The following thesis explores the physiological effects on European sea bass (Dicentrarchus labrax) and shore crabs (Carcinus maenas) resulting from the dissolution of anthropogenic carbon dioxide (CO2) into seawater: known as ocean acidification. It assesses how ocean acidification, characterised by elevated seawater pCO2 (1200 µatm) and lowered pH (~7.7), affect the internal chemistry of these animals through the homeostatic process of acid-base regulation. Control conditions used for comparison were close to current ocean average values for CO2 (~400 µatm) and pH (8.2). The proficiency and magnitude of these compensatory mechanisms was explored. Both sea bass and shore crabs were found to be highly effective acid-base regulators and employed the same strategy to compensate the hypercapnia-induced respiratory acidosis: namely an elevation of extracellular bicarbonate (HCO3-). It then considers how these regulatory mechanisms both affect, and are affected by, simultaneous exposure to a ubiquitous coastal metal contaminant, copper. Evidence for a hitherto undocumented protective effect of elevated HCO3- against copper-induced DNA damage was found to be afforded to both sea bass and shore crab cells. DNA damage was used as a sensitive toxicity marker and blood cells were used as proxies for other internal tissues. Erythrocytes exposed in vitro (2 h) to copper (45 µg/L) showed significant DNA damage under control [HCO3-] (6 mM) but were completely protected when exposed under high [HCO3-] (12 mM). A similar protective effect was apparent in crabs under in vivo exposure (14 d) to 10 µg/L waterborne copper. Conversely, during exposure to higher waterborne copper concentrations (sea bass: 80 µg/L, shore crabs: 40 µg/L), animals showed a severe or total inhibition of acid-base regulatory ability in the face of simultaneously elevated seawater CO2 (1200 µatm). The downstream effects of longer-term (28 d) exposure to high CO2 and copper, both individually and in combination was assessed. Food conversion efficiency (FCE), growth and copper accumulation were quantified in juvenile sea bass as economically relevant endpoints. Growth and FCE remained unaffected by either stressor and copper was not accumulated in the muscle tissue: pertinent to human consumption. As a bi-product of this longer term study assessment of gut calcium carbonate production rates in these animals was possible, providing some of the first evidence of excretion rates in fish fed on naturally high calcium diets. A directly proportional influence of feeding rate on gut carbonate excretion rates as a result of increased dietary calcium was observed, and novel evidence provided of the proportional contribution of dietary and seawater calcium to excreted carbonate. Both findings have considerable application to global models of fish contribution to the oceanic carbon cycle.

The concept of soil sustainability has been concisely reviewed, to show the central role of biogeochemical cycling in sustaining fertility of both natural and managed soils. The role of sea salt inputs from the atmosphere within the context of biogeochemical cycling of base cations, concentrating upon the ameliorative effects that base cation inputs from the atmosphere may have against soil acidification in acidification-sensitive upland soils in Scotland, is then discussed more fully. Three approaches were used to try to confirm the importance of the sea salt effect to Scottish upland soils. Studies under controlled laboratory conditions provided strong evidence that maintaining soils under field moist conditions caused considerable increases in exchangeable Ca2+:Na + ratios, which could be attributed to internal soil action redistributions in the absence of a sea salt input. The changes in soil pH over time were not as simple as had been initially expected, partly as a consequence of the complications caused by organic matter oxidation. This study clearly showed it is unwise to store field moist soils in a cooled room for a few weeks prior to analysis. Samples stored for 20 months were re-analysed to look for effects that could be attributed to the elimination of sea salt inputs, but the results did not provide evidence for a sea salt effect. Interpretation was difficult because of the possibility of errors occurring as a result of soil storage in a cold room for up to a few weeks prior to soil analysis, and the high degree of organic matter oxidation. The latter results in release of SO42-, which was removed by precipitation of aluminium sulfate. Repacked soil columns containing individual soil horizons were subjected to simulated high sea salt and low sea salt rainfall treatments over three months. One set of soil horizons was pre-treated to remove organic matter. The results of this experiment were much more unequivocal, with large increases in exchangeable Na+ and Mg2+ concentrations and corresponding soil pH shifts. Finally, it was hypothesised that, if soils with low mineral weathering rates in north east Scotland were susceptible to strong sea salt effects, this should be reflected directly in the associated river water composition. This was confirmed experimentally, and there was a strong link between susceptibility to sea salt effects and susceptibility to acidification.

Pineapple juice of low acid content was prepared by removal of acids by using weakly basic anion exchange resin, IRA-93. The changes in the contents of titratable acid, pH and total soluble solids of model solutions that contained the principal constituents of pineapple juice (citric acid, citrate salt and sucrose) were investigated. The adsorption of individual acids and changes in composition of juice after a de-acidification process were explored. The adsorbed acids were recovered as solutions by some eluants, and studies on colour development in the recovered solutions carried out. The solutions of adsorbed acids recovered by NaOH from the resin, which had been treated by model solutions, were brown in colour. The brown colour was also found immediately when NaOH was added to the resin treated with pineapple juice but it was not found in the treated juice during acid removal treatment when its pH rose to 10. A greater amount of the dark colour was observed in the desorbed solution from the resin that had been treated with pineapple juice. The use of sulphuric acid, sodium chloride, sodium sulphate, sodium bicarbonate and phosphate buffer solution to desorb the acids from pineapple juice-treated resins reduced the intensity of the colour, measured at pH 3.5, of desorbed acid solutions. The colours of the desorbed solutions were pH dependent. Either solution of sulphuric acid or sodium chloride has a comparable desorbing power to a solution of sodium hydroxide whereas the rest has a lower desorbing power / Master of Science (Hons) (Food Science)

Iron mining began in Wawa, Ontario in the late 1800s and ceased in 1998. The sintering process of iron pyrite produced sulfur dioxide which led to the acidification of nearby lakes. Benthic macroinvertebrate samples were collected from lakes along a gradient of historical impairment in Wawa to examine the extent to which the benthos of the lakes would separate along the historical impairment gradient. The results show that the lakes are not separated along a gradient of impairment, and acid-intolerant taxa were collected in previously acidified lakes. There was no ameliorative intervention to combat the historical acidification and the observed recovery of water chemistry and benthos is entirely due to natural ecosystem processes. The two sampling methods (littoral kick sampling using a D-net and Hester-Dendy substrates) used to sample the benthos in these lakes can lead to substantial differences in the taxa collected.

Iron mining began in Wawa, Ontario in the late 1800s and ceased in 1998. The sintering process of iron pyrite produced sulfur dioxide which led to the acidification of nearby lakes. Benthic macroinvertebrate samples were collected from lakes along a gradient of historical impairment in Wawa to examine the extent to which the benthos of the lakes would separate along the historical impairment gradient. The results show that the lakes are not separated along a gradient of impairment, and acid-intolerant taxa were collected in previously acidified lakes. There was no ameliorative intervention to combat the historical acidification and the observed recovery of water chemistry and benthos is entirely due to natural ecosystem processes. The two sampling methods (littoral kick sampling using a D-net and Hester-Dendy substrates) used to sample the benthos in these lakes can lead to substantial differences in the taxa collected.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

The geographic range of the panmictic American eel (Anguilla rostrata) has contracted in recent years because of the pronounced decline in recruitment of glass eels and elvers to the Laurentian Basin. In consequence, the American eel was assessed in 2006 as a species of special concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). The evident sensitivity of American eel status to elver recruitment highlights the importance of understanding both the mechanisms contributing to the delivery of glass eels from the Sargasso Sea to continental waters and mortality following their recruitment to coastal and inland waterways. The potential for variability in environmental quality at localized geographic scales to affect American eel productivity and hence the status of the species and the fisheries it supports is not fully understood. The Atlantic coast of Nova Scotia is an ideal location to examine the relationship between water quality and American eel productivity. Within Nova Scotia there is wide natural variation in freshwater pH, which has been further increased in recent years by the effects of acid precipitation. This variation occurs over a small geographic range of several hundred kilometres that overlaps an area of high elver influx. As low environmental pH is known to adversely affect aquatic ecosystems, it has been identified as a possible threat to elver survival. In this study, the effect of low pH on elver survival was examined in both laboratory and field based trials using wild glass eel/elvers that were captured upon entry to fresh water. Trials examined the mortality rate of elvers at pH levels within the range of 4.0 - 7.0 over a 10 day period. The relationship between elver development and mortality at low pH was also examined through pigmentation analysis. Laboratory and field based studies resulted in zero mortality among elvers in natural and artificial acidic environments with pH levels as low as 4.0., thus indicating that the American eel is fully acid tolerant upon initial migration into fresh water. Sub-lethal effects of acidification were explored by examining the hematological parameters of river resident yellow-phase American eels exposed to varying levels of acidity in the laboratory. The level of acidification proved not to be a factor in determining both hematocrit and blood plasma osmolarity levels, as there were no significant differences in these variables between eels exposed to acidic conditions and those exposed to control neutral pH conditions. These results suggest that through the use of a highly effective mechanism for regulating blood ion concentration, the eel is able to tolerate low pH conditions.

Hydrological pathways and episodic stream acidification were investigated by monitoring water quality in the Coalbum catchment during the later stage of canopy closure. Coalburn is a long-running experimental site, almost completely covered by a commercial coniferous plantation (part of the Kielder Forest in northern England). Regular sampling, event sampling and continuous monitoring were used to establish an extensive water quality data-base between 1993 and 1997. Cloud mist and precipitation at Coalburn are slightly acidic and the catchment can receive moderate levels of dry and wet acid deposition when the winds have tracked from an easterly direction. Coalburn streamwater chemistry displays well-buffered base-flows and acid episodes during high flows. Duration-frequency-magnitude analysis of the Coalburn acid episodes reveals they were less frequent than expected but had a longer duration. The acid events exceeded environment quality standards for freshwaters: pH and aluminium concentrations suggest a toxic impact on freshwater biota. However, the elevated calcium concentrations and presence of humic substances reduce the biological impact. The chemical signatures and variations in solutes were identified and used to postulate the causal mechanisms of the hydrochemical response and to produce the conceptual Coalburn runoff model. Mixing modelling was then applied to introduce a robust analysis into the process and produce the simplified Coalburn Model of acidification. Broadly, the Coalburn hydrochemical response can be explained by pre-event water sources and 'normal' catchment processes. However, during extreme events catchment conditioning and event-water can also influence the response. In improving knowledge of the likely water quality effects of coniferous plantation afforestation, the Coalburn study has contributed to calibrating the temporal and spatial variability of headwater acidification (and hence risks). This allows policy makers and environment managers to make informed decisions about land use/management and to apply the precautionary principle; the research findings were used to suggest a basic policy framework and protocols for catchment assessments to manage acidification issues through the cropping cycle within a headwater catchment.

Thesis (Ph.D.)--Georgetown University, 2009. / Includes bibliographical references.

Thesis (M.S.) in Earth Sciences--University of Maine, 2006. / Includes vita. Includes bibliographical references (leaves 97-103).