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Key Findings

Nitrate

Nitrate concentrations behaved as expected below the thermocline, where plankton concentrations were in abundance and concentrations were depleted. Interestingly, one of the station exhibited a significantly greater concentration of nitrate at a depth of approximately 10m, which could be indicative of increased mixing.

Phosphate

Phosphate as a nutrient is a key variable for primary production, and due to the fact that at all three stations the phosphate concentration decrease between depths of 15m to 25m, this is suggestive of this process.

Silicon

Silicon concentrations were significantly diminished from depths of 5m to 20m, likely due to the uptake of this nutrient by phytoplankton that inhabit the thermocline between these parcels of water. At depths greater than 20m, silicon concentrations exhibited a steady increase for all three stations as expected due to a reduced uptake and increased mixing.

Phytoplankton

The phytoplankton population of the Fal estuary from Mopus Reach to Black Rock was varied in terms of both population composition and number. Station F73 had the highest number of organisms with approximately 675 organisms per ml. All other stations had less than 350 organisms per ml. Both station A69 and G75, the furthest upriver and the closest to the mouth of the estuary, had phytoplankton populations dominated by Tintinnids.

Zooplankton

Both zooplankton populations of station A69 and G75 were dominated by copepods; whereas the middle station, E74 was dominated by hydromedusae. Station G75 had the highest number of organisms with 78 organisms per m3. Station E74 had the lowest number of organisms with only 53 organisms per m3.

ADCP and CDT

The measurements made by both the ADCP and the CTD show the Fal estuary is well-mixed. The depth profiles produced by the CTD show little variation with depth, which is a sign of a well-mixed estuary. As well as this the lack of variation with depth is seen at all seven stations indicating that the estuary is well mixed throughout. The ADCP transects for each station show that flow velocities are almost constant, although a slight variation can be seen in a few of the transects, also suggesting the estuary is well mixed. The closer the sample sites were to Black Rock, the higher the flow speed. This can be explained by high tide as the volume of water entering the estuary would have slowed down as high tide approached. This can be seen on the figures on the results page by the colour transitioning from blue to purple as the sampling nears Black Rock.

Met data

Date: 29.06.16

Time Range: 08:45 BST 15:30 BST

Co-ordinates: : E181983.9m; N31650.546m

Air Temperature: 14°C

Cloud Cover: 7/8

High Tide: 00:26 BST

              13:09 BST

Low Tide: 07:06 BST

              9:37 BST

Introduction to Estuary

Estuary data was collected from the Bill Conway, factors investigated included temperature, depth, salinity, chlorophyll and dissolved oxygen at various depths across different sites along the estuary and river. The results of this data collection are displayed in the accompanied tabs. Once data was collected, in was analysed in labs the next day.

The aim of this survey was to provide an overview of the physical, chemical and biological components of the Fal estuary. There was a specific focus on the changes in these parameters from Mopus Reach to Black Rock.

Aims and Objectives

Estuary data was collected from the Bill Conway, factors investigated included temperature, depth, salinity, chlorophyll and dissolved oxygen at various depths across different sites along the estuary and river. The results of this data collection are displayed in the accompanied tabs. Once data was collected, in was analysed in labs the next day.

Methodology