Disclaimer: The above statements and views are those expressed by the team members of group 5 and do not reflect those of the University of Southampton or the National Oceanography centre staff or other students
Estuary
Nutrient concentration showed a common trend of decreasing concentration, moving down the estuary. Low tide was at 10:10 and high tide was at 16:09. The outgoing tide contributes to the distribution of nutrients throughout the estuary. As the tide floods, the nutrients are diluted by the nutrient limited, saline seawater. This appears to have impacted the populations of phytoplankton and in turn the communities of zoo plankton. This is due to nutrients limiting the growth of phytoplankton. The surface waters of the estuary have high nutrients due to stratification by density, this promotes the high levels of primary production seen throughout the upper river.
Chlorophyll concentration was low at all stations, even in the area where a red tide bloom was found. This is most likely due to sampling error rather than actual results, as the method used to obtain the samples is unreliable and easily flawed. In reality chlorophyll is likely to be higher in the layer that can be penetrated by light. The deeper layers where turbidity is higher the levels of chlorophyll will decrease rapidly.
Dissolved oxygen saturation becomes more depleted at the surface towards the estuary mouth. A red tide bloom was found at the last station. The dinoflagellates form a microfilm at the surface which prevents oxygen diffusion at the interface. Oxygen concentration increases in the presence of the bloom by dinoflagellate photosynthesis, however, this is quickly recycled within the bloom itself.
Discussion