This thesis reports a series of experiments investigating some aspects of seasonal C and nutrient cycling and microbial community responses in an alpine heathland under three environmental pressures: N deposition represented by N additions at four levels (0, 10, 20, 50 kg N ha^-1 yr^-1), climate change simulated by open top chambers (OTCs) and accidental burning (one low intensity fire event that occurred in autumn 1999). The Culardoch experimental site was used, which is located on an alpine heathland in the Eastern Cairngorms mountains, Scotland. The responses studied were related to litter decomposition dynamics, soil processes and the soil microbial community. Mass loss and nutrient status during decomposition of litter from the plots (“native”) and collected outside the plots (“standard”) were studied. Litter decomposition was not affected significantly by the treatments. Despite the decrease in initial C:N ratio by N additions, this treatment affected only phosphomonoesterase activity and a trend for increasing glucosidase and xylosidase activity with increasing N additions was seen. OTC impacts were limited to effects on P cycling in “native” decomposing litter in the later stages of decomposition and more P was accumulated in litter from the plots with the OTCs. Burning affected N cycling in “native” decomposing litter (more N was accumulated in litter incubated in the burnt plots) and mass loss, C, N and P content in “standard” litter. Increased cellulolytic activity was observed in litter from the burnt plots. Those changes were attributed to shifts in the bacterial and fungal communities due to burning and warming treatments, while N additions had only a minor effect on microbial community structure. Decomposition phase had the greatest effect on microbial community structure suggesting that a succession of communities occurred during decomposition. One of the most important findings was the lack of interactive effects among the three main treatments, indicating that they act independently on particular components of the ecosystem.

Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on Apr. 21, 2009). Includes bibliographical references.

No description available.

Seagrasses provide an important habitat for gillfish, crustacea and migratory birds. Extensive losses of seagrass in the Northern Hemisphere have occurred since the 1930's in what has been described as a 'wasting disease'. More recently, point-source contamination by nutrient inflows, herbicides (anti-fouling agents used on commercial shipping), heavy metals and fresh water inflows have helped explain localised losses of seagrass amounting to 20% in the case of Adelaide's metropolitan coastline, South Australia. However, losses of seagrass acreage have also occurred in regions that are far removed from anthropogenic activity and these are less easily explained by pointsource contamination. Intertidal seagrasses, such as Zostera muelleri, are subjected to environmental pressures imposed on them by the marine and terrestrial environments. For the purpose of this thesis, the intertidal environment is regarded as a complex of several components or micro-environments, each imposing a selective pressure or stress upon seagrass. The many stress factors create a tolerance zone in which Z. muelleri can survive. Zostera muelleri has adapted its physiology and biochemistry to the selective pressures that operate within the intertidal region. Zostera muelleri's internal leaf morphology has many gas storage compartments (lacunae) that extend from the leaves to the roots of the plants and its photosynthetic biochemistry has also adapted to the intertidal region enabling the sequestering of carbon under conditions of high irradiance and temperatures. It is evident from the literature that the survival of intertidal seagrasses requires effective photosynthesis. It is also evident that events that interfere with the synthesis, translocation and release of photosynthesised oxygen from the roots of Z. muelleri will compromise seagrass survival. The present study has revealed that herbicides, used in broad- acre farming, can be transported to the intertidal environment and negatively impact upon Z. muelleri. Extensive studies by others have shown that transport mechanisms, such as 'spray drift' and 'run-off', can move herbicides from their point of usage. However, 'dust' (wind-eroded soil ) as a transport mechanism for herbicides to the intertidal environment is less well studied. This is surprising, inasmuch as there is a known rate of pedogenesis in Adelaide of five to ten tonnes per km2 per annum from the accretion of dust. Results of the present study suggest that farmed soils of the Yorke Peninsula have a range of potentials to form fine particulate matter ('dust') and this potential is likely determined by the soil type and farming practices. Soil surface applied herbicides, such as 2,4-D, are 'lost' from land at 5% of the applied rate while soil-incorporated herbicides, such as treflan (trifluralin), are lost at 1.5% of the applied rate. Indeed, such herbicides can be transported as dust for tens to thousands of kilometres. Instrumental analytical techniques used in the present study have detected 2,4-D, trifluralin and sulfonylurea herbicides on whole soil. Additionally, 2,4-D- like chemicals have also been detected in whole soil and in dust obtained from whole soil. Bioassay techniques using Z. muelleri have shown that its photosynthetic pathways are negatively impacted upon by micromolar concentrations of 2,4-D that are similar to the known losses of this herbicide from land. It is concluded that, at these concentrations, 2,4-D acts as an auxin, up-regulating growth in affected plants. Such up-regulation is unlikely to be problematic in terrestrial plants since gas flows to the external environment are largely controlled by stomata. However, seagrasses lack stomata and the auxin-like activity of 2,4-D appears to have a negative impact on Z. muelleri. This is probably caused by an up - regulation in oxygen production and a subsequent oxygen-inhibition of a key enzyme ( ribulose 1,5- bisphosphate carboxylase, RUBISCO ) used in the carbon-sequestering photosynthetic process. The proposed inhibition of RUBISCO is then likely to cause a carbon deficit and a subsequent energy deficit within affected plants. One interpretation of the results presented is that Z. muelleri simply outgrows its intertidal environment after a transient exposure to an auxin-like concentration of 2,4-D. With increasing use of auxin-like herbicides, and the associated increasing stress imposed on photosynthetic processes, it is likely that further negative impacts will occur on intertidal seagrass species. Continued depletion of seagrass acreage will further adversely affect fishing yields unless appropriate measures are not taken. Closer collaboration between regulators, farm managers and herbicide manufacturers is now necessary in order to minimise the negative impact of herbicides on intertidal species. / Thesis (M.App.Sc.)--School of Earth and Environmental Sciences, 2005.

Thesis (M.S.)--Western Washington University, 2009. / Includes bibliographical references (leaves 44-47). Also issued online.

Thesis (M. Sc.)--University of Canterbury, 2003. / Typescript (photocopy). Includes bibliographical references (leaves 104-110). Also available via the World Wide Web

Thesis (M.Sc.)--Memorial University of Newfoundland, 2001. / Bibliography: leaves 117-125.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains ix, 104 p. : ill., maps. Includes abstract. Includes bibliographical references (p. 41-49).

Ihis work on the Sado outer estuary (western coast of Portugal) considers its bio-sedimentary characterization, and evaluates the prevailing hydrophysical and sedimentary environmental conditions. The quality status of the estuary is discussed. The thesis is based on the analysis of superficial sediments and benthic macrofauna collected from 133 sites, and on hydrodynamical data obtained from a mathematical model. The environmental variables considered were the superficial sediment temperature, granulometry and organic matter content, together with the water current velocities, flow and shear stress. The macrofaunal characterization and the analysis of the state of disturbance was based on a study of the composition, structure and spatial distribution of faunal assemblages and their relationship to the prevailing environmental conditions. The Sado was shown to be inhabited by an abundant and diversified fauna with high biomass. Two major faunal assemblages have been identified, a marine and an estuarine community, separated by a transition region. The estuarine community comprises the majority of the area and contains important subdivisions. The regions identified have been shown either to be controlled by anthropogenic inputs or to reflect mainly the effects of natural forces. The main structuring factors influencing the benthos are the hydrodynamic conditions, coupled with sediment type, and organic matter of natural and anthropogenic origin. Sedimentary organic enrichment effects have been noted in all the areas studied and in general the Sado outer estuary reveals signs of eutrophic conditions. In the more disturbed regions the macrofauna data also suggest chronic toxicity effects. Although disturbance effects due to anthropogenic inputs are suggested through the biosedimentary approach, the estuary as a whole can not be considered badly polluted. However, defaunated, impoverished and over-enriched areas, appear as a result of localised severe pollution indicating the need to improve effluent treatment systems. The methodological approach followed in this study has been shown to be effective in assessing the quality status of the Sado outer estuary. Multivariate and direct gradient analysis proved to be very useful methods and a detailed analysis of the macrofaunal species has been shown to be effective in the detection of organic enrichment effects in some of the areas. The extreme aspects of the gradients were identified by all the analytical techniques, but the univariate methods were shown to be poor at discriminating the more subtle effects.

The influence of sedimentary variables on the structure and function of infaunal estuarine and marine communities is well studied but less is known of the influence of biota on sediment properties. Feeding and burrowing activity, locomotion, the production of faecal pellets and biological secretions (bioturbation) have important implications for sediment structure, chemistry, transport characteristics and the flux of nutrients and contaminants. Although spatial and temporal patterns in bioturbation have been studied to some extent, little attention has been given to the effects of pollution. The present study examines the effects of an intertidal petrochemical discharge into the Humber estuary (UK), from BP chemicals (Saltend) Ltd on the structure and function of the communities. Field and laboratory techniques were used to determine the effects of community change on bioturbation potential. In addition, a laboratory flume was constructed to measure sediment erosion potential with field measurements being taken using a Cohesive Strength Meter (CSM). The physico-chemical properties of the sediment, changes to the infaunal community structure, bioturbation potential and the interaction of these variables were used to explain differences between the erosion potential of sediments subject to varying levels of contamination. The main study was carried out on the Saltend mudflats near Hull, with sites at various distances from the outfall being used. A further set of control sites on the adjacent, and largely unaffected, mudflat at Paull were also used. In terms of the sediment properties, sites closest to the outfall showed the greatest degree of anoxia and the highest chlorophyll-a and carbohydrate concentrations, with all three parameters being seasonally influenced. No consistent spatial or temporal patterns were found for any of the other parameters (water and organic content, particle size). Whilst the infaunal communities were characteristic of estuarine areas, macrobenthic community response followed the Pearson & Rosenberg (1978) model for organic discharges with high abundance and low species diversity being associated with the more polluted sediments. Close to the discharge, there was an impoverished community consisting predominantly of highly abundant oligochate worms. With increasing distance from the outfall, species diversity and biomass increased with Hediste diversicolor becoming increasingly dominant and the appearance of Corophium volutator, Streblospio shrubsolii and Macoma balthica. Bioturbation potential was significantly reduced (in terms of depth and burrow volume and density) by increasing effiuent concentrations and with proximity to the discharge. The diversity of both feeding and sediment modification guilds was also reduced as a result of the discharge. Both field and laboratory studies indicated a stabilising effect of this type of pollution. Using the CSM, critical shear stress values were found to be significantly lower from unpolluted sites, indicating higher erosion potential, than those from sites close to the discharge. As a result of this, the total mass of sediment eroded from unpolluted sites was significantly higher than that from polluted areas. A similar trend was observed in the laboratory with sediments treated with an effluent concentration of 32% being considerably more stable than untreated sediments. Flume studies also indicated the stabilising effect of pollution with suspended particulate matter (SPM) concentrations and mass of sediment being transported as bedload being significantly higher for unpolluted sediments. These differences in erosion potential were attributed to the direct effects of the effiuent on the physico-chemical properties of the sediment, the effects of the effiuent and sediment type on macrofaunal community structure and function and the differences in bioturbation potential between sites. The implications of these findings in the wider context of coastal management are discussed.