The biological structure of the Tamar Estuary follows the expected trend that higher up the estuary you are likely to find more phytoplankton and plant detritus increasing the chlorophyll A levels within the water column. The opposite occurs downstream number of phytoplankton present decreases due to predation from the increased amounts of zooplankton present, as a result Chlorophyll A levels also decrease. The physical composition of the Tamar Estuary stratifies at high tide and when the tide starts to ebb, as would be expected and there is no stratification in the estuary as low tide is reached. The tide also greatly affects the biological and chemical composition of the estuary.
Conclusions
The biology fluorescence is highest at thermocline. Phytoplankton inshore was mainly Chaetoceros. Chlorophyll maximum is located at the thermocline and nutricline. Zooplankton samples were dominated by copepods mainly found offshore between 12-18m.
Water temperature inshore is relatively homogenous indicating mixing. In contrast, the waters further offshore are significantly stratified indicated by a sharp change in temperature. The Richardson Number at C27 confirms this. The front was identified as a transitional boundary between the two water masses.
Some species of plankton may move with the tide, in order to stay at the salinity they inhabit. The nutrient distribution will also vary with the tide, due to the changing location of the plankton within the estuary. The chemical processes occurring in the Tamar Estuary vary between nutrients. Nitrate is removed upstream due to uptake by phytoplankton for growth; however, downstream conservative behaviour is displayed due to remineralisation and zooplankton predation. Silicate shows removal for a majority of salinities due to uptake by diatoms; however, at high salinities silicate shows conservative behaviour, because similar to nitrate it is remineralised at depth.
The sediment of the area Plymouth Sound we sampled can be categorised into two types; bedrock and fine sediment. Although the sediment was much more diverse than just fine sediment in the small portions of video we recorded ourselves, we cannot classify the sediment further. As a result we were unable to classify the habitats but the literature around some areas such as Duke Rock provided us some insight into the possible habitats and biotopes in the survey area.
The geology of Plymouth Sound had a direction of compression from the South East. The rock formations are suggestive that the distal alluvial deposits have undergone intense and extensive folding and faulting which the geofield survey confirms. The terrestrial soil deposits resemble those of Devensian age and alluvial origin. In terms of habitats, one can expect to see sandy plains separated by rocky, deformed outcrops, possibly with antiforms and (inclined)synclines. In addition, one may find sand (size undetermined) between faults in the outcrop, further expanding the range of habitat niches in the area.
