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Caffeine, a biologically active drug with many known molecular targets, is recognized as a contaminant of aquatic systems including marine systems. Although the concentrations of caffeine reported from aquatic systems are low (ng/L to μg/L), harmful ecological effects not detected by traditional toxicity tests could occur as a result of caffeine contamination. The goals of this thesis project were to: 1) quantify concentrations of caffeine occurring in the coastal ocean off of the Oregon Coast and to determine if higher levels were correlated with proximity to caffeine pollution sources; and 2) investigate the sub-lethal cellular toxicity of environmentally relevant concentrations of caffeine on Mytilus californianus, an intertidal mussel that is one of the dominant species of the Oregon Coast.
Caffeine was analyzed at 14 locations in the coastal ocean off of the Oregon Coast. Sampling locations were stratified between populated areas identified as having sources of caffeine pollution and sites located in sparsely populated areas not in proximity to major caffeine pollution sources. Caffeine concentrations were also measured in the major water body discharging near sampling locations. Caffeine was detected in water from the coastal ocean off of the Oregon Coast at concentrations ranging from below the reporting limit to 44.7 ng/L. The occurrence and concentrations of caffeine in the coastal ocean did not correspond well with pollution threats from population density and point and non-point sources, but did correspond with a storm event occurrence. Caffeine concentrations in rivers and estuaries draining to the coast ranged from below the reporting limit to 152.2 ng/L.
Hsp70, a molecular biomarker of cellular stress, was used to investigate the sub-lethal toxicity of environmentally relevant concentrations of caffeine to the mussel M. californianus. Hsp70 concentrations in the gill and mantle tissue of mussels exposed to 0.05, 0.2, and 0.5 μg/L of caffeine for 10, 20, and 30 days were compared to basal levels in control mussels. Hsp70 in the gill tissue of M. californianus had an initial attenuation of the stress protein followed by a significant albeit moderate up-regulation relative to controls in all but the 0.5 μg/L treatment. Hsp70 in the mantle tissue of mussels exposed to caffeine did not differ from control mussels.
This study confirms the presence of caffeine in Oregon’s coastal ocean and provides laboratory evidence that environmentally relevant concentrations of caffeine can exert an effect on M. californianus gill tissue at the molecular-level.
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