<p> An understanding of the spatial and temporal diversity of benthic invertebrates is necessary to understand, manage, and protect freshwater habitats. Benthic invertebrates are important components of aquatic ecosystems and are frequently used in bioassessment and biomonitoring programs. Benthic invertebrates can also play a role in nutrient cycling in lentic environments through bioturbation activities. This dissertation uses a range of techniques and analyses to understand the arrangement of benthic invertebrate diversity in Upper Klamath Lake, Oregon, and several watersheds in northern southern California. </p><p> Upper Klamath Lake (UKL) is a large, shallow, naturally eutrophic lake that has experienced declines in water quality, which has led to annual cyanobacterial blooms of <i>Aphanizomenon flos-aquae</i>. Benthic invertebrates can increase autochthonous nutrient cycling through benthic bioturbation activities. In order to better understand the role that benthic invertebrates play in UKL, I studied the density, taxonomic richness, and species composition of benthic invertebrate assemblages in three geographic regions (north, central, and south) and three habitats (littoral, open-water and trench) across UKL. I also characterized sediment composition and water quality at each collection site and determined which environmental variables correlated with differences in benthic invertebrate composition. This research is located in Chapters 1 and 3 of this dissertation. </p><p> Like benthic invertebrates in UKL, the mayfly <i>Baetis tricaudatus </i> is an abundant and ecologically important organism of freshwater ecosystems. Despite its widespread distribution, <i>B. tricaudatus</i> cannot be consistently and accurately identified and belongs to a species group known to have cryptic species diversity. While previous studies have examined the spatial distribution of this diversity, none have studied the temporal distribution. To better understand the temporal arrangement of diversity at the cytochrome oxidase subunit 1 (CO1) mitochondrial gene region, I collected <i> B. tricaudatus</i> specimens from 3 sites over 4 years and used haplotype networks to visualize diversity. Because my results were different than those from other studies on the same taxon, for my final chapter I analyzed <i> Baetis rhodani</i> group COI sequences from northern and southern California using Bayesian phylogenetic analyses and haplotype networks. This research contributes to our understanding of genetic diversity, which is an important component to biodiversity.</p><p>

Two compartment (sediment and water) flow-through model ecosystems were constructed to investigate the compartmentalization of different organic chemicals. Lindane, naphthalene, and mirex were pumped into the systems and resultant compartmental chemical concentrations determined. Steady state concentrations were compared to those predicted by two environmental fate models - EXAMS (Exposure Analysis Modeling System) and SLSA (Simplified Lake and Stream Analysis) which were developed by EPA-Athens, Georgia and HydroQual, Inc., respectively.

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Many species of stream invertebrates gain most of their energy by the consumption of coarse detrital materials. While most of these organisms are univoltine or semivoltine, the biomass of assimilable detritus varies seasonally as a result of several processes. The period of detritus input is highly seasonal, decomposition rates are positively temperature dependent, and winter spates result in fragmentation and flushing of detrital materials. From two years of measuring detritus inputs and standing crops, I showed that the abundance of this resource varied by almost two orders of magnitude seasonally. Since many consumers which rely on this resource have generation times equal to that of the period of resource variation, individuals and perhaps populations may be faced with periods of low food abundance. This work addressed the consequences of seasonal food limitation of stream insects. To test this food Limitation hypothesis, I experimentally manipulated detritus input rates to otherwise natural communities of stream benthos using a replicated, 3 - treatment design. These experiments were conducted in experimental streams in the University of British Columbia research forest over the course of one year. Increasing input rates of detritus resulted in large increases in size at maturity and growth rates for 7 of 9 common species. This was true for both summer and winter emerging species. Increased supply of detritus also resulted in increased densities and higher rates of colonization for some species. There was no evidence of change in phenology for any species. The densities of the chironomid Brillia retifinis (the only species studied that had a short generation time) underwent exponential growth during the first 3 months of the experiment, reaching densities 10x those of the control and natural streams. This species apparently fills the role of a "fugitive" in this system. One alternative hypothesis for increased densities following addition of whole leaf detritus was a significantly altered microhabitat. To test this possibility I compared the use of real and artificial (polyester) leaf packs by stream invertebrates. Those species which typically consume coarse detritus were almost never found on the artificial leaf packs, while they attained high densities on the real leaves. In contrast, fine-particle, and algae consuming species were found in similar densities on artificial and real leaf packs, although there was a time lag in colonization of the polyester leaves. These results suggest that microhabitat alone cannot lead to increased densities of detritivores. The densities of species which do not consume large particles of detritus also were affected by whole-leaf additions. Density of total consumers of fine particles of detritus increased when coarse detritus was supplemented and most taxa showed this response. This result was apparently an indirect effect of diminution of detrital particle size by larger detritivores. Predaceous species also increased in density under detritus supplementation. Increased densities of taxa other than large-particle-detritus feeders indicates that effects at one trophic level can affect other trophic levels. / Science, Faculty of / Zoology, Department of / Graduate

Squoxin, 1,1'-methylenedi-2-naphthol, is a pesticide developed to eradicate the northern squawfish, Ptychocheilus oregonensis. Investigations concerning the acute toxicity of the pesticide to aquatic invertebrates and an assessment of its fate in aquatic ecosystems are reported. Squoxin was found to be much less toxic to aquatic invertebrates than it was to squawfish. It was proposed that the toxicity of squoxin to aquatic invertebrates is inversely proportional to their adaptations to habitats having low levels of oxygen availability. The most sensitive invertebrate species tested was the blackfly larva, Simulium canadense, which is distributed in streams having high current velocity and abundant dissolved oxygen. These larvae exhibit an LC50 value of 60 ug/l in 48 hours. Chaoborus trivittatus larvae, known to tolerate anoxic conditions, were resistant to treatments up to 10 mg/1, exhibiting a maximum response of 30 percent in 96 hours. The degradation of Squoxin was monitored in surface waters of diverse origin. Degradation was most severe in water having a high pH and high alkalinity. Degradation was also found to occur due to the presence of dissolved organic compounds of high molecular weight. Freshwater bacteria did not exhibit any ability to utilize Squoxin as a carbon source in short term tests. A 100 ug/l Squoxin treatment depressed the natural heterotrophic activity of bacteria by nearly 25 percent based on studies of uptake of ¹⁴C-glucose over a 2 hour period. ¹⁴C-Squoxm residues initially adsorbed to phyto-plankton and organic sediment in simple laboratory microcosms. However, the residues steadily desorbed from these components and became increasingly soluble throughout the test period. Daphnia pulex and Hyalella azetca in the microcosms took up Squoxin rapidly in the first 24 hours after treatment. Uptake then levelled off and tissue concentration of Squoxin increased only at a very slow rate during the remainder of the test. Only small amounts of Squoxin were transferred to organisms feeding on contaminated food items when compared to the dose obtained from a contact exposure. C. trivittatus fed contaminated D. pulex retained only 6 percent of the ingested Squoxin residues. These residues, however, appeared to be retained for a longer period than tissue residues gained through a contact exposure. Invertebrates exhibited an ability to excrete Squoxin residues given time and an uncontaminated environment. D. pulex excreted over 90 percent of the toxicant in 96 hours; H. azteca required 275 hours. It was postulated that because of Squoxin's water solubility, low partition coefficient, rapid degradation, and the ability of a wide variety of organisms to excrete it, the toxicant would not be biologically magnified to a significant degree in aquatic ecosystems. / Science, Faculty of / Zoology, Department of / Graduate

The purpose of this investigation is to determine if there was a metabolic relationship between the actinomycetes and the gram positive, spore-forming becilli in surface waters, and, if such a relationship was evident, to relate the association to the disappearances of typical actinomycete tastes and odors from waters.

Degradation of aquatic ecosystems is an unfortunate consequence of industrialization, urbanization and general societial activity. The health of biological communities in these systems is subject to chemical stressors including emerging contaminants and legacy compounds that inevitably transit from land-based ecosystems into aquatic habitats. Fish have been utilized as preferred vertebrate sentinels of these systems for decdes; however, base-line data regarding disease, immune responses, endocrine function and other physiological responses is often not experimentally qualified prior to field application. Here, the presence of estrogen receptors (ERs) in channel catfish ( Ictalurus punctatus) leukocytes is demonstrated. Estrogens affect the responsiveness of channel catfish peripheral blood leukocytes (PBLs) to mitogens in vitro. The ERs, ERα and ERβ2, are differentially expressed depending on leukocyte lineage, phenotype, and state of activation. Estrogens are likely involved in the regulation of immune responses in vivo, and estrogenic endocrine disrupting chemicals may directly impact leukocyte function. Additionally, laboratory studies established a better understanding of immune and endocrine responses to polychlorinated biphenyl (PCB) exposure in brown bullheads (Amieurus nebulosus) and Atlantic salmon (Salmo salar). This legacy compound clearly modulated the immune response in both species, and likely predisposes these animals to disease. Interestingly, short-term short-duration exposures to environmentally relevant concentrations during early development can have long-term effects on T-cell populations of the immune system in salmon. These laboratory studies facilitated the interpretation of data collected from a multi season field study in the Ashtabula River where PCB contamination is thought to have negative impacts on resident biota. This applied field study utilized brown bullheads and largemouth bass (Micropterus salmoides ) collected from the Ashtabula River and a reference site, Conneaut Creek. Histological, immunological, allometric and endocrine biomarker endpoints provided strong evidence that fish from the Ashtabula River are biologically different than those from the reference site. Data also emphasized the advantage of a multi-tier, multi-species, multi-season sampling approach. The biological data were supported by body burden chemical analysis. Lastly, two diseases of bullheads resulting from Edwardsiella ictaluri and Henneguya gurlei were descrbed, and further the understanding of infectious diseases of this sentinel fish.^

The following purposes were established for the study: 1. To determine the scope of the area known as aquatic art. 2. To determine the basic knowledge and understandings necessary for competent teaching in the area of aquatic art. 3. To present in the form of a handbook principles and procedures for organizing, administering, and conducting an aquatic art program.

Biogeographic barriers have limit the movement of organisms, leading to speciation and shaping the development of unique regional biotas. Human-aided circumvention of biogeographic barriers, however, has increased the connectivity of isolated biotas, while changes in climate have been altering species geographic ranges, restructuring ecological networks, modifying ecological niche arrangements and increasing the frequency and intensity of natural pulse disturbances. In this context, examination of some of the most fundamental processes underlying the patterns of species diversity and community structure across biogeographical scales is therefore vital, especially as humans increasingly modify these relationships established over the course of geological history. The latitudinal diversity gradient is the most well-established and predominantly studied biogeographic diversity pattern on Earth. Higher tropical biodiversity with a decline towards higher latitudes occur in both hemispheres and has been observed for various systems including terrestrial, freshwater and marine. In my dissertation, I explored latitudinal variation in factors that can inform and modify fundamental ecological principles such as coexistence, community stability, and resistance. I studied communities of marine invertebrates across over 7000 km of continuous coastal habitat spanning 47-degree latitudinal range on the Eastern North and Central Pacific coast, from tropical Panama to subarctic Alaska. Experiments were based on the manipulation of recently recruited or adult communities of sessile marine invertebrates, such as barnacles, marine worms and encrusting colonial organisms. These organisms inhabit coastal ecosystems across continental scales and can colonize artificial substrates such as hull of commercial vessels that travel across oceans serving as vectors for marine biological invasions. Among my three aims I was able to: (1) examine how the complementarity of ecological niches varies from the tropics to subarctic among recruiting taxa, and how the differentiation of these recruitment pulses through time help inform coexistence across large spatial scales; (2) document distinct resilience responses to pulse disturbances between lower and high latitude sites, while exploring the interplay between compositional and functional recovery in biological communities; and finally, (3) implement a novel component to pre-existing models to predict probability of biological invasions based on the distinct pressures of propagule introduction, environmental similarity between donor and recipient regions, and the potential for biotic resistance. My dissertation yields empirical evidence of processes varying with latitude, advancing our knowledge in some of the most fundamental questions in classic and contemporary ecology. Large-scale documentation of the mechanisms and processes that maintain global patterns of biodiversity are uppermost in the design of global conservation strategies, especially in a more connected world. / Biology

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