The present research aims to establish the depth of abiotic and invertebrate edge-effects occurring in plantations of two conifer species, and the resulting effects of management practices on 'edge' and 'core' invertebrate communities. Near complete invertebrate samples were collected using chemical knockdown allowing analysis of invertebrates at the order, family, genus, species and guild level. Similar invertebrate densities per m[2] ground area occurred in both tree species, although communities differed between them, Pinus sylvestris supporting a more diverse community than Picea sitchensis. Species richness, diversity and densities varied with distance from plantation edge with the Acarina, Araneae, Coleoptera, Collembola, Diptera and Hemiptera showing particularly strong responses to edge proximity. Abiotic edge-effects, although variable between transects, occurred to an average depth of 30 metres with an approximate 1 C drop in temperature and a 5% increase in relative humidity towards the core. Invertebrate edge-effect depths varied with species, ranging from 5 to 80 metres. In P. sitchensis invertebrate richness and densities, particularly for Coleoptera, Araneae and Hemiptera were higher in the edge habitat, whilst increased richness and diversity occurred in the core of P. sylvestris. Edge habitat is key to optimising richness in P. sitchensis, however application of core-area models shows that current plantation management fails to maximise edge habitat. Reduction of patch size and/or increasing edge features will increase species richness. In contrast core habitat is vital to species richness in P. sylvestris. Current small patch size limits invertebrate richness, increased patch size and implementation of edge buffer zones would protect core habitat thus enhancing invertebrate species richness.

Thesis (M.S.)--Ohio University, June, 2006. / Title from PDF t.p. Includes bibliographical references (p. 97-104)

Access to abstract restricted until 05/2015. / Access to thesis restricted until 05/2015. / Department of Biology

Globally, stream invertebrate communities have been shown to respond to habitat degradation as a result of land use hanges. The effects of land use changes on stream communities have been well documented in temperate regions, however, their effects in the tropics are relatively unknown, particularly where land use activities can differ markedly (e.g., tea, maize and Eucalyptus plantations). To understand how land use affects tropical highland Nigerian stream communities, I surveyed 55 second and third order streams across four land use categories, ranging from continuous tropical montane forest to intensive crops/pasture. Streams were sampled in the dry season (October to March) for physico-chemical parameters (i.e., temperature, pH, conductivity, turbidity, current velocity, channel morphometry and riparian characteristics) and ecological characteristics (i.e., fine particulate organic matter [FPOM], coarse particulate organic matter [CPOM], algae and benthic invertebrates). Water temperature in all streams was high (up to 25oC) while levels of dissolved oxygen were frequently low (15–79 %). Physico-chemical conditions varied across land uses with continuous forested streams being cooler, with higher dissolved oxygen, larger bed substrate and more stable channels. Similarly, benthic invertebrate communities showed a strong response with the highest taxonomic diversity in forested streams and the lowest in streams within intensive crops (e.g., cabbage crops). Several of the taxa which occurred in forested streams (e.g., the mayflies Heptageniidae and Oligoneuridae and brachyuran crabs) were rare or absent in streams with more intensive land use. In contrast, damselflies and several true bugs (e.g., Notonectidae and Corixidae) were rare in forested streams but more common in other land uses. In order to test land use impacts on stream processes leaf litter decomposition experiments were carried out in nine streams, three in forest, three in tea plantations and three in maize fields. Leaf breakdown rates were slow compared with other reports for tropical streams, however leaves in forested streams broke down significantly faster (on a degree day basis) than in other land uses. This faster break down seemed to be driven by greater shredder densities in forested streams. Significantly lower densities of invertebrates were found in leaf bags incubated in streams draining tea plantation and maize fields than in forest streams. In the same nine streams food web components were sampled and analysed using gut content and stable isotope (N and C) analyses. Stream food webs in continuous forest were more complex than plantation and maize field streams. Stable isotope analysis indicated that primary consumers assimilated a mixture of autochthonous and allochthonous carbon resources, but the proportion varied among sites. Overall, my results suggest that in Nigerian highland tropical streams more intensive land use activities strongly affect the diversity and composition of benthic stream communities and ecosystem function, in similar ways to those reported in temperate streams.

Thesis (Ph. D.)--Illinois State University, 2006. / Title from title page screen, viewed on May 14, 2007. Dissertation Committee: Steven A. Juliano (chair), Roger C. Anderson, L. Philip Lounibos, Wade A. Nichols, William L. Perry. Includes bibliographical references (leaves 145-162) and abstract. Also available in print.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2004. / Thesis documentation sheet inserted. Appendix reproduces three papers and manuscripts co-authored with R.K. Johnson and two papers co-authored with R.K. Johnson and L. Sandin. Includes bibliographical references. Also issued electronically via World Wide Web in PDF format; online version lacks appendix.

The aim of this thesis has been to: 1) assess the state of pollution in the two study areas and relate them to recent changes found in the Kattegat - Belt Sea area; 2) examine the observed spatial and temporal variability in species composition, abundance and biomass in Arhus Bay and the Formes area and relate the variability to antropogenic and natural causes; 3) discuss and assess methods, particularly for the estimation of secondary production and the use of multivariate analyses as methods for examining changes in macrozoobenthic communities. Macrozoobenthos were sampled at 15 stations in Arhus Bay, Denmark from 1985 to 1991 while data from Formes (reference area) included 55 sampling stations from 1986 to 1990. Monthly sampling took place at one station in Arhus Bay in 1990 and 1991. The two study areas are both situated on the eastcoast of Jutland in the Kattegat - Belt Sea area at 13-17 m depth and both receive waste water from long sea outfalls. Although both areas are Subjected to salinity stratification for most of the year, the exposed position of the Formes area on the open Kattegat coast prevents it from suffering from severe oxygen deficiencies, unlike the Arhus Bay which is a sheltered, semi-enclosed sedimentation area where oxygen concentrations in the bottom water can be very low. At Formes the sediment is sandy while it is silty in Arhus Bay. The spatial and temporal variability in the benthos in Arhus Bay could to a great extent be explained by the variation in 7 important species: Abra alba, Corbula gibba, Mysella bidentata, Nepthys hombergii, N. ciliata, Ophiura albida and Echinocardium cordatum. The fluctuations in the number and biomass of A. alba had a pronounced effect on the total abundance and biomass in Arhus Bay. The severe winter of 1986/87 with low temperatures and oxygen depletion under the ice cover practically eliminated A. alba from the bay. A. alba quickly recolonized the area and was found in high numbers in 1988. Studies of growth of A. alba in 1990 and 1991 showed that by the end of 1990 the population had reached an average length of 10 mm while the average shell length was only 5 mm by the end of 1991. The difference between the two years could be attributed to the difference in sedimentation of phytoplankton from the water column. As in other parts of the Kattegat - Belt Sea area, Arhus Bay has experienced low oxygen concentrations in the bottom water in late summer early autumn throughout the 1980s. Only the oxygen depletion under the ice cover in early spring 1987 and the local oxygen deficiencies south of the outlet in 1989 and 1990 actually killed parts of the benthic fauna. Apart from 1981, the oxygen deficiencies have thus been less severe in Arhus Bay than in other parts of the southern Kattegat in the 1980s. The number of species, abundance and biomass decreased at Fornres from 1980 to 1985 while the discharge of BOD was fairly constant during the same period. From 1986 there was a slight decrease in the discharge of BOD but a considerable increase in the number of species, abundance and biomass. At least for the second half of the 1980s there was no straightforward relation between the organic enrichment from the outlet and species composition, abundance and biomass and suggests that other factors are also important influencing the fluctuations in the benthic fauna. Estimates of total secondary community production were found to be very dependent on the method used. The method described by Brey (1990) was found acceptable for estimating secondary production in Arhus Bay but care should be exercised when comparisons are made with other areas where different methods have been used to estimate production. Secondary production was estimated more accurately for some of the abundant species in Arhus Bay on the basis of monthly samplings by the method described by Crisp (1984). Among the multivariate analyses the Detrended Correspondence Analysis (DCA) and nonmetric Multidimensional Scaling (MDS) proved to be the most successful with the Arhus Bay and Fornes data sets. Two Way INdicator SPecies ANalysis (TWINSPAN) did not work well with the Fornes data because it imposed discontinuities on data sets with continous variation in distribution of species among samples. As community types existed to a certain degree in Arhus Bay TWINSPAN worked well with these data. DCA and MDS were found to be useful techniques for analysing large data sets because they can summarize the data matrices to a manageable form and find possible patterns in the data sets. The results of the analyses can then be used as starting point for more detailed investigations of single species/samples or groups of species/samples. By using different transformations of the raw data the role of dominant or rare species can be assessed. A major 'problem in the assessment of multivariate techniques is the lack of external standards to compare with. The results of multivariate analyses must therefore be assessed critically on the basis of a careful examination of the species list combined with the knowledge and experience of the investigator. The methods used all had their advantages and limitations but each of the different methods added some important information to the picture of the benthic community in Arhus Bay and Fornes. It was thus an considerable advantage to use several different methods to analyse the spatial and temporal variability in the benthic fauna in relation to antropogenic and natural causes.

Ferreira, M., Dr.; Van Vuren, J.H.J., Prof. / The Wilge River is one of many adjoining tributaries of the Olifants River located in the Olifants Water Management Area (WMA4) within the Highveld (11) – Lower Level 1 Ecoregion (Dallas, 2007). These river systems experience extreme demand for natural resources, as they flow through heavily utilised economic hubs. They are closely associated with land modification and pollution, primarily mining and industrial-related disturbances and extensive agricultural activities, all of which are the primary cause of impairment to river health. The primary aim of this study was to study the aquatic macroinvertebrate communities at six monitoring sites along the Wilge River, coupled with two monitoring sites on adjoining tributaries, and to further identify the driving variables that influence these communities both spatially and temporally. Functional Feeding Groups (FFGs) of the aquatic macroinvertebrates and the surrounding land use in the project area was taken into account. The analysis of in situ water quality measured during the period March 2010 to May 2013, clearly illustrated high levels of variation both spatially and temporally. In situ water quality was a limiting factor to the aquatic ecosystem from a Dissolved Oxygen (DO) and Percentage Saturation (DO%) perspective. The remaining parameters were within the South African guideline for aquatic ecosystems (DWAF, 1996). Habitat availability illustrated clear seasonal variation as well, of which the wet season indicated better habitat availability compared to the dry season. The dominant biotopes in the study area were vegetation (VEG) and gravel, sand and mud (GSM). Site WIL04 illustrated the poorest habitat integrity overall primarily attributed to the site’s steep incised banks and deep channel which lacks the stones biotope. The South African Scoring System, Version 5 (SASS5) results indicated that there was a change in the integrity of the aquatic macroinvertebrate community’s in the study area and further illustrated variability both spatially and temporally. It was evident that the aquatic macroinvertebrate communities within the Wilge River and two adjoining tributaries sampled, were generally in a slightly to modified state with moderate variations. The lowest number of taxa, SASS5 and average score per taxon (ASPT) values was recorded at site WIL04 and this was mainly brought about due to changes in flow and habitat availability. The ASPT score ranged from 3.8 at site WIL04 to 7.7 at site WIL02, indicating that the aquatic macroinvertebrate communities were primarily composed of tolerant and moderately tolerant taxa. Of these mostly tolerant taxa, predators and gathering collector populations were the most dominant FFG, with the shredders being the least abundant within the study area. The Bray-Curtis cluster analysis of the aquatic macroinvertebrate communities clearly illustrated a high level of similarity and seasonal variation among the communities. The high similarity was an indication that similar taxa occurred at the sites within the groups identified. However, in accordance with the Similarity Percentages (SIMPER) analysis, there was no clear indication of dominant taxa. There was however a separation of sites TRI01 and WIL04. This was expected due to differences in the physical stream condition (flow) and other habitats / general biotopes, primarily at site WIL04. Stream bed composition is one of the most important physical factors controlling the structure of freshwater invertebrate communities (Mackay and Eastburn, 1990). The separation and similarity of these two sites were not a consequence of dominant taxa, but rather a consequence of differing water quality, habitat availability and common tolerant taxa driving the system. Inclusive, the seasonal variation illustrated was contributing to the changes in the in situ water quality and habitat availability, thus making seasonal variation also a driving variable, in the differences between the sites. The Redundancy Analysis (RDA) bi-plots indicated, as with the Bray-Curtis similarity matrices and related NMDS plot, that there was a distinct seasonal separation. It further illustrated a clear separation of site TRI01 and WIL04 due to reasons mentioned above. All the environmental variables, with the exception of pH, was identified as significant drivers in the river systems (p<0.05). This however varied seasonally. During the wet season, clarity, DO and pH were the significant drivers, while clarity, TDS/EC, percentage saturation and pH were the significant drivers during the dry season (p<0.05). These drivers were expected due to possible sources namely intensive agriculture in the project area. The RDA tri-plots further indicated the significant role that the ASPT, SASS5 score and the IHAS played within the aquatic macroinvertebrate community (p<0.05). This confirms the importance of habitat as a driving variable in aquatic macroinvertebrate community structures. Consequently, the driving variables in the separation of the sites along the Wilge River and two adjoining tributaries, appear to be a combination of variables (DO, percentage saturation, TDS/EC, clarity and pH), including habitat availability (based on IHAS scores). To determine the effects and relations between the primary driving changes, to the surrounding land uses in the project area, further multivariate analyses were conducted, which included the FFGs. It was clearly indicated that predators have a negative correlation with the rest of the FFG’s which was expected. As the percentage of predators increase at a site, the percentage of the other FFG’s decreased. Therefore, there was a large variation and clear changes in the food sources constantly entering into the river system. This is normally related to changes in the land use.

Thesis (M. Sc. (Zoology)) -- University of Limpopo, 2019 / Many South African rivers, including the Ga-Selati River have been deteriorating for the past few decades, due to an increase in mining, industrial, agricultural and domestic activities. Around mid-January 2014, the Ga-Selati River was contaminated by mine spills from a nearby phosphate mine, which polluted the river and killed many fish species. This river is a primary source of water for many activities (e.g. mining, industrial, agricultural and domestic activities), and as a result, large numbers of reservoirs, farm dams, and inter-basin transfer schemes have been constructed to increase the reliability of water supply along this river. Contamination of surface waters by agricultural pesticides and fertilizers, as well as by industrial metals, is a cause of increasing public concern. The Ga-Selati River is a major tributary for the Olifants River, among other tributaries (Steelpoort River and Blyde River) and it plays a significant role in the Kruger National Park and other private game reserves in the catchment. This River is also known to supply water of very low quality into the main stem of the Olifants River. The Olifants River System has been described as degraded and is contaminated with metal and chemicals, and is considered to be one of the most threatened river systems in South Africa. The aim of the study was to investigate the ecological state of the Ga-Selati River and the impact of water and sediment quality on the aquatic invertebrate communities, and to propose measures to prevent further degradation of the river ecosystem by human disturbance. The main objectives were to: (i) establish the current physico-chemical composition of the river water and sediment along the entire length of the Ga-Selati River, (ii) to determine if poor water quality at the lower end of the river is due to pollution inputs in the lower reaches, or the result of cumulative pollution inputs along the entire length of the river, (iii) Assess the impact of water and sediment quality on the aquatic macro-invertebrate assemblages in the river. The concentrations of pH, and DO were high at all sites. If there was any sort of pollution in the river, especially downstream by the mining sites, we expected these two variables to be lower. The water variables such as EC, TDS and salinity showed a gradual increase from upstream to downstream. There were also elevated levels of certain metals, such as Mg, Na, Ti, B, Sr, K and Ca showing a pollution gradient. The v high concentrations of metals in water samples indicate that the Ga-Selati River is heavily impacted downstream by anthropogenic activities such as illegal dumping/littering at site 6 and mining activities at site 7 to site 9. Some of the metal concentration (Na, Mg, K and Ca) in the river were found to be extremely high compared to other rivers in the region. Metal concentrations in sediment samples were very high compared to water samples River. The nutrient concentrations at the Ga-Selati River were high but did not show a pollution gradient. The macro-invertebrate assemblages in the Ga-Selati River were rich in Ephemeroptera, Diptera and Trichoptera. Site 1 and site 2 accounted for most of the sensitive families, reflecting good water quality at these two sites, while site 9, a downstream site recorded the highest number of tolerant families.. The variations in the macro-invertebrate distribution were shown by the differences in the water quality at the various sites by the CCA plot. The effects of main pollution factors such as, EC, TDS, turbidity and nutrients were correlated with the distribution of tolerant taxa. / National Research Foundation (NRF) and Vlir

Agricultural practices may influence stream biological communities by removing riparian vegetation and modifying stream channel morphology, both which may reduce water retention time. I collected benthic invertebrates and fishes in seven headwater agriculturally-influenced streams in central Indiana, to quantify controls on invertebrate and fish community assemblage variation. Invertebrates were collected at 14 sites and fish were collected at 12 sites in Buck Creek watershed. The abundances of invertebrates and fishes were analyzed in Detrended Correspondence Analyses (DCA) in PC-ORD software and correlated with abiotic and biotic factors. The sites located in close proximity to Buck Creek have increased stability of biotic (fish assemblages) and abiotic (flow and water depth) factors. Abundances of invertebrates of headwater streams in east-central Indiana agricultural landscapes are influenced by distance between sites, distance to Buck Creek, and presence of fish species. Abundances of fishes were correlated with water quality and distance to Buck Creek. / Department of Biology