Spatial variability in the hyporheic zone refugium of temporary streams

A key ecological role hypothesized for the hyporheic zone is as a refugium that promotes survival of benthic invertebrates during adverse conditions in the surface stream. Many studies have investigated use of the hyporheic refugium during hydrological extremes (spates and streambed drying), and recent research has linked an increase in the abundance of benthic invertebrates within hyporheic sediments to increasing biotic interactions during flow recession in a temporary stream. This study examined spatial variability in the refugial capacity of the hyporheic zone in two groundwater-dominated streams which flow permanence varied over small areas. Two non- insect taxa, Gammarus pulex and Polycelis spp. Were common to both streams and were investigated in detail. Hydrological conditions in both streams comprised a four- month period of flow recession and low flows, accompanied by reductions in water depth and wetted width. Consequent declines in submerged benthic habitat availability were associated with increases in population densities of mobile benthic taxa, in particular G. pulex

The ecology of constructed ponds on the lower Waikato River floodplain: implications for waterfowl management

Numerous ponds have been constructed in recent years on the lower Waikato River floodplain yet many waterfowl populations are in decline. Overseas research highlights the importance of constructed ponds for waterfowl populations; however, no comprehensive research has been carried out in New Zealand. The overarching aim of this research was to investigate how the ecology of constructed ponds on the lower Waikato River floodplain influences waterfowl densities, community composition and juvenile productivity. The study involved 34 constructed ponds which were predominantly found around Lakes Waikare and Whangape, and the internationally significant Whangamarino wetland. Data were collected on the physicochemical, landscape and vegetation characteristics of the ponds, as well as macroinvertebrate and fish assemblages to determine relationships between and within abiotic and biotic pond factors. Waterfowl communities were observed four times between September and December 2013 to determine mean densities of waterfowl per hectare and the mean community composition of each pond. The waterfowl data were used to explore key relationships with abiotic and biotic factors. Site hydrology was found to have a significant influence on macroinvertebrate and fish community composition. The relative abundance of macroinvertebrates was predominantly lower in degraded ponds which were characterised by water supplied by swamps that frequently flood. Benthic macroinvertebrate abundance was lower in temporary ponds, indicating pond permanence was important. Fish communities of frequently flooded ponds were characteristic of pest fish as a result of increased connectivity. Ponds with high pest fish biomass, especially koi carp (Cyprinus carpio), tended to be more turbid with relatively low macroinvertebrate abundance. The percentage of pond margin fenced had consistently high explanatory power for differences in community composition of macroinvertebrate and fish communities. Food availability and physical pond characteristics were important for waterfowl. Higher waterfowl abundances were found on ponds with high food availability, larger areas, and high pond complexity. Waterfowl densities were higher on ponds with lower fish biomass which is likely a result of decreased competition for macroinvertebrates as food. The suitability of a pond for waterfowl appeared to be species-specific. Broods were often encountered on ponds with large areas, high complexities, and increased marginal fencing. This study has allowed for the development of a conceptual model of the relationships between pond attributes and waterfowl communities. The findings of this study indicate habitat heterogeneity at the landscape scale is important for waterfowl. Providing a network of heterogeneous ponds across the landscape will provide enough varied habitat to support diverse and abundant waterfowl communities, and should include ponds of varying sizes, shapes, depths, vegetation and hydrology. It is also important to construct permanent ponds with limited flood frequency. Excluding pest fish and livestock from ponds will likely increase waterfowl use, and brood occupancy, of ponds as a result of improved water quality and reduced competition for food with fish

Dispersal Capabilities of Two Plecopteran Species and Macroinvertebrate Community from Four Watersheds in Northeast Ohio

This dissertation focused on the insect order Plecoptera, and hypothesized that Allocapnia recta populations would have lower genetic diversity than Leuctra tenuis between adjacent Chagrin and Grand Rivers due to wing structure and season of terrestrial adult emergence. Genetic variations within the 16s rRNA region of mtDNA in A. recta, a winter emerging adult with rudimentary wing structure, and L. tenuis, a summer emerging adult with fully developed wings, were compared and revealed significant genetic variability between A. recta samples from the two rivers (FST = 0.20) but not between L. tenuis samples (FST = 0.07). Further genetic variation investigation used A. recta, populations, within and between the Chagrin River and Grand River, hypothesized that differences in populations is a function of distance, and that greater distance leads to greater genetic variability. To strengthen the robustness of this work, samples were collected from two additional watersheds, the Rocky and Cuyahoga Rivers. Genetic variation of A. recta populations differed significantly across all four watersheds, especially between the Cuyahoga and Grand Rivers (G\u27ST = 1), Rarity of movement regardless of distance suggests that other factors have a more profound effect than previously thought - factors that include human influences. The unresolved genetic variation of A. recta and potential human influence resulted in a holistic examination of macroinvertebrate community structure and ecology within the four watersheds. Both legacy land use and anthropogenic disturbance effects on seasonal variation were examined and it was hypothesized that: (1) greatest species diversity and richness among stoneflies and other macroinvertebrates will occur during the summer months, when weather conditions in Ohio are more conducive. (2) The greatest species diversity and richness among stoneflies and other macroinvertebrates will occur where the landscape has been historically less disturbed. The results revealed inconsistencies in season

Dispersal Capabilities of Two Plecopteran Species and Macroinvertebrate Community from Four Watersheds in Northeast Ohio

This dissertation focused on the insect order Plecoptera, and hypothesized that Allocapnia recta populations would have lower genetic diversity than Leuctra tenuis between adjacent Chagrin and Grand Rivers due to wing structure and season of terrestrial adult emergence. Genetic variations within the 16s rRNA region of mtDNA in A. recta, a winter emerging adult with rudimentary wing structure, and L. tenuis, a summer emerging adult with fully developed wings, were compared and revealed significant genetic variability between A. recta samples from the two rivers (FST = 0.20) but not between L. tenuis samples (FST = 0.07). Further genetic variation investigation used A. recta, populations, within and between the Chagrin River and Grand River, hypothesized that differences in populations is a function of distance, and that greater distance leads to greater genetic variability. To strengthen the robustness of this work, samples were collected from two additional watersheds, the Rocky and Cuyahoga Rivers. Genetic variation of A. recta populations differed significantly across all four watersheds, especially between the Cuyahoga and Grand Rivers (G\u27ST = 1), Rarity of movement regardless of distance suggests that other factors have a more profound effect than previously thought - factors that include human influences. The unresolved genetic variation of A. recta and potential human influence resulted in a holistic examination of macroinvertebrate community structure and ecology within the four watersheds. Both legacy land use and anthropogenic disturbance effects on seasonal variation were examined and it was hypothesized that: (1) greatest species diversity and richness among stoneflies and other macroinvertebrates will occur during the summer months, when weather conditions in Ohio are more conducive. (2) The greatest species diversity and richness among stoneflies and other macroinvertebrates will occur where the landscape has been historically less disturbed. The results revealed inconsistencies in season

Dispersal Capabilities of Two Plecopteran Species and Macroinvertebrate Community from Four Watersheds in Northeast Ohio

This dissertation focused on the insect order Plecoptera, and hypothesized that Allocapnia recta populations would have lower genetic diversity than Leuctra tenuis between adjacent Chagrin and Grand Rivers due to wing structure and season of terrestrial adult emergence. Genetic variations within the 16s rRNA region of mtDNA in A. recta, a winter emerging adult with rudimentary wing structure, and L. tenuis, a summer emerging adult with fully developed wings, were compared and revealed significant genetic variability between A. recta samples from the two rivers (FST = 0.20) but not between L. tenuis samples (FST = 0.07). Further genetic variation investigation used A. recta, populations, within and between the Chagrin River and Grand River, hypothesized that differences in populations is a function of distance, and that greater distance leads to greater genetic variability. To strengthen the robustness of this work, samples were collected from two additional watersheds, the Rocky and Cuyahoga Rivers. Genetic variation of A. recta populations differed significantly across all four watersheds, especially between the Cuyahoga and Grand Rivers (G\u27ST = 1), Rarity of movement regardless of distance suggests that other factors have a more profound effect than previously thought - factors that include human influences. The unresolved genetic variation of A. recta and potential human influence resulted in a holistic examination of macroinvertebrate community structure and ecology within the four watersheds. Both legacy land use and anthropogenic disturbance effects on seasonal variation were examined and it was hypothesized that: (1) greatest species diversity and richness among stoneflies and other macroinvertebrates will occur during the summer months, when weather conditions in Ohio are more conducive. (2) The greatest species diversity and richness among stoneflies and other macroinvertebrates will occur where the landscape has been historically less disturbed. The results revealed inconsistencies in season

The hyporheic zone as an invertebrate refuge: a review of variability in space, time, taxa and behaviour

The hyporheic zone is a potential refuge that can promote persistence of benthic invertebrates during adverse conditions in surface streams. For decades, changes in invertebrate depth distribution have been investigated in relation to flood, low flow and drying events, but evidence for use of the hyporheic refuge remains equivocal. This review examines the evidence for the hyporheic zone’s refugial role during adverse hydrological conditions. Refuge potential is influenced by determinants in four categories. First, refuge use varies spatially in relation to physical habitat parameters, including sediment porosity and hydrologic exchange. Second, refuge use is temporally variable and reflects disturbance characteristics including rate of onset. Third, refuge use is taxon-specific, depending on a range of morphological, behavioural and physiological traits. Fourth, the behaviours governing refuge use vary, with both active migrations and passive habitat use playing important roles in community persistence. These four determinants interact to influence refuge use; for example, the physical habitat providing an adequate refuge will vary between taxa. Despite this variability, the hyporheic zone is an important component in the suite of refuges that facilitate community resilience to disturbance events. As such, its ecological integrity should be safeguarded through sensitive management and effective rehabilitation schemes

ECOTOXICOLOGICAL IMPACTS OF RUN-OF-RIVER DAMS ON THE AMERICAN DIPPER (CINCLUS MEXICANUS) AND MOUNTAIN STREAM FOOD WEBS

Run-of-river (RoR) hydroelectric dams are an increasingly common alternate energy source on mountain streams. Despite reductions in size and greenhouse gas emissions compared to conventional impoundments, RoR dams may have ecotoxicological impacts through disruption of the natural flow regime. The American Dipper (Cinclus mexicanus) is a high trophic-level river bird that occupies mountain streams year-round and is a well-described indicator of stream health; thus, it is an ideal species to study potential impacts of RoR hydropower on river food webs. From August 2014 to November 2015, I conducted seasonal river bird surveys at 14 streams in coastal British Columbia, Canada and sampled food webs at 13 of these streams (7 regulated and 6 unregulated). Regulated streams create stable habitats that consequently supported significantly higher dipper densities (β=0.78, SE=0.36, p=0.030), a higher proportion of after hatch year (AHY) dippers, and consistent occupancy during breeding and non-breeding seasons compared with free-flowing streams. Analyses of stable isotope ratios in dipper whole blood revealed strong model support for differences in blood isospace between regulated and unregulated stream types, likely driven by the significantly lower invertebrate δ34S below RoR dams (p=0.010) and 34S-depleted blood at regulated streams (β=-2.42, SE=0.95, p=0.029). Given that the bacteria responsible for 34S-depleted food webs are also the primary methylators of inorganic mercury (Hg) into its toxic and bioavailable form, methylmercury (MeHg), I further investigated Hg levels in American Dippers and their prey. Despite the observation of distinct dipper isospace between stream types, there was no model support for differences in mean dipper blood (417.6 ± 74.1 S.E.) ng/g ww at regulated streams, 340.7 ± 42.7 S.E. ng/g ww at unregulated streams) or feather (1564 .6 ± 367.2 S.E. ng/g dw regulated, 1149.0 ± 152.1 S.E. ng/g dw unregulated) Hg concentrations between stream types. One recently regulated stream (Douglas Creek, Harrison Watershed), however, supported dippers with MeHg concentrations of toxicity concern (up to 8459.5 ng/g dw in feathers and 1824.6 ng/g ww in whole blood). With a negligible salmon subsidy at these streams and the absence of a known anthropogenic Hg point source, the elevated Hg concentrations recorded in dippers at this regulated stream could be explained by a combination of a) elevated atmospheric deposition of Hg in densely forested, temperate mountain streams, b) Hg-methylation by sulfate- reducing bacteria under anaerobic headpond conditions, and c) increased availability of high-protein prey. Slow-flowing, stabilized stream reaches regulated by RoR dams potentially offer an opportunity for dippers to exploit a consistent food resource closer to their high elevation breeding territory, enabling them to take on a year-round “resident strategy” that is more typical of low elevation river habitats. The enhanced microbial activity and MeHg production that can occur in RoR headponds, however, suggests that even small dams with minimal storage can create pond-like habitats that may act as ecological traps for river bird specialists. Although at this point there appear to be no effects of river regulation on body condition, future work is needed to determine if long-term chronic MeHg toxicity can impair productivity or survival of predatory river birds

Detecting Ecosystem Response to Restoration Efforts with Implications for Recovery of the Threatened June Sucker (Chasmistes liorus) in a Shallow, Eutrophic, Utah Lake

Environmental damage associated with a growing human population will increase globally without active management. Restoration can promote ecosystem recovery, yet often fails to produce desired results and may require decades to achieve noticeable benefits. Detecting small, incremental change sis imperative in these difficult situations. Here, I demonstrate that restoration focused on fish removal triggers incremental responses in aquatic plants and animals. Removing common carp is expected to encourage recovery of aquatic plants, increasing animal habitat, resulting in more macroinvertebrates (e.g., aquatic insects, snails). Carp removal should also increase water clarity, improving visibility for fishes, thus increasing their ability to find food. I examined the response of aquatic plants, macroinvertebrates, and fishes’ weight to carp removal in Utah Lake, UT, to demonstrate that plants and animals can serve as indicators of incremental changes following restoration. Submerged, native, non-woody, and mixed-plant communities were most common when carp were reduced. Macroinvertebrate predators, total unique types, and total weight varied among plant habitat types, where, in general, all were higher in plant habitats than bare sediment. Macroinvertebrate predators were highest in mixed plants, and total weight and total unique types were both much higher in mixed plants than bare sediment. Neither total unique macroinvertebrate types nor total weight were influenced by carp population changes, but white bass (Morone chysops) weight was much greater when carp were reduced. However, other environmental conditions can also influence aquatic plants and animals, and may limit the benefits achieved with carp removal. Indeed, I found that the benefits of carp removal are reduced if water levels are not maintained. Aquatic plants decreased as lake level declined and plant habitat was completely absent at very low lake levels. Additionally, the total unique types of macroinvertebrates and walleye (Sander vitreus) weight both decreased with lower lake levels. Water clarity did not respond to carp population changes, nor did it influence fishes’ weight. Identifying relationships between carp removal, aquatic plants and animals, and other environmental conditions provides a useful framework for detecting incremental changes caused by restoration, while simultaneously capturing the effects of multiple environmental conditions including drought