| Summary: | 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 ...
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