The southern Appalachian forests of the United States are undergoing changes due to the death of hemlock trees attacked by the hemlock wooly adelgid. This paper addresses the management impacts of Rhododendron maximum removal in the riparian and upslope areas previously occupied by hemlock. This study measured the consequences macroinvertebrates faced due to riparian Rhododendron removal from 300 m reaches of two low order streams. Two additional low order streams served as reference sites for the experiment. The stream macroinvertebrate communities were assessed using a before-after controlled impact model comparing communities between fall 2014 to those from fall 2015 and from spring 2015 to spring 2016. Macroinvertebrate collections consisted of 288 samples with a total of 61,056 individuals. There was a significant increase in collector-gathers in both removal sites, mostly from increases in Ephemerellidae and Chironomidae. There was also a significant decrease in filter feeding organisms in the removal reaches. Traits analysis also revealed that several traits that are shared by collector gathers also increased, e.g., short life cycles that are related to the increase in Chironomidae. Using Nonmetric Multidimensional Scaling (NMDS) and permutational MANOVA significant annual differences in macroinvertebrates were found in all of the stream reaches during both seasons. However, the trait based NMDS and permutational MANOVA found significant change only in one removal site between fall collections based on traits. These finding are consistent with findings from logging and other riparian removal projects; suggesting that the short-term impacts of selective Rhododendron removal on benthic macroinvertebrates are comparable to that of logging activity. / Master of Science / The southern Appalachian forests of the United States are undergoing changes due to the death of hemlock trees attacked by the hemlock wooly adelgid. This paper addresses the management of Rhododendron removal in the riparian and upslope areas previously occupied by hemlock. This study investigates the consequences stream insects face due to near stream Rhododendron removal from 300 m section of two small streams. Two similarly sized streams served as reference sites for the experiment. The stream insect communities were assessed using a before-after controlled impact model comparing collections from the fall 2014 to those from fall 2015 and from spring 2015 to spring 2016. Insect collections consisted of 288 samples with a total of 61,056 individual insects. There was a significant increase in generalist feeding insects in both removal sites, mostly from increases in common mayflies and small non-biting midges. Analysis of insect attributes also revealed that attributes shared by generalist feeding insects also increase, e.g., short life cycles that are related to the increase in nonbiting midges. Looking at the insect communities we found annual changes in all of the stream reaches during both seasons. However, analysis of insect attributes found significant change only in one removal site between the fall collections. These finding are consistent with findings from logging and other riparian removal projects; suggesting that the short-term impacts of selective Rhododendron removal on stream insects are comparable to that of near stream logging activity.

Understanding the influence of disturbance, both natural and human-induced, is a persistent challenge in ecology. Recently, attempts to predict future environments have focused on the consequences of broad scale disturbances. In this thesis I focus on environmental and trophic disturbances as shapers of benthic assemblages. There is growing recognition of the need for greater scientific investment in understanding environmental disturbances to balance the continuing focus of research assessing trophic theories (e.g. herbivory). Historically, it is these theories that have provided a cornerstone to describe and manage subtidal rocky coasts worldwide. In this thesis, therefore, I first assess how our ecological perception of such disturbances (i.e. water pollution and harvesting grazers) may vary as a consequence of the choice of taxonomic classifications used to observe benthic patterns (Chapter 2). I then assess how mechanical disturbance (i.e. wave exposure) may affect the morphology of benthic habitat (Chapter 3) and how temperature disturbances (i.e. oceanographic, cold water pulsing) may affect the consumers of these habitats (Chapter 4). The critical first finding centred on the effectiveness of alternate scales and metrics of taxonomic classification to detect the effects of water pollution (i.e. nutrient enhancement) as the largest disturbing agent on the benthos, and that this effect may be exacerbated by loss of grazers. While observations of the benthos as morphological groups detected the effects of enhanced nutrients, species diversity (as a measure of phylogenetic relatedness) was the only one of the chosen measures sensitive enough to detect the interaction of both top-down and bottom-up stressors. This chapter highlights the importance of choice of classification (e.g. morphology v. species) and indices (e.g. Shannon index v. ABC curves and phylogenetic diversity) in their potential to predetermine our perception of ecological change and thereby predict future environments. Mechanical disturbance (i.e. wave exposure) has been widely studied as a mechanism that creates new space for colonisation by alternate species, but is less well studied as a force that can change the shape of communities by mediating their morphology. Macroalgal morphology varies in response to wave exposure such that individuals at high exposures are often smaller than individuals in more sheltered environments. Observations not only confirmed these patterns for a general assemblage on a wave exposed southern coast, but reciprocal transplants of assemblages between exposures also revealed that morphological differences were likely to be a product of flexibility in morphological response of algae to local environments (Chapter 3). In contrast to the often multi-directional responses of a complex suite of morphological characters (e.g. smoothness, stipe length, frond width), overall size has the potential to be used as a broad and predictive tool to identify hydrodynamic stressors across an entire exposure gradient or geographic range. Strong trophic interactions are often considered characteristic of aquatic systems and due to their perceived ubiquity on temperate rocky coasts, there has been an emphasis in the literature on the influence of herbivores in determining assemblages. Given the importance of the link between herbivores and assemblage structure, in my final chapter I investigated the potential for disturbance to act indirectly on benthos by affecting the survivorship of an herbivorous urchin (Chapter 4). I used observations of variable temperature regimes in a region of upwelling to design an experiment that tested whether this temperature variation could negatively affect the survivorship of settling sea urchins (Heliocidairs erythrogramma). When exposed to cold water, mortality increased by up to 70 %, within 12 h of settlement, representing a massive loss of benthic consumers within a very short time scale. This result was used to assess the potential of temperature to indirectly influence benthic habitats across several spatial scales, a process that may have been profoundly underestimated. In summary, this thesis provides insight into environmental and trophic disturbances as shapers of benthic assemblage patterns, both as natural and human-induced phenomena. I show that our perception of ecological response to the combination of such disturbances can be contingent on the organisational scales and metrics used. Subtle differences in initial choice of such observational units may not only have large affects on the kinds of benthic patterns and disturbances ecologists detect, but also those that they pursue. I recognise that while some physical disturbances can appear subtle (e.g. morphological variation) or strong (e.g. high mortality rate of herbivores), their relative impacts on the broader assemblage (e.g. understorey flora and fauna) will often be dependent on biogeography. Integrating local-scale biological interactions with regional-scale physical processes, therefore, appears to be a potentially progressive line of future enquiry. Indeed, consideration of responses from the physiological through to physical and biogeographical scales will not only strengthen our understanding of the effects of alternate disturbance regimes, but also our predictive power to anticipate future change. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339116 / Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2008

Thesis (Ph. D.)--University of Tartu, 2004. / Includes reprint of 6 previously published articles. Includes bibliographical references.

The benthic animals have important roles in benthic communities. Indicator organisms can tell things about a lakes status. Many of them are sensitive to acidification but there are also tolerant taxa. Some prefer eutrophic environments. The benthic fauna can therefore decide a lakes status since some species prefer different environments. The focus of this study was to compare benthic fauna within the littoral in the lakes Sidsjön and Vintertjärnen. They are situated a little south of Sundsvall, central Sweden and belong to the water system of Selångersån. The comparison was done at eight random locals in each lake at two occasions, during early and late summer to analyze if the benthic fauna differed between the two lakes and if it changed through the season. Five of the locals in each lake were protected and had soft bottoms and the remaining were exposed locals with hard bottom. Sidsjön is bigger than Vintertjärnen and has more variated bottom types so the biodiversity should be higher in Sidsjön. I also expect that the number of taxa should decrease during the later occasion due to hatchings. Three statistical analyses were done to see if these hypotheses were right or if they should be rejected. The two first analyses were ANOVA analyses, two-way with replication. The first ANOVA was for number of taxa and the second was for number of animals. The third analysis was a DCA analysis with the variables lakes, bottom types and emergent plants. ASPT index and Eq was also calculated and pH was measured during autumn for the lakes. The conclusion is that the there is no difference between the lakes but a significant effect when it comes to seasons according to the first ANOVA analysis. The second ANOVA analysis show that the lakes are not differing, that no factor is significant and there are no interactions. According to the DCA analysis there are differences between lakes and occasions when it comes to the variables. / <p>Datum för godkännande 2016-03-31</p>

Riparian buffers along stream margins have been widely adopted as a management strategy to mitigate the adverse effects of plantation forestry on stream ecosystems. However, the efficacy of these riparian buffers can be jeopardised by variations in width, length, and vegetation which can range from native and exotic scrub (including bracken, gorse, broom and blackberry) to remnant beech forest. This thesis investigates the influence of riparian vegetation age and composition, on stream ecosystems within exotic pine plantations. Initially, a survey of 50 streams within pine forests of various ages and riparian composition was conducted at sites from mid-Canterbury to Hanmer Springs over the summer of 2004-2005. Additionally, terrestrial subsidies were compared between young pine, mature pine and indigenous forest streams to ascertain differences or similarities between vegetation types. A range of physico-chemical and biological characteristics were recorded, while vegetative age and composition with catchment, riparian buffer and reach scales were determined using GIS. Forestry activities were found to vary temporarily and tended to adversely impact upon streams where riparian buffers were narrow and lacked indigenous vegetation. Stream instability and sedimentation were consistently higher in catchments lacking indigenous riparian vegetation, and more markedly so in recently harvested catchments compared with more mature forests. Streams dominated by pine forests had finer substrates with higher water temperatures and levels of turbidity, while those dominated by indigenous forest had coarser substrates, higher flows and dissolved oxygen levels, and less in-stream debris. Benthic community composition was similar among sites, although taxonomic richness, EPT diversity, and invertebrate abundances were enhanced by indigenous riparian vegetation.

Physicochemical factors, algal diversity, taxonomic composition and standing crop were investigated across a broad gradient of AMD stress in streams and rivers. 52 sites were surveyed in the vicinity of Greymouth, Reefton, Westport and Blackball, on the West Coast, South Island. Seven sites in the Reefton area were sampled from April 2006 - February 2007 to establish changes over time in benthic algal communities of AMD and reference streams. Longitudinal change and ecosystem recovery were also investigated by sampling eight sites down Devils Creek, Reefton, and two of its tributaries. AMD has negative impacts on algal diversity, generally increases the dominance of certain taxa and, where metal oxide deposition or hydraulic disturbance are not great, can lead to algal proliferations. These proliferations were chlorophyte dominated, predominantly by filamentous Klebsormidium acidophilum. From the general survey a total of 15 taxa were identified from the most severely impacted sites (pH <3.6), which included both acidophiles and acidotolerant algae. Multivariate analyses strongly suggest that pH was the dominant factor controlling taxonomic occurrence of diatoms, macroalgae and the structure of the total assemblage. Other factors such as conductivity, metal oxide deposition, temperature, depth, month, geographic location and altitude were also important. Algal communities changed over time and this became more marked as AMD impact decreased. This was presumably due to AMD stressors reducing diversity, and thus the available scope for assemblage change. Longitudinal differences in assemblage structure within Devils Creek appeared to be in response to dilution of AMD in upper reaches and to changes in natural physical features such as gradient in mid and lower reaches. After a distance of 7.2 km the physicochemical effects of AMD and suspended clay inputs were minimal. At this site and at several previous sites, the assemblage exhibited a degree of recovery towards that found at unimpacted sites. A range of algae found in the broad scale-survey are potentially useful 'sensitive' indicators. These included: Heteroleibleinia purpurascens; Achnanthes oblongella; Oedogonium sp. and Spirogyra sp. In contrast: Euglena mutabilis; Navicula cincta; K. acidophilum; Microspora quadrata and Microthamnion kuetzingianum may be useful 'tolerance' indicators. These data show that AMD has a range of negative impacts on algae, and algae may be a useful tool for monitoring these impacts in West Coast streams.

This paper is about analyzing water quality of a stream that flows in southwest of Swedencalled Hasslebäcken. The stream is a tributary of Suseån and has its springs in the naturereserve Biskopstorp and flows through a mixed landscape of mostly spruce forests andagriculture land. Little is known about Hasslebäcken and its water and therefore a study by request of Suseåns vattenråd was performed. The study consisted of analyzing the water ofphosphorous, nitrogen, pH, suspended particles and conductivity. To broaden the examination of water quality sampling of benthic macroinvertebrates and two index (ASPTindex and Shannon’s diversity index) of water quality were used. Another part of the study were to search for fish barrier in the stream and to evaluate the possibilities for troutspawning and habitats. The whole stretch of the stream were examined and eleven differentsampling sites were used. The results show that Hasslebäckens upper parts have low levelsof nutrients while the lower parts show intermediate to extremely high levels. The indexresults points at low ecological values for Shannon and high ecological values for ASPT. Thisis normal for a stream that flows through an agricultural landscape. The results concerning pH show a lower pH in the upper parts than in the lower parts. This is also normal for a stream in a production forest of spruce in these parts of Sweden. Hasslebäcken also have several fish barrier that prevent various fish species to migrate up along the stream from thesea. The evaluation of trout habitats and spawning area show decent possibilities for successful reproduction and growth.

The effects of thermal discharges on the density, distribution, production, and drift of benthic organisms were studied at North Lake reservoir.

The Early Jurassic was a time of rapidly rising sea-level associated with the extensive spread of anoxic bottom waters. Sea-level rise across the Pliensbachian - Toarcian boundary culminated in the falciferum Zone of the Toarcian and is one of the best authenticated eustatic events in the Jurassic. This major transgressive pulse was marked by deepw ater marine sequencesa nd was associatedw ith the deposition of organic-rich shales. The development of anoxia coincides with a notable period of mass extinction of the marine fauna. High resolution sampling and study of the microfaunast hrough sequencesin N. W. Europe confirm that benthic foraminiferal. faunas were similarly affected by an early Toarcianfalciferum Zone event. Samples were analysed from Pliensbachian - Toarcian mudstone,c lay and shale sequenceso f the south Dorset Coast,t he Midlands, the Yorkshire Coast, southern France and southwest Germany. The sections studied show distinct changes in assemblagesa cross the Pliensbachian - Toarcian boundary and in the basal zones of the Toarcian. Evidence for a foraminiferal extinction event in the Pliensbachian - Toarcian includes the elimination of the important Lower Jurassic Lingulina tenera, Frondicularia terquem! and Marginulina prima plexus groups, initiating a significant period of turnover of the microfauna. The foraminiferal extinction event recorded in the Lower Toarcian sections of north west Europe is only significant at species level. No extinctions at the family-level occurred. A marked changea lso occurred in the charactero f associatedn odosariid assemblagest:h e uniserial forms of Nodosaria, Frondicularia and Lingulina, dominating the Pliensbachian assemblagesw, ere largely replacedb y coiled Lenticulina in the early Toarcian. A reduction in test size and a decline in species diversity, compared with Hettangian to Sinemurian foraminiferal assemblagesr,e flect the developmento f low oxygen conditions followed by a subsequenrte newal of the microfauna in the Middle Toarcian. The foraminiferal data show no evidence of progressive displacement of older by younger faunas. Instead certain species only expanded their populations and diversity significantly after the extinction of similar niche-occupying species. The Pliensbachian - Toarcian (Lower Jurassic) sediments of the north Yorkshire coast contain highly organic-rich shales where the sequence stratigraphic significance is somewhat obscure. Benthic foraminiferal species distribution (as a function of organic flux and oxygenation) allowed palaeobathymetry to be determined on quantitative assemblage characteristics. In parallel with this methodology, a suite of trace elements (including Mn, Ca, Fe, and Al) have been analysed following nitric and hydrofluoric acid digestion. Maxima of Ca and Mn occur at the base of the falcifierum Subzone (falcifierum Zone). It is suggested that these maxima are an artefact of condensation of carbonate fossiliferous material due to sediment starvation and correspond to published estimates of a maximum flooding surface. Interpretations of the benthic foraminiferal assemblages surrounding this event provide further support for a transgressive event -associated with the development of low oxygen conditions and the deposition of organic-rich shales. Additional Lower Jurassic,H ettangiant o lower Pliensbachian,s equencesw ere investigated for the purposes of establishing their foraminiferal correlation potential as candidate Global Stratotype Sections and Points for the basal Sinemurian and basal Pliensbachian.

In biology, the winter season is less studied than other seasons partly due to technical and logistical difficulties. The Arctic region is undergoing rapid changes with shorter and warmer winters, shorter snow duration and considerable changes in snow and ice cover as a result. Climate change also has other consequences such as added influx of DOC to aquatic systems which may have repercussions for aquatic food webs. This study investigates the effect of ice melt on benthic oxygen production and also investigates the pelagic counterpart. This study also investigates levels of light, CO2 and DOC and their impact on benthic and pelagic oxygen production in a simulated climate change scenario. Sampling for the study took place at the Umeå University Experimental Ecosystem Facility which exhibits artificial ponds, some of which had been treated to simulate changes caused by climate change such as added DOC or having been artificially heated during summers. Measurements for O2, CO2 and light (photosynthetic active radiation) were collected from these artificial ponds at three different occasions around the time of ice release: Iced over conditions, after ice melt and later in spring. Ice melt was not proven to result in a difference in benthic oxygen production, as no significance could be found between O2-production during ice-covered conditions and later during the spring. Ice release did however seem to be the cause of a significant effect in the pelagic habitat which exhibited higher O2-production during the period of ice release. A significant difference in O2-production was also found in the pelagic habitat between ponds treated with added DOC and ponds that were not, but no such difference could be found for the benthic habitat. This highlights important differences between the habitats. The study proposes that earlier times of ice release, higher levels of DOC and higher summer temperatures may perhaps influence the oxygen production in the benthic habitat to a lesser extent than the pelagic habitat in northern aquatic systems, but this requires further studies.