The Trinity River is an urbanized, effluent-dominated river, and is heavily relied upon for drinking water. The benthic macroinvertebrate community has been monitored for over 20 years, with the focus of this dissertation on three studies (1987-88, 2005, and 2011). Water quality improvement following dechlorination resulted in increased benthic metrics. Overall habitat quality, in-stream cover, surface water total organic carbon, sediment total organic carbon, near-field urban land-use, near-field forested land-use, surface water surfactant toxic units, and depositional sediment biofilm fatty acids all have statistically significant relationships with benthic macroinvertebrate metrics. These relationships are better defined with increased taxonomic resolution at the genus/species level for all benthic taxa, including Chironomidae and Oligochaeta. It is recommend that benthic identifications for state and city water quality assessments be done at the genus/species level. A novel method for quantifying depositional sediment biofilm fatty acids has been produced and tested in this dissertation. Benthic metrics are directly related to fatty acid profiles, with several essential fatty acids found only at upstream sites.

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This post-fire study was conducted to characterize and observe fire induced changes in physical habitat parameters, water-quality conditions and macroinvertebrate assemblages in the Little Creek watershed, a tributary to Scotts Creek located in Cal Poly’s Swanton Pacific Ranch in Davenport, California. Pre-fire data was collected by a Cal Poly student, John Hardy, for his 2017 thesis. Post-burn bioassessment surveys for this study were repeated at four of the same study sites used by Hardy to provide comparisons to the California Stream Condition Index via a modified version of the State of California’s Surface Water Ambient Monitoring Program protocol. Macroinvertebrates were taxonomically identified to the family level. Commonly used bioassessment indices were utilized in conjunction with Stepwise regression and Analysis of Variance on both pre- and post-fire datasets to illustrate how physical habitat and water quality parameters changed after the fire and to determine the significance of collected environmental variables (stream shading, cross sectional area, and median particle size) as predictors of macroinvertebrate community structure. Despite most of Little Creek having moderate and high burn severities, it was found that physical habitat, water quality and benthic macroinvertebrate populations were not greatly disturbed by the 2020 CZU lighting complex fire. Proportions of highly disturbance/pollution sensitive taxa and increased following the wildfire and there was a dramatic shift from collector-gatherer to predator organisms. Comparison of pre- and post-fire data in this study showed fire having a minimal effect on the studied watershed. Difference in study goals and associated protocols used in the pre- and post-fire studies and the low water year following the wildfire, complicates statistical comparisons and poses threat to the validity of results. However, there is opportunity for further investigation about the ability of an ecosystem to successfully recover from natural disasters and disturbances, specifically when there is little human impact (or influence) on the ecosystem.

Acid rain alters freshwater pH and ion composition, preventing organisms from performing essential bodily functions causing mortality. Macroinvertebrate communities in acidified streams are characterized by species loss in response to physiological stress and altered food quality resulting from the degradation of microbial (e.g., fungi on leaves) communities. Although freshwater acidification in the U.S. is lessening following reduced industrial emissions, little is known about macroinvertebrate recovery. Often, biotic recovery is assessed by looking at changes to what taxa and how many individuals are present in the community (e.g., richness, density). While providing a metric for change, changes in "who" is there (i.e., richness) doesn't necessarily tell us changes in "what" they are doing (i.e., function). The relationship between diversity and function requires linking a "who" to their "what" with direct measurements or as indicated by their traits. Traits are attributes of an organism that aggregate biological, morphological, and behavioral information and may relate to their success in a particular environment. For example, taxa that cannot survive with stream drying (not desiccation resistant) may only be found in streams with permanent water. Trait-based taxonomic metrics could bridge "who" and "what" and expand the impact of stream recovery assessments. My objective was to assess trends over time in water chemistry and macroinvertebrate taxonomic and trait richness and density following reduced industrial emissions. To do so, I studied two long-term data sets from Shenandoah National Park to assess trends in water chemistry and macroinvertebrate taxa and trait composition over a 30-year period to identify taxa and traits that are sensitive to acidification. I also measured how much biomass macroinvertebrates produced in a year (i.e., secondary production) in two streams (1 acidified; 1 not acidified) to determine taxa and traits that are functionally sensitive to acidification. I used these structural and functional measures of sensitivity to determine if changes in trait richness or density predict changes in the function of that trait (e.g., secondary production). Changes over time show that streams have some recovery from acid rain with increasing stream pH and a greater number of taxa and traits present in the community. Changes in taxa were greater than changes in traits over time. While this result was expected as multiple taxa make up each trait category, it may also suggest minimal or delayed functional recovery over time. Still, macroinvertebrate secondary production indicated that function did differ with differences in acidification. Therefore, observed small changes in traits over time mirror prior studies that found other variables, such as competition for food or space, delay or inhibit macroinvertebrates from returning to the recovering streams. Additionally, there were similarities between traits changing over time and the secondary production of traits that differed between more and less acidified streams. Taxa characterized by long life spans and large body size (e.g., semivoltine, long adult life, slow seasonal development) appeared to be the most sensitive to changes in acidification. These findings suggest that some compositional attributes, like taxonomic or trait richness, may predict functional changes measured as secondary production while others, such as density, do not. / Master of Science in Life Sciences / Acid rain causes the acidification of freshwater stream water observed as decreased stream pH and decreased ability of watershed soils to neutralize or "soak up" acidic inputs before they enter the stream. These changes in stream water chemistry inhibit the ability of aquatic animals to perform essential bodily functions resulting in mortality. The total number of aquatic insect taxa and total number of individuals in the community have been found to decrease in response to acidification. Although freshwater acidification is lessening following reduced industrial emissions, little is known about if and how aquatic insects can recover. Often, aquatic insect recovery is assessed through looking at changes to what taxa and how many individuals are present in the community. While providing a metric for change, changes in "who" is there (i.e., richness) doesn't necessarily tell us changes in "what" they are doing (i.e., function). The relationship between diversity and function requires linking a "who" to their "what". This is often done by assessing changes in the taxa present but also looking at how the composition of traits associated with those taxa also change. Traits or taxa-specific characteristics aggregate biological, morphological, and behavioral information and may relate to their ability to live in a given environment. For example, taxa that rely on filtering and consuming fine particles may only be found in faster flowing streams where they function to remove fine particulates. Trait-based assessments could link "who" and "what" to expand our understanding of how stream ecosystems change with a stressor. My objective was to assess recovery of streams in Shenandoah National Park following reduced industrial emissions. To do so, I studied two long-term (1987-2017) data sets from to assess trends in water chemistry and macroinvertebrate taxa and traits. This enabled me to determine "who" is changing in these streams over time. I also measured how much insect biomass s produced in a year (i.e., secondary production) in two streams (1 more acidic; 1 less acidic) to determine what taxa and traits alter "what" (e.g., secondary production) they are doing. I found that long-term trends indicate some recovery from acid rain with improving water quality and an increased number of insect taxa and traits present in the community over time. Changes in insect taxa were greater than changes in their traits suggesting that stream acidification did not greatly alter "what" the insects are doing greatly to begin with or that recovery may be delayed. In contrast, my secondary production study showed that "what" macroinvertebrates are doing does differ in more or less acidic streams. Therefore, our observed minimal changes in traits over time suggest that other variables, such as competition for food or space, delay or inhibit macroinvertebrates from returning to the recovering streams. Additionally, there were similarities between traits changing over time and traits that were different in the more or less acidic streams. Taxa characterized by long life spans and large body size (e.g., semivoltine, long adult life, slow seasonal development) appeared to be the most affected by differences or changes in stream water acidity. These findings suggest that changes in "who" can predict changes in "what" to some degree though static metrics of abundance do not always reflect the function of the taxa or community.

I investigated the role of land use in structuring benthic invertebrate assemblages in agricultural streams in the French Broad River drainage in western North Carolina. I sampled six agricultural streams (3 with cleared headwaters and 3 with forested headwaters) at three points along a gradient (headwaters, a midpoint, and a downstream site). At each site, I measured a variety of physico-chemical parameters, including temperature, chlorophyll a, discharge, nutrients, and suspended solids. Invertebrates were sampled at all sites in October 1996 and April 1997. Riparian vegetation was assessed for each site at mutiple spatial scales using GIS data from the 1950s, 1970s, and 1990s. Forested agricultural (FA) streams had more riparian vegetation than cleared agricultural (CA) streams in both the 1950s and the 1970s. Cleared agricultural streams had less organic matter, more primary production, higher nitrates, and warmer temperatures than FA streams. Total and EPT taxa richness was greater in FA streams. Pollution-sensitive Plecoptera were relatively more abundant in FA streams, while tolerant Diptera were more abundant in CA streams. High diversity and Plecoptera abundance was related to high habitat quality, more riparian vegetation, low nitrates, and low summer temperatures. Higher invertebrate diversity was related to the land use 25-50 years as well as the current land use (forested, moderate agriculture, or heavy cattle impact). These results indicate a long-term legacy of agricultural influences on stream invertebrate assemblages. / Master of Science

A wetland passive treatment system (PTS) was used to treat mine effluent flowing into East Prong Creek, Virginia. Prior to treatment, copper concentrations in the stream ranged from 8.9 to 32.0 μg/L at the impacted sites and from 0.1 to 7.7 μg/L at the reference site. In kick samples, insect abundance (n) and the number of taxa (#) were reduced at the impacted sites (n = 31, 22, 33, 24 and # = 190, 246, 266, 345, at sites 2 - 5, respectively) relative to the reference site (n = 52, # = 973). Red maple (Acer rubrum) leaves broke down twice as fast at the reference site (k = -0.029) than at sites receiving the untreated effluent (k = -0.016, -0.013, -0.013, -0.013 at sites 2 - 5, respectively). In benthic samples and leaf packs, abundances of all functional groups were reduced at the impacted sites relative to the reference site. In terms of abundance, scrapers and predators were most and least affected by copper, respectively. Following treatment, copper concentrations at the impacted sites in East Prong Creek ranged from 0.1 to 14 μg/L. The wetland PTS was most effective at reducing metal concentrations in the effluent from July to December, when dissolved oxygen concentrations in and flow through the wetland cells were low. Functional recovery preceded recovery of community structure by at least six months. Decomposition rates were similar at all sites in Fall 1994, after six months of treatment (k = -0.012, -0.011, -0.011, -0.012, -0.012) at sites 1 - 5, respectively). Recovery of community structure was not complete after 1 year of treatment. Abundance of collector-filterers and predators recovered quickly following treatment, while recovery of collector-gatherers and shredders was slower. / Master of Science

Associative relationships among mangrove species and macroinvertebrate species were analysed for ecosystems of Xuan Thuy National Park. Census of mangrove species with allometric measurements was conducted in selected plots, and census of macroinvertebrate species was conducted in quadrats inside of mangrove species census plots. Correlational analysis among allometrically estimated aboveground biomass of mangrove species and population of macroinvertebrate species was examined by clustering method. High level of similarity was resulted for specific macroinvertebrate species with specific mangrove species in annual and seasonal basis. Moreover, indicator macroinvertebrate species is proposed based on indicator value index method. / Các mối quan hệ giữa thực vật ngập mặn và động vật không xương sống cỡ lớn được phân tích trong các hệ sinh thái của Vườn quốc gia Xuân Thủy. Khảo sát về số lượng của các loài cây ngập mặn cùng với các phép đo tương quan sinh trưởng được tiến hành trong các ô tiêu chuẩn, và nghiên cứu về thành phần loài và mật độ động vật không xương sống cỡ lớn được thực hiện trong các ô tiêu chuẩn này. Phân tích tương quan giữa sinh khối ước tính trên mặt đất của các loài cây ngập mặn và các quần thể động vật không xương sống cỡ lớn đã được thực hiện bằng phương pháp nhóm. Giữa các loài động vật không xương sống cỡ lớn đặc trưng với các loài cây ngập mặn đặc trưng đã cho thấy mức độ tương đồng cao theo năm và theo mùa. Hơn thế nữa, các loài động vật không xương sống cỡ lớn chỉ thị được đề xuất dựa trên phương pháp chỉ số giá trị chỉ thị.