GROUP
Plymouth Field Course 2019
4
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Oxygen Concentration
Oxygen Concentration Depth Profile:
OFF-SHORE
Oxygen Concentration against Temperature:
Comparing the O2 concentration data from both the offshore samples and the estuarine samples revealed stark differences between the data. The median values were similar at 250.105μmol l-1 and 242.405μmol l-1 respectively, but both the interquartile ranges (28.305μmol l-1 and 9.3μmol l-1) and the ranges (135.89μmol l-1 and 25.8μmol l-1) were both much larger for the offshore data. This showed a greater variation in oxygen concentration at sea. One outlier was identified as the highest value in its respective dataset. However, these values may not have been anomalous should they be the result of physical, chemical or biological processes. Click to see estuarine oxygen concentration page
Click on graph to enlarge
Click on graph to enlarge
Click on graph to enlarge
Oxygen Calibration:
Although the oxygen concentrations of the offshore samples correctly
displayed the trend expected from each station, the oxygen concentrations in these
samples were greater across the board than those typically observed. This was likely
due to some contamination of oxygen within the bottle samples during the collection
of the water into the bottle samples, with signs of addition of oxygen into the samples.
Oxygen showed an increase in concentration with temperature (R2=0.43, P=0.0066), which was consistent across all stations. Typically, O2 concentration decreases with temperature increases due to increased respiration rate and reduced solubility of O2. However, this unusual observation may have resulted from the warmer waters coming from the stratified surface layer, where O2 appeared to be more saturated.
O2 concentration varied with depth at all stations, typically showing a decrease in concentration with depth. Station C25 does show a slight increase at a depth of 13.9m, but then concentration decreased again at 50m. Station C27 had significantly greater O2 concentration than any other station, being supersaturated at all three points sampled. However, the profile for station C27 was incomplete, as the deepest bottle sample gathered was contaminated and no chemical analyses could be conducted. This decrease in oxygen with depth may have been a result of both aerobic respiration and stratification in the water column.