Three populations of Glossosoma nigrior Banks (Trichoptera: Glossosomatidae) were compared to determine how differences in thermal regime might affect their life history as well as the growth of individuals within each population. Two populations were located in Big Stony Creek (Stations 1 and 2) while the third was located in Sinking Creek (Station 3). The thermal regimes at each station differed in their seasonal patterns of temperature change and the amount of heat accumulated annually. Aside from a brief period during the spring, Station 1 was the coolest, Station 2 was intermediate, and Station 3 (Sinking Creek) was the warmest of the three sites. Populations of G. nigrior at Stations 2 and 3 ex- hibited typical bivoltine life histories. However, the population at Station 1 was univoltine with larvae present only during the summer. Comparisons among the three summer cohorts present at each station indicated that individuals growing under cooler thermal regimes were larger and grew more rapidly than did individuals exposed to warmer temperatures. A similar pattern was observed between the winter and summer cohorts located at Stations 2 and 3; members of the winter cohort at each station attained higher final dry weights and entered the prepupal stage more rapidly than did their summer cohort counterparts. The larger body size attained by G. nigrior living under cooler thermal regimes suggests that this trichopteran is metabolically more efficient at cooler temperatures. With less of its metabolized energy being allocated for maintenance costs, a large individual may channel more energy towards reproductive efforts. The flexibility in voltinism and differing body size (and thus reproductive capacity)of each cohort are advantageous life history features that have allowed G. nigrior to inhabit areas that may be only thermally suitable for this species during certain periods of the year. This ability to adjust its life history strategy to thermal conditions of a given habitat has allowed G. nigrior to expand its geographic distribution from cool mountain streams to warm water lotic habitats. / Ph. D.

The purpose of the investigation presented in chapter 1 was to determine which of the following artificial stream designs would be most logistically simple yet effective in maintaining riffle insects during a 30-d bioassay: 1) static and no current (S-NC); 2) flow-through and no current (FT-NC); 3) static with current (S-C); or 4) flow-through with current (FT-C). Flow-through and current, when provided, were 12 ml min⁻¹ and 30 cm sec⁻¹, respectively. Streams were covered by emergence traps, and daylight equivalent lights provided a natural photoperiod. The four stream designs were evaluated in triplicate based on changes in insect species-abundances after 30 d. Test organisms were transferred to the artificial streams in rock-filled containers previously colonized for 30 d in a third-order mountain stream riffle. Relative to benthic samples taken directly from the source riffle, the artificial substrates selected for collector-filterers and against collector-gatherers. The FT-C and S-C stream designs maintained most taxa at or above initial densities. Emergent adults comprised a large proportion of mayfly and chironomid densities and must be monitored during bioassays with aquatic insects. The Investigation reported in chapter 2 was conducted to determine if contaminant-induced changes in macroinvertebrate and periphyton communities in laboratory stream microcosms could be used to predict macroinvertebrate and periphyton responses In a natural stream receiving the same contaminant. The microcosms were dosed in quadruplicate with four (0.0, 0.1, 1.0, and 10.0%) concentrations of a complex effluent; these concentrations reflected those in the field. Mayfly densities in the microcosms were significantly (P≤0.05) reduced at 1.0 or 10.0% effluent depending on species. Hydropsychlds were not affected by the effluent, and chironomids and periphyton were stimulated. Overall, the stream microcosms accurately predicted the macroinvertebrate and periphyton response observed in the field. Chapter 3 compared responses to a complex effluent from microcosms of indigenous macroinvertebrates and protozoans to responses observed in acute tests with Daphnia magna, Ceriodaphnia dubia and Pimephales promelas and chronic survival and reproductive tests with C. dubia The predictive utility of these various tests was then evaluated against observed effects in the receiving stream. The LC₅₀_s (% effluent) from the acute tests were 63.09 for Pimephales promelas, 18.8 to 31.3 for Daphnia magna and 54.7 for Ceriodaphnia dubia. Results from 7-day chronic tests indicated that C. dubia survival was significantly (P≤0.05) affected at 30% effluent and reproduction was affected at concentrations ≥3.0% effluent. In the protozoan microcosms, community composition was significantly (P≤0.05) changed at 1.0%; while protozoan species richness was significantly reduced at 3.0% effluent. The microcosms not only were the most sensitive indicators of effluent toxicity, they also correctly predicted which indigenous organisms would be lost and which would be stimulated at various ambient concentrations of the effluent. In the fourth chapter canonical discriminant analysis, 2 diversity indices, and 7 community comparison indices were evaluated to determine their utility in quantifying macroinvertebrate response to a complex effluent in laboratory microcosms. A permutation and randomization procedure was used to test the hypothesis of no treatment effect based on the community comparison indices. The Bray-Curtis index provided the most meaningful condensation of the data. / Ph. D. / incomplete_metadata

Grazing pressure is important in structuring plant communities, particularly in aquatic environments. Eelgrass (Zostera marina), a keystone species in estuaries across North America, is experiencing widespread population declines. As a keystone species, eelgrass provides numerous important functions, including: 1) water filtration, 2) sediment stabilization, 3) providing refuge and nursery habitat for numerous species, and 4) carbon sequestration. Benefits which could be lost if eelgrass beds continue to diminish. California has experienced some of the greatest eelgrass declines, and Morro Bay, CA experienced a 96% decrease in eelgrass from 2007 to 2017. Most studies to date have examined bottom-up stressors, such as sedimentation and nutrient load, but little research has been done on top-down effects. Brant geese (Branta bernicla) are specialist grazers of eelgrass, feeding voraciously on it in the winter and spring months to build energy stores for their flight to summer breeding grounds in Alaska. Simulated brant grazing studies conducted in Humboldt, CA indicate brant might play an important role in maintaining the health and productivity of eelgrass communities through selective grazing and overcompensation – where plants purportedly grow more in response to herbivory. While there has been some experimental evidence of overcompensation, the idea is not well supported overall. Research was conducted on eelgrass beds in Morro Bay over the 2018-19 brant season. We hypothesized that: 1) brant grazing would decrease growth and overall condition of eelgrass; and 2) brant would selectively graze younger, nitrogen-rich blades. Four study sites were established, each with four open plots that allowed for natural brant grazing (treatment), and four enclosed plots that excluded brant and prevent grazing (control). Polyvinyl chloride (PVC) pipe was used to create cage-like structures around small plots of eelgrass, thus excluding brant, and exclosure effectiveness was confirmed with rigorous observations. Data on eelgrass growth and brant activity was gathered regularly at each site. We predicted that: 1) eelgrass open to brant grazing would show decreases in blade length, stipe density, and other growth and condition proxies before and after brant season when compared with eelgrass protected from brant grazing; and 2) eelgrass grazed by brant would have more epiphytes because brant selectively graze younger blades and leave older blades that accumulate more epiphytes. There were no significant differences in growth or condition of eelgrass between grazed (treatment) and ungrazed (control) plots. Brant activity was detected at each study site and brant exclosures were effective, with no evidence of brant grazing found in control plots. There was no difference in epiphyte load between grazed and ungrazed plots. The findings of this study are contrary the only previous studies examining the relationship between brant grazing and eelgrass growth. Our study suggests brant do not have a significant effect on eelgrass in Morro Bay.

Leaf litter is a major nutrient source for aquatic detrital food webs, fueling the microbes and macroinvertebrates that colonize it. Litter is especially important as a nutrient source for macroinvertebrates in headwater streams that tend to have lower primary production than higher-order stream systems. Understanding how litter decomposition and macroinvertebrates interact at large scales facilitates predictions about how stream ecosystems will change over space and time with regards to allochthonous nutrient inputs. We utilized a subset of the National Ecological Observatory Network's wadeable stream sites to deploy a litter pack study across the United States and Puerto Rico to determine the controlling factors for litter decomposition and associated macroinvertebrate assemblages, abundances, and species richness at a national scale. We found that litter species was the most important contributing factor to litter decomposition, and despite litter decomposition differences from stream to stream, the relative differences in decomposition rate between litter types was very similar. Stream identity, temperature, and flow also played roles in affecting decomposition patterns. In contrast to litter decomposition, litter species did not significantly contribute to variation in macroinvertebrate assemblages, abundance, or species richness, though environmental variables did impact abundance and species richness. These results suggest that there is functional redundancy in aquatic detritivore communities at large scales, and that the assemblages colonizing different species of leaf litter–despite being similar–might be functioning differently.

This thesis looks into the use of historical macrophyte records to assess long term changes in macrophyte communities in lakes and potential reasons for these changes. In particular it uses historical records to assess changes in macrophyte communities in the Norfolk Broads and West Midland Meres, two sets of lowland, eutrophic lakes in England. It provides a critical examination of the use of historical records, highlighting some of the constraints common to such data such as variations in recording effort, and bias in species recording and site selection. Having acknowledged these issues we then go on to develop a robust way to interpret such data, using a “change index” based on species persistence over the last 200 years within individual lakes. Species with high change index values, which represented species which had persisted or increased within the lake districts, were those known to be characteristic of eutrophic lakes. Conversely species with low index scores, which had declined in both the broads and meres over the last 200 years, included species associated with less fertile conditions but also a selection of typically eutrophic species. Averaging of change index scores in present day survey data served to identify the historically least changed lakes and to rank lakes in order of degree of botanical change over the last century. We then analysed the ecological basis of the change index in order to better understand the processes behind the decline of some species and survival of others in the Norfolk Broads and West Midland Meres. Functional groups determined from morphological and regenerative traits displayed significant differences in change index values in both groups of lakes, but declining taxa occurred across a wide range of plant growth forms. Non-hierarchical clustering of species based on their ecological preferences, obtained from published literature, resulted in groups with distinct change index values, indicating that changes in the status of species could be partly explained by these preferences. Of these, trophic preference was consistently the most important, with species of less fertile habitats consistently experiencing the greatest declines. However, some characteristically eutrophic species have also declined significantly, particularly in the broads. In these cases increasing loss of shallow water, low energy habitats in the broads, or loss of fluctuating water levels and less alkaline backwaters in the meres, appear to have been contributory factors. In addition to the change index approach, we also used historical records at a site level to complement palaeolimnological analysis and investigate the change in macrophyte community composition and structure at Barton Broad, Norfolk. Sediment samples were extracted from the bottom of the broad and analysed for sub-fossil remains and pollen of macrophytes. The historical records and palaeolimnological analysis combined showed that early communities did not consist entirely of low growing, oligotrophic and mesotrophic species as previously thought, but in fact comprised a mixture of these and other more characteristically high nutrient species associated with taller, or free-floating growth habit. As eutrophication progressed throughout the last century, the community was increasingly dominated by these latter growth forms. Diversity was maintained, however, since encroaching reedswamp generated a mosaic of low energy habitats which supported a range of species unable to withstand the hydraulic forces associated with more open water habitat. When the reedswamp disappeared in the 1950s, many of the dependent aquatic macrophytes also declined resulting in widespread macrophyte loss. The thesis demonstrates not just the complexities of using historical records, but also ways in which these can be overcome to make useful observations about macrophyte community change and lake ecological integrity to inform conservation and lake management, both on a site and lake district level.

Annual energy budgets of dominant benthic macro-invertebrates were examined during November 1973 to October 1974 from the benthos of a small pond ecosystem in north-central Texas. Estimates of annual secondary production (Hynes and Coleman 1968) were Procladius s. (Diptera, Chironimidae), 2.4 g m^-2 y^-1 (13 kcal m^-2 y^-1 ); Tendipes decorus (Diptera, Chironomidae), 6.0 g m^-2 y^-1 (40 kcal m^-2 y^-1 ); Brachycercus sp. (Ephemeroptera, Caenidae), 1.9 g m^-2 y^-1 (11 kcal m^-2 y^-1). Energy metabolism was measured in the laboratory at six seasonally encountered temperatures (5, 10, 15, 20, 25, and 30 C) on an acclimatization basis, and then extrapolated to the field. Estimates of annual energy metabolism are Procladius sp., 5.0 kcal m^-2 y^-1 ; Tendipes decorus, 17.2 kcal m^-2 y^-1 ; Brachycercus sp. 40.0 kcal m^-2 y^-1.

Phylogeography aims to understand the processes that underlie the distribution of genetic variation within and among closely related species. Although the means by which this goal might be achieved differ considerably from those that spawned the field some thirty years ago, the foundation and conceptual breakthroughs made by Avise are nonetheless the same and are as relevant today as they were two decades ago. Namely, patterns of neutral genetic variation among individuals carry the signature of a species’ demographic past, and the spatial and temporal environmental heterogeneity across a species’ geographic range can influence patterns of evolutionary change. Aquatic systems throughout Mexico provide unique opportunities to study phenotypic plasticity and evolution in relation to climatic and environmental selective forces. There are several unique, often isolated aquatic environments throughout Mexico that have a history of geographic isolation and reconnection. The first study presented herein shows significant mitochondrial sequence divergence was also discovered between L. megalotis populations on either side of the Sierra de San Marcos that bisects the valley of Cuatro Ciénegas and that the populations in the valley are genetically distinct from those found outside of the valley. The second study recovered signals of two divergence events in Cuatro Ciénegas for six codistributed taxa, and reveals that both events occured in the Pleistocene during periods of increased aridity suggesting that climatic effects might have played a role in these species’ divergence. The final study presents an Illumina-based high-resolution species phylogeny for Astyanax mexicanus providing added support that there are multiple origins to cave populations and further clarifying the uniqueness of the Sabinos and Rio Subterráneo caves.

Chaoborus Lichtenstein (Diptera: Chaoboridae) é um gênero de mosquitos com 44 espécies descritas, das quais 13 ocorrem na região Neotropical. Os adultos são frágeis e delicados, às vezes pouco pigmentados variando entre esbranquiçados, amarelados, acastanhados e acinzentados, sendo conhecidos em países anglófonos como \"phanton midges\". Possuem dimorfismo sexual facilmente reconhecido, pois os machos possuem corpos alongados e transparentes, pedicelos largos e antena plumosa e as fêmeas são menores e mais robustas, devido à presença de ovos em seu abdome, pedicelos globosos, pequenos e antenas verticiladas, com poucas cerdas. Os últimos estudos sobre as espécies neotropicas remontam da década de 1950, as descrições, chaves de identificação e pontos de ocorrência são desatualizados e pouco informativos, motivando o desenvolvimento desta revisão taxonômica. Estágios imaturos de caoborídeos, especialmente as larvas planctônicas, são conhecidas pelos hábitos predatórios na coluna dágua onde fazem migração vertical, agindo no controle populacional das presas em ambientes aquáticos lênticos - de poças a reservatórios. Neste estudo, quatro espécies novas foram descritas, 13 espécies são redescritas e ilustrações do abdome, tórax, terminália masculina, habitus de fêmeas e machos são apresentadas. Mapas de distribuição para cada espécie e uma chave de identificação foram também atualizados. / Chaoborus Lichtenstein (Diptera: Chaoboridae) is a genus of midges with 44 known species, of which only 13 ocurs in Netropical Region. The adults are very delicate and fragile, usualy whitish, yellowish or brownish to grayish, known in Anglophone countries as phantom midges. The sexual dimorphism is easily recognized, as males have long body, transparent, enlarged globular pedicel, plumose antenna while females are shorter, broad, because of the eggs in your abdome, have small globular pedicel and antenna merely setose. The last studies about the Neotropical species are from the 50\'s and the descriptions, identification keys and geographic records are not informative, motivating this taxonomic revision. Immature stages of chaoborids, especially the planktonic larvae, are known for predatory habits in the water column where they migrate vertically, acting on the population control of prey in lentic aquatic environments - from pools to reservoirs. In this study, four new species are described, 13 species are redescribed and ilustrations of abdomen, thorax, male terminalia, habitus of male and female are presented. Distribution maps of each species and an identification key were updated.

Resumo: Clicar acesso eletrônico abaixo. / Orientador: Edivaldo Domingues Velini / Coorientador: Fernando Tadeu de Carvalho / Banca: Luis Fernando Nicolosi Bravin / Banca: Robinson Antonio Pitelli / Mestre

Hui Shun Ki. / "Architecture Department, Chinese University of Hong Kong, Master of Architecture Programme 2003-2004, design report." / Includes bibliographical references (leaf 42).