochondrial gene COI was sequenced from individuals from nine populations ranging from southern California to northern Oregon. Although haplotype diversity was high, no genetic structure was found between populations. Rather than an indication of high dispersal potential and a panmictic species, the lack of isolation by distance may be a result of range expansion following the last glacial maximum. / Committee in charge: Patrick Phillips, Chairperson, Biology; Alan Shanks, Advisor, Biology; Craig Young, Member, Biology; Richard Emlet, Member, Biology; Jon Erlandson, Member, Anthropology; Gregory Retallack, Outside Member, Geological Sciences

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Thesis (Ph. D.)--Joint Program in Biological Oceanography (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 1999. / Includes bibliographical references. / Odontocetes are assumed to use echolocation for navigation and foraging, but neither of these uses of biosonar has been conclusively demonstrated in free-ranging animals. Many bats are known to use echolocation throughout foraging sequences, changing the structure and timing of clicks as they progress towards prey capture. For odontocetes, however, we do not know enough about their foraging behavior to describe such sequences. To conduct detailed behavioral observations of any subject animal, the observer must be able to maintain continuous visual contact with the subject for a period commensurate with the duration of the behavior(s) of interest. Behavioral studies of cetaceans, which spend approximately 95% of their time below the water's surface, have been limited to sampling surface behavior except in special circumstances, e.g. clear-water environments, or with the use of technological tools. I addressed this limitation through development of an observation platform consisting of a remote controlled video camera suspended from a tethered airship with boat-based monitoring, adjustment, and recording of video. The system was used successfully to conduct continuous behavioral observations of bottlenose dolphins in the Sarasota Bay, FL area. This system allowed me to describe previously unreported foraging behaviors and elucidate functions for behaviors already defined but poorly understood. Dolphin foraging was modeled as a stage-structured sequence of behaviors, with the goal-directed feeding event occurring at the end of a series of search, encounter, and pursuit behaviors. The behaviors preceding a feeding event do not occur in a deterministic sequence, but are adaptive and plastic. A single-step transition analysis beginning with prey capture and receding in time has identified significant links between observed behaviors and demonstrated the stage-structured nature of dolphin foraging. Factors affecting the occurrence of specific behaviors and behavioral transitions include mesoscale habitat variation and individual preferences. The role of sound in foraging, especially echolocation, is less well understood than the behavioral component. Recent studies have explored the use of echolocation in captive odontocete foraging and presumed feeding in wild animals, but simultaneous, detailed behavioral and acoustic observations have eluded researchers. The current study used two methods to obtain acoustic data. The overhead video system includes two towed hydrophones used to record 'ambient' sounds of dolphin foraging. The recordings are of the 'ambient' sounds because the source of the sounds, i.e. animal, could not be localized. Many focal follows, however, were conducted with single animals, and from these records the timing of echolocation and other sounds relative to the foraging sequence could be examined. The 'ambient' recordings revealed that single animals are much more vocal than animals in groups, both overall and during foraging. When not foraging, single animals vocalized at a rate similar to the per animal rate in groups of>=2 animals. For single foraging animals, the use of different sound types varies significantly by the habitat in which the animal is foraging. These patterns of use coupled with the characteristics of the different sound types suggest specific functions for each. The presence of multiple animals in a foraging group apparently reduces the need to vocalize, and potential reasons for this pattern are discussed. In addition, the increased vocal activity of single foraging animals lends support to specific hypotheses of sound use in bottlenose dolphins and odontocetes in general. The second acoustic data collection method records sounds known to be from a specific animal. An acoustic recording tag was developed that records all sounds produced by an animal including every echolocation click. The tag also includes an acoustic sampling interval controller and a sensor suite that measures pitch, roll, heading, and surfacing events. While no foraging events occurred while an animal was wearing an acoustic data logger, the rates of echolocation and whistling during different activities, e.g. traveling, were measured. / by Douglas Paul Nowacek. / Ph.D.

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