1,720,982 research outputs found
Biotic interactions shift across temperature and ontogeny in an intertidal barnacle
Get PDFThesis (Ph.D.)--University of Washington, 2019Natural systems provide beneficial goods and services to humanity. To maintain these benefits, modern science is tasked with predicting how natural systems respond to global change. Understanding the ecological processes that underly natural systems, such as interactions between organisms, can help improve such predictions and is thus a research priority. In this dissertation, I present novel findings on how ecological interactions vary across biotic and abiotic factors, and some potential consequences thereof. The hallmark of global change is warming. Warming is important because temperature controls biology at all levels of organization. Many organisms are also shrinking. This is important because body size is a fundamental driver of ecological processes. From survival and growth to reproduction, organismal vital rates vary with ontogeny. Research over the past two decades emphasize that knowledge of the direct effects of temperature and body size on organisms is inadequate to forecast community trajectories. Organisms do not exist in vacuum; they interact with neighbors and with predators. To improve understanding of how natural systems respond to global change, knowledge of the indirect effects – how biotic interactions change with temperature and body size – is required. The rocky intertidal zone provides a valuable system in which to study the ecological impacts of global change. Sessile ectotherms in particular have been used to elucidate principles that now pervade ecology. For example, the acorn barnacle Balanus glandula, though mostly mute and wholly illiterate, tells excellent ecological stories. Seemingly shy in its “squatter’s nutshell” , a barnacle can reveal much about competition and facilitation given the right coaxing. Then there is the whelk Nucella ostrina. All who know them admire these “tiny wet beings straining calcium from the water and spinning it into polished dreams on their backs” . All except perhaps the barnacles, whom the whelks eat. Using organisms in the rocky intertidal zone, this dissertation examines how biotic interactions shift across temperature and ontogeny. In Chapter 1, I examine how multiple physical drivers concurrently affect a consumer-resource interaction. Evidence suggests widespread non-additive effects between multiple drivers; most of this evidence, however, is based on species-level responses, which is problematic because community responses to environmental change also depend on species interactions. To address this knowledge gap, I experimentally manipulated two physical drivers fundamental in intertidal systems – air and water temperatures – and examined the responses of the predator–prey interaction between B. glandula and N. ostrina. I obtained two key findings. First, air and water warming non-additively affected interaction strength: warm water mitigated a decrease in mean whelk feeding rate caused by warm air. Second, air warming had contrasting effects on individual growth rates of predator and prey. While whelk growth decreased in warm air, barnacle growth increased. These findings suggest that combined air and water warming will benefit barnacle populations more than their whelk predators. This study highlights the value of integrating species performances and interactions to understand how multiple physical drivers may affect community structure. In Chapter 2, I examine how environmental context governs trait-rate relationships. Trait and environmental controls on individual vital rates have been well documented, but the potential interactive effects between these controls have been less studied. This is problematic because global change often alters traits and environmental factors simultaneously; to predict the responses of systems, the interaction effects have to be understood. To investigate the links between traits, environmental factors, and demographic processes, I tested how the vital rates of B. glandula respond to the interactive effects of body size, temperature, and crowding. I found that body size and crowding interact to set barnacle survival and reproduction. In the field, crowding increased survival, an effect which became stronger with increasing body size. This effect was likely due to a shift in the balance of size-dependent competition and temperature-dependent facilitation. In mesocosms, crowding increased probability of being reproductive for smaller barnacles but decreased it for larger barnacles. I also found that warmer low tide temperatures decreased barnacle survival (field and mesocosms) and growth (mesocosms) regardless of body size. These findings suggest that incorporating environmental context is necessary to predicting vital rates from traits in barnacles. In Chapter 3, I examine how ontogenetic shifts in intraspecific interactions affect population dynamics. Compared to consumer-interactions, there is a dearth of information on how ontogenetic shifts in interactions within a trophic level affect population dynamics. This is problematic because interactions within a trophic level (e.g., competition and facilitation) are critical determinants of community structure. I used population models to investigate the conditions under which ontogenetic shifts in intraspecific interactions affect the population dynamics of B. glandula. I obtained two key findings. First, crowding modified the effect of body size in an important way: the direction of intraspecific interactions on barnacle growth shifted from negative to positive across size. At a small initial size, high crowding decreased barnacle growth. At a large initial size, however, crowding increased barnacle growth slightly. Second, populations modeled with theoretical crowding distributions showed differences in population growth rates consistent with the observed ontogenetic shifts. Populations with low crowding in established individuals and high crowding in recruits had the lowest population growth rate. Conversely, populations with high crowding in established individuals and low crowding in recruits had the highest population growth rate. This difference in population growth rate was mediated by changes in the population size distribution. These findings highlight the importance of considering how ontogenetic shifts in competition and facilitation alter population size structure and dynamics when predicting the responses of sessile ectotherms to global change. The firmament of ecology is vast. Although this dissertation focuses on a small subset of ecology, it crosses levels of organization, drawing concepts from physiological, population, and community ecology. It also combines fieldwork in the spirit of my academic ancestors (including G.E. Hutchinson and R.T. Paine) with modern techniques in statistical analysis and mathematical modeling. Together, this dissertation contributes basic knowledge on how biotic interactions shift across temperature and ontogeny, and how the latter shift may scale up to population dynamics. In doing so, it bolsters the foundation on which science builds to address global change
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Biology and Ecology of Hexacorallians in the San Juan Archipelago
No full textThesis (Ph.D.)--University of Washington, 2019Hexacorallians are one of the most conspicuous and dominant suspension feeders in temperate and tropical environments. While temperate hexacorallians are particularly diverse in the northeast Pacific, little work has been done in examining their biology and ecology. Within this dissertation, I describe a novel method for marking soft-bodied invertebrates such as hexacorallians (Chapter 1), examine the prey selectivity of the competitively dominant anemone Metridium farcimen with DNA metabarcoding (Chapter 2), and explore the distribution of the most common hard-bottom hexacorallians in the San Juan Archipelago (Chapter 3). In the first chapter, I found that both methylene blue and neutral red make excellent markers for long-term monitoring of M. farcimen with marked individuals identifiable for up to six weeks and seven months, respectively. I also found that fluorescein is lethal in small dosages to M. farcimen and should not be used as a marker. Neutral red could be used for long-term monitoring of growth and survival in the field, and in combination with methylene blue could be used to mark individuals in distinguishable patterns for short-term studies such as examining predator-prey interactions, movement of individuals, and recruitment survival. In the second chapter, I found that M. farcimen captures a wider variety of prey than has been previously described, likely all prey that are large enough to detect and that cannot escape. Additionally, comparisons between DNA metabarcoding and published results from traditional gut sampling techniques showed that many more taxa can be found by DNA metabarcoding. Terrestrial prey were surprisingly high in abundance within the diet of M. farcimen, likely due to the animals living on floating docks. These data highlight the need for consideration of space and time in a sampling regime and the usefulness of the metabarcoding method in identifying prey within the gut of planktivorous animals. In the final chapter, I found that depth, light, flow, and substratum slope had significant impacts on the distribution of hard-bottom hexacorallians, whereas predation pressure and temperature had no detectable effect. Depth and light have a strong relationship with algal cover and most hexacorallians were conspicuously missing from high algal cover surfaces. Additionally, nearly every species increased in density with increased flow. These data call attention to the need for experimental studies examining the interactions between temperate hexacorallians and algae as well the effects of flow on distribution of anthozoans
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A community approach to understanding patterns and processes on rocky subtidal reefs in the Salish Sea
Get PDFThesis (Ph.D.)--University of Washington, 2018The structuring of marine benthic communities is driven by a diverse set of ecological factors, each exerting its influence to differing degrees across all spatial and temporal scales. Here we’ve leveraged a decade of ecological data of the algal, sessile invertebrate, and mobile fauna assemblages on rocky subtidal reefs to present a community approach to understanding the patterns and underlying processes shaping the subtidal seascape in the Salish Sea (inland waters of Washington State). Specifically, we investigated at multiple spatial scales the structure of these communities along a depth gradient, on surfaces with diverse substrate orientations, and across a spectrum of flow regimes to reveal the associations of hundreds of organisms interacting in a mosaic of patchy habitats. We also strongly advocated for the continued efforts to quantify ecological change in our coastal oceans and its long-term consequences. In the first chapter, we compared the rocky subtidal communities of the San Juan Archipelago to similar temperate habitats worldwide and discovered similarities, such as the characteristic zonation patterns of a shallow subtidal macroalgal-dominated zone shifting to an epifaunal invertebrate-dominated deep subtidal zone. We hypothesized that sessile invertebrate communities would exhibit vertical zonation patterns in diversity and percent cover across a depth gradient and now provide evidence for depth as a strong ecological axis in determining community composition. Contrary to our further hypothesis, the mobile fauna assemblages showed very little evidence of strong zonation patterns across depth in either abundance or diversity; this is perhaps the most surprising result from this study. After our initial bottom-up approach to understanding depth zonation patterns on our reefs, we took a top-down approach to investigating scale-dependent patterns and processes in the second chapter. Starting first with the big picture at the habitat scale (hundreds of meters), then at the individual substrate-slope scale, and finally focusing in to sub-meter reef features, we now see a highly nuanced image of the communities across the underwater seascape. Assemblages on horizontal surfaces change much more dramatically with increasing depths than those found on vertical surfaces, although the diversity and abundance of taxa across all substrate orientations on converges in the deep zone, a condition referred to as the ‘depth emergence’ phenomenon. Regardless of depth, assemblages at the extreme ends of the substrate orientation spectrum (i.e. horizontal vs. vertical) have significantly different community structure owing largely to the increased cover of crustose coralline and foliose red algae on horizontal surfaces. And sub-meter vertical features in shelf habitats took on the characteristics of the surrounding surfaces, a pattern we did not expect to find but lends more evidence to the overall identification of light levels as a strong driver of community composition in all habitat types, substrate orientations, and at all spatial scales. Lastly, at all 60 transect locations, we deployed alabaster dissolution blocks in an effort to connect small-scale localized flow patterns to community composition. In the third chapter we designed flow-mediated species response models and then fit long term ecological monitoring data of algal and invertebrate assemblages to these models to characterize the communities along the flow regime spectrum. As we suspected, differences in community structure are greatest between the lowest and the highest flow rates, with little overlap in the taxa found in the lowest and highest flow rates. Coherent species curves were generated and show clear abundance patterns related to local flow regimes with the taxa found together having the strongest association to each other in terms of showing a similar type of response (abundance in this case). We did not previously identify habitat-wide patterns of zonation in the mobile fauna, but abundance patterns in these taxa do appear to be flow related due in large part to an organism’s ability to adhere to the substrate and its phenotypic plasticity. In conclusion, we found that many subtidal benthic species flourish in particular flow conditions and fit within predicted flow-mediated response curves based largely on organismal body plans, attachment to and elevation from the substrate, and feeding strategies. This study encompasses multiple years, sites, and community components and as such we anticipate this study will contribute to a better understanding of subtidal community patterns locally and provide comparisons globally for years to come, especially as we have barely scraped the surface of the massive underlying data set. We believe we have created a solid foundation for quantifying ecological change in our coastal oceans and its long-term consequences
Diversity and structure of subtidal rock walls in the Salish Sea: the roles of grazing, oceanography, and long-term change
No full textThesis (Ph.D.)--University of Washington, 2012The assembly and structure of communities is dictated by a number of ecological processes at a variety of spatial scales. Here I present an `ecology of places', to emphasize the need for both intensive, small-scale experimentation and the larger-scale context from which to interpret the importance of less easily manipulated processes. Specifically, I investigated the roles of local-scale grazing, mesoscale oceanography, and decadal-scale variation on the diversity and structure of benthic communities on subtidal rock walls in the Salish Sea (inland waters of Washington State). In the first chapter, I tested the hypothesis that consumers mediate natural variation in the relationship between prey richness and resource use on epilithic communities. Ecological theory and previous experimental work in dock communities predicted that resource (space) use is a negative, linear function of the number of sessile species present. Contrary to these predictions, a three-month field experiment demonstrated that the relationship between prey richness and resource use was dependent on urchin density, because urchins control the structure of this community by grazing spatially dominant clonal ascidians and facilitating smaller consumers. Following this work, I tested the effects of consumer identity and the predictions of a structural equation model I had developed in chapter one. Namely, do urchins exert indirect effects by facilitating other consumers? In a year-long factorial field experiment, I reduced the densities of urchins and chitons and discovered that the removal of both consumers resulted in unexpected, non-additive changes in community structure. These results suggest that facilitation and redundancy among consumers contribute to the resiliency of species-depauperate habitat dominated by encrusting algae, even if urchins are transient and do not persist indefinitely. To place the local-scale experiments into a broader geographic context, I quantified the effect of mesoscale (10 - 100km) oceanographic variation on the diversity of epilithic communities in my third dissertation chapter. I used a hierarchical sampling design to survey 18 sites, nested within five distinct oceanographic seascapes in Washington. The most striking variation in diversity and composition was observed between seascapes with high and low water retention. Three abiotic correlates of water retention (sediment cover, mass flux, temperature) support the qualitative generalization that waterways and inlets represent distinct physical environments, and consequently harbor unique subtidal biota. Larval delivery and post-settlement mortality are likely to be important mechanisms related to the covarying effects of reduced water flow, sedimentation, and light limitation in high-retention sounds and fjords. Long-term datasets provide a baseline for evaluating temporal variation in biodiversity and are critical for distinguishing between natural and anthropogenic mechanisms of change. My last dissertation chapter tested the hypothesis that the diversity and composition of contemporary (2006-2011) epilithic communities on subtidal rock walls in the San Juan Islands, WA, USA, have changed over thirty years. Despite changes in seawater temperature and chemistry, univariate and multivariate analyses suggest limited differences between historic and modern communities. Historic communities were more even, and characterized by a high percent cover of available space, suggestive of urchin grazing. Despite the initiation of urchin no-take restrictions in 1984, our data indicate that contemporary urchin densities are lower than urchin densities in the 1970's. Declines in biological disturbance (i.e., urchin grazing) will accentuate the naturally low physical disturbance levels on vertical surfaces in subtidal habitats. Although rock walls serve as natural refuges for many invertebrates, a lack of disturbance may allow `weedy' species to dominate and reduce the local diversity of these subtidal communities
Effects of fish predation on benthic communities in the San Juan Archipelago
Get PDFThesis (Ph.D.)--University of Washington, 2015-12Predation is a strong driver of community assembly, particularly in marine systems. Rockfish and other large fishes are the dominant predators in the rocky subtidal habitats of the San Juan Archipelago in NW Washington State. Here I examine the consumptive effects of these predatory fishes, beginning with a study of rockfish diet, and following with tests of the direct influence of predation on prey species and the indirect influence on other community members. In the first chapter I conducted a study of the diet of copper rockfish. Food web models benefit from recent and local data, and in this study I compared my findings with historic diet data from the Salish Sea and other localities along the US West Coast. Additionally, non-lethal methods of diet sampling are necessary to protect depleted rockfish populations, and I successfully used gastric lavage to sample these fish. Copper rockfish from this study fed primarily on shrimp and other demersal crustaceans, and teleosts made up a very small portion of their diet. Compared to previous studies, I found much higher consumption of shrimp and much lower consumption of teleosts, a difference that is likely due in part to geographic or temporal differences in prey availability. Given that copper rockfish diet was so dominated by shrimp, in the second chapter I used field experiments and surveys to determine the top-down effect of rockfish and other large demersal fishes on shrimp and other prey species. In three years of predator and prey surveys I found that shrimp abundance was negatively correlated with pooled predator biomass, but not abundance. Small fish and crab abundance were not correlated with predators. In two rounds of experimental exclusion of predatory fishes I found elevated abundance of both shrimp and small fishes in areas protected from predators. Despite this direct effect of predators on their prey, I did not find evidence of an indirect predator influence on the encrusting assemblage in the exclusion experiment. Trophic cascades are common in temperate marine ecosystems, often mediated by predators consuming urchins and urchins grazing on kelp. The San Juan Archipelago is notable for its lack of both urchin predators and strong grazing pressure from urchins. In the final chapter I looked for evidence of trophic cascades structuring the benthic community in this system. I surveyed the mobile invertebrates and sessile epibenthos at 12 sites within San Juan Channel, and compared these assemblages to predatory fishes to test for co-variance between the groups. Despite some limited evidence of co-variance between the predatory fishes and the other groups, the species involved did not suggest trophic relationships as the causal agent. Instead, predatory fishes may be responding to the biotic habitat provided by benthic organisms. Co-variation between the mobile invertebrates and sessile epibenthos provides supporting evidence of a three-species interaction between urchins, chitons, and social ascidians, and evidence of urchins reducing kelp cover. Finally, I compared these three assemblages to current flow and found strong evidence of current influencing assemblage composition. Although this benthic community does not appear to be controlled by a fish-initiated trophic cascade, consumptive interactions at lower trophic levels and dependence on abiotic factors play important structuring roles
Benthic subtidal assemblages and ecological processes in urbanized seascapes of Puget Sound, Washington, USA
No full textThesis (Ph.D.)--University of Washington, 2017-08Urbanization is a major process altering nearshore habitats in many parts of the world. One important aspect of urbanization in marine settings is the proliferation of artificial structures, such as seawalls, breakwaters, and jetties. Urban artificial structures can fundamentally shift marine communities and alter ecological processes at multiple spatial scales. Though they are common in both intertidal and subtidal habitats, their effect on subtidal ecosystems is particularly understudied. I examined the communities that form in association with subtidal artificial structures and their effects on surrounding sedimentary habitats in an urbanized estuary. In the first chapter, I evaluated detrital influx from artificial structures to surrounding sediments. Photoquadrat and sediment surveys indicated that red macroalgae and epilithic invertebrates were the major producers of detrital material on artificial structures in the Seattle area and that detritus from artificial structures was moving into adjacent sediments. Through a series of experiments, I then assessed the potential effects of these detrital inputs on macrofaunal assemblages. Sediments receiving one-time additions of red macroalgae and shell material were relatively resilient to detrital influx and exhibited little to no change in macrofaunal composition. However, rapid reductions in sediment chlorophyll and phaeopigment following detrital additions suggested that delivery of red macroalgae into sediments surrounding artificial structures may be frequent. In a follow up experiment, sediments were enriched with red macroalgae on a weekly basis to reflect more frequent delivery rates. Though I hypothesized that red macroalgae would serve as a subsidy for macrofaunal assemblages, I observed no positive opportunistic responses among macrofauna to weekly additions. Rather, frequent inputs of red macroalgal detritus led to decreases in abundance for the majority of macrofaunal taxa. Red macroalgae may therefore have negative impacts on macrofaunal assemblages, though this effect is likely minor compared with hydrodynamic alterations and other changes to sedimentary habitats that are associated with artificial structures. In the second chapter, I examined urban-related spatial distribution patterns and habitat-use the giant Pacific octopus (Enteroctopus dofleini). Urbanization is known to facilitate certain terrestrial mesopredators and I sought to evaluate whether similar patterns relative to urbanization were evident for this marine mesopredator. Modeling of citizen-contributed octopus presence/absence data suggested that urbanization impacts differed with depth. Octopus occurrence probability was positively correlated with urbanization intensity in deeper habitats only (> 24 m). In shallower environments (< 18 m), occurrence probability was higher in rural areas than in urban areas. In separate field surveys, I found that octopus diets were unrelated to urbanization, and that octopus abundance was positively correlated with the number of artificial structures on the seafloor. Though trophic mechanisms for urban-related distribution patterns of giant Pacific octopus are therefore unlikely, provisioning of shelter and denning habitat from artificial structures may be an important factor for octopus populations in urban areas. In the final chapter, I examined benthic composition on rocky artificial structures and natural reefs across an urban gradient. Photoquadrats were collected at 36 sites across Puget Sound. Consistent with studies in other regions, I found that artificial structures supported distinct and more variable benthic assemblages than natural reefs. In addition, rocky subtidal habitats in heavily urban areas had fewer kelps and more filamentous algal turf than those in less urban areas. Importantly, analyses from this study highlighted an important challenge in evaluating benthic composition relative to urbanization. Coastal cities tend to be located in protected bays and at the mouths of rivers, where benthic communities are subject to strong salinity gradients and low water flow. Strong collinearity in these naturally occurring environmental variables and urbanization intensity will be an important consideration for future studies that aim to characterize effects of urbanization on marine ecosystems
- …
